A PRIMER OF

FIRST EDITION

A PRIMER OF OFFSHORE

First Edition

OPERATIONS

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Foreword to the First Edition

Energy requirements are increasing wolld wide. Available supplies of

natural gas and crude oil are being depleted at a rate which threatens acute

shortages rvithin the foreseeable future. Alternative sources- of energy are

being exploited by both government and industry. Some of these are nx-

clear, geothermal, and coal deposits. Each of these a'lternatives requiresmany i*p.ouements in technology to meet the potential dangers inherent in

tltem. Radiation, destrrrction of the balance of nature, and air pollution areamong the ofrenders.

A desirable solution to meeting energy needs may lie in the improvementand expausion of currently succissful technologies of exploration and pro-duction of oil and gas. Beneath the seabeds and the ocean floors are theremaining areas in *t ich to find and recover the additional hydrocarbonsso necessary to tfe present economy.

Inland and ofishore technologies have many similar or identical character-istics. Since onshore operations are discussed in A Primer of Oilwell Drillingand A Prhner of Oil and Gas Production, this publication will devote itselfprincipally to equiprnent ancl methods trsed to iolve problems encoupteredin offshore operations,

Witlr this purpose in view A Primer of Offshore Opetatiorw is submiited.

Curtis F. KrusePetroleum Extension ServiceThe University of Texas at Austin

Austin, TexasAugust 1976

CONTENTS

Introduction

Marine Exploration .L -

Environmental Information . ! 7

t3Rigs for Offshore Explory

Moving on Location .

Station Keeping . .

tory Drilling

,.,t15

Rig Components and Procedures Peculiar to Floaters .

BOP Stacks .

Rotrtine Drilling Operations and Relaled Services ..

.1," !4

Production Well Testing .Abandonment Procedure 39

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45

C rews-Q u artef, s-TransP ort at ion

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Safetyandsurvival . . . . .:.

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Ofishore Drilling/Production Platforms

Storage and Transport to Shore

Bases-spills-Reguf ations-Contingency Planning

G l o s s a r y . . . ..

Acknowledgements , . 73

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II

-"INTRODUCTION

Offshore operations of the petroleum industry !"Sul^ll extensions of

.-oo,'rfttt" "-pfori'r,g, 4rilling, and^productttg' gy the late l93os,seismic. surveys

had be"r, madl of "oori*l maril lar,ds, 5*yuut, and -shallow bays adjacent'to

,:tlte Gulf of Mexico. In Louisiana barges sunk in dredged channels with water

'iiH, "f;;;';il and secured in iositio' with sptid and cluster'-piles'hacl

proyed themselves ", arUing ptatfo^rms. Drilling operations in sha$ow blys

tr;;""ffi";;r *;od"r,"il*tfor*, mounteii tln timber piles' supplies,' were brought to these op"oiiotrr !)t b"tge- throrgh access channels o: 9Itrestles f.oit n"orbf titoti ot boat landin[ tu"*tio"t'-ot.:"tP " tfl,tl*

' i,rg *o, done fronr'wlrarves extending out into the Pacific from L;alilornra

ilil;.;"rn "l'irt" early activities ii water covered areas were to extend ''

;;lil;;"rlr ""a a.ecou", oil from reservoirs already defined on shore'--nub.y odu"n""*"* "*uy from the solid ground.of prairies and dry land

, toward the bpen r"*rir"r bi'o,.,ghtconfrontaiions with problems that-had to'|1e

solvecl. T'fte rrsuirl patteru *'",,s for tlre operator to first try the.equipment

and skills already in his possession; and wlren tlris was not enough, the oper-

ator had to seek itew rnaferials, designs, and methods''

S,,"""rsful adaptations of existing resottrces were quickly imitated or im-

proved by cor-,rpeii'g operato's. OfEn the e'rphasis was more o' cooperation

io achieve ,, "un,,rloro, gionl tll,.n on individtraigains. The net resttlt has been

a fairly steacly evolution in every aspect of offslrore activity'

, As ofis6ore operatio's rnove into greater water dept6s aud more lostile

,' .envirorrmelts, tr'il costs ilcrease raplily' Ole of t[e-most striking effects is

" irr.f.," in"r"nrl i' size of petroleurrir"rlru", r'equired to iustify tt::9:::t:t:'

ment of a discovery fieldi,In sorne areas a ,*r"iu" estimated- at 100'000,000

- frfri of' petroleum irt st be considered margintll l$ ."y,"it development on

;ro .that basis. Comrnercial reserves begin at 3d),(n0,000 bbl of anticipat"d Pt-,l tluctiou for some fields.

otlrer fact'ors u4rich are influencing rising costs and feasihility of develop-

ment are iucreasirrg patticipation of host cottntries in leases, bonuses'.anu.: :ii'op"Jil;i

;t"d;Jtion. ltestrictions and regulations i*p".t* :.*T*:::

opirations ar.e generally repressive in efiect since larger capital outlays are

needed., lVith this backgrolncl tlre entire field of exploration has become muchii' bro".l".. All the tiols available to geophysicists are used: seismic, gravity'

magnetic, surveys based upon core drilling are comrnol].

;il;;;;;;i'iu*g #-;;' greatlyiixpa'ded' **: iTt l",ii*9to determinu ,ur".uoiito"*tiotr uni rir". ThJnumber and design of drilling/

ilJ;;;;;;; ;i;;f;'*r is determiued by i'formation.obtainable onlv from

actual drilling. Production and transportation facilities will not be con-

structed until their need is assured.A; ;,I.*;^,,.fi,,! "f ofislrore operations reqrrires tlrat eli4talq{-#9$r r^--^r^---^--+ J-;t l:*- L.o ̂ loo.l., . l istincrrislred- ExnloratOrv dri l l tng rs

a'd developme*t Iritbng -b_. "_!.gedndg!,ll-guis6ed. Exploratory--*F#

oilffii *6il1b rigs, and the we.lMtlg!g-?j-*

**r-- In *ater deepgructlon alx

than abotrt 1000

Firsi semisubmersible rig.

First ofishgre .Platform'

floating rigs.

drilled from mobile

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Areas of ofishore activify.

Activifies start with exploratory surveys. Erploratory

drilling is nert. Production drilling is last. Mobile drill-

ing rigs test the ProsPective reservoirs to determine

the feasibility of develoPment.

Rig count---€arly 1976.

!^JORKING RI qS -

L o u i s i a n aTexasU . S . P a c i f i cAfr i caAt l an t i cAus tral i aCanada and Great LakesCari bbeanCel t i c SeaMedi terraneanMex i coMi ddl e EastNorth SeaSouth Ameri caSoutheast As i a

286

I d l e R i g sEn route

UNDER CONSTRUCTION

266

1 2 7

D r i l l s h i p sJ ac kupsSemi subrnersi bl es

Firsi self-elevating rig.

Self-elevating rig with open-fabricated legs.

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1 B52

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45473031

29504B Large drilling ship.

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Subsurface formations

Introduction

Oil and gas reservoirs under bays, gulfs,

and seas ar; just like those ttnder lancl sur-

fac;es; sonretirnes these reservOirs arc exten-

sions of those alre"dy proved on shore. Irregtr-

larities in subsurface strata exist iu such forms

as sdlJlpgs gi. dgryes, bqrig* Iqgfs,-.f+slls, .folds, anticlines, synclines, oi- otlrej geqtgglg

e i-egularities or anomalies

@the presence of oil or gas de-posits;' Tlrere must be 'a sou_{9e:tlpe__Lo..ckformation, a reservoir-type rock rvith porestructqre able t bons, aird abarrier-t@ich will trap And retain.hydrocarbons'migrating from their source bed.

Exploration Techniques ,

Geophysicists and geologists have severalsources of data including magnetic, gravity,

electrical, radioactivity, geothermal, geochem-

ical, slim hole drilling, and seismic surveys.

Exploratory drilling,is the final method-

EIPL0RlTl0r TEcllrlqu Es

SE|S$C

Excltrsive of actual drilling the seismic

method accounts for riiore than 95% of monies

spent each year for acquiring and Progessinggeophysical data.

Satellite-Doppler sonar navigator

Position determination 0 ,The rfifila Wtreophvsical ffiodepends

ruporl tne ffii" ;$F6fF Fo#rettirn tothe precise location of the prospective struc-tnre. An accrlracy to a horizontal error of 16feet and an altittrde error of six feet is possiblelry taking 20-30 satellite observertiort rccord-ings frorn a fixed position for an offshore loca-tion.

Integrated navigation systerns pcrrlrit all-weathsr, 24-hotrr-a-day navigation withouttlre need to establish base stations for radiopositioning. The navigation glrtion of a typi-cal integrated system consists of r ( 1) a gyro-compass, ( 2 ) a fotrr-beam Doppler sonar, (3 )a satellite navigation receiver, and ( 4 ) a cen-tral digital computer.

Otlrer ftrnctions generally performed l>y theintegrated system include :

o Automatic logging on magretic tape ofnavigation and geophysical data

o Steering the ship along tlre desired sur-vey track

' I)riving a plottcr to rccord ship's track,shot point iverit.s, and. time ann;tation

' Atrtomatic firing of seismic shots based onuniform incren-ents of tirne or distance

' AScepti'g, corlverti'g, and recordirgoth,er geophys ical da ta

4

/ l ' t f ' : - q' seismic survey JtrkfiA.Hi*"Vessels equipped f6r seismic suryeys are in

the 165-175 feet range in length. Op"ratingspeed is 4-6 knots which pennits rechargrngof the compressed air guns between shots andholds within acceptable levels noise interfer-ence and motion accelerations ( trim, pitch,Iist, and roll ).

An acoustic wAve train or impulse is trans-rnitted through the water column into theearth and is fiactionally reflected from inter-faces of strata lraving unlike velocity and den-sity characteristics. These acoustic echoes aredetected by groups of hydrophones ,mountedin a plastic covered streamer or seismic arraytowei behind the vessel. Depth controlleismaintain a constant depth of tlie streamer be-low the vessel. The acoustic data is gathered,digitized apd stored on mag4etic [ap*r forcomputer analysis, resulting in displays whichprovide a graphic representation of thestructure of the earth over which the vesseltraveled.

Sotrnd sorlrces of marine seismic surveysincltrde:

o Ai,_ guns or air gun arrays using compres-sed air discharge

' Single pulse using compressecl air. Small chemical explosive chargeso Vibratory ( non-dynamite )o Acoustic pulse ( Exxon )o sparker (electrical ) for minimal penetra-

tio', high resolution ( shallow gas, mudline data )a Courtesy Seismic Engineering Company.

Diqital recorder

SHOT f, SHOT 2 SHOT I

Seismic Survelor:-a speed of | 2.5 knots and | 0,000-

mile range t"'ku possible long moves to remote areas.

ONE SECTTON - DETAIL

3O-5O HYDROPHONES, LINEAR OR TAPERED SPACING

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fr-,r'

Typical 48 trace geophysical array.

Hydrophone, acfual size.

Streamer, reel, and depfh controller.

Strrveys are initiadd io't.rr"iul'*"ytt (1)

A sirrgle company may contract for a survey.( 2 ) A combination of several companies mayshare the cost of a spqcifie contract. ( 3 ) Theseismic survey corporation may speculate bymaking a survey in promising territory withthe expectation of profitability when industryattention focuses on this new area. I)ata bankseventually acquire much of the information,and participating companies have access tothem.

Seismic common reflector point technique-

Detectors used in marine seisrnic work arepressure sensitive devices called hydrophones.These are placed in long cables called streanFers and towed behind the survey vessel. Cablelength may reach 3600-3800 meters with2000-3000 hydrophones. For marine Lrse hy-

I l -drophones replace the geophones Lrsed or]land. I

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Surface synoptic clrart prePared by NWAC'

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.SYMROLS FOIT SIGNIFICAN"I' WE,ATHE,IT SYMBOI,S FOIT FRON'TS, ( :ONVNITCNN(:N I , INNS, ETC:.

K THUNDERSTORM

R TROPICAL REVOLVING STORMa> (HURRICANE/TYPHOON, ETC.1

-. . SEVERE LINE SQUALL

nf i HAILV

c_ WIDESPREAD SANDS-I'ORMJ OR DUSTSTORM

(\) FREEZING RAIN

. RAIN

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COLD FRONT AT-

^ ^ - T H E S U R F A C E

COLD FRONTABOVE THESURFACE

WARM FRONTI '-' lJ;lx8'WARM FRONT

N N N ABOVE,THESURFACE

OCCLUDED FRONT,. - ^ fJ;$i8,OCCLUDED FRONT

r^ \ r1"-A ABOVE THESURFACE

^= o FfS'ii'IfJi?"+'.tJ' SURFACE

CONVETTGENCE I,INE

INTER.TROPICAI,CONVERGENCE ZONE

NOTE: THE SEPARATION OF THE TWO LINESGIVES A QUALITATTVE REPRE.SENTATION OFTHE WIDTH OF TIIE ZONE, THE HATCHEDLINES MAY BE ADDED TO INDTCATE AREASOF ACTIVITY.

AN ARROW INDICATES THE EXPECTED DIRECTION OF MOVEMENT OF A FRONT ANI)

IIE,,X-[. TO THE ARROW 'I'HE

EXPECTED SPEEI) OF MOVEMENT (IN KNOTS). IS GIVEN'

Symbols and notation commonfy used on radio facsimile weather repork-

Sea conditions

the surface of the ocean and water bodies ( tt

gulfs and bays ) connected with the ocean that

occur twice a day and are caused by the gravi-tational attraction of the sun and moon occur-ing uqeqnally on different parts of the earth.Ordinary tides are completely predictable andtide tables can be obtained which indicatehigh and low tirnes for ahnost any water bodyconnected with the oceAns.

Storm tides are associated with the move-ment of hurricanes. In the Gulf of Mexicostorm tides of 20 feet inundate beaches andlorvlands as a maior storm system approaches-sornetirnes as mlrch as 24 hours in advance.In other parts of the world hurricane-typestonns rnay be called typhoons or cyclones, btrtthe basic frnr*rds are itr* same.

Currents are a part of the circulation sys-tem of the eartlr's water which covers approxi-nrately 7LA of the surface. Major currents suchas tlre Gtrlf Stream and the Japanese Currentare well known to residents of coastal {.f.S. andshippittg interests. The Gulf Stream is a warmocean current in the North Atlantic flowingfrorn the Gulf of Mexico N. along coast of (f.S.

to Nanttrcket Island and thence E. The weath-er of the British Isles and the English NorthSea are products of this current. The japaneseCurrent moves northeastward from Japan to-ward the Arctic, ttrnrs southward and sironglyaffects the weather and clirnate of Alaska, Can-ada, and the U.S. Pacific Coast. Other majorcurrents are the Labrador, tlre Htrmboldt, thtrEquatorial currents and their counter currents.Tidal currents occrrr where water flows intoor from tidal basins. The B"y of Fundy, an in-Iet o[ the Atlantic SE Canacla with r:eportecltidcs of 40 feet, is one exirmple of strorr! ddalcurrents. It has been reported that at one pointalong the coast of India tidal flow limited drill-

Waoe,s are formed by the frictional contactof the blowing wind upon the surface of thewater, Windslre seldom calrn because thecirculation system of the atrnosphere kceps alllevels of air in. constant motion either verti-cally or horizontally. Horizontal motion of qiris wirrd. On the surface of the water first ruflesthen waves are formed. Waves ar€ not masstransfers of water; wsves transmit,.,pnery.Forces generated by wind velocity are trans-mitted frorn one particle of water to the nextparticle with only a minute loss of ener$r (thesame principle which operates in a hydraulicsptem. ) The area of wave propagation iswhere a certain wind force prevails from thesame direction for a period of time. This iscalled the FETCII. Wave movement expres-sed in feet per se(nnd is called CELERITY.

Once in rnotion waves will continue untiltlre energy they contain has been transferredto the blanket of air above or to the oceanfloor. In the shallows waves crest and breakand become suRF.

'waves which travel be-

yond the wind which formed them are calledSWELLS. Swells may occur many miles fromthe area that produced them. suRGEs areIarge waves ot i*"lls or a series of them.

Ts.unaffib, notably in the North Pacific, arelruge shock waves produced by submarineearthquakes. Effects of this energy transferare less serious in deep ocean waiers, but inshallows and on shore immense breakers mayinunda'te and destroy boats and installations.Often there is no warning unless it is observedand reported by a ship a-t sea,

The following definitions are related to seaconditions:

( 1) A cunent is defi'ed by the directiontou;ard which it flows; ihir is the SET.

(2) Rate of flow of a current, the velocifr,is called the DRIFTing operations to three hours a d*y.

( 3 )

( 4 )

( 5 )

Winds are named for the

fromwhich they flow

Rate of flow of the wind

WIND FORCBBoth curent and wind velocities are

expressed in KNOTS( 6 ) A knot is a velocity, not a distance; it

is one nautical mile per hourThe nautical mile is 6080 feet ( 1.15statute miles )A time rate of linear motion in a givendirection is a VELOCITYA time rate of charlge of velocity is artACCELERATION.

direction

is called

( 7 )

( 8 )

(e )

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Sources of oceanographic information

Oceanoqraphers' charts and tables of dy-

namic o"""ttograPhy strpply basic informatior"t

on crtrrents, tides, and waves for variotrs parts

of the earth's oceans.Tables of tides are available in book form

arrd rnuclt of the information is available otl

regular radio broadcasts.Logs and recorded observations of both

fixed and mobile platforrns c?n be obtained.Indus t y publications often report unusual

sea states that have occtrrred.First hand observations of ships at sea with

facilities to transmit ship's rveather messages

and storm data to coastal radio stations are

sometimes a good source.Special studies irrcltrding

"hindcastiug" re-

late observed weather conditions to the seastates that might have been expected.

Company retained consultants interpretand predict conditions requiring special Pre-catrtions.

Ice

Tlre presence of sheet ice may limit drilling( 1) to short seasonal operations of 4-Srnonthsduring srunmer ancl early fall when there istro sheet ice, or (2) to specially designedfixed drilling lilatforms with caisson-typel"g consh uction as those used in the CookInlet, or ( 3 ) to dynamically positioned drill-ships with capability for quick disconnectsand reconnects.

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Cook Inlet platform.

Pack iceis sea ice formed into " *rrs by the

crtrsltirtg together of pans, floes, and brash-

L pan is a drifting fragment of the flat thinice that forms in bays or along the shore.

h fl,oe is floating ice formed in a large sheeton the strrface of a body of water.

Brashis a mass of ice fragments.Icebergs are large floating masses of ice de-

tached from a glacier. The average iceberg iscalculated to weig\ one million tons. Hun-dreds of lcebergs threaten drilling from 100-300 miles off the shore of the Labrador Sea'. Aswith pack ice drillshipr with qtrick disconnectand reconnect capabilities can functiotr, leav-itrg the BOP stack on the sea floor.

Major iceberg detection is by radar. Heli-copters can spot approaching pack ice or ice-bergs in time for disconnects to be performed.In some instances icebergs can be torved bytugs or other auxiliary craft to a course thatwill bypass the dril'lship if the BOP stack isthreatened. fu a safety precaution a workboatmay be stationed within one mile of the drill-ship to assist when icebergs threaten the oper-ation. In a danger zone an ice managementconsultant supervises the safety procedures.

Freezing spray and build up of ice on thesrrperstrtrcttrre from freezing rain can halt orhinder drilling operations. In some instancessmall craft have been lost because of super-strtrcture ice accumulations. Day rates for ice-troubled operations are two to three timesthose of mild conditions.

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Weather

Weather is defined as a state of the atmos-

phere with respect to heat or cold, wetness or

dryr"ss, calm or storm, clearness or cloudiness.In many sittrations the term "weatller" is usedprincipally to indicate conditions hazardousor unfavorable to the operation in progress.

Sea states and weather are so conrpletelyinterrelated that both figure in long tenn plan-ning as well as daily work schedules.

Circtrlation of the earth's ahnosphere, Iikethe circulation of its water, is constant. Thesun supplies the energy. The rotation of theearrtlr is a factor. Differences in heating andeooling rates of land and water surfaces havetlreir effect. The zane of maxirnum heating b)'incoming solar radiation changes throtr{h ;range of 47 degrees as the surl reaches its ze-nith between 23.5 N. Lat. abotrt June 21st and23.5 S. Lzrt. ahout December 2L. Heating inequatorial or tropical erreas, cooling at bot'hprles and the two temperate zones betweentr<lpic.s urrd thcr polcs givc risc to cli.stirrct cir'-ctrlrrtion patterns of the carth's atmosphere.

Seasonally cold air advances from polarareas into temperate areas; the warln equa-torial band of atmosphere moves northward orsotrthw:rrd into the temperate zolles.

Air masses acquire their temperature andrnoisttrre characteristics from the surface overwhich they originate. Arctic or polar airInasses fomred over continents have lowerteurperattrres and contain less moisttrre thanltrctic maritinle arir nrasses. Tropicrll air mrrsscsresulting from heating of land strrfaces lravehigh temperattrres and low water vapor corr-tent; maritinre air masscs have lower tempera-trtres and rnuch higher water vapor content.The chief point of interest in these rneteoro-Iogical facts is that the energy to prodtrce lraz-arclotrs weather lies in lncl is transported bythe \,vater content of the atmosphere, added intlre form of vapor. The release of this euergy atthe tinre it conderlses from the gaseous form tothe liqtrid forrn supplies the erlergy to producefronttrl st'o'rnls, thunderstorffis, hurricalles, anclrelated disturbances.

Drilling rig tender during a severe storm.

Fronts are strrfaces of discontirruity or inter-faces between unlike masses of air. Cold frontsmove toward warmer air; warm fronts rnovetoward cooler air. Stationary fronts appear toremain motionless; an occluded front existswlrcn a cold front ovcrtakcs a warm front lift-irrg the warm air above the earth's surface.Lows are potential storm centers. Fronts lie introuglrs of lowcr prcssure where wind shiftsitrrtl ternperature clranges will occur. Rapiclrnoving cold fronts sometimes produce squalllines ( a squall line is a line of prefrontal rain-showers and thunderstorms which form inwarm air masses ). At the front, precipitationwill occur if the warrn air contains adequaternoisture. Cold fronts move faster than warmfronts. Warm fronts may actually indicate coldair receding

Some areas, the North Sea is one, have ahigh incidence of frontal storms with highwinds and dangerous sea states. Rigs musthave t}e capability to operate in this hostileenvironrnent. Iluy rates are based upon rigcapability and include rig rental, drill prp€use, and fuel consumed. Rates for severeweather areas are about double those of mildweather locations. .

A hurricane forms as an extremely low pres-sure system along an easterly wave. For theGulf the months of June to November are themost critical.

To'radoes develop as spin offs from hurri-canes coming aslrore; at sea they are calledwater spouts.

--E:l'.rys.;i".:'-arc-;s:

Areas where cyclones {hurricanesl forrn.

SoiI conditions

Every phase of drilling and producing off-shore petrolerlm is affected by soil conditionsat the site of the operation. For jacktrp rigs

penetratiorr depths of the legs, the use of mats,footings, piles, arld anchors to stab ilize the rigrnust be accurately predicted. Floaters mustassess their anchoring and mooring needs.Fixed platfouns and. pipeline construction re-

quire accurate soil condition surveys in orderto design footings, clttster piles, artcl piles to bedriven,

Soil tests include combinations of :

( 1) Core drill ing and sampling(2) Side-scan solrar to detect pipelines or

other sea floor structures.( 3 ) Ivtagnetometer to detect caprocks or

other rocks( 4 ) Precision echo sounder to obtain accu-

rate water depths and mud thickness( 5 ) Laboratory analyses to determine shear

strength, load bearing capabilities, arrdestirnate pile depth penetration

Specialists perform these soil tests. Bottorrrsoundings to deternrine the suitability foranchoring and mooring a dlillship or semisub-rnersible may cost $30,000 a duy.

10

Corrosive elements

The composition of the waters in whichsteel structures are submerged varies widelyin dilferent environtnetlts. The degree of sa-linity and the prevailing temperatures affectrates of corrosion and methods used to oombatit. Natural seawater, brackish water, and P"t-lution-laden water all differ.

Contact and abrasion by water in splashzones or spray generally require coatings de-sigrred to prevent air or water frpm contactwith metal. The coating should also preventor reduce flow of electric current.

Corrosion occurs when unlike metals eitherin direct contact or proximity in an electrolyteproduce a flow of low electrical current whichdissolves one of the metals and either takes thernetal into solution or deposits it on anothersurface as in electroplating and anodizing

Processes.Cathodic protection is based upon the es-

tablished principle that both the amount anclclirection of current flow can be controlled bytlre placing of anodes in strategic locations.Various metals and metal alloys and impressedcurrent systems are used. The desired result isto prevent the protected metal from dissolvingand instead to deposit a thin protective metal--lic layer on it.

Station: BOSTON, MASS. (NMF, NIK, IVOU)

drca afcctcd:r

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r8+0

0n receipt2:H+lE or H*{8; eon receipt and evenHt2O until next.sched-uled broa<lcast

( 2 )

( 3 )( 4 )

(s )

( 6 )( 7 )( B )

lce bullerin lce relxrrts dtrring the icc seasoe. March l-f ulyl, approxirnarely. Broadcast at l6 wpm,-fol-lowed try a rcbroaclcasr at 22 wpm.

Forecast Forecasts anrl warninpi for ar€:rs h, c. and d.

t ine<ast Forccaslr arxt warrr i l rgr for:rreas tr. <. and d:localir.crl rnarine for,ecasts.e

Forecasr Forecasts and warning-s for areas b, c. d, e, and f.

Forct'as( Forccasts and warningr for areas b, <- d, e, and f;l<rcalized marine forecasts.i

Forccast Forccast an<t warnings for area d.

t'orc<:ast F<u'ccast arrd warrrings lirr arca a. lce lrtrllitinrin scasorr ar 0130 and 1330.

Ifarnings (ialc/storm/hurricane warnings.

\'l'arrrings Gale/storm/hurricarre warnings.

Worldwide Marine Wealher Broadcastr, a United Sfates Department o{ Commerce publication, is tfie princi-pal source of information on marine weather broadcasls for all U.5. ships.

Forecast services

Information and forecasts by radio and

,r'adiolelephone are available in all parts of thewoitd with the obvious differences that widely

' $paced reporting stations produce." Lii-t.ed below are the principal sources:

, ,(t)Worldwidg Marine Weather Broad-casts, a publication of the {,t.S. Depart-''' ment.,of Commerce, National OceanicService; revised annuAlly, changes ancl

I ,, , .: , 'Sgpelintendent of DocumentstI.S. Govenrment Printing OfficeWaslrington, D. C. 2A402

Continuous Weather Broadcasts, tI.S,National Weather Service, VHF-FMradio stationsRadio Facsimile Transmissions(J.S. Offshore Marine Weather Broad-casts-RadiotelephonelU.S. High Seas Marine Weather Broad-casts.RadiotelephoneHurricane Warniog Servicel{WS Severe Weather CircuitProfessional forecasting services,weather consultants in company em-ploy.

11

Jackup Drillship

u

Semisubmersible

L2

I,RIGS FOR OFFSHORE EXPTORATORY DRILLTNG

J '--y

*oY -7-F .e f I

comparative view "f ,Sfft" ris "o#g?l"WtQ+itp^.+- -

The,,.e:ryironnrent in which each type_. gf ̂ ̂ nnrobil" .iiiii irrg ng func tions best ir-de tffi Y' dDrillshipr.yfi"fty range inlength from 200

ate in water depths of 3000 feet, Engineeringsttrdies for the Mohole proiect and the coreclrilling successes of the Eureka, the Glomar

JnckupiliCvelargelyreplacedsubmersibles. Cftalle"nger, and a predecerso., Cuss l, haveAiackup.rig: (1)provides-affxeddrillingpfaf proved ihe capability "f drillships for opera-forlr, ( 2 ) its initial cost is less than others, (3 ) iio,r in deep iater. Li-it"tiorrs:are fouid ioit can wor\,r"l,rl"Uorn areas of deltas if the lack of suitable risers to suppdrt drillingdntpPdd with fi'fffto srrpport the legs, (4) it mud circulation-wellhead to di-Uins foor.

-rr

can be designed,to:withstand hurricane-type r. /i\storms, (5) it is the best tool available for [:# gtiprtrep-s- incl-udq qftbc[e=ArilUng+lat-water depths of less than 300 feet.

-zf""riiiir"i( t ) "r" self_pronellE *a UG ih"rrer oeprns or tess uran ;rOU teet. rforms that ( I ) are self_pronelled arrd have the

t l'ffigii;;131i-t_fJjh$'ft In5%itri#fficun to tow' (z) legq..must P-e-!gid*q"o^up-.g {n{(2) d:4lips@oti:i1lu,tf-lf"tg:g;:;j'"(q[Fi'{,#es'+ ,ig-6lr,"{m *y'il*"1..b+:stle:ts-u*rts, (4) gr.'"Bg e.q gJ_g$ ,;-*rT;EIiiI'Ab"-;g; "il-"ta lie a1istfi!fiffi

-Ios.ttig.Lis

lraz4r{ls5iacking.to raise or low- t\ro* the $fifff6frn:fffiier commonty usi4wig*_* .;:::"i3'.t',:k: "l:]-ti*_np s-+-4prrev n a,1x4qd 4",5"*' $ ;i'iJ;fitrfflavg pr-gdgcg{po.qJ t$*p.Jy;egoid. f"ffi.Fui6i66oittol by a'barsemasterralherraYP Pr-gg!l-c-9{P9.9J -s=$*9-JyJegord. feattii'esl! its control b

Drillships liave a number of advantages. than a "ffi-ffi6Amo.ng them are: (1).proven deep water ;nEcEsfffrffie-bodiedsea'-"rr*refn"h*rg

r.?:i'I}?d?l *Xffi";?;.;,T::, rT ffii a-".lfl*""ff:":?,x'n:il*fJ:"il*'i:*,_ _.travcl times to remote locatibns, (4) no need "'.,,-catering costs continue. Drilling U"rguJ:EffifrT**'for ffi"i3 they are self-propelled, (f ) lower /' these costs.costs to operating company-maintenance "l ,,

$..Tl,il;iffi '*ff il.&Jffffii.#"i;:iln:H,i,T::i".I:l#Eii,HffiIn:. ot.o!l't"s*",! ih;Ttrilffi ;FF,^A * fir#ffirllrc its limited capacity to operate i'-riind or' r.tla1r ,t " ott "rl-iH-ftfiffi5ilrrtil'for waterwave conditions which produce ekf6ffil06plat. eAffijronrl rnouou. 2000 fert, (+),g!r*gggg-$fqy r"gqrCJ

s1

13

DE' LOADING FOR DISCO\IERER CLASS

TYPICAL SUMMA.RY 9I VARIABLES

'- : .ITEt"l:

FueIBrake Cooling Water

Engine Cooling Water

Lube, Hydraul ic & Gear Oi l

Wash WaterDri l l ing WaterPotable WaterBulk Mud & CementLiquid lvludFlume Stabil ization Water

ChemicalsDri l l Pipe , Col lars, Casing and t ' lar ine

RiserChain, Wire RoPe & Anchors

Dry Stores, Misc. Toolg e Misc. Equipment

Mooring Line PulI DownBal las tContingency

TOTAL:

Semiqu,bmersi'bles have : ( 1 )--linnlte-{Seqt?::

QUANTITY

4250 bbl.460 ,, bbl .,!NONE

1000 bbl .4000 bbl.

825 bbl.

.7060 f t . 3

1700 bb l .5'800 bbl .5000 sacks

WEIGHT

7 A7 tons85 tons

5 tons180 tons700 tons148 tons400 tons600 tons

1020 tons300 tons

500 tons50 tons40 tons60 tons

57 5 tons

5370 tons

ilv {'ol.LgHggjHlryIF:li9sJ? J r e-qsirs rgprestrouort tffiffimfrjply, aqqlror \andlipg,*i$Ei, ls]-]frfft "ci.4ffi,*!ilef_ t_et-r.r*ee-ddDy_ IacSgP!.

,"* '.biitti"g

barges have the advantages of ( 1)'i

l.r.rror ,^r^r.r rl'rnr. nfhcr foaters^ ( 2\ smallgri lo*"t "oit than other floaters, (2) smalleri { i { ' , i

r v Yr \

'e:-i i crew and quarters needs. T'heir disadvantaggt

i *r", (1) low towing speeds, and (2) depend-i -'?, ence on tugs and other work boats-

(semisubmersible drilling rigs cArne into use

its it became clear that floating drilling plat-

forms instead of bottorn supported must be

used in cleeper waters.>A few strbmersibles

were convett".t to ,"*irubmersibles. Newer

sernisubrnersibles resemble their prededessorsin rlppearance btrt improved streamlining and

design changes in the buoyancy and flotation

clrambers have increased towing sPeeds from

3-4 kno ts to 9-10 knots.'$-L9W-ip*isubmersi-t, tu n ir;"""1+ pr:qpglled . .d:-*;T,I lit' ff- lmiaifrbG: #eed-ing balast cTrambers with seawater. The ves-

r"i G1fixin"ond-*rd-ufffiffi-tfi6Test wave,ctrrrent, and wind relationships ancl tnoored

ancl anchored.-

L4

NONE

If the semispbmersible is self-propetled, itwill have a shipmaster who will suPervise its

propulsiott, towing, moorinS, iind anchoring.

to 1000 feet. Under construction and testing

are a number of semisubmersibles with nomi-

nal depth ratings of 2000 feet. )

Relative initial costs are statistical in nature

btrt to indicate the range, these figures are

suggested:

]ackup ( 100-150 ft.) $10,000,000-$12,000,0m

Jackup ( 100-300 ft, ) $20,000,000-$25,000,q00

Semisubmersible

( 600-2000 ft.) $40,000,000-$50,000,000

Drillship( 600-2m0 ft.) $35,000,000-$40,000,000

D"y rates or rentals will likely be approxi-mately $1200 lday per $1,000,000 of invest-

ment with additional charges for support basefarcilities. Severe weather locations and ice-

ffi-.bt. n'fiiwai6'ffiBa-gjtsA**ffi;iffi. A few aie 6ilBa-Efu of *odiftcition to drill in water depths uP

trotrbled areas will increase rates.

MOVING ON LOCATION

lackup Platfonns

Towing

Igs5yp*{lgt,t.{eT,grgdJrg$"'9n9}*Rgp*J.oq--rl-.a.Lhgi.-bj _J,gS":. Average towing speeds in

calm seas aie 4 knots using three 9,000 ltp seatugs. Under less favorable conditions the tow-iug speed will be slower. The daily cost of a9,000-hp ttrg is at least $3,000. A rePresenta-tive figure for towing is $10,000/day. Modernsupllort vessels are capable of serying as a tug,a supply boat, or an anchor handlittg boat.

-gJ gyed i a ck u p r i gs.€I g_l_Bg1^9J_gI _

I " ff bi; -6

; ffii& ri ts*i tian.th s"di; ;iJi_fr fu

a t r . r .

_ ;

ing crews with special trainitrg have been de-veloped bv several contractors for in transitand going off or on locatiorl.

Close-up of footing

Setting the legs on bottom

Sea floor and soil conditions will have beend" 6ftffi ;affi ce- Tfiralaili;;m;tid-;ili" 6JRfi6ffi .*itootings for iackup plat-forms sometimes are

"of ' cffibn-3a]rii,r-iH;a

iil|.ffi s;1a;tr6;nr#ir*ffi rthe legs reduce the depth of-"Lqg*pg,gg*trj-slt1into tft r&-floo;.' r"g'fr"?il"tioil;rnffmesl h aJ ZOO feet of soil depth'Tlre use of mats permits erection in dJltasand shallow bays where mud deposits have

accumulated.Preloading of jack*p legs helps assure, tle

suitability of the sea floor as a foundation.,.i , I '

: : : : - r '

'.,i:,:-,-,:=...,:1-': '. .:::::. j : _ i:.:..�.,,.t :1 . ,

i : . :

',":'i -

: : - .

Jackup rack-pinion teeth.

Positioning the platform

With the legs on bottom, jacking crews ele-vate the drilling floor to the height abovewave action anticipated to be safe for the sea-son and the area. In the Gulf of Mexico clear-itncc for t lrc stonrr scasorr is 35 fcct,25 fcct lorrest of year.

Three areils with the tytry of pertineut in-formation to be used in positioning a clrillingcleck .bove nlear level water follorir:

Offshore Louisiarra ( I00 year storm )L?.5 rnph winds ( I0gk )57 ft. waves2.4 fpr current280 ft. water depth

North Seaf 30 mph winds ( ltg k )94 ft. waves

420 ft. waterPersian GuIf

94 k wincls ( I08 mph )39 ft. waves

' .0,9, ft. tide154 ft. water

t,,c::npariso. of ratcd water depths withavafltrble

l.q le'gtlrs in tlr"' n""o*pr,nying

table will indicate=that l% Iengt6s *ili permirft'onr apploximately 40 to-90 flet of Air^spacebetween meiln water level and the hull.

16

Overall view of iackup during ouffifting.

On location legs are lowerecl to bottom.overall I"g length of nine jackup rigs in theZapata fleet ranges from 2L3 feet to 460 feet.Available l"g length below hull ranges from165 feet to 390 feet. Watet d"pth ratings rangefrom 100 feet to 300 feet with two depths ratedfor North Sea operations.

l

Year Nameof H"iil T:ft #*lli,,Briilt ]ackup Rating Lenglh Below Hutt

r96619651966r9641967196819561967r972

300'250'�300'300'100'115'165'230'NS300'Ns

460'�360'48A'460'213'�22L'�245'�363'�400'

390'290'390'3g0'L7O'�165'�2Lg'�306'�339'

ChapparalEndeavourHeron{ntrepidTopper ITopper IIVinegarronExplorerNordic

seven of the above have three triangularlegs, one has three square legs, another has.three rectangular legs. six of lhe above haveslant I*g design, three have straight legs. Six

:rre eqtripped with Le Tournea,, J*"trif i""lq.,

ing and slanting systems, electromagnetic

Drilling equipment stot.

brakes and with rack and pinion final drive;three are eqtripped with'siraight I"g designjacking systems. )

jagking speed at maximurn load is approxi-"rn[ef vi"-tnibrlrriiirti'ftlT6l:i6rn"E]ildl{iiils1*--***

g*d -".{**;",r-:r-'r\rri:i+r-*sa*-*q <rr.;rr.,*.d

(.i*;:==r*"--".. --.-**Or****3tl-ti+'rtit "

Anchorin$systems vary with size. The basicpattern is the use of four wire line .anchorwinches rated 50,000 lb. pull at ?n fpm and.fotrr 10,000-lb. anchors.

Zapafa Ugland underway-self-propelled.

SEDCO 135-note winches and anchor chains"

Mr. Sam uses cylindrical legs. Note anchors at right

< . - . . 4 7 . ' : 4 i - \ -

Mr. Charlie, first submersible barge capable of operating in open sea at 4O-foot depths, photograph on seatrials by J. M. Payne of Shell, fint user.

Moving on location and riggitrgup semisubmersibles

lone of the newest semisubmersibles with anominal water depth rating of 2000 feet has atowing speed in calm sea or ro knots. some ofthe early sernisubmersibles were rated at tow-itrg speeds of 3 knots.

zapata's ugland, a semisubmersible built inL974, is self propelled. It has a speed in calmseas of I knots. Its platform specifications are3ff7'x 210' X B0', displacement of 90,000short tons and variable deck load capability of3,000 tons. The deck area is approximatelyL.75 acres. on its trip from sabine Pass, Texas,to Aberdeen, scotland, it set a record time of2l days, L4y, hours. It crossed the Atlanticfrom North Ameri'ca to Europe without assist-ance from a towing vessel. Other featuresworth noting are:

Ability to continue operations in seas of 40-50 feet

Ability to remain moored in seas trp to 100feet

1B

3. Surveys made and buoy markers placed

Load capacity enabling all movcments to bemade witli anchors and anchor chainsstowed aboard the vessel

Mooring system for at least 1,000 feet ofwater

'HS,[qLg-*$e dritlllg rig .arlives on locationrg1'"1"!-ptgp-a_rSiory-op;agong_iho:trlA-Ey"f *x - - r - r "n ' :F . - . . !

: * .+ : - r

b_9S1_c_oygJiteted:

1. Bottom soil conditions deterrnined2. Prevailing winds and sea states known

for exact anchor locations4" i"-

ventoried -- -

5. f,iiiEffcommunication deftnitely estab-Iished: operating companl, drilling con-tractor, anchor handling boat, and qpecialcrew.

Tlre sequence of anchor placing includessuch considerations as placing stern anchorsand mooring lines as the rig cornes on site, fol-lowed by placing of bow anchors in the direc-tion of heading, pr€vailing winds, and seastates.

STATION KEEPING

DRILLING EQUAND SUPPLY

DRITUNENTrDS

rtPLCo

t\[E])AD

IWEIGHI

IWIND FORCES

'HOORING FORCES

Forces acting on floafing rigs.

Station keepittg of a semisubmersible

Semisubmersibles are crested with hg*gn fr;- a re-; apabilitv

F b!.s.{df4?F-..*.t*-<.r+,-,e-.V-s-1qr::iEsrf.r.ii-Fi--.njr;:€t4erJa,1'-q:..?@ i

o[_gg:ftif "rU"lng:ape;ati_o-nl.ggd=g"f _*g,tq.d,gygeW$g$gj;J9-31,"-*,+tes. They are positioned toresist the maximurn anticipated loadings fromqtrartering winds and c,rri"uts. fn roml areasa cornbination of wind, waves, and currentstnay el from an !.iiqrf 150

$qg6;r ratheStation keeping involves all of the opera-

tions used to keep the platform over the hole.It is to be expected that floating platforms willlrc in coustant rnotion. &p ru *qtiop;5"._,[g-* l-':gh*1 = fl$ glg.. yess*l. ir, ji;ffii rrrg",

WATET

€ Ar&

{*"a{, **l { { #t} { {i;t'ku {d?:'r} n ?''"r':r-:'6"

19

t*.lv/

-p,.#Syrnm ef ric E ighf- | i ne (8 s)Symmet r i c S i x - l i ne ( 6s )

\Fff

Symrnet r i c N ine- l ine (9s)

Symrnetr ic Twelve- l ine t l2s) 45o-90" E i gh l - l ine (8o)

3O"- 60" Eight-f ine (Bb)

Spread Mooring patterns.

Careful monitoring of individual line loadsis essential. A number of line load measuringancl indicating devices are used. Some meas-rrre line deflection. Others involve very com-plicated electronic compu'ting and recorditrgfaciliti*r,-, p-

osite tlfe:'applied=tffit" nothinaud- qre tlackened to reduce tension on linestrnder full load @eloa,@mooring Tinei, called pretension, can be ac-cornplished with a mooring cunputer pro-grrun. Better horizontal control can be achiev-ed r,vithout overloading the mooring lines.

The hardware for anchoring systems ofsernisubrnersible,s varies. In the examples usedhere differences are based upon nominal op-erating water depths, 2,000 feet for Concordarncl 600 feet for Ugland, and in the overallsize.

2A

Anchors.

( 1) Zapata Concord :

night Vincinay Offdrill 40,000 lb. on-chors with eight 2,500 lengths of 2y4steel stud length chain and eight 4,500-ft. lengths of 21[-in. wire rolry for Skagitdouble drum wildcat windlasses:ratedat 450,000 lb. tension with release up to900,000 lb. tension.

(2) Zapata Ugland :Ten 40,000 lb. Baldt Moortast anchors,ten 3" x 3,500' chain lines; four dualand two single wildcat anchor'windlass

a

units.

Modiftcations of mooring systems of semi-submersibles require longer lines and largeranchor flukes when depth capabilities are in-creased. One example aaaed SO0 feet to eachline and enlarged anchor flukes by g0% for1200 feet water depths.

Symme tr ic Ten- t ine ( lOs)

45o-90"Ten- l ine ( lOo)

l . ; .

f i '

DANFORTH

t 4 5 "

tlgo"

)

c";DesU. S . NAVI ' L IGHT \ \ 'E IGHT (LWT)

, ....:,

,' :i,il,i: . : . t ,

, , : : r , l . , r :' ' , '

, 1 , . ; .

, .i:;:' :'.::.::l'..'-i,'::':. .t::.:t:':,.

":-:.. , : . i . .

. i : : - , . : . . j- : ' i '

i r r - i . . . : "J'..:'.i . : . ; .

: : , ' : , , i .-ri !;i.

';:..:,:-1:

, . r r , : ; _ . -1 ' : ; f - i . :

;;!;i:

. !at:.tr.

: : 3 a - ': ! :n i - r

" i , i . r '' : i . : a .- - : - a e r

, ii;i,:i j . i i '

' : - .+ ;

- :.-l'

- t,;.

: ; i i

M o o e , / N q S v s r E ^, s

Station keepir,g systems for drillships

Turet mooring

Mooring turrets used bvfrhe Offshore Com-?'po"v ilffiir Dffi,6"6ffi#6ss enabte rrr" ship'sffi_i. frry'li"ffiffi;-a*-Bt@Serutftji{$mop.lhg*rggll. From a roller-mounted tu*et inthe shipk well beneath the derrick, eight an-chor lines extend outward to the anchors. Themarine conductor is the vertical axis aroundwhich the entire ship rotates. One bow thrust-er and two steryr thrusters supply a total of2250 hp to change headings. The vessel can berevolved 360 degrees around the mooringpl.rg by the bow and stern thrusters.

Dynamic positioning

E"rly successes in maintaining a positionover the wellbore by use of dynamic position-ing equipment were achieved by Shell's Eu-reka and Global Marine's Cuss I. The Moholeproject led to progress in core drilling wheremud rettrrns to the drillship were not made.Dynarnic positioning has as its principal ob-

iective maintaining the horizontal position ofthe rnoonpool over the marine riser and theBOP stack on the ocean floor.

The Royal Dutch Shell Group and South-eastern Drilling and Exploration Companyengineerr ioined in develo'pit g dynamic sta-tjonilg equipment and techniques using adrillship also equipped with conventional &point mooring and anchorittg capabilities.

SA-Q9-A--4'€'=w.?,s*$S3gl,9g,"-tg;dgi-l'k5gk*.,gf yg.lls-+S]9. ..:Pi**_"_g*,gYgi" "*g_^=dwithout anchor-type mooring. Dynamic sta-

ffffias$d,{6rs;;-ffi.bffi

r i,:, i i

ti ti sn qf a qpssel-bJaJrl g gs .g[. thrus tTiopellersexert thrust in controlled directions and these

2l

MOORTt{G

R O L L E R S

_'._"- ---TRAAISV€RSE S€CNOil

propellers can be activated by controls which

3rce-P3L!-gfj}hgmt4isSensing equipment includes acoustic positioiindicators, taut wire position sensing systeffi,and a riser a_ngle method of controllins the

l-ailmprtet

PendulumPotentiometer

I

2?.

Taut Wire Inclinometer

BASIC AUTOMATIGSTATIONKEEPING

SYSTEM

THBUST, FilMAIN SCREW

TAUT WIBEMARINT R

Position SensingSystems

r - - -ITHRUSTER AND SCREW COMMANTIS:

COMMANDED POSITIONAND HEADITUG

ASK c0MPu_TlE _i

'vACgUSTfC BEAC0N

rHydrophone Array Top VieW

//'?-\Thrusters

II

-Riser

-l

II

SYSTEMCONTROT

TOGIC

THRUSTiil.A[[0cATiofU

RTFERENCEPOSITION

ANDHEADING

WIND SENSOR{.-WINO F0RCE, F

,.#--,'\-.J€

- suBtAcE GUBRENT F0RCE, FcTHRUSTTRS

HYDROPHONES

\

'N)Hydrophones

-T-r

u

Operational performance :

o SEDCO 445 can rotate 360" to align tlreship with the best ship to wave-windrelation.

' Tlrrtrstcrs nurintain a {ixcd hcacling;change of heading is manual

Typlcal ThrusterConfiguration

Cycloidal Thrusters

Main Screws ControlSurge Motions

LENGTH BEAM DRAFT DISPLACEMENTFT FT FT LONG TONS

Thrusters Control Sway,Yaw Motions

Tunnel Thruster

o Variable Pitch

o Fixed or Azimuthing

Six of the twelve 7ffi hp main screwmotors supplv required thrustDyrrarnic stittioning system is capable ofoperating in water depths as shallow as100-500 feet.Ilolds position in 50 knot wincls , LZ feetsignificant waves and 1.5 knot ctrrrent.

M A I NSCREWS LATERAL THRUSTERS

s @

r l: !

l / |/ l

CHARACTERISTICS OF DYNAMICALLY POSIT IONED DRI t tSHtPS

:,t'f'.9.1i:i:i;:,:,

-'.',$: -

ti:.'-: :- .'"!i:"

. ':.r t'!: '

; 'r€:]..'tl . i .

' r'.;-.1

. . i :' : , . '' i", ' ' i '' j , . - : : ' .

-,, ::.'- t ;

:ti:...;.i

! ' : : l a

VESSE L

DISCOVERER 534

SAIPEM DUE

LE PE L ICAN

SEDCO 445

GLOMARCHALLENGE R

534

431

490

445

386

70 24

70 22

22

22.5

18400

12795

1 5500

15100

10500

2 @ 8000 HPEACH

2 @ 3000 HPEACH

2 @ 4254 HPEACH

2 @ 2250 HPEACH

6 - BIRD.JOHNSON RETRACT.ABLE, CONTROLLABLE -PITCH @ 25OO HP EACH

4 - VOITH SCHNEIDERCYCLOIDAL ,2 FWD @ 11OOHP EACH,2 AFT @ 2550 HPEACH (AFT THRUSTERS USEDAS MAIN SCREWS)

5 _ TUNNEL THRUSTERS,CONTROLLABLE PITCH @15OO HP EACH

11 _ BAYLOR RETRACTABLE,FIXED PITCH @ 8OO HP EACH

4 - SCHOTTEL TUNNELTHRUSTERS, F IXED PITCH@ 750 HP EACH

.;!iJ:

65 20

23

,>-tr-

' - J

Typical combination wire-chain mooring system .#

Setting and retrieving anchors

Z$uqbgl lg"digg il"d" hy tand succirrllv eouipued ancltor harrdling boats.)r----*.--Je-< *"A.* 4*d*il;.fr.**E@#qqeFyfFs,-r*F<'r-'€.#

-r'tq r -*-ffi

The directional orientation of the vessel to

prevailing or anticipated sea conditions, thetype of anchors used, the compass direction ofsettitrg for each anchor, and the proper lengthof the anchor lines are basic consideratiolts.

/.Se,nisubmersiblescustomarilyuselonglines.>Anchors are transferred bv deck crane.s

tl"g":tdF"ll,F,th*-e-.,*.I}"qhgl,hqrl*li"_rg,b_g*J=grsyffMntthe rig. rvindlasses or winches pay out the"!ia ii frt ;ii" Ii,r".

-tri" ;;.ffiffieilffi:

r;i;;;;iliffi;-ilim.ient power to'drag up to3,500 feet of 3-inch anchor chaih. t'h" inaivia-trirl anclrors are transported on the cleck of theartchor handlit,g boat. Pendant lines supportthe anchor as it is being trarrsferred, raised orlowered. "glines to prevent chain or wire line frorn

4o -*r"r*--..\-t\-*# -*\+*-*+sr'@k-?t_.#

fiotrliug. --F-

./

24

BUOY

/BUOY/

\ PENDANT

TRIPLATE 30,ooo LBANCHOR

ZYr" '6ANCHOR CHAIN

{ Atthe anchor btroy anchor flukes are set and.

r#+i'*r1oJ*-trv:re%-*"8;'q-{ftJ*sh.{'6t4t+--s&{F^aL;L1*' ,*r*#r4:r*4ies

o,a-a*l,-'

tlls4ehodo-wp-redi,*IgplggS_,After all anclretrs have beeq Lu4i4d set, an-

t -

#ee {r% erl"gd, g +"s.'4"t##*linps_ to a maxrmnm of one-halt breanng+JHryi

strenqtlt( Maximum allowable working loadis one-third breakittg strength.)

L\islelsiqrlils.il*,4j=1-qli"9_tl9.glll,l_9ggsjq9l1 lire to the forces it ir *lgg"ted fo dry.g;ltence on a Continuin$b3gi$,. fili""ffiilil;;fiffi'C-ffiiilih"rir iif=ffi0 lbs. to as much as200,000 tbs. in the North Sea environment. >

The anchor chain itself lies on bottom at theanchor and contributes to the total holdingability of the anchor. $_e.$,_9-tiggg.=1'"Whg",g2 softbottom conditio4s r"qd{#agiti"ili''FF'+'*;.- -^. *.-- ̂ *.--at . .*1i'."{. *-fi=F1T'**:ryforce, a "p_iggyhrsk

. . g{" .gg9.9}g='?l:bg_L5'**t-t?,gl d'*,--

lv{oving off location requires the use ofanchor handling crews and equipment. Ingeneral, sequences of anchor setting are re-versecl. All anchors, chains, and lines are re-ttrnred to the rig and stowed for moving. g.

RIG COMPONENTS AND PROCEDURESPECUTIAR TO FIOATERS

lvlarine risers

Floating rigs used in gathering core samplesncconrplished this withotrt retnrn circtrlation.Drittittg fluids used for cleaning cuttings fromthe borehole 'and cooling the lrit *"t" nottecovered.

The drilling of explorator.y wells requiresthat drilling fluids be^utilized for maintalningwell pressure control in addition to the twolunctions already suggested. Mud pumpedclorvn the drill string, through the bit no riles,and back up to the drilling platform must havea conduit through which it can be returned tornud supplies on the platforrn deck for con-tinued uss;

Marine risers are used to provid.e a return-flow path between the weilfure and the drillvessel and to guide the drill string or casing tothe tsOP stack on the ocean floor.

The .corypoJr_eJrts of aJnariqgriser systemfrom bottom to top inciude:

fiydraulic cohnector4-ower flexible ioint ( ball joint )4lexible piping for cfoke and kill lines4iser pipe and connectors4hoke and kill lines and connections-'Telescooic ( slip ) joint

Diverter systemRiser tensioning equipment

COMPONENTS OF THE DRILLING RISEB SYSTEM

BELL N IPPLE

TENSIONER SYSTEM SLIP JOINT BARRELBALL JOINT

RISER CONN,ECTORGUIDE L INES

BALL JOINT

RISER JOINTCHOKE AND KILL L INES

MARINE CONNECTORBOP

2,5

o Comuensates for vertical movement of

ffi"#iffi r";ilT;"'tiiiiffi 6;-[di"-aa;Iadtlffi&;6;-"t"qitred for" any horizontaldisplacement of the platfonn

o Provides fitfing for choke and kill linefiil;rJ

. -**.=,...-.-.-e.'.-.<..v:2ii-,i..+a,,*-+!-hL -,:?i.*s;,,+{-:,}i,{r+rjet*s&

o tr6ffies for connecting bg-ll,-ttpCg-"g:"9i-vertei'assgmbiy

' ;'r1P-:;t**E€'= *

' Irydvide5Toi"attachmcnt of riser tensioner:rni r

-... . ...i.r._ .i ,-..;.-,.-_--.;..11- :*+.-::,::jrj-:'ri-=,,.;:,.-:";1aL_.rea;.i3.:.i.:!t,.::,-r'j9::,,:

,teji,-jJ;:ig*3(g**!

sljlem:E . - r - " _ . r . J ,

The otrter barrel of the telescopic ioint is at-tacii ed to-fiie"

.*;;;"*iGa? ffiidiffiry

- ifi fi*i},"

tached to the inner barrel which is suspendedlrom the rotary supl]ort beams of the rig. Thestrength of the telescopic ioint in tension issufficient to support the weight of the BOPstack and rnarine riser. Resilient seals or pack-ing elements betweerr the inner and outer bar-rels provide a pressure seal. Oil or water lub-rication reduces wear.

ojhq' _n" i€ .y,lt*b, qgv_gqlgt @un d e Lgt ess st q br **r*-fbe SgP:std*g ndjhegasing:vbighJepgg*g i!_Iays "hessrsr. Thediverter is an integral part of the bell nipple.It rnay be a bag-type unit or a modified rotat-ing BOP. Control is from a hydraulic system.It is valtrable when drilling through shallowgas zones or for divertitrg gas kicks in deephigh-pressure zones.

Iliser tensioners support a maior portion ofttrefrffiit ;f iil" il;ii,i; Til"r$m

rr':: ".-.*.

_*_,* -*a*.tr4*r*tt':r*F.-:i.+E 4:-=.'t-:\...r r\a4r1+31: i..+.{ii'64 .JJ{a?ictr.c#FfnGh*l"gag.'n^C-'*-,xf

drilling mud it contains. These tensioners alsop'*li["'{, s'A$::motiorqE "pJ *bg*_p1**lgg. Without i6e riseitensioning system only a very short riser couldbe supported by the BoP stack. Drilling atgreater water deptlrs has shown the need forflotation equipment to support part of tbeweight of the marine riser.

Maxi.mum load ratings vzgt but range be-tween 45,000 and 80,000 lb., and,allq, r{'linetravel between 30 and 50 feet. Normal'maxi-mum operating loads are limited to f$-flgg sgthe *"*i*.,* rated tensioner loads. Undersome operatirrg conditioni' the system willcycle almost 6,000 timei in one d*y.

ti.on of the maring_Iger. IJgggly fggr_!ipg."t arg

@ ffie are affected5V "*aiffisamd?isturbing forces which aet on the ma-rine riser. tare necessarrt. Makers of tensioning syqlqs

ff' uFTire-Iame engtneering principles for both,the guide,line tensioners having leis dyo"micload cap?city. Both are gllerated from thesame control panel. Aftei the marine risei isin plac€, guide lines can b" pretensioned andattached to the outer barrel of the telescopic

ioint. Television cameras for use in subsea ln-

spections are run on these lines.

Connectors used in making up integratedchoke and kill lines and riser pipe connectionsare designed to reqtrire a minimum number ofoperations. Connectors can be actuated hy-draulically, making diver assistance unneces-sary. TV cameras have been used to assist inalignment, stabbirrg and attaching connectors.Special clamps are used instead of some of theflange-type connectors used on land. If diversare used, fast operating air powered tools areused to reduce diver time on bottorn.

The major components of a pneumatic risertensioning system are:

o Tensioner cylinders and sheave assem-bliesHydropneumaticpressure vesselsControl panel andHigh pressure airStandby air pressure vessels.

a

o

o

accumulators and air

piping manifoldeomPressors

Guide liqer gry-_uwd..tg:l ,qll equipmept-', :..: . T**=t-ta

IOm r-l

NNSNSNt-'TTlF{-j-j-i:ffill:.!1:rr.:.:.t t

T O W P R E S S U R E A I R

H I G H P R E S S U R € A I R

T O W P R E S S U R E O I T

H I G H P R E S S U R E O I I

Diagram showing tensioner operation.

Heave compensation

The vertical motion of the drilling rig overthe borehole is called heave as it relates towave action. The telescoping joint of the ma-rine riser provides the means of returnirrgdrilling fluid to the rig ,while the entire plat-form is rising and falling.

.In the center foreground two tensioners are visible.Compare this phoiograph with schematic of RiserTensioner Systern. Guide lines must also be kept un-der tension.-rhir phofograph of the Zapafa Uglandshows tensioners in place.

The drill string must also be'compgnsatedfor thi.s rnotion to sustain the proper weight

9'. 1ltg_b-Sff;i;.ffieaff6lii e' ( t ) the use -of b'_rmper subs, and (Z)heave compensators placed between the trav-..lnglMggd."thq,Irmk-or.*Ileriltef,rwirrcL bit remains constant as

A t placed in thedrill string capable of transmitting torque ate\,'ery position in its stroke" Its five-foot strokeis ldeqtrate for the two or three-foot averages

28

Heave compensators' have' " typical stroke'of f8 feet. The weight of the ittirrg pullsdown; cCImpensators push up. Wglgblggu[k:

to eight,-foot seas.

trol.

Drill string compensation on the Zapata Ugland is achieved with the pictured equip-ment. Nofe also the traveling block and the guide track which limits its oscillafion.

6aL)f*il>-'-Z

ANNULAR

CONNECT

C O N N E C TL - - l

Present day blowout preventer arrangement.

A N N U L A R

SHEAR-BL IND.F5

F ,F S

PIPE

F 5

L PIPE

PIPE

2":

*3,t*4

BOP STACKS

BOP stack*o^9t

\t;''r.iit'

\ Subsea blowout preventers and their acces-\ory equipment give the driller the capabiilty ,.o..rtO: ,,,J,:0-"jt''*,

'

l,{glose the top of the borehole at the seafloor

Q.Ycontrol release of high pressure forma-tion fluids that enter the wellbore

{e) Pump weighted mud under high pres-sure in the well to restore balanced

Pressure{*f Move pipe while the well is under pres-

sure

$5) Disconnect, cut off, or hang drill pipein the well

*( 6 ) Disconnect or reconnect marine riser

In the section on marine risers the use ofsubsea two stack systems on the Zapata rigswas mentioned. It should be noted that at anygiven time only one riser and BOP stack wasin use. Larger diameter risers and preventerswere used first; then smaller diameter pre-venters with higher working pressure wereused. The two stack system required two sepa-rate riser systerns, BOP stacks, and connectors.

A trend toward the single stack system isevident in rigr currently beit g delivered. Fouro,f Zapata's ttl*est semist,bmersibles have thefollowirrg:

BOP equipment: Cameron L8ri." singlestack system with four 10,000 psi wpCameron type U ram preventers and two

Subsea BOP stacfc.

ber packing element can effectively fill the an-nular space or the total we'llbore if drill pipeis otrt of the hole.

Rarn tvne Dreventers enable ttre driller toorzot;sa1a:i=-n*;14xL;o1;r.{^:. , :\il.*:.i

'---=t1;1?-.':t:.-:r .:::..- €.:.r}. ":+:itl:iEa€-!t:-tEtpg*lF =e!@+

strip driil prpe either into or out of the well-

of miitril;[_p$,b . Dlfferent sized ramblocki are used for drill pipe and casing; rtrnsfrom opposite sides center the plpe or casirrgand the rubber packing is extruded to com-pletely- fiU -the annular space.''

Sb"qtHhrr..gag"be us--ed to cut o€.drill-g-ry".

*'+"'v'';qt<-.:-:j. .'-.'-r l"- :":l

':"::.: ij:t'' ::'

rn an ernergency. Some shear rams also seal the.-.F : :t-\- 4 . . ---. -, --;':..-V- I . r-" - ., 7 {4* l;

wellbore in the same operation.

head.2. $nn'\ Sh+r

3 i? op;

iSof

{..s*,f

lt";.-'" 5

31

Schematic shows landingelernenfs.

Running the BOP stack

Running the subsea BOP stack with itschoke and kill lines, hydraulic hose bundlesancl control pods, and the top and bottom con-rtcctors of the preventer, assembly is clone orlthe marine riser.

Tlre following steps are included:

( 1) A riser runnirrg tool is made up on thedrill pipe, Iowered throttgh tG rotarytable and connected to the riser stabassenlblv.

(2) The pr"rr"nter stack is positioned ontlre spider beams and guide lines strtrngthrough guide fnnnels.

(3 ) The riser stab assembly is rnade up ontop of tfre Preverter ,[nck a'cl the As-sembl-y is pressure tested.

( 4 ) Next the riser nrnning tool is releasecl.and the next joi't of riser is made upon top of the riser stab iusembly.

32

(5 ) The assembly is lifted to clear thespider beams; the spider beams are re-moved, and the nss€rnbly is lowered to

, h*g ofi on the first joi"t of riser.( 6 )

'The remaining joints of ,riser pipe areadded as the assembly is lowerid.

( 7 ) The, telescqping ,joint is added to thetop of the riser, the risei tensioning sys-tem is connected and the BOP stackIanded on the wellhead.

( B ) The connector is latched,( I ) The diverter, bell nipple,

and kill lines are connectedof the riser. r

and chokeat the top

( t0 ) The preventer stack and choke and killlines are pressure checked.

BOP operation. . _ . 1 . . . -

' - ^ * ' ' - {L \ - r .o t to r t

' i

i I$$=ere drillirg,generall;r.. €$,*&'*pr€*f,s;rr€ri\. g.rrerbalance of at least 200 psi. The weight of'T"m"t611itd

il 6r' d i iil iq -ff

ilid+."" " rt, u pt o sureat the bottom of the wellbore greater than theformation pr€sslrre at the bit. ff the rnud col-umn exerts too much pressure, the formationmay be fractured and mud goes into the for-rnation. If the mud co,lurnn exerts too littlepressure, formation fluids will enter the well-bore. In either case a potential blowout condi-tion exists. The BOP stack and its accessoriesare indispensable to offshore drilling opera-tions.

Kill linep enable. the driller: tg-pgpqg.mgd

ilii_ggtut$g$-if .a.b-b-vvofi ".J-ffi,tffi

ffi "wh i le t h e d ril! = gtg rn, i $,, o,,ug,.ojJhs -hp& . R epl ace -**i't

"o'-rrii *;;J i; ;l*;;i ;i-S- circ^ tated

d own t k*t-ijl*p-kgasr. q : il l.i,i: $ ._.+€!' * -, ̂ i;.. s tu.***

ffipd,ffil"ffiffiililiffi"ffiiffia\,-}g-.3I*.f g9g-+d-*l^::$eqf eJllp.*.h*qke^Jine--"-*-

Hydratrlic power actuates the ram blocksand packing elements of preventers. Basicunits for the power prodrction and distribu-tion of tlris hydratrlic system are the compres-sors, accumulators, control manifold, hosebturdle, corltrol pod, and tlre auxiliary accumu-Iators on the BOP stack.Jn accumulator is a

cararor

rultrtttt ccrl lo!

.r.r.!

' - tocttrto

to?cr.

l-

L E V . \ a , \ . - l l l t t '

"colRpressed air with the capacitv to stone;dHddlp-*-4td-isl[fffit:mthq,;.g.g",.ggg_ry"g,.-{k

ffiffiffi

@EE

EE

3[ DISCOVERER I I

Driller's control panel.

C,.p.ntrol pJ=tlrc s,yqtem,lnqg! be fapt, p"e. $i.Llyg,ancl reliable. The location of the auxiliary ac-I,, iii,ilaitoiTldjacent to the preventeruoroi anclpacking elements assures fast action to appliedc o n t roL fu t?'dfr$frffiffi: ii6

"e itn-e i-#l f :I&inf)

--*Gl{gr--*.-qgg*LrO-J-agf,9j*,A"Sgs*i,g &i"a""ts)'stcnr assrrrcs operating control capabilityeven if one system should fail. A rednndantpower delivery unit duplicates co,mpletely thealternate Unit. hya,d. hi r ebr**-h'rrdy tullrrub A

Subsea tsQP control systems are either hv-

{L'i L{i{ sil*]g-ggntusu*$" AiT 1;;;; *tpower pack is incorporated fri tlre system. Thedriller's electric panel is the primary controlstatiorr. An elcctric mini-pancl, ustrally locatcdirr the toolptrsher's office, is the alternate corl-trol .stittion.

Actiors ttrken include the following:

( I ) stop p*nrl^ t'rcl begi' to r*ise thekelly I

(2) Check tlre flow( 3 ) Close the annular preventer( 4 ) Li*e up the chokeha'ifold with the

choke open as the well is shut i'( 5 ) close choke mr'rifold whe' Iower

kelly cock is at ustral break out level

. ; f f i ,nE

.t&f f i f f it r f f i

-E

hffi

. E

( 6 ) Check drill pipe pressure; allow tostabili ze; rectp*""te drill prpe at oneminute intervals

(7 ) Begin mud weight build up proced-ure

( s ) cease reciprocation ancl close piperams if drill pipe pressures "*ceedpermissible limit.

Blowout -drr!!s are held each week. Bops*5rt?ilo$s*j.+s*--*.s*;"g'a+v*r+ *i;**;**;.:.*;*Gi*- ?+-+.--,.-.1.--*..;..

are"h"dKi[F r driil,;ffi

';A .GiA..i['"t;fi;;." dilL' seneydrilts may

be initiated by either th€ driller or the tool-ptrsher, both being aware that a drill is to beheld. No prior warning is grven crews or otherrig personnel. All smoking and welditrg activi-ties cease. Every action ls taken thai wouldI . r l

o t F

t

, tbe required if a ,threatening well conditionexisted. Crewmen have specific drty stationassignments; the contractir's toolpusher andthe operator's drilling superintendent super-vise and observe.

g;__p,ggkets3lly}g.s=c€*L_q-qr---.4&-di.'vs$-eilJs,+t--_d.ffi ff_orJheJsg:*9,.**r j::xA{grsst-#:sffiouts unti! _tI_e__,DQP " stack.*js-.run.' fhe BopS*i["ir-ngru...,lrliL.lh*ap,ffibeen run. The diverter is also "ied art"i ther[*"ii iffi" if ls,ti" casing has not yetbeens e t' The diy-er.tpJ b*I" Igg*Ugg&asd& rdorm*-"r$- 19 l-T.: g gJ. flsifi ,lwedung. ih* rcIlbro,

33

trIJ'-ffi'ro

HEff i

rFil

,stus

ffi

: a '. '-G.-rl.

t l / - f f "

-ad-..:):' ' ,--t:/

H

H

TNtr5,ffitr

Wffi

ROUTINE DRILLING OPERATIONS ANDRETATED SERVICES

Percent

20.88.3

8.34.9

Routine drilling, operations

Several variabLs-water depth, targetdepth o'f the well, and remot"r"rr^of the oper-ation from supply sources-affect time proiec-tions. Severe weather and sea states furthercomplicate projecting time calculations.

A sample distribtrtion of rig time as proiect-ed for a mild weather location follows:

Operation Percerrt

Drilling and tripping 57.0Fishing, logging, or cement 21.0

7.0Runnitrg casingRunnittg BOP stack or riser 15.0

100.0

Distribtrtion of drill rig time for a severe seaand weather location follows:

Operation Percent

Drilling 15.4Tripping 11.8Runnirrg casing and cementing 11.0Circulating 4.9Reamirrg 2.LCoring 1.4Logging 5.5Drill-stem test 2.8PIug and abandon 2.8

5?1

Associatecl operations pcculiar' to offshoredrilling accotrnt for the rernainder of the rigtirne:

Operation

Waiting on weatherNlooring aud anchoringRturning and retreiving

stack and riserOther

Tripping time is reduced substantially with powerpipe handling sysfems.

The jackup rig is a fixed platform and itsinitial operations resemble those on land. TheBOP stack may be placed either below thedrilling deck oi ot, the sea floor. The well riseris a ccnductor pipe without the features of themarine riser.

Initial operations in beginning a well varyon floaters. One method includes ( 1) inspect-ing the ocean floor for debris or slope, (2)making up ̂ "I" running tool on drill prpe andtemporary guide ,base under the rotary, (3)weighting the guide base, ( 4 ) attaching guidelines, ( 5 ) lowering to ocean floor on drill pipr,( 6 ) releasing "I" running tool and retriwingwith drill pipe (7 ) rigging up guide lines totensionitrg systern.42.3

35

Typical subsea wellhead system.

Another method is to iet 30" conductorpipe without using a drilling ternplate. Theconductor pipe is made np and suspended be-Iow tlre rotary. The jetting string is nrn insidethe conductor. The guide base and housing areinstalled on top of tlre conductor. The t,tnt ingtool is rnade up or the ietting string and drillpipe and is installed in the housing. The con-ductor is then ietted down and lowered intoplace on drill pip.. The running tool is releasedand retrieved. The guidelines are rigged up tothe guide line tensioning system on:the ti!.

If a hole is drilled to receive the 30' con-ductor pipe, the drilling template is used,.step_s will include ( l ) making up drill stringto drill a 36-inch hole, (Z) install guid;frarne on gtride_ Iines and around drill rLing,( 3 ) lowerirtg drill string and guide frame,stabbing into template. ( 4 ) drilling hole withretums dumped on ocean floor,.(s) retrievingdrill string and guide frame, ( 6 ) repeatinfprevious steps until open hole reaches s6,,.

usually at least zaa feet of conductor pipeis used. Maximum lengths can be prewela"a

36

to save time. Most op,erators use "squnch"

ioints or some other raprd makeup joint.A guide frame is'used to lower the bottom

section of conductor pipe through the drillingtemplate, then the guide frame is retrieved-.The conductor, housing, and guide base is low-ered with drill pipe and landed in the drillingtemplate, then cemented through 'the drillPIPE.

A good bit program c?n speed the rate ofpenetratiorr attd reduce the time spent in trip-ping by lowering the frequency of bit:changes.Inventory must include sizes for drilling theinitial hole for corrducdor prpe, and sizes need-ed for drilling the different hole sizes for theclsing program. Drilling engrneers select typesof bits best suited for penetrating the rp"clft"formations to be encountered. A typical bitinventory rnight include B0 or more bits rang-ils from one 36-inch bit for drilling the con-ductor hole to 15 bits for making hole for thefinal casing string.

GUIDETINE

gO. WELLHEADHOUSIN

30'cAstNGNA UDLINE

CTNNENT

Landing base and casing landed on bottom.

Latching casing

Ileurning, coring, and loggirlg proceclures onfloating platforrns differ very little from thoseon fixe,l plirtforms.

_ Tripping for changing bits, rturning cirsing,

logging, coring, drill-stem testing *nd fishingall trtilizc spccial equiprnent. Sbrne lloatersIrave eqtripnrent to l*y down pipe stancls forbetter load distribution and "*t"t of gravitylocation.

--Rtyning casing in coastal waters is gener-ally clone by casing crews brought in frJm themainltrnd. Casing and rnnning *q.ripment canlr: brought to the ,location ur ,r"iaea by sup-ply or work boats. For rernote areas casing *"annlrring tools ilre part of the rig inventory andrcgtrlar cl'ews mn casing. Ceinenting opera-tions reqtrire special eqiripment "trJ ri,p"r-vision.

Related serviees and equipment

casing crews, their tools, and the casing it-self are lrg"ght to the mobile platform "r ilr"yare needgd if !h" rig location is within rangeof shore based contractors who specialize irtthis,s'ervice. When drillirg is don"jr a remotelocation, casing and t.mri-rg tools will be partof the vessel's inventory "t a regular driliit gcrews will run the casing.

v

Prirnary cementing is the typical operationrequired for exploratory wellsl This includescernenting of strrface, intermediate, and pro-ductio' strings of castlg. skid-mounted pilp-ilg units, either diesel or electric powet6d, "i,the conventional installations for ofirhore drill-r^ru rigs. Also available are pumps rated to20,000 psi for controlling ana Flhng wellswhere extremely high pre-ssures are encount-ered. It is likely that foi remote locations a ce-me,ting technician would be part of the ves-sel's personnel.

Drilling-fluids technicians representing thesupplier of mud and its additives perforil all

T"d quality testing and mud "tr"lysis. Theydirect tlre derrickman in maintaini"s t6e drili-ing fluids programs.

A mud engineer supervises mud mainte-nance for proper weight and quality control.Mixi'g equipment, water supply, mud tenks,pits, pumps, gooseneck and kelly direct drill-ing fluid to the drill pipe. From the bit fluidsreturn with cuttings, shale, sand, and some-ti'res gas or salt water to the surface. shaleshakers, desanders, and degassers {emovethese impurities. The mud "rglrreer uses addi,tives to produce the weights a;d qualities thatthe formation requir"t, Stroke counters for themtrd pumps enable drillers to know exact rate.sat which drilling fluids are entering the well-bore. Pit level measuring devices- and fluidIevel measuring systerns for the open hole givethe driller the means of knowing instaitl;,when drilling fluicls are being lost"to the for;mation or when formation fluids are enteringthe wellbore.

elevators,r f

F-"":t{^--&r-&\-" . /

37

The pnrpose of an exPloratory well is to de-

termine the potential productivity of all the

formations between the wellhead and target

depth. In order to do this a complete record

of every formation penefrated by the boreholeis kept.

A mud logging laboratory provides meansto make a continuous examination of all drill-ing fluids returns for evidence of gas or oil con-tent in the ctrttings.

Electrical well logging, trsually a contractservice, provides geologists with records ofefectrical characteristics of formations trans-versed by the borehole, identifying them, andrnaking determinations r"gordi"g the natureand amounts of fluids they contain, and their'location in terms of depth.

A radioactivity well log records the radioac-tive characteristics of the strbsurface forma-tions. Generally two logs are run simultane-orrsly. The two are the gamm a ray curve andtlrc ncutron curvc. TIri.s is rrlso a scrvicc con-tract operation.

Cores may be either side-wall samples orcylindrical cores. Side-wall samples are takenwith specierl tools lowered on wire line equipment. Cylinclricarl cores 25 to ffi fcet in lengthare obtained trsing cutter head and core barrelassemblies lowered and rotated on drill pipe.Core samples reqtrire special handliog to ie-tain the information they contain for .labora-tory analysis. Cores yield information on po-rosity, p€rrneab,ility, fluid content and othergeological data.

Driil-stem testing on offshore platforms islirnited to cased holes; no openhole drill-stemtesting is clorie. The use of packers, testirrgtools, and perforations of casing at the ,levelsbeing tested are similar to thosJ.rsed for pro-cltrction well testing.

Although direeti"onal drilling or slant drill-ing, is not commonly associated with explor-atory wells, there are instances in which a tar-get area is directly under a fairwey, sea lane,or other area where no obstruction to navigo-tiorriSpennitted.

: : '- --

38

Diving bell and decdmpression chamber.

Diving capability with effective results towater depths of 300 feet has been demon-strated and capabilities are being extended to600-foot depths. Floating drilling rigs with oP-erating capabilities of 1000-3000-foot waterdepthi "t" being tested and delivered. Bothdiving research and engineering are presentlyworking to extend their operating limits toequal.those of the rigs.

Saturation diving describes a type of divittgirr wlriclr tlrc divcr's lxldy becomes saturatedwith the inert gases which he breathes whileunder pressure exerted by the mass of watersurrounding him. The time required to com-pletely reverse this saturation is decornpres-sion time. It is determined by the length'oftime the diver is exposed and to the pressureor depth whi,ch was iustained.

^ '

Sattrration is counted ,as being the point atwlrich no further quantities of gas are beingabso'rbed by the diver's body, U;der this con-cept a diver can extend his time on bottomvery rnaterially without increasing his deggm-pression time requirement. A rq,Ie ,9f thumbindicates that one d*y of decompiession timeis required for each 100 feet of depth, Ugingthis scale a diver working at toda)"s 50-'foot depths will require a week or: more'ofdecompression time.

Diving equipment is found on the decks ofalmost all floating platforms. ft will consist ofa diving bell with deck decompression cham-bers, the necessary mating and handlirrgeqtripment and saturation habitat to give th;diver safety *ld comfort during the decorn-pression lleriod.

. i

PRODUCTION WEIL TESTINGABANDONMENT PROCEDURE

Production well testing

In exploration drilling the trigh point of in-terest is reached in production well testing.The purpose of tlre "rrtir" prograrn is to det;mine whether or not hydrocarbons exist inquantities which warrant the capital expend-ittrres required to prodtrce and irarket ihem.A second purpose of each well tested is to de-fine reservoir boundaries and cletermine sitesfor future drilling/production platforms.

A procluction well testing iool or tree islarrded in the preventer stack and pipe ramsclosed to support it. A packer is set and thecasing is perforated to permit flow from theformation being tested into the test assembly.well pressure is allowed to stabilize. The for-rnation will produce gas, oil and salt water tovarying proportions. separators, heating units,

Burners consume all fluids produced during production well testing.

and. high and low pressure flow paths enablesgparation of salt water, gas, and oil. Each ofthese fluids is run through met'ering and re-cording devices. From the meterl ail theproduced fluids continue to a burner whichdisposes of them, The burner is located zo-g0fee't downwind frorn the deck area, mountedon a special boom.

where burners are not used, all solids andliquids are retained in storage units for laterdisposal; nothing is released which will con-tarninate the environment.

Production well testing on floaters is doneduring daylight hours, not at night. Twelvehours is the usual testing period. ih" desiredinformation is the produ"tio" rate, not volume.

Bottorn hole pressure is another item of in-formation which is essential. Bottom holebornbs are used in acquiring this data.

WETTHEAD BTOWN OFF 1 25 FT BETOW SEA FTOOR

TOP PLUG 30" cAslNG

20" cAsfNG

l3r/s" CASING

PIUG TAGGED

CASING ERIDGE PIUG(PRESSURE TESTI

PTUG 3CASING

(PRESSURE TESTIBRIDGE PLUG

PIUG 2

PtuG | -PTUG TAGGED

CASING

Typical abandonmenf schematic.

Abandonment procedure and retrieval

When production well testing has beencompleted, the exploration well has no furthervalue. Both the operating company and thedrilling contractor are concerned with movingto the next location and minimal time is spentin retrieval.

The abandoned well casing is closed byplugging or cementing. A casing ctrtter sepa-rates the landing base and wellhead from the

strings of casing in the well. The landing base,wellhead, BOP stack and controls, marineriser and choke and kill lines, guide lines, ten-sioning units and motion compensating equip-ment are retrieved. Shaped charges are oftenused to save ctrtting time. No effort is made tosalvage casing since rig time costs make thisuneconomical. It is possible to place caps orlw'ells but the subsequent use of the boreholeis highly unlikely.

PILOT HOUSECRANE

/ \CRANE D

H E L T P o R T | (

PIPE RACKQUARTERS

L - ]GALLEY PIPE RACK

WATER I ST'G. MUD PUMPS MUD PITS SACK ST'G.

P L U GCEM. SACK

ST'G. IENERAToR RooM ltBtiitF L U M ESTAB'Z'N

TANKPROP'S I WASH'N lware n

D R I L LWATER

FUEtorr

FLUM€TANK

DBrLL lpr-unl t r I ruel I eaLLasr!4\rERl TANK I Otr ; waren,/

356 FT

Discoverer ll-f nboard profile.

C R E Ws-Q UA RTE RS-TRAN SPO RTATI O N

PORT AFT PIPE RACK

STBD AFT PIPE

TWEEN DECK BULK MUD & CEMENT STORAGE-

RACJI cnarue

ct!F

EFoa.

:t&, :o i

MUD PUMPS

CHEMICALSTORAGE

P r r 4 p i r z '

D R I L LWATER

FLUME ST.

SACKSTORAGE

FL UME ST.

FLUME BALLAST

TANK

BALL ASTNO. 7

AIRCOMP.

PUMPS & FRESHWATER GEN.

ENGINE STORES

ENGINE ROOM

-. i---]-_-

p t r r i r , r , lI

FU EL

FST

FLUME F U E LorL

(roF

_ _ :_STOR. HEAVY TooLs i sacr ;

i STORAGE i

INNER BOTTOIY1

D R I L LWATER

D R I L LWATER

I

I

I

? rF O0 7trJ \.r,E Z- i <d F

Qo,=:lo-

I

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ABR

TANKNO. 4

WEATHER DECK

QTJAR TE RS

. f i -A U X . I D R T L L I

Y1S

t',oiD R I L L

WAT€R F U E L O I L

Discoverer ll Stowage plan.

4L

Crew'-working hours - duties

Offshore mobile rig personnel generally

have dtrty hours of s-eyel d*ys orl' seven days

off. Twelve:hours daily for seven days totals

84 hotrrs of duty time. For employees on hour-

Iy wage scales this means 40 hours at the base

rate and 44 hours at an overtime rate.

The actual number of men on a mobile plat-

forrn at a given time will vaty with such fact-

ors as the accessibility of shore-based suplnrt

services and the drilling operation in progress.

Qtrarters and accomrnodations available on a

rig furnish a god indication of the expected

size of crew membership. A limited survey

produced these averagc figures on quarters ac-

cornmodations:

|ackttp: Srnall 52 Large 75

Sernisubmerisible: Small 62 Large 84

Drillship: Small 53 Large 85

self-propelled rigs will have a qualifted capl

tain rn'lio is responsible for handlittg the vessel

rvhile it is in motion. Tl:e captain u'iil have de-

signatecl ship's officer.s and able-llodied sea-

nlen. Thcse tnen are qtrartered and food is

caterecl for them. Thev have no duties except

as ship's crew.Tlre rig tnanoger or cotttpony ntan is in di-

rect charge of all comPany activities on loca-

tion. He is generally shore based. He doe.s

planni,rg, seti up lead time for supplies aud

special services and is responsible for carrying

otrt contingency measures. He may have as as-

sistauts drilling supervisors or all on-board

clrilling engineer.Tlre toolpuslter is the drilling contractor's

top man on board. He supervises all drillingoperations through the driller and coordinatescompany and contractor affairs with the rig

lllrtllager.

lv{any contractors have a rig superintendentwho is above the toolpttslter.

A nutd engineer, alrnost always an em-

ployee of the mtrd supplier, supervises alldrilling fluids quality control including mix-ing, conditioning, and weighting up the mud

for pressure conh'ol.

42

Ofishore supply vessel and iaclcup rig.

Drillers, ttnder direct supervision of the tool-

pusher, perform alt drilling oPerations with

i"sponsibility for the performance of their

crews.

Deririckmen are trsually more experienceclrig r,r'orkers who assist the drillers and the

nrird engineer in their duties. The title "der-

ri.ckman" originated when a man was stationed

in the derrick to unlatch or latch elevators

from the 90-foot stands of drillptp" while trip-

ping otrt of or into the hole.

Fbormcn do the stabbing and. make uP

additional ioints of drilt prpe as the drilling

progresses or breakittg out and making uP

stands of plpe when tripping is in progress.

The motorm&n has charge of operating and

maintaining llower units most of which are

diesel-electric ins tallations.

An electrician operates the generating anddistributing system for electrical Power sys-tems on the rig.

Crane oper&tors move drill pipe, casing, andother materials and equipment on deck or toload and trnload supply and work boats.

Roustabouts are new men at the bottom

rung of the ladder. They assist crane oPeratorsand perform various repair and maintenancetasks.

Offshore crew boat.

F:rcilities for personnel

Quarters on mobile rigs provide comfort-able, air-conditioned living and sleeping ac-conlnronclations for off-duty men. Diningr ooms with good food ftrrnished at no cost tocrew rnenrbers is an attractive feattrre of anoffslrore rig assignment. Recreation rooms, firstaid or lrosp'ital facilities are provided for re-nrote locartions. Eighty-four hours of assigneddtrties during a seven-day tour provides a fullschedtrle, It is worth noting that separatesleeping quarters and mess facilities may berequired when both expatriates and foreignnationals are aboard.

Transportation is ftrrnislred without cost tocrew members. This saving is an additional in-dtrccment when comparedwith self-paid crewtravel costs for some remote land locatiorrs.

A crew boat or a helicopter takes the newcrew to the offshore rig and returns the crew toshore which has finished its seven-d*y tour.crew transportation is generally arranged bycontract. Costs vary with time, distanc€, sizeof the crew boat, and combinations of crewancl strpply movelnellt.

La'ding pads for helicopters are an impor-tant design consideration for every rig, somebeing designed for specific helicopters.

Safety precautions to protect all personnelfrom dock to rig deck are rnandatory.

Transportation of Personnel

A. Boats

1. Boarding Boats at Docka. Engines should be stanted prior to any

personnel boarding. This would helpminimize chances of a disaster in caseof an explosion.

b. No personnel should board a boat thatis not tied securely to the dock.

c. The passenger hsf should be signed assoon as possible after boarditrg boat.

d. All passengers should be informed bythe boat shpper thi location of lifesaving 1t d ftre fighting equipmentprior to boat leaving dock.

'

2. Riding In Boatsa. Passengers should never ride on the

outside of boats. The boat skippgrshould be in control and not allowthisto happen.

b. Passengers should keep to their seatsas much as possible and not be walk-ing up and down the aisle.

c. Passengers should not be allowed tovisit in the pilot's cabin.

3. Boarding Tender From Boata. All_passengers should put on life jacket

,to leave boat and board tender.

Crew transfer baslcet.

43

b, Tender personnel on dyty when boatarrives at tender should be made avail-able to assist passengers in boardiogtenders as well as loading their l.rg-

". $:3:ngers boardi'g tender should al-ways have both hands free in order tograsp, grab and scramble aboard incase it is required of them. No at-tempts to board with objects in handshould be rnade by any passenger.

d. Transfer should. "t*"yt U* *id" atthe peak of the rise of the boat, neverwhen it is dropping down.

e. Passengers should not be rushed intotransferring, but should be allowed todetermine the best possible time to go.

4. Rope Transfersa. Swinging ropes should be L" in di-

ameter with a knot every foot or so inthe section to be grasped by p"rsonnel.

b. Ropes should be htrng in easily avail-able places and placed so that swing-ing personnel will not collide withs trtrctllres.

c. Transfers should be made when boatis at its highest peak.

5. Personnel Basket Transfersa. Baskets should be provided with a

bumper to protect riders against pos-sible collisions.

b. Baskets should be equipped with stab-ilizers to keep net in upright positionon a rising arrd falling boat.

c. Hooks used on personnel basketsshould always be provided with asafety latch.

d. Rig personnel on duty at time of trans-fer of personnel should be sent downto assist in loading personnel and log-gage as well as steady basket.

e. All persons riding basket should haveon a life vest.

f. Persons riding basket should stand onoutside of basket holdit g to net andfacing into basket. Never allow per..sonnel to ride inside baslcet.

g. After a person is transferred to rig orplatform he should remove life vestand put it in basket for personnel setup for next trip up.

h. Personnel should stay inside boat ofideck unless they "i" preparing tomake trip up in basket.

B. Helicopters1. Passengers should be ready to board

helicopters at scheduled departure time.2. Passengers. should never ipproach or

leave the helicopter if the blades are stillturning except on signal from pilot.

3. Passengers should always leave or a1>proach the helicopter toward the frontin order to avoid tail rotor blades. Neverapproach or leave around rear of heli-copter.

4. upon entering cabin passengers shouldput on life vests and sectrre thernselveswith seat belts. seat belts should stay se-cur-e until the pilot gives signal to looserl.

5. {11*pqlp_glggrs shos!{ leceive, instnrc-tion before every flight.

c" Paisengeri shotila "6ilrrr* smoking reg-ulations.

7. Passenger and cargo weights should beaccurately furnished to pilot prior totake off. Never guess weight.

B. Luggage or cargo rnust never be storedor allowed to remain on landing deck atany time.

9. Pilots only shall determine whetherheli-copter flies or not due to inclementweather or any other reason.

Turb ine-porvered helicopter.

44

SAFETY AND SURVIVAT

on shore based drilling rigs certain hazards'exist at all times such as blowouts, fire, fallingobjects, fallirrg, electric shock, conta- t wittmachiner/, injury while performirrg routinedtrties, carel*rrness of fello* .r"**in.

off.shore drilling operations have all of thesedangers. fn addition there are:

o Personnel transfer to and from the rigdeck

o Severe weather, *irr4 waveso Slippery decks, sp raf , moistureo lv{ore walkways and ladderso Additiorral equlpment: risers, motion

cornpensators, cranes, and, handlingequipment

o peci motion: sectrring all items againstrnotion, observing load distribution as re-Iated to deck stnrctural strength and loadbalance

. Falt into the ocean.

operating companies and drilling contrac-lors are familiar with the perils their perso''elare likely to encounter. posted insiructions,warning lights, bells, communications equip-metrt and training Programs are provided to allpersonnel. , sorne ourJtvers have noted thatIaxity' on almost every one's part is the weakPoint in the system. T1e lasf itern of t6e fol-lowing may be the solution.

Essentials of good safety program

1. Preparation and observance of compre-hensive and clearly written operating in-structions on things to do otrJ thingJnotto do.

2. Formal personnel trainir,g programs forevery man involved.

3. First aid training and drill.

' . . ' . '.. ,,,

' . .'.i',1'"

- t ' " - ' -

I , -r 4; Preventive inspection and maintenancePrograms.

'5. Disaster plans with station and job as-

tions:6. freQuent practice of disaster proce-

dures. : 1

7. Hazards of uninformed repair or modi-

" 8. Free'discussion of-operating proc"dures

9. 'Prompt reporting and discussion of newor indicated,op€rating problems.

10. Disciplinary action lot witlful or re-' . i . ' " ' : ' 1 . '

peated disregard for' approved operatinginstructions.

Platform abandonment

Escape and survival systems include combi-nations of slide systems similar to those usedfor ttg: aircraft, suryival capsules, seu-righ,t-iog lifeboats, in{atable lif; rafts, and lir"jackets. The efiectiveness of all of these itemsr-equires familiarity of all deck occupants with

+r proeedures necess'uy to ptoperlv usethem. Drills and instruction can accomplishthis.

Facilities for survival sho3rld be adequate toprotect the maximum ,rrr*Ler of p"rr#s whoare expected on the drilling platform at,onetime. This will include personngf ,gg temno-rary

-assignment in addition to' crews q.i"r-tered on the platform. ,:, :

The , Brucker ..s.urvivel capsule accomrflo- ,9"t* 213 prrs"ngers. Pota,bd,water and foodfor' 'ftr'e dals--is itored on 'board. A two-w ayradio is installed. The capsule is self-propelleiand ineorporates air puriftcation "ni vintila-tion. In addition to desigtt features makirg the:aps_.lle very stable, the flotation is guaranteedby the use of individually sealed rinits in thebuoyancy chambers even if flooding shouldoccur.

45

OFFSHORE DRILTING/PRODUCTION PLATFORMS

fntroduction

Explorrrtion drilling is the final step in de-ter"nrinirrg rvhether a petroleuln reservoir holdsenough oil or gas reserves to justify field devel-opment. A sedes of dry holes will likely resultin cessation of all activity and termination o'flerrses. N{argirral quantities of reserves will cle-l*I development. If the reservoir potential jus-tifies development, & program of ietrelopmentwill be forrnulated. This program will includethe clesignirg and consrructing of all drilling/production platforffis, storage facilities, load-ing sy_stems, pipelines, compressors, and ever)'installation used between the reservoir andthe initial purchasers of crude oil or naturalgus. A tin-re log of two to five years may existlle'tween tlre colnpletion of **pinratio, dritl i 'gancl delivery of the first barrelof crude oil.

v

It is con'rrnor] practice for sevcral cornpirniesto slrare both exploration a*d clevelolmentc'ost.s- capital requirements generalty exceeclthc arlrotrnt of money that o rirrgle conrpa'y iswif ling to invest.

Platform history

The first specifically designed steel struc-ture wAs i'stalled in tlre Gtrlf of Mexico inL947 in a water depth of za feet. In almosttlrree decades since this beginning the ind*s-tty hrrs installed over 3000 fixed platforrns i'water depths ranging to 400 feet. p,latformsfor use in the North sea \ rill be installed in460-foot depths. A Santa Bartara Channelplatform will stand in a water depth o{ BsOfeet.

Approximately 2000 of the 3000 drilli nglproc{uction platforms of the world are locatedin the Gulf of Mexico. The irnproved tech-'iques of fabrication and erection gained intlrc Gtrlf structtlres ltarre infltrcnced p,latfonrr

constmction worldwide. Several Arnericanfirms operate in the Singapore area designitrg,constructin$, and erecting platforms.', The in-dustry saf,gy record for' fixed platforms hasbeen excellent. A few incid*rL 'have beenmtrch pu;blicized bec,ause of their s.pectacularnature, but the overall record is excellent. Themasritude of offshore operations in the Gulf

l*r gener"Ily been unrecognizd, by the pub-Iic because of their good record.

Water depth

sha'llow de'pths permit the use of smallerand less expensive structures. E'arly dritlingwas done from posted pladorms in *"t"idepths of 20-30 feet. small fixed platformswith minimum equiprnent were built,as a partof the p.latform-tencler rig combination, usual-Iy in water depths of 60 feet or less. The ten-der was an Lsr of ww rI surplus or similartype and egtripped for supply and auxiliaryservices. After a well was completed ( some-times four wells fro'm a single platform), thetender was moved to the nJxt iocatiorr.

'

At water depths of 50-300 feet two factorsfavored the use of more complex structures.First, Iess sheltered locations procluced moor-ing and anchoring protrlems roo"iated withdamage to the platfo,rm caused by motions ofthe tender. And, second, the costs of separa-tors, storaqe pipelines, and loading bq*,p*.nt .required that a large number of ;eilr beclrilled from a centt*l lo*otion.

The need for constructi* of pladorms inwater d*ptltr greater th,an s00 leet will beclosely related to production technol oWgaip. current drilling capability can be "*-tented toward 3000-foot oi*t"t depths but itr"constnrctiop o{ deep water ptqd;ction plat-forms -will be contiigent upon capabitity ofs,ullsea lxoduct ion sys tems.

47

Monopod plafform installed in Cook Intet.

Environmental factors

Fixed pla'tforrns must be designed to with-stand environrnental forces. In the Gulf ofMexico the forces of winds, waves, and cur-rents control design considerations. The his-tory of hurricanes over a one-hundred yearperiod is one basis for design. Ice in the CookInlet dictates both design and structuralnraterials trsecl. Earthqtrakes in the Pacific af-fect constnrction characteristic:s of fixed plat-forms frorn California to Alaska.

Soil and bottom conditions affect founda-tion strrrctrlres. Generally soft bottoms arecommon in the Gulf of Mexico and these re-quire deep pile penetration and cluster pilesaround each footing of the platform. Boulderson the floor of the North Sea have led to thedevelopment of gravity-type structures lessdependent upon driven piles. other areas ofthe world have other problems, and each areamust be surveyed before the platform is de-signed.

. one estimate of elapsed time between thedecision to build and the conrrpletion of a plat-form follows:

DesignC'onstructionErection

8 monthsl year

3-4months.

The effects on structural materials of con-tinuous stresses produced by waves, winds,and currents is of concern to both operatingconlpanies and governments. More completestudies are proposed.

48

Earfy posted platfor ,

Basic steel structures

The jacket pladorrn is basically an evolu-tion of the many posted platfonns of earlyoffshore drilling. Steel construction providesthe required strength. Steel permits designswith good wave transparency. Template con-struction enables the drilling of multiple wellswith rigs which can be skidded on deck.sleeves welded to legs of the platform providefor attachment of skirt piles to form the foun-dation. Steel platforms in the Gu'lf are four-or eight-pile structures. one North Sea plat-forrn is a 32-pile stnrcture.

Tender-fyp" platform.

10,000

5000

YEAff

A proiection of industry caPability.

25OO METERS

MOBILE DRILLINGAND UNDERWATER

COMPLETION ,,SYSTEMS

ta t - t '

2OO METERS

\UNDERWATER PRODUCTIONAND MANIFOLD SYSTEMS

.< FIXED PLATFORMS

*-l_ | "-r I _l_- r___l_ t. I I

1950 '60 '�70 '80 '90 2000

Current depth capabilities

Using platfonns under-construction or in thedesign stage as a guide to depth capabilitiesthese available figures indicate:

o Approxirnately 75% in water,depths 20-300 ft.

o Thirteen percent in water depths 300-400

o Eight p€rcent in water depths 400-500 ft.o Less than 296 in water depths 500-600 ft.. Other: 850.ft. in Santa B'arbara Channel

1020 ft. and 1050 ft. for completion 1978'-1980

Corrosion protection

Cathodic protection for steel structures is oftwo types: one uses a very small imlxessedelectrical current flow; the other uses sacri-ficial anodes. Both methods are based uponthe principle that a controlled direction ofelectric current through a metal structure willprevent the metal from eorrodittg.

In splash zones protective coatings are usedwhich prevent corrosive elernents from con-tacting metal struchrres.

Ja ,

a'*'a ' t

0,

ft.E soo-FgulclGr!l=

=100

Production Drilling from Fixed Platforms

Movable drilling rigs are mounted on a grid

somewltat resembling a checker board. Slots

are spaced laterally io allow for the installa-

tion of ttt* christmas trees when the wells are

, .completed" Multrple drilling s!9ts *tg used by

s.krdding the rig frOrn 'one:,drilling slot to the

next, OI platforms culrently under constfuc-'

tiou most- are l2-slot; the seCond most com-:' . mon is the Z4rstbt platfolm.

' .' ',,' '' ' ,r ,"'Many"plaiforms have deruicks whidh can be

used for two or more wells by skidding thecrown block, the'rotary, and. dt"wq{k* Forsevere weather locations drilling slots have ac-cess to the seafloor ,through the piles whichsupport the platform.

floor trs in decp well drilling ashore.

52

Rig slcidding tubttructure rack.

C R E WOUARTER S

D R I T T I N G R I G

- - P IPE T INERISER

r PRODUCTION

Workover

Offshore production has the same problemsthat are encountered ashore. Paraffir, sand,repair or replacement of qubsurface equip-ment require the same corrective measuresthat are used on land.

Skid-mounted well workover masts andtools are part of the permanent equipment ofmany multiwell platforrns.

Special well workover equipment whichcan be handled with deck cranes is used onsmaller platforms,

Emergency escape drills

Per:isdig drills are necessary for personnelsafety. Every occupant of the platforrn needsto be farniliar with escape routes and alternateroutes. Specific duties should bc assigned forhasty abandonment of the platform if systemsare to be stopped from op€tating.

Thc platform may be equipped with a chuteor slide from deck to water surface. A suffi-cient number of Jifeboats or escape capsuleswill be availabl;. The proper ftethoar ofboarding and launching *.rit be known byeveryone. Some survival capsules are poweredand provided with air supplies. rt is necessarythat specific instruction and drills be given toeffectively use the equipment.

-_- t

U P T O300 '

II

I o ,ooo ToI5 ,OOO FEET

II

i

tvznra7p77

DIRECTIONALwErr s

Directional drilling techniques.

Directional or slant drilling

In order for maximurn efficiency in d.raininga reservoir from a platforrn, directional drillingis trsed to penetrate thc most productive for-nrations and, to achieve the widest pattern ofspacing in the reservoir. Sometirnes direc-tional or slant drilling is used to penetrate for-rnations under sea ways and Areas where plat-fornrs cannot be erected.

THUMS man-made island off Long Beach.

*,f '. 'o; i. t '

5.000 To7 ,OOO FEET

53

Concrete ( gravity) structures

Concrete gavlty stnrctirres have been

built for use in the North,$"". Their enormous

bulk afiords protection from storrns and sea

states common to that area. The size of struc-ture supported by the ocean floor is adaptableto bottom conditions. Spaces between 'the

structure :and the sea floor can b€ filled witha grout which provides a very good degree ofresistance to erosion by currents. Rock is builtup around the perimeter of the base to pro-vide protection. The huge vertical concretelegs contain cells with storage calncity offrom 800,000 to one million barrels of cmde.The gross weight of tlre structure is over 300,-000 tons, approximately ten times the weightof a steel structure.

The concrete legs are built first, then thedecks are cornpleted rvith the drilling and pro-duction modules. The entire structure is towedto its site and put on bottom. During towingthe structure is 40% submerged, A verticaldimension of 680 ft. fro'rn base to top of thedrilling mast gives an idea of its size.

Cost figtrres range from $140 million to $200million. Its water depth capabilities basedupon present use is in water depths of 38H74feet.

Towing energy to rnaneuvergravity structure exceeds 75,-000 hp in this view.

Construction nearing complefion, second platformfo rear. Note storage tanlrs af base.

ll\ .\! -l\

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Proposed platfonns

Two experimental platforms are beingtested; they are ( 1) a slim to#er-typ" sup-ported by guy wires, and (2) a tension-legplatfonn. At this time all evaluations have notbee.r completed.

Above is a diagram of a tension teg plafform.

on the left is a diagram of a cornpleted 1500-footguyed tower.

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1955

1966

1967

1958

1969

1970

1971

1972

1973

1974

1975

WELLS IN WATER DEEPERTHAN 5OO FT.

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oFFSHORE PRODUCTTON SYSTEMF

fntroduction

satellite wells are generally single wellswlrich are the sorlrce of crude oil or nahlral gasfor a gathering systern. Their location will berelated to the horizontal shape of the reservoir,btrt trsuall v a central gathering point for sepa-rating, storing, or transfer of the product isjoined by flowlines to the individual wells.

In tlre Gulf of Mexico hundreds of wellshave been drilled in shallow water areas, manywith mobile rigs. Upon completion christrnastrees sirnilar to those used on land wereinstalled. These single well christmas treeswere installcd on several types of structures.

Tlt" fiTpt.st form was a well guard extending10-15 feet above mean water level. It was on aplatform which supplied minimum work spacefor

-operating valves, changing chokes, andsimilar tasks. Another forrn h;d more clear-ance above water and was fitted with a heli-cop!9r pad. A third type of platform was thesmall fixed platforrn similat to those used inplatform tender opemtions.

Satellite platform.

Well plafforrn with helipad.

As offshore operations moved to deeperwater, production was confined almost totallyto the larger and very exllensive platfomrs.wells drilled for purposes of exploration wereabandoned. The capability of drilting in waterdepths well beyond present limits of platformconstruction or gathering systems became ap-parent. Tlris situation spurred researctr ancldevelopment of subsea production systems.

Status of subsea completions

E*p*rirnents which were.begun in the early1960s were hindered by failures of untestedmaterials and equiprnent. Hurricanes darn-aged and slowed some of the experiments.

. Apqroxirnately 100 subsea completionshave been made in fifteen years of researchand developrnent. Successes in experimentalwork indicate that the indus try is lapable of

57

developing a completel)' feasible productio'

technology for subsea oil and gas _recovery.Produ.iiott frorn subsea completions will

pass from wells throtrgh flowlines' manifold-

ing systems, separators, storage, and pipeliues

or-loading facilities. Equipment for seafloot:

rnanifolding and bottom-suPPorted seParators

is being develoPed. Experiments include in-

stallations moored and anchored; some float

on the surface, others are str,bmerged. MoOred

loading systerns with limited storage ltave

lreen used. A few systerns have operated with

taukers alternately serving as storage or

transportatiorl.

than those currently accessible, to divei as-

sistance.j : '

A Wet christmas tree is run to- replace the

BOP stack. The use of comPatible wellhead

guide line strugt_ures and hydraulic control of

connectors enable this operation to be accom-

plished without diver assistance. Basic units

include: (1) wellhead, (2) tree, (3) valves,

(4) flowline connector, (5) controls, and (6)

a TFL ( tluough flowline ) loop. Other installa-

tions pre T"{"-

witb diver assistance. Valves

are controlled frorn the rig or control station.

Fail-safe valves proVide automatic closure if

hydraulic control is 'lost. One of two rnaster'

valves affords manual control by a'diver in

emergencies.

Flowline connectors are positioned for ease

of ioining flowlines to the christmas tree and

sometimes diver assistance is not needed.

Special tools are used when seafloor lines are

pulled to ioin tree and manifold or seParator.Divcr assistallce is required in cases of .mis-

alignment.

TFL loops are wellhead attachments ofclrrved pipe connecting flowlines to the welltubing. These loops permit pump down toolsto enter the well for well servicit g tasks. Paraf'ftn removal at rbgular intervals and perforat-ing have beeq successfully done.

Dry christmas trees have been develoPedby several groups. At this time only one

dty christmas tree has been tested veryexterrsively. :

Production risers

A well producing from three zones throught l r r e e s t r i n g s o f t u b i n g w i l l r e q u i r e a r i s e rtubing bt nlle from til flowlinei to the pro-duction platform for separation and commit g-tring before delivery to pipeline'or tanker. Crrr-rently almost all production risers are from

seafloor to production platform and require

diver assistance for makittg connections. , ,

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POSITIONINGP T A T E

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Wef Christmas free.

Subsea christmas trees

Two types of wellhead installations for sea-floor prodtrction are wet, and dty christmastrees. A wet tree is exposed to the salt waterand the currents'thai *" the natural environ-ment on bottom. A dry tree is oue that can beserviced in a one-atmosphere environrnentwithout the assistance of professional diversfor perforrnarlce of rotttine rvorkover iobs.The special reason for interest in the dty treesterns frorn the expectation that proclttctioncapability will move to water depths greater

58

COLLECTCONN€CTOR

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Shallow-wafer well iackets and produclion plafforms.

Shallow-water production complex.

Concrete production plafform.

A Shell platform in the Gulf of Mexicowildcat acreage.

produces from

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Deep-water production complex.

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STORAGE AND TRANSPORTATION TO SHORE

Offshore storage facilities

In areas of shallow water depths limitedstorage capacities on production platforms ex-ist. For North Sea operations steel platformsare_ being designed with underwater storagetanks of steel. several concrete ( gravity ) typ".clrilling and production platforms in the North'sea are being built with up to r,000,000 bblof crude oil storage space located in cellsilround the corlcrete legs.

Floating storage frequently is available inthe forrn of tankers whicS alter'ately load andtr:ansport crude oil to shore facilities.

strbsea storage systems composed of multi-ples of hernispheric concr€te tanks have beentused in one Asian locale.

Oil storage sphere.

Crude and gas transport facilities

Subsea pipelines provide the best transportmethod that can be devised for both crude oiland natural gas. Limitirg factors are the costof construction and the capability of pipe lay-ing in water depths of more than 400 feet.only a few pipelines have been built in waterdepths between 500 and 000 feet. The con-struction of produetion risers is an additionalproblem.

shuttle tankers are used for the transport ofcrude oil. Two_ge_neral methods for usin! shut-tle taskers include; (I) a tanker fo*Tor"g"and loading of other tankers which shuttle b!-tween offshore and land, and (z) shuttle tank-ters alternating.---one loading one transport-itrg to shore.

Gas-satt:n1 plafform.

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Oil storage tanker.

Open sea mooring

Open sea mooring systems provide'Ioadingfacilities for strbsea production without stor-age capabilities. SBM, single buoy mooring,aud SALM, single ancllor l"g mooring, are thebirsic s1'stems. Refinements of the single buoymooring system for the North Sea arer ( 1)SPAR, a vertically floating storage cylindervvith 300,000 bbl oil storage flowing from arrranifold on the seabed, and (2) ELSBM, anexposed location single btroy mooring system.

Loading crude oil from ELSBM. One of fwo tanlcersshuttling between exposed location single buoy moor-ing and a refinery. '

Exposed location single buoy mooring in Shell/EssoAul field. Height-243 feet.

Single mooring tower headpiece for servicingfa n ke rs.

WELDING

LAY BAR,GE

offshore Pipeline construction Methods

water depth capability for subsea pipelinecorlstruction has advanced to the 500-feetrange in the North Sea. Pipe diameters havebeen increased .from gatharing line sizes of6-10 inch diameters to 32 inches. A few off-shore loading facilities are 48-inch diameterpipe for *ouing oil from shore to ship.

Rough seas limit pipelaying operations.Larger_ vessels r,vith construction design useclirr stallle semistrbmersibles meet this pioblem.

Thc lirybarge method includes atl of thebasic operations of a pipeline constructionspread on shore. Route selection, right of way,tuud surveying problems are solved firit.Trenching is accornplished by dredging sleds:rnd pipe trenclJing barges, some .,ring waterietting ?r placed explosives. Filling mat be re-quired for uneven or boulder-strewn seafloors.welding, coating of field joints, Iowering toseafloor, covering, and checking are maior op-erations. Special equiprnent and techniqulsfor each of these offshore tasks have &"rtdeveloped.

coatilgs which protect the pipeline andgive it the required negative buoyancy mustbe i'tact afteibeing loivered into'the Ler"lr.o'e method is the pulling of long sections ofpipe i'to_ position. nlaboLt" ryri"*, of pon-toons and stingers have been used to minimizethe bendi'g forces which destroy concreteand mastic coatings while the pipe is beinglowered.

offslrore pipeline risers should have an arcof curvature which will penrnit travel of pipe-Ii'e pigs for cleanitrg oi inspection.

66

X-RAY INSPECTION

JOINT COATING

PIPETINE

Combination derrick and pipelaying barge.

Reel-type pipelaying barge.

' Gas pipeline-Federal Power Commis-sion

o Conservation proration allowables-(1)agency of adjacent state, ( 2 ) supenrisorof USGS

o Obstructions to navigation-Us Corps oftrngineers and US Coast Guard; Fair-ways-Us Corps of Engineers

o Platform design-Us Corp,s of Engineerswith USGS

' Vessels-US Coast Guard using theAmerican Bureau of Shippi.tg recommen-dations

o Safety-the US Coast Guard speciftessalery devices, inspects for compliance,enforces

o Radio communications-Fcc( I ) Assigns frequencies(2) Approves equipment

' Air transportation-FFAo Pollution-,both state and federal agen-

cies' saf_ety and Health-occupational safety

and Health Agency-OSHAo Workmen's cornpensation-injtrries

( 1) ReErlations of adjacent state(2) Outer continental shelf U.S. Long-shoremen's and Harbor Worker's Com-pensation Act

Contingency Planning

For every offshore drilling operation thepossibility exists that some totally unforeseenoccurrence will begin a sequence of eventswhich are catastrophic. A blowout, a fire, aplatform collaps", ot a ship/platform co'llisionare a few examples.

In any incident which violatesregulations indicated previously,ate notiftcation of the regtrlatingbe made.

contingency plans for a mobile rig wouldlikely exceed this publication in size. Detailedinstructions on corrective measures to apply,pro?e_r notiftcation of the operating companyand all of the agencies having jurisdlction overthe operation that has been affected. by theincident are included.

some of thean immedi-

agency must

6B

G T O S S A R Y

A :

accumulafor n: A vessel contain ing both hydraul ic f lu id and a com-

pressed gas wiih the capacity to store energy to operate opening

and c losing of b lo*out preventer rams and annular preventer e le-

ments. Accumulators supply energy for connectors and valves re-

motely contro l led. Tensloner sysiems also ut i l ize accumulators.

acoustic wave n: An emission from a sound source used in subsea

seismic surveys.

ai r mass n: A volume of the earth 's atmosphere which has acquired

distinctive heat and moisfure characterisf ics from its exposure to

heat ing or cool ing and to moisture gain or loss in a g iven area.

anchor buoy n: A f loat ing marker urud in posi t ioning each anchor of

a spread moor ing paf tern for a semisubmersib le or dr i t l ship.

anode n : A moss o f meta l o r an a l loy wh ich is a par t o f a co thod ic

proiection syste' l i to prevent comosion. A sacrif icial anode is con-

sumed in the process of producing electric current.

anomaly n: A deviation from the normal pattern. As applied to geo-

logic formai./ons it suggests distorf ion or unconformity of sedi-

mentary beds such as faul ts, fo lds, or domes.

B

blowouf n: An uncontrol led f low of wel l f lu ids f rom the wel lboro ei ther

at the wellhead or into the forrnation. Blowouf preventers enable

the dr i l ler to pr 'event damage af the surface whi le restor ing the

bolonce between the pressure oxertod by the column of dr i l l ing f lu id

and format ion pressure.

bumper sub n: A uni t pfaced in the dr i l l s t r ing of a f loal ing r" ig fo

compensate for heave or verf ical mof ion. l t enables the dr i l ler to

keep a constant b i t weight .

bund le n : A group o f severa l para l le l cab les , hoses , l ines , o r fub ingleading f rom plat form contro ls to remote actuat ing uni ts.

burner n: A device mounted on a boom from a mobi le p lat form to

ccnsurne by f i re the f lu ids which f low f rom a wel l dur ing product ion

wel l iest .

ccased hole n: 'A wellbore containing tubr.r lar steel to separafe the

format ion and the space occupied by dr i l l ing f l u id, dr i l l s tem, or

reproduction tubing after cornpletion. The wellbore is cased in suc-

cessive operat ions wi th smal ler p ipo diameters as the wef l is deep-ened.

casing str ings n: Three str ings of coslng of d i f ferent d iameters are ot-tached to the wel lhead wi th casing hangers. .The uppermost casingstring has the largest diameter, the lowesf or production str ing thesmal fes t d iameter .

cafhodic proteci ion n: The appl icat ion of an electr ic current in sucha way that the structure is made to act as the cathode or negativeterminal instead of the anode of +he resuhing eletrofyt ic cel l . Ei theran anode or dn impressed electr ic current may be used

cel lar n: The space beneath the chr is imas t ree of a producing wel land the base structure to which a personnel capsule can .be at-tached ior. *orkover of a subsea well equipped with a dry christmastreo.

cement ing n: The appl icat ion of a cement s lurry to anchor and pro-tect the conductor p ip" and the casing str ings. Squeeze cement ing

is used to isolate a producing zone. Cement p lugs for the casing

are used when abandon ing a we l l .

choke n: A var iable d ia*eter or i f ice through which high pressure wel lf lu ids can be refeased at a contro l led rate. Hydraul ic chokes givethe dri l ler control of high borehofe pressures when a blowouf

threafens- Manual chokes are c lassi f ied as ei ther posi t ive or adiusf-able. Posif ive chokes are nipples with f ixed orif ices and ore remov-

able for change of s ize. Adjusfoble chokes have a conical noedle

and seat to permit chonge of orif ice size. Production chokes are part

of the chr istmas t ree assembly.

conducfor pipe n: A la rge diameter pipe extending f rom the wef l-head through the mudl ine and shal low format ions to provide sol idsupport for the casing and wel lhead assembl ies.

connectors n: Hydraul ical ly contro l led c lamps to mate and securemarine r iser segments, and choke and k i l l l ines. One connector io insthe lower bal l io int of the mar ine r iser to the BOP stack and anothersecures the BOP stack to fho wel lhead. Ths uso of connectors re-

duces the need for d iver assistance.

core n: A cyl indr ical sample taken f rom fhe format ion for purposes ofanalysis. A sidewall sample is faken frorn the wall of the boreholewith a speciat wirel ine tool.

core barrel n: A device used in rofary dri l l ing to cuf cores. A sample25 to 60 feet in length is cuf from the formation being penetrated,reta ined inside fhe uni t . and brought to the surface.

correlation n: Combining data from several sources to support a pro-cedure or confirm a proposit ion

corrosion n: The disintegrofing of a metal structure through environ-mental exposure to chemical or elecfrolyf ic action. Rust is o primeexample. Pitt ing and scaling are evidences of corrosion.

current { impressed} n: Electrical energy transmitted to a metal sfruc-ture or pipeline to afford cathodic protection.

D

development well n: A well dri l led to produce hydrocarbons for trans-portation and sale, not fo be'confused with an exploratory wellwhich. is a lmost never used for product ion.

diverter n: An integral part of the bell nipple at the top of the marineriser; controls f low of gas or other f luids which may enter the wefl-bore under pressure before fhe BOP stack has been run. l l may bea bag-type unit or a modif ied rotafing BOP. Control is from a hy-draulic system. lt is useful when dri l l ing fhrough shallow gas zonesor for divert ing gds kicks in deep high-pressure zones. Alfernafeflow l ines provide means to f lare gas downwind at al l t imes.

69

dome n: An efevafed'surface above a salt plug. ln Gulf coastal oreassalt domes hbve defined boundaries of oi l producing formafions.

dri l l Pipe n: In rotary dri l l ing the heovy searnless tubing used to ro-fafe the bi t and c i rcula ie the dr i l l ing f lu id. Lengths are general ly30 feef. Three ioints, fotal l ing approxirnately 90 feet are called asta nd.

' F

fcirway n: A designated route along a coast or the approach to aport in which no obstrucfion to navigation is parmitted.

faul t n: An inter face between sedimentaf layers which have been dis-pfaced by fracturing. Along faults are found traps which may con-ia in petro leum.

fetch n: An expanse of open water where a wind from a consfant di-rection over a period of t ime produces waves. Wind velocity. dura-t ion of t ime, ond distonce determine the rnagni tude of fhe wavos.

f ishing n: Recovering from a weflbore any fragment of casing, dri l ls t r ing, b i t , wire l ine fool or p laf form equipment losf in the hole. Inworkovers f ishing may be for pockers, l iners, screens, efc.

f loes n: sheet ice which forms in bays of Art ic areas.

f lules n: Proiections of an anchor assembly which dig into the seafloorand prevent the onchor f rom being dis lodgod.

footings n: Structurol supports for legs of plafforms or jackup rigs toprevent excessive boltorn ponetration and provide stabil i ty.

forrnalion prossure n: Pressure exertod by formotion f luids, recordedin the hole at the level of the formation, wifh the well shut in.

front n: The inlerface or surface disconlinuity between unlike airmasses. Fronts l ie in low pressure oreas or troughs and are thespawning ground of frontaf storms. Storm tracks are along fronts.

g

gravify meter n: A sensit ive weighing instrumenf that measures thevar iat ion in the gravi tat ional f ie ld by detect ing smal l d i f iorencesin the weight of a consfant mass at different points (as on the earthor seal. l f can be used to help classify the type of rock structure inan expforafory survey.

heave comPensation n: Counteraction of vert ical movemont of thedrilf ifring. Heave compensotors have a fypical stroke of I g feet.The weight of fhe str ing pulfs down: compensators push up. Thiscornpensation keeps a constant weighf on the bit and aids in di-recfional control.

J

J- tool n: A uni t at tached to the dr i l l s t r ing used for running and po-s i t ioning downhole equiprnent . The two s lots and two direcf ions ofro laf ions combined wi th weight changes on the tool g ive contro l .

iett ing n: Use of a stream of water under high pressure fo open a holefor p lacing conductor p ipe at . the ocean f loor. Afso a method ofoponing a french for pipolaying beneath the seofloor.

70

K '

telly cocl n: A valve instafled belweon the swivel and the lcelly. r\Mhena high Pressure baclcflow begins, the operator can close this vatveand keep the pressure off the swivef ond rotary hose.

ki l l l ine n: A high-pressure l ine connecfing the mud pump and thewellhead through which heavy dri l l ing f luid can be pumped infothe well to control a threafened blowouf. On a f loafer ki l l l ines meybe inlegrated wifh the rnarine riser. Flexible l ines wil l be used atthe s l ip io in i .

M

magneiometer n: An instrument for measuring the inlensity and di-rection of magnetic forces. Data obtained is sornetimes used withgrovi ty and seismic data.

manifold n: An accessory to a piping system or other conductorswhich sorves fo divide a flow to any one of severaf possible destina-f ions. Separation and disposit ion of subsea producfion is one useof o manifofding system.

marler buoys n: Buoys indicating exacf points for ptocing rigs andother offshore structures. Conventional surveying methods or safel-f i fe observations may be used for pfacing the buoys.

mafs n: Load bearing surfaces placed in soft bottom seafloor areas.

modules n: Units of complete systerns fabricated on shore with di-mensions and weights adoptable to the crones ond derr ick bargesto be used. Construcfion is speeded since only posit ioning, as-sombl ing, and connecf ing are done on s i te.

moonpool n: The opening belo* the derrick on a dri l lship throughwhich the marine riser and dri l l str ing aro ioined +o the wellhead afthe ocean f loor.

/u/mooring n: Securing a floating vessel in o specific area. Anchors,

anchor chains, wire l ines, and winches are sysfem components.

mud pit n: The open tonk which is bofh the originating and terminolpoint for dri l l ing f luid circulated down the dri l l pipe a'nd bacL ,pfhe annulus. Pit level changes are used to detect either loss of f luidfo the formation or incursion of gas or salt water into fhe wellbore.Either indicates a blowouf threat.

o

open hole n: Wellbore in which casing has nof been sef.

P

pacter n: A device for isoloting sections of +he weflbore by filling thespace befween the inner wall of the casing and pipe or fubing usedin production well testing. Used in perforating ond other well com.pletion procedures..

pendant l ines n: Lines ioining anchorsl ine fouling and to provide a meansfor seft ing and retrieving.

penetrafion rate n: The rote at whichening of the wel lbore. l t is usual lyhour .

and buoys designed to preventof lowering and raising anchors

the dri l l ad*rances in the deep-expressed in ferms of feet per

.l,I

I

posi t ioning (dynomic) n: Maintain ing a f loat ing vessel over the bore-hole by use of thrusters rather thon by un on.hor mooring system.

gsretensioning n: Adiusting the pull load of each l ine of a mooring sys--tem to the forces it is expected to encounfer in ifs specific lo.otion.

piles n: Large diameter steel pipe driven info o sed ffoor fo resr'stvert ical and lateral forces; load bearing strucfuraf parfs of plat-form legs. Skirt pi les are welded fo larger pifes to increur" ,tr"ngth.skirt pi les usualfy do not extend into fhe wave zone.

pod n: An assernbly of hydraulic volves situated on the BOP stack,io ined to lhe dr i l l ing plaf form by o bundle of hydraul ic f ines whichgive f lre dri l ler controf of fhe opeling and closing of blowouf pre-venters.

production

p rod ucedwell iesting n: Measuring the rafe of production of f luids

safurafion diving n: Diving for a fengfh of tirne which resutts in adiver's body absorbing a maxiinum of inerf gases used in breathingat'a given pressure level. Decornpression t ime and equipment arerequired.

seismic suryeys n: Determining subsu#ace sfrata by transrnissions ofpulses through the water cof umn into the earth ond ,"cording thefractionaf reflections from interfacos having unlike velocify anddensity characterist ics.

Shipshapes n: Floating vessels resembling in planform a conventionalship. Included are dr i l lships ond barges.

sidewall. coring n: Obtaining samples for analysis from walf s of theborehofe. A special wirdl ine tool is used-

significanf waves n: wave heights observed and recorded by ex-perienced seofarers. A signif icant wave is equal in height fo theaverage of the one-fhird highest w6ves under fhe same seo con-dit ions.

slcidding fhe rig n: Moving the derick and dri l l ing equipment to thenext slot when a wefl . is completed on a dri l l ing platform having amultiple slot pottern. For some platforms with special derricks ontythe crown block and rotary are moved for two or. fo6 slot patt"rnr.

s l im hole n: A wef lbore of smal l d iameter dr i l led for core sampl ing orstrafig raphic testing.

slots n: Platforrn locations of equipmenl used in dri i t ing devefopmentwells from a f ixed pfatform. Sfots aro usually in a grid pattern withspacing to permit instal laf ion of production irees upon complotionof each wel l .

/spr""d mooring n: A system of mult iple anchors and l ines distr ibutingthe loads imposed by currents, wavos, and winds. Pretensioning ofanchor l ines determines the init ial f ine loodings. A continuous moni-toring of individual f ino loads and automatic adiustmenfs in tensionincreose the effectiveness of this stotion keeping system.

sfabbing n: Aligning and bringing together fwo compatible units for' rnakeup or connect ion. Examples: BOP stack a nd wel lhead; mar ineriser and top of BoP sfaclc; Bop confrol pod and mounting.

station leeping n: Mainfaining o position of the rofary over the well-bore which wilf pormit the dri l l ing to confinue. Mooring sysfems-turret and spread are used. Dynamic posit ioning is anofher methodof station lceeping.

in an exploratory well. Produced f luids ore separated,and disposed of by burning

pulse n: A brief disturbance iransmifted through a medium apulse of l ight, sound, or pressure.

measured,

R

radioactivify welf log n: The record of theof subsurface format ions consist ing of

radioacfive cha racterisl icsa gamma-ray curve and. a

neufron curve. The two logs may be run sirnultaneously.

To enfarge tho wel lbore by redr i l f ing wi th a speciaf b i t .

roughneck n: Workman on a dr i l l ing r ig d i rect ly responsibfe to thedr i l ler- Also cal led f loorman or rotary herper.

roustabout n: Laborer who assists crane operafor, performs repairand main tenonco tasks .

s

SALM n: Single anchor teg moor ing. A buoy wi th fonlcor loadingequipment is connected to a rigid, boom-lik'e sfruclure hinged orattached at fhe seafloor

SBM n: Singfe buoy mooring. A f loating faci l i fy for shuttfe tankerfransportat ion of crude oi l . A tanker somst imes is moored and usedfor storoge and fransloading of shutt le tankers. In ofher cases onefanker loads whi le other shut t le tonkers are in t ransi t .

samples n: Cutt ings removed by the bit and brought to the dpil l inglevel by the dri l l ing f luid. Examinations of sampl", ,"rr"al formationinformation: identif ication of roctr types, thickness, and evidence ofgas d rid/or oi l confent.

satel l i tes, navigation n: Mon-made space vehicles orbif ing the earth.instrumented for transmiit ing data or ofher signafs. A series ofrecorded observations from a f ixed posit ion can be used to estab-l ish an exact poinl on the earth's. surface with a high degree of ac-curacy.

satel l i te wells n: Wellheads located over a large areo with f lowlinesinto a central ized producfion system. Widefy dispersed welts froman i r regular shaped reservoir can be added fo the gather ing sys-tem.

siorm choke n: A downhole fai l-safe valvo for sloppingsubsea welt when the wellhead is dornaged. The termtary narne.

flow from ais a proprie-

submersible r ig n: A barge-l ike vesset supporfing a drif l ing rig andits equipmont- l f wos fowed to its locaiion, submerged to sit onboftom and senved as a f ixed pfatform fhat was also mobile. l tsfuncfions have been assumed by iackups. l t was a forerunner of thepresenf generafion of sernisubmersibles.

submersib le (underseas vehic le l n, Sef f -propet led underwater craf tfrom which a number of diving iasks can be perforrned. l t is ineffect a miniaturo submarine.

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templafe n: A design.pal ter :n wi lh bui f t - in guides for speci f ic equip-ment and structures to assure fheir , r " fuf n"rr . Exomples, +emplaiefor insta l l ing wel l -conductor p ipe; p lat form iacket wi th wel l s lots,guides. sfeeves for insta l lat ion of p i les; subsea product ion systemswith spacing to accommodate the wells i t wil f produce. ,

tender n: A supporf vessel used extensively in the sheftered watersof the Gulf of Mexico with minimum-type plafforms. The fenderhouses crew, suppf ies, and general ly a l l equipmenf excepf thederr ick, rotary, and drawworks. Somet imes mud pumps and the mudpi t were on the plat forrn. Most popula. tenjsr was the LsT, aWodd War l l surplus vessel which could be converted at a costw e | | b e | o w t h e n e \ , / c o s t o f a c o m p a r a b | e y " , , " | . �

tensioners n: Equipment used to maintain tautness or constant pul l ingsfross on marine risors, guide l ines, drif l sfr ing, and applico+ions oiwire and control l ines on f loating vessels. Heave .ornp"nsafion isaccomPl ished through air pressure vessols. contro l panel , o i r com-pressor, a i r dryer uni ts, dnd id ler sheaves.

transparency n: Capocity of ti structure fo permif wave forces to passthrough rather than be absorbed. l f is ochieved by l imit ing the sizeof surfaces exposed to the wave zone. ; ,

tr ipping n: Hoisting the dri l l str ing out of and returning if into thewellbore. This is done for ihe purpose of changing bits, preparingto take a core. efc.

file!. n: A rof ler.ffiouoted sfructure beneath the derriclc of a floatingdri l l ing vessel to which anchor l ines are atfached. The vessef .ulbe revolved 360 degrees around the mooring plug by fhe bow andstern thrusters.

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wellbore n: The hole made by the dri l l bif.

well complelion n: Sett ing packers, perforoting cosing opposife theproducing format ions, insta l l ing producf ion tubing, und connect ingthe christmas tree.

well fogging n: The recording of information aboul subsurface geo-logic formations. Logging metho"ds include records kept by thedr i l ler , mud and cut t ings analyses, dr i l l s tem tests, e lectr ic andradiooctivity logs.

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Acknorvlcdgments

TIte assistan"" "f ' lt l:l l l ittrcle of lxrsy pcrsons from the petroleum inclustryItas made possible t'e gatrrerirrg of pr.,.rtog,-"prr*;J;;5; and data for thisptrblication.

The gtridance of seferal verv knor+'ieclgeable inclividuals 6as co'tributedttrateriall.v to tlre accuracy of reprcsentatious in the text.For ull tlte courtesies extenclecl to nre clrrring the cornpilation of materials,I cxprcss rrrv gratitrrcle.

Elclon I{olcomb

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