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Advanced Oil & Gas Exploration

and Production Technology

Course No: P07-001

Credit: 7 PDH

Gilbert Gedeon, P.E.

Continuing Education and Development, Inc.9 Greyridge Farm CourtStony Point, NY 10980

P: (877) 322-5800F: (877) 322-4774

[email protected]

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ENV I RONMENTA L B EN E F I T S

of ADVANCED O I L and G A S E X P LO R AT I ON

and P RODUCT I ON T E CHNO LOGY

U. S . D E P A R T M E N T of E N E R G Y

O F F I C E of F O S S I L E N E R G Y

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Better

Wellbore

Control

Protection of

Habitats,

Wildlife, and

Cultural

Resources

O I L A N D G A S I N D U S T R Y

T E C H N O L O G Y

Smaller

Footprint

Fewer Wells

or

Dry Holes

E X P L O R A T I O N

1 3-D Seismic

2 4-D Visualization

3 Remote Sensing

4 Subsalt Imaging

D R I L L I N G A N D C O M P L E T I O N

5 CO2-Sand Fracturing

6 Coiled Tubing

7 Horizontal Drilling

8 Hydraulic Fracturing

9 Measurement-While-Drilling

bl Modern Drilling Bits

bm Multilateral Drilling

bn Offshore Drilling

bo Pneumatic Drilling

bp Slimhole Drilling

bq Synthetic Drilling Muds

P R O D U C T I O N

br Acid Gas Removal and Recovery

bs Artificial Lift Optimization

bt Coalbed Methane Recovery

bu Freeze-Thaw/ Evaporation

cl Gas-to-Liquids Conversion

cm Glycol Dehydration

cn Advanced Data Management

co Improved Recovery Processes

cp Leak Detection and Measurement Systems

cq Low-Bleed Pneumatic Devices

cr Offshore Platforms

cs Downhole Oil /Water Separation

ct Safety & Environmental Management Programs

cu Vapor Recovery Units

S I T E R E S T O R A T I O N

dl Advanced Approaches to Site Restoration

dm Rigs to Reefs

dn Road Mix and Roadspreading

S E N S I T I V E E N V I R O N M E N T S

do DOE-BLM Partnership

dp Coastal and Nearshore Operations

dq Insulated Ice Pads

dr North Slope Operations

76 E N V I R O N M E N T A L B E N E F I T S

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E X P L O R A T I O N A N D P R O D U C T I O N

FA C T S H E E T SOptimized

Recovery of

Valuable Oil and

Gas Resources

Enhanced

Worker

Safety

Reduced

Greenhouse

Gas Emissions

(e.g., methane)

Reduced Air

Emissions

(e.g., HAPs,

NOx, PM)

Reduced

Power

or Fuel

Consumption

Protection

of Water

Resources

Reduced

Waste

Volumes

The technologies described in these Fact Sheets are merely representative of the numerous advances in exploration and

production technology over the last three decades and, as such, are not intended as an exhaustive inventory of these advances.

O I L A N D G A S T E C H N O L O G Y 77

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Two decades of successively better geologic interpretationdemonstrate tangible results and environmental benefits


Advances in 3-dimensional

(3-D) seismic technology

over the past 25 years

have enabled oil and gasproducers to evaluate

prospects more effectively,

drill fewer exploratory

wells, and develop fields

more efficiently. The result

is decreased environmen-

tal impact and increased

profit. To establish a visual

orientation of the subsur-

face without drilling,

energy waves directeddownward through the

earths strata are reflected

off the rock layers and

sent back to the surface.

The resulting data under-

go complex processing

and interpretation and

provide explorationists

with a 3-D visual charac-

terization of the subsur-

faces geological features.

This allows detailed

assessment of the oppor-

tunities and risks of devel-

oping a reservoir, an

increasingly important

capability as the search for

resources pushes into new

exploration frontiers, such

as deepwater and subsalt

formations.

From 2-D to

3-D technology

U N TI L T HE ,developers had to relyon inaccurate, low-resolutionanalog data in planning theirexploration investments. Inthe s, improved -D seis-mic techniques enabledexplorers to characterize sub-surface opportunities withgreater effectiveness. Now,with -D seismic, they can

establish more accurate -Dcharacterization of geologicstructures. Reservoir charac-terization is key across allstages of a hydrocarbon fieldslife. Seismic information,critical during the explorationand appraisal phase, is nowused for development until

the field is abandoned. In thelast years, the discoverycost has decreased from per barrel with -D seismic tojust under per barrel with-D seismic. Better geologicrepresentations, coupled withadvanced drilling and pro-duction technologies, alsolead to increased recoveryefficiencies.

Several major improvements

in -D surveying occurredduring the , in seismicdata acquisition, processing,computer hardware, andinterpretation and display.Particularly remarkable havebeen the hardware improve-ments. Within the last fiveyears, recording systems have

increased capacity from to, channels, as many as seismic data lines can berecorded in a single pass, andsatellite navigation systemshave evolved to pinpointaccurate positioning ofsources and receivers. At thesame time, technologicalimprovements have reducedcomputing time and loweredcosts. -D stack-time migra-tion can now be performed in

a few hours on massively par-allel processors, and between and , costs droppedfrom million to millionfor a-square-mile surveyusing-D post-time depthmigration. By, costs foran equivalent survey areexpected to be near ,.

3-D SeismicLocations: Worldwide, onshore and offshore

B L U E P R I N T O N T E C H N O L O G Y

T E C H N O L O G Y

S U M M A R Y

More accurate exploratory well-siting reduces

the number of dry holes and improves overall

productivity per well drilled

Less drilling waste is generated

Better understanding of flow mechanics

produces less water relative to oil and gas

Overall impacts of exploration and production

are reduced because fewer wells are required

to develop the same amount of reserves

E N V I R O N M E N T A L B E N E F I T SE C O N O M I C B E N E F I T S

Helps explorers to better identify oil and

gas prospects

More effective well placement improves

development of resources

Fewer dry holes ultimately reduces drilling and

exploration costs

Can substantially improve project economics

by reducing overall drilling costs

Exploration time relative to successful

production is cut

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Evolving seismic technologies improve accuracy andinterpretation, allowing operations to be tailored toprotect the environment


Three-dimensional (3-D)

seismic technology has

revolutionized oil and gas

exploration and served asa springboard to visualiza-

tion technology. Now

emerging visualization

and 4-D time-lapse moni-

toring technologies are

improving interpretation

of the data 3-D seismic

imaging provides.

Invaluable in locating

bypassed reserves in exist-

ing formations and discov-ering new resources, seis-

mic reservoir characteriza-

tion can now incorporate

perceptual cues such as

projection, lighting and

shading, depth, motion,

and transparency. This

technology enables a

more consistent, detailed

picture of a complex for-

mation. 4-D monitoring

goes one step further,

providing a dynamic

picture of hydrocarbon

flows and other reservoir

changes over time,

information valuable for

both exploration and

reservoir management of

existing resources.

Adding a fourth

dimensiontime

P E T RO L EU M E N GI-neers, geologists, andplanners have a far betterunderstanding of the geologicstructures of potential hydro-carbon-bearing formationsnow that reservoir images areprojected in three dimen-sions. Four are better still,largely due to DOE-supported

research. A reservoirs fluidviscosity, saturation changes,temperature, and fluid move-ments can be analyzed bytime-lapse monitoring inthree dimensions. The time-lapse picture is built out ofdata re-recorded at intervals,compared and plotted bycomputer onto a-D model.Engineers can view changes

occurring over time and linkthese to static and dynamicreservoir properties and pro-duction techniques. They canthen follow the consequencesof their reservoir managementprograms and make predic-tions as to the results offuture activities. -D monitor-ing is an offshoot of the com-puter processing techniquesdeveloped for -D seismic

interpretation.

With improved visualizationtechniques, petroleum engi-neers, geologists, and geo-physicists are integratingmany types and ages of data(well logs and productioninformation, reservoir tem-peratures and pressures, fluidsaturations, -D and -D

seismic data) into time-lapseimagery and reservoir perfor-mance modeling. As thistime-dependent tool is correlated with physical dataacquisition, more accuratecharacterization of subsurfacereservoirs will be possible,pushing maximum recoveryefficiencies.

Geologists and planners are

better able to understand thestructure of promising forma-tions. As computing scienceadvances, further gains will bemade. Already, audio technol-ogy is being added, both forcontrolling images and pre-senting complex geologicaldata so that scientists canshare data in real time fromremote locations.

4-D VisualizationLocations: Worldwide, onshore and offshore


T E C H N O L O G Y

S U M M A R Y

Reduced drilling due to more successful siting

of wells, with greater recovery from existing wells

Less drilling waste through improved reservoir

management

Lower produced water volumes through better

well placement relative to the oil/water interface

in the formation

Increased ability to tailor operations to protect

sensitive environments


Improved recovery due to precise placement of

injector wells and infill drilling

More efficient operations due to better

identification of drainage patterns

Lowered operating costs because of improved

program timing and fewer dry holes

Increased identification and ultimate recovery of

as yet untapped resources

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Remote exploration helps pinpoint hydrocarbon resources,

pollution sources, and sensitive environments


Used in conjunction with

other exploratory tech-

niques, such as 3-D seis-

mic imaging, remote sens-ing systems detect and

map concentrations of

hydrocarbons with greater

accuracy than other tech-

nologies alone, and with

less environmental

impact. Technologies such

as satellite imagery, aero-

magnetic surveys, and

gravimetry are now being

applied by the largestexploration companies to

attempt to detect the ver-

tical or near-vertical

migration of oil and gas to

the earths surface and

help identify promising

geologic structures. These

systems measure gases,

solids, and liquids, using

their physical properties to

attenuate or reflect beams

of electromagnetic energy.

Resulting geophysical data

are processed into easily

understood images and

maps, and form an inte-

gral part of current

onshore and offshore

programs throughout

the world.

Enhanced satellite

imaging systems

O P T I CA L S AT E LL I TEimagery has been thepredominant source of datafor identifying and mappingonshore geology since theearly, when the firstLandsat Earth Observationsatellite was launched. Today,satellite imagery, onshore andoffshore, is also provided byradar satellites very sensitive

to the earths surface con-tours. For example, varioustypes of satellites can seethrough feet of clear waterand up to feet beneath thesurface. Early optical satellitesdepended on visible or near-infrared light to collect energyreflected from the earthssurface. By contrast, radar

satellites emit energy atmicrowave frequencies,enabling them to acquireimagery under nearly anyatmospheric condition.Sophisticated digital imageprocessing systems can nowconvert and sort raw satellitedata into thematic maps thatpoint to the location of pro-ductive formations, evendetecting oil and gas seepagesthat indicate migration path-

ways from undrilled traps.Similarly, remote sensingtechniques can also identifyhydrocarbon spills and leaksin remote areas, such as alongpipelines.

Current multispectral satel-lites such as the LandsatThematic Mapper create

images by gathering up toseven bands of light spectra inprism-like fashion. In ,when the U.S. Navy plans tolaunch its Navy EarthMapObserver satellite, an excitingnew satellite technologycalled hyperspectral analysis,accessing upwards ofbands of light, will furtherincrease imaging accuracy.

Improved aeromagnetic

surveysInitially developed for mili-tary applications, aeromag-netic surveying has evolvedinto a productive explorationtechnology that can recognizethe magnetic signature ofpotential hydrocarbon-bearingbasins from altitudes over, feet. Using a

Remote SensingLocations: Worldwide (especially deepwater)


T E C H N O L O G Y

S U M M A R Y

Accurate identification of fragile ecosystems,

enabling care when drilling

Increased ability to address environmental needs

Fewer dry holes and nonproductive exploratory

wells are drilled

Improved characterization of earths natural

systems

Identification of spills and leaks in remote areas


Increased exploratory success rates

Dramatically reduced exploratory costs

Access to geological data otherwise

unobtainable

Increased recovery of resources from frontier

basins

Identification of hydrocarbon seeps as

distinguished from oil spills or pollution

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C O N T A C T

Corbley, K. Landsat ImagesAssist in Mapping Caspian

Bathymetry. Oil & Gas Journal

Offshore, 7/1/97.

Detecting the Sleeping Giants of

the Caspianfrom Space.

Offshore Magazine, 7/1/98.

Koger, D., and R. Dodge. Geosat

Starts Up R&D on Exploration

Sector. Oil & Gas Journal,

10/5/98.

Petzet, G. Explorers LookToward Better Remote Sensing

Data. Oil & Gas Journal, 3/9/98.

Remote Sensing Terminology.

Journal of the Air and Waste

Management Assoc., 11/91.

Wagner, M. Radar Imaging

Matched with Gravity and

Bathymetry. Oil & Gas Journal

Offshore, 5/1/98.

S O U R C E S A N D A D D I T I O N A L R E A D I N G

Success in the Field

C A S E S T U D I E S

magnetometer mounted on

a magnetically cleaned air-craft, explorers are success-fully mapping sedimentaryanomalies critical to oil andgas exploration, detectingsalt/sediment contact, min-eralized shear zones, andintrasedimentary markers.

Recent improvements inmagnetometer design, digi-tal signal processing tech-niques, and electronic navi-gation technologies, incombination with fastersampling of the magneticfield and the use of moredetailed survey grids, allowmapping of subtle magneticsignatures. These advancesimprove the interpretationand visualization ofgeological data.

Measuring gravity to gauge

resourcesGravimetry measurement isnow derived from bothsatellite and airborne obser-vations. Gravity anomaliescan be measured andmapped to give geoscientistsan idea of the size anddepth of the geologicalstructures that caused them.

Satellite gravity imaging

uses radar to measure undu-lations in the sea surfacethat reflect density varia-tions in the earths uppercrust. This technologyenables mapping of areas ofmass deficit, where sedi-mentary deposition is likelyto have occurred. Identifi-cation of such areas givesexplorers a better idea ofwhere hydrocarbons may belocated.

Putting it all together

Exploration companies likeBP Exploration, Exxon,Mobil, Texaco, Unocal, andRTX are tailoring theirremote sensing programs tocombine technologies asneeded. Recent advancesin radar imaging andsophisticated image-process-ing packages, combined

with satellite-derived gravityand bathymetry data, forexample, present newopportunities to use remotesensing for deepwaterexploration. Remote sensingis now considered critical tosuch operations. It is alsoextraordinarily cost-effective.

Satellites help explore in the Caspian Sea

After water-level changes along the shallow coast of the Republicof Kazakhstan made their bathymetric maps obsolete, Oryx

Energy and its exploration partner, Exxon, turned to remotesensing to gauge depths. Water depth fluctuations caused by

wind can make movement of seismic and drilling equipmentchallenging. With satellite image processing technology, the teamcreated new bathymetric maps (e.g., the , square kmMertvyi Kultuk block, some km south of the giant Tengiz field)and used these maps to position a successful new drilling programin one of the worlds most productive oil exploration areas.

U.S. Department of Energy

Office of Fossil Energy

1000 Independence Avenue, SW

Washington, DC 20585

Edith C. Allison

(202) 586-1023

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]

Russia

Azerbaijan

Iran

Turkmenistan

Kazakhstan

Caspian

Sea

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Interpretation of formations hidden under layers of salt

allows more accurate siting of new reserves


Now that most easily

accessible domestic

resources have been dis-

covered, oil and gasexplorers are investigating

the promising but more

inaccessible resources

beneath saltsheet forma-

tions in the Gulf of

Mexico. Large, irregular

saltsheets may cover 60

percent of the slope

beneath the Outer

Continental Shelf in the

Gulf and are foundthroughout the world.

Advances in 3-D imaging

technologies are crucial to

providing reliable images

of what lies below the

thick layers. A 3-D

prestack depth migration

method of seismic data

processing and an advanced

marine magnetotellurics

technique are now making

it possible to image the

structure and thickness of

subsalt sediments.

Together, these technolo-

gies provide sufficient

information to help locate

new oil or gas deposits,

estimated at 15 billion bar-

rels of oil equivalent in the

Gulf of Mexico alone.

Getting under the salt

DE V EL O PI N G I M AG E Sof subsalt structuresposes a critical challenge toexploration. Seismic imagingis based on the transmissionof sound waves and analysisof the energy that is bouncedback. But large amounts ofenergy are lost when soundwaves pass through salt; thus,an extremely strong seismicsource is required. Often seis-

mic data are incomplete, pre-venting explorers fromobtaining accurate readings ofa structures shape and thick-ness. Traditional imagingmethods cannot deliver accu-rate readings when seismicsources are blocked by saltsqueezed into sheets betweensediment layers from anunderlying salt base. The oiland gas sandwiched betweenthe salt layers can only be

imaged by a combination ofadvanced seismic source tech-nology, complex mathemati-cal modeling simulations, andimproved data processing andimaging techniques. DOEspublic/private Natural Gas andOil Technology Partnershiphas helped develop severalsuch technologies, amongthem improvements to thespeed and reliability of-Dprestack depth migration,

which creates a coherent imageby processing as many as million records.

Using electromagnetic

resistance

As a part of this DOE part-nership, the NationalLaboratories and industry arecurrently investigating thefeasibility of marine magne-totellurics, which is ideal forsubsalt exploration since it is

based on electrical resistance.Because salts resistivity is times greater than that ofsurrounding sediments, thecontrast between salt and sed-iment resistance to low-fre-quency electromagnetic radia-tion from the earths ionos-phere makes it easier to mapthe extent and thickness ofsalt structures.

Stealth imaging breakthrough

The latest technology usedto enhance seismic data is-D full tensor gradient (FTG)imaging, originally developedby the U.S. Navy during theCold War for stealth sub-marines. A-D gradiometersurvey takes real-time mea-surements of very smallchanges in the earths gravityfield, each relaying informa-tion directly related to massand geometry of subsurface

Subsalt ImagingLocations: Gulf of Mexico, West Africa, and other salt formations


T E C H N O L O G Y

S U M M A R Y

Increased resource recovery due to better

reservoir characterization

Better, more careful siting of new drilling

operations

Reduced drilling wastes as fewer wells are

drilled


More efficient exploration to pinpoint new oil

and gas, reducing the financial risks

Cost-effective exploration: an average 30-image

seismic survey costs $500,000, while an MT sur-

vey covering the same area costs about $50,000

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Edith C. Allison

(202) 586-1023

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]

C O N T A C T

Camp, W., and D. McGuire.Mahogany Field, A Subsalt

Legend: A Tale of Technology,

Timing, and Tenacity. Houston

Geological Society Bulletin,

10/97.

Coburn, G. 3D Full Tensor

Gradient Method Improves

Subsalt Interpretation. Oil & Gas

Journal, 9/14/98.

Cold War Stealth Technology

Can Aid Seismic Interpretation.

Journal of Petroleum

Technology, 1/98.

Earth View Associates. SubsaltExploration Methods

Information Brochure.

Hoverston, G., et al.

Magnetotellurics for Petroleum

Exploration. Case for Sea MT.

Minerals Management Service.

Gulf of Mexico OCS Region,

Subsalt Exploration.

Petzet, G. Anadarko Find,

Technology Gains Renew

Subsalt Hopes. Oil & Gas

Journal, 8/17/98.

Prutzman, J., and G. Coburn.Technology Pinpoints Base of

Salt. The American Oil & Gas

Reporter, 7/98.




Beneath the Mahogany field salt

Drilling beneath the salt formations of the Gulf of Mexico, anexploration play spanning, square miles south of theLouisiana coast, began in the . A decade of unsuccessfulexploration followed, and it took advanced subsalt technologies tobreak through the visual block. Nine subsalt discoveries weredrilled in the play from to , representing a phenomenalsuccess rate of percent. The centrally located Mahogany field(the Gulf s first commercial subsalt play) was discovered in ,and four wells were completed by, now flowing at a daily rateof, barrels of oil and million cubic feet of gas. Mahoganyfields total reserves are estimated at million barrels of oil-equivalent, and total recovery from this and the Gulf s other sub-

salt discoveries is estimated to be million energy equivalentbarrels, resources that would have remained inaccessible withoutadvanced subsalt imaging technology. A new discovery, theTanzanite field, is estimated to hold reserves of million barrelsof oil-equivalent. Due to the size of this discovery, subsalt explo-ration in the Gulf is likely to remain active. Future subsalt technol-ogy advances may be the key to discovering other large untappedfields. As technology progresses, so will resource recovery.

geological bodies. FTG pro-

vides the depth and shapeof almost any geologicalstructure, independent ofseismic velocities, allowinggeoscientists to developmore complete images ofcomplex salt formations.Two field tests have

demonstrated a significantly

improved view of the Gulfssubsalt geology, and FTGpromises to be an affordabletool with which to enhanceexisting-D seismic imagingtechnology in salt forma-tions around the world.

SPE, 1993

United States

Gulf ofMexico

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In widespread use in Canada, a stimulation techniquenow successfully demonstrated in the U.S. has outstandingresults without formation damage


Fracturing has been widely

used since the 1970s to

increase production from for-

mations with low permeability

or wellbore damage. Unlike

conventional hydraulic and

acid fracturing techniques,

CO2-sand fracturing stimu-

lates the flow of hydrocar-

bons without the risk of for-

mation damage and without

producing wastes for dispos-

al. A mixture of sand prop-

pants and liquid CO2 is forced

downhole, where it creates

and enlarges fractures. Then

the CO2 vaporizes, leaving

only the sand to hold the

fracture openno liquids,

gels, or chemicals are used

that could create waste or

damage the reservoir. Any

reservoir that is water-

sensitive or susceptible to

damage from invading fluids,

gels, or surfactants is a candi-

date. The process has had

widespread commercial

success in Canada, and

recent DOE-sponsored field

tests have demonstrated

commercial feasibility in the

United States.

Using CO2 to fracture

oil and gas reservoirs

RE C OM P LE T IN G A N Dfracturing an existing oilor gas well to stimulate produc-tion that has declined over timeis significantly less costly thandrilling a new well. First used inthe mid-, fracturing treat-ments inject fluids under highpressure into the formation,creating new fractures and

enlarging existing ones.Proppants (usually large-grained sand or glass pellets) areadded to the fluid to supportthe open fractures, enablinghydrocarbons to flow morefreely to the wellbore.Fracturing is widely used tostimulate production indeclining wells and to initiateproduction in certain

unconventional settings.More than one million frac-turing treatments were per-formed by, and about to percent of existing wellsare hydraulically fractured atleast once in their lifetime.More than eight billion bar-rels of additional oil reserveshave been recovered throughthis process in North Americaalone. Yet conventional frac-

turing technology has draw-backs. The water- or oil-basedfluids, foams, and acids usedin traditional fracturingapproaches can damage theformationfor instance, bycausing clay in the shale toswelleventually pluggingthe formation and restrictingthe flow of hydrocarbons.Conventional fracturing also

produces wastes requiringdisposal.

An advanced CO2-sand frac-turing technology overcomesthese problems, and is prov-ing a cost-effective process forstimulating oil and gas pro-duction. First used in bya Canadian firm, the processblends proppants with percent liquid CO2 in a

closed-system-pressurized ves-sel at a temperature ofFand a pressure of psi.Nitrogen gas is used to forcethe resulting mixture throughthe blender to the suctionarea of the hydraulic fracturepumping units and thendownhole, where it createsand enlarges fractures. TheCO2 used in the process

CO2-Sand FracturingLocations: Canada (commercial) and United States (demonstration only)


T E C H N O L O G Y

S U M M A R Y

Using liquid CO2 creates long, propped frac-

tures without formation damage

No wastes requiring disposal are created

Conventional fracturing gels and chemicals,

which may damage the flow path between

wellbore and formation, are not used

Groundwater resources are protected


Eliminates hauling, disposal, and maintenance

costs of water-based systems

Can significantly increase well productivity and

ultimate recovery

CO2 vaporization leads to fast cleanup, whereas

water-based fluids sometimes clean up slowly,

reducing cash flow

Recovery of valuable oil and gas is optimized

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Elena S. Melchert

(202) 586-5095

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]

C O N T A C T

Arnold, D. Dry Frac Damage

Control. PTTC Network News,

2nd Quarter 1997.

Arnold, D. Liquid CO2 and Sand:

An Alternative to Water-Based

Stimulation Fluids. Harts

Petroleum Engineer

International, 1/98.

DOE, Office of Fossil Energy.

Fracturing Gas/Oil Formations

with Reservoir Friendly

Carbon Dioxide and Sand.

Investments in Fossil Energy

Technology.

Petroleum Technology Transfer

Council. Needed: Demonstration

Sites for New Stimulation

Process. PTTC Network News,

2nd Quarter 1997.

Raymond, Johnson, et al. CO2

Energized and Remedial 100%

CO2Treatments Improve

Productivity in Wolfcamp

Intervals. Val Verde Basin,

West Texas, SPE 39778, 1998.

Yost II, Mazza, and Remington II.

Analysis of Production Response

to CO2/Sand Fracturing: A Case

Study. SPE 29191, 1994.

1995 National Assessment of

United States Oil and Gas

Resources. USGS Circular 1118,

U.S. Government Printing Office.




Increased Gas Production per Well

Results of fracturing technique tests

in Devonian Shales wells after

37 months

600%0%

CO2-Sand vs.

Nitrogen Gas

(no proppant)

CO2-Sand vs.

Nitrogen Foam

(with proppant)

400 %

200%

vaporizes, leaving behind a

dry, damage-free proppantpack. The technology hasgained widespread commer-cial acceptance in Canada,where it has been used some, times. In the UnitedStates, use has been limitedto demonstrationsmanysponsored and cofunded byDOEtaking place overthe last two years in aboutwells in Kentucky, Ohio,Pennsylvania, Tennessee,Texas, New York, Colorado,and New Mexico.

CO2-sand fracturing treat-

ments average from ,to ,, depending onwell depth and rock stresses.While often higher-costthan conventional methods,these costs are offset by sav-ings realized through elimi-nating both swab rigs andthe hauling, disposal, andmaintenance costs associat-ed with water-based sys-tems. As in conventionalfracturing, CO2-sand treat-ments can significantlyincrease a formations pro-duction and profitability.

M E T R I C S

Source: Arnold, Harts Petroleum Engineer International, January 1998

Successful DOE-sponsored field testsThe U.S. Geological Survey estimates that to trillioncubic feet of natural gas resources exists in unconventional set-tings in the United States. Developing cost-effective advancedfracturing techniques is crucial in our quest to recover theseresources. A number of field-test fracturing projects sponsored byDOE recently evaluated and proved CO2-sand technologys effec-tiveness in gas recovery. In the Devonian Shales in Kentucky, fourof gas wells were stimulated with CO2-sand mixture, seven

with nitrogen gas and no proppant, and four with nitrogen foamand proppant. After producing months, wells stimulated withthe CO

2-sand process had produced four times as much as those

treated with foam, and twice as much as those stimulated withnitrogen gas. In central Pennsylvania, three gas wells were stimu-lated using CO2-sand fracturing. Immediately after fracturing,two of the wells exhibited production increases of, percentand percent. Over a year and a half later, production fromthe wells had increased percent, percent, and per-cent, respectively.

s Major areas of oil

and gas potential

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Successively better coiled tubing technologies drive

improvements in cost, productivity, and efficiency of

drilling operations, while reducing environmental impact


Continuous coiled tubing

can dramatically increase

the efficiency, profitability,

and productivity of drillingfor oil and gas. Whereas in

conventional drilling oper-

ations, the drilling pipe

consists of several jointed

pieces requiring multiple

reconnections, a more

flexible, longer coiled pipe

string allows uninterrupted

operations. A cost-effec-

tive alternative for drilling

in reentry, underbalanced,and highly deviated wells,

coiled tubing technology

minimizes environmental

impacts with its small

footprint, reduced mud

requirements, and quieter

operation. Quick rig set-

up, extended reach in hori-

zontal sidetracking, one-

time installation, and

reduced crews cut operat-

ing costs significantly. For

multilateral and slimhole

reentry operations, coiled

tubing provides the oppor-

tunity for extremely

profitable synergies.

A strong portfolio of benefits

P A RT I CU L A R LY VA LU-able in sensitive environ-ments such as Alaskas NorthSlope, coiled tubing technol-ogy has far less impact on adrilling site than conventionalequipment, in addition toperforming drilling opera-tions more efficiently andcost-effectively. Although thefirst coiled tubing units were

built in the , only afterrapid technological advancesin the late did the tech-nology start to gain industry-wide recognition. From

operating units in , usagehas grown to some unitsin , and many drillingcompanies are now revisingtheir rig portfolios.

In a variety of drilling appli-cations, coiled tubing elimi-nates the costs of continuousjointing, reinstallation, andremoval of drilling pipes. It isa key technology for slimhole

drilling, where the combina-tion can result in significantlylower drilling costsa typical,-foot well drilled insouthwest Wyoming costs

about ,, but withcoiled tubing and slimhole,the same well would cost, less.

Reduced working spaceabout half of what is requiredfor a conventional unitis animportant benefit, as arereduced fuel consumption andemissions. A significant drop innoise levels is also beneficial in

most locations. The noise levelat a,-foot radius is decibels, while at the sameradius a conventional rig has a-decibel level.

Coiled TubingLocations: Worldwide, onshore and offshore


T E C H N O L O G Y

S U M M A R Y

Reduced mud volumes and drilling waste

Cleaner operations, as no connections to leak mud

Reduced operations noise

Minimized equipment footprints and easier site

restoration

Reduced fuel consumption and emissions

Less visual impact at site and less disturbance,

due to speedy rig set-up

Reduced risk of soil contamination, due to

increased well control

Better wellbore control

E N V I R O N M E NT A L B E N E F I T SE C O N O M I C B E N E F I T S

Increased profits, in certain cases, from 24-hour

rig set-up and faster drilling

Smaller drilling infrastructure and more

stable wells

No interruptions necessary to make connections

or to pull production tubing

Reduced waste disposal costs

Reduced fuel consumption

Increased life and performance from new rig

designs and advanced tubulars, reducing

operating costs

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Elena S. Melchert

(202) 586-5095

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]

C O N T A C T

Adams, L., and C. Overstreet.

Coiled Tubing Facilitates Deep

Underbalanced Workover. Oil &

Gas Journal, 3/31/97.

Berning, Isennock, and Coats.

Composites Extend CTs

Applications. The American Oil

& Gas Reporter, 9/98.

Electric Coiled-Tubing Drilling.


Technology, 9/98.

Faure, A., and J. Simmons.

Coiled Tubing Drilling: A Means

to Minimize Environmental

Impact. SPE Paper 27156, 1994.

Furlow, W., Lake Maracaibos

Depleted Fields Continue to

Produce. Offshore Magazine,

9/1/98.

Kunkel, B. Benefits Fuel CT

Growth. Harts Petroleum

Engineer International, 7/97.

Newman, K. Coiled Tubing

Technology Continues Its Rapid

Growth. World Oil, 1/98.

Schutz, R., and H. Watkins.

Titanium Alloys Extend

Capabilities of Specialty

Tubulars Arsenal. The American

Oil & Gas Reporter, 9/98.

Strunk, C. Slim Hole, Coiled

Tubing Combine to Enhance

Well Economics. The American





M E T R I C S

Field trials in the Netherlands

demonstrate environmental benefits

Fuel Consumption and Gas Emissions:

Coiled Tubing vs. Conventional Rigs

Med Land Coiled Tubing

Workover Drilling Drilling

Rig Rig Unit

Diesel m3/month 35 160 25

Gas CO2 3,293 15,055 2,122

Emissions CO 3.7 16.8 2.5

kg/day NOx 4.6 21 2.1

HC 3.9 17.8 2.8

HC (Gas) 1.8 8.4 1.1

SO2 4.2 19.4 2.2

180

160

140

120

100

80

60

40

20

Conductor Tophole

Intermediate Reservoir

Completion

Conventional Coiled Tubing

Conventional drilling fluids volume com-

pared with coiled tubing volumes (m3)

At Lake Maracaibo field

Advanced coiled tubing drilling is helping operators optimizeresource recovery at Venezuelas Lake Maracaibo field. BakerHughes INTEQs first-of-its kind Galileo II hybrid drilling barge,containing-inch coiled tubing and slimhole drilling measure-ment-while-drilling tools, drilled its first well at the end of.It was the first time an underbalanced well had been drilled onLake Maracaibo, and it promises good results. Galileo IIs uniquedesign is also expected to significantly increase the life of its coiledtubing, ultimately reducing operating costs. Operating in a fragilelake ecosystem presents unique waste management challenges,

and all drill cuttings and waste mud are transported back to shorefor disposal.

Technology advances

in the 90sDramatic advances haverecently brought new coiledtubing technology to mar-ket. For example, newdesigns from leadingdrilling service companieshave eliminated coiledtubing rigs guide arches; inthese new designs, eliminat-ing the bending in the tub-ing at the guide arch hassignificantly increased its

life. The newest advance isan electric bottomholeassembly offering immedi-ate data feedback on bot-tomhole conditions,reduced coiled tubingfatigue, maintenance of bitspeed independent of flowrate, and improved reliabili-ty. New materials likeadvanced titanium alloysand advanced metal-free

composites have improvedthe reliability, performance,corrosion-resistance, weight,and cost-effectiveness ofcoiled tubing assemblies. Incertain cases, titanium tub-ing offers an estimated reel-ing cycle life to timesgreater than steel. SPE 27156, 1994

Photo: WZI, Inc.

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Without any increase in environmental impact, horizontal

drilling allows developers to reach reserves beyond the

limits of conventional techniques


Horizontal drilling targets

oil or gas in thin, tight

reservoirs, reservoirs inac-

cessible by vertical drilling,and reservoirs where hori-

zontal wellbores signifi-

cantly increase flow rates

and recovery. Horizontal

wells maximize utilization

of drilling sites and infra-

structure. While vertical

wells drain oil from a sin-

gle hole and have limited

contact with oil-bearing

rock, horizontal wells pen-etrate a greater cross-

section of the formation,

allowing substantially

more oil to drain. A hori-

zontal well is drilled later-

ally from a vertical well-

bore at an angle between

70 and 110. It can tap the

hydrocarbon supplies of a

formation without further

environmental distur-

bance, of particular value

in sensitive areas.

Breaking geologic barriers

T H E C UR REN T B OO Min horizontal drilling isdue to rapid developments intechnology over the past twodecades. Although severalhorizontal wells were success-fully drilled between the and , these were limitedto expensive - to -footforays. Interest waned in suchonshore applications after thedevelopment of hydraulicfracturing technology madevertical wells more productive.The offshore industry contin-ued to pursue horizontaldrilling, but the limitations ofthe available equipment oftenresulted in ineffective, expen-sive, and time-consumingdrilling operations.

In the mid-, several sig-nificant technology advancesstarted breaking down thesebarriers. Steerable downholemotor assemblies, measure-ment-while-drilling (MWD)tools, and improvements inradial drilling technologieswere the breakthroughs need-ed to make horizontal drillingfeasible. Short-radius technol-ogy had been developed in the, the earliest curvaturetechnique used to drill laterals;in the , long-radius tech-nology allowed lateral dis-placement away from the rigto penetrate the reservoir.Then, in the , medium-radius techniques permittedre-drilling horizontal intervalsfrom existing wellbores, andwith this advance producerscould build rapidly to a

angle. Today, horizontalwells are being drilled longerand deeper, in more hostileenvironments than ever before.

Horizontal drilling is nowconventional in some areasand an important componentof enhanced recovery pro-jects. At any given time, hori-zontal drilling accounts for to percent of the U.S. landwell count. The Austin Chalkfield has been the site of over percent of the onshorehorizontal rig count since thelate , and still accountsfor the majority of horizontalpermits and rig activity in theU.S. today. Thirty percent ofall U.S. reserves are in car-bonate formations, and it ishere that percent of hori-zontal wells are drilled.

Horizontal DrillingLocations: Worldwide, onshore and offshore


T E C H N O L O G Y

S U M M A R Y

Less impact in environmentally sensitive areas

Fewer wells needed to achieve desired level of

reserve additions

More effective drilling means less produced water

Less drilling waste


Increased recoverable hydrocarbons from a

formation, often permitting revitalization of

previously marginal or mature fields

More cost-effective drilling operations

Less produced water requiring disposal and less

waste requiring disposal

Increased well productivity and ultimate recovery

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C O N T A C T

Cooper, S., and R. Cuthbertson.Horizontal, Underbalanced Wells

Yield High Rates in Colombia.

World Oil, 9/98.

Department of Energy. Using

Horizontal Drilling to Give a

Michigan Oilfield New Life.

Deskin, W. et al. Survey Shows

Successes, Failures of Horizontal

Wells. Oil & Gas Journal, 6/19/95.

Gas Research Institute.

Measuring the Impact of

Technology Advances in the

Gulf of Mexico.

Horizontal Well SuccessfullyDrilled in Black Warrior Basin.

Oil & Gas Journal, 7/22/96.

Knoll, R. Buzzwords Can Lead to

Poor Results. The American Oil


Mason, R. Horizontal Drilling

Broadening Mindset, Opening

New Possibilities. The American


Natural Petroleum Council. The

Potential for Natural Gas in the

United States, 12/92.

Philips, C., and D. Clarke. 3DModeling/Visualization Guides

Horizontal Well Program in

Wilmington Field. Journal of

Canadian Petroleum

Technology, 10/98.

Potter, N. 3D, Horizontal Drilling

Changing Clair Development

Economics. Offshore Magazine,

5/1/98.




of, barrels. Success has spawned the drilling of nine otherhorizontal wells here, and nearly others in geologically similarfields in the basin. If successful in other depleted Dundee fields,horizontal wells could produce an additional to millionbarrels of oil, worth about million in tax revenues alone.

In the United States, according to a recent

DOE study, horizontal drilling has improved:

Potential reserve additionsby an estimated 10 billion barrels of oil equivalent,

nearly 2% of original oil-in-place

The average production rationow 3.2:1 for horizontal compared to vertical

drilling based on field data, even though the average cost ratio is 2:1

Carbonate numbers are even betterproduction is nearly 400% greater than verti-

cal wells, yet costs are only 80% more

Worldwide Horizontal Wells

3,000

2,500

2,250

2,000

1,750

2,750

1,500

1,250

Pre-1988

1988 1990 19911989 1992 1993 1994 1995 1996

1,000

500

250

750

0

Number of Horizontal Wells

Success in the Black Warrior Basin

In , after six years of production, the Goodwin gas field in theBlack Warrior Basin was converted to gas storage by the MississippiValley Gas Co. Only conventional vertical wells had been drilledin the thin ( feet), tight, abrasive formation. The operatorsuccessfully drilled and completed the first horizontal well in only days, utilizing MWD and gamma ray tools, a short radiusmotor, and a polycrystalline diamond bit. Overall costs approachedtwice that of a conventional well in the field, but the deliverabilityof the horizontal well was six times that of a vertical well. Since onehorizontal well is producing the equivalent of six vertical wells,maintenance and operating costs are lower, and fewer meter runs,flowlines, and other facilities are required.

New reserves in the Dundee Formation

Only percent of the known oil located in the Michigan BasinsDundee Formation had been produced when a DOE co-sponsoredhorizontal drilling project brought new life to the formationsexhausted Crystal field. The new horizontal well now producesnearly times more than the best conventional well in its field barrels of oil a dayand boasts estimated recoverable reserves

M E T R I C S

Source: U.S. Department of Energy and Maurer Engineering, Inc., 1995

Source: Oil & Gas Journal, November 23, 1998





Elena S. Melchert

(202) 586-5095

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]


and gas potential

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Assisting operators to bring new life to mature fields

and make unconventional fields commercially viable


Routinely applied to over

half of U.S. gas wells and

a third of oil wells,

hydraulic fracturing hasbeen proven to enhance

well performance, mini-

mize drilling, and recover

otherwise inaccessible

resources. It makes the

development of some low-

permeability, tight forma-

tions and unconventional

resources economically

feasible. When the flow of

hydrocarbons is restrictedby formation characteris-

tics, injecting pressurized

fluids and solid additives

can stimulate wells to

increase production. Fluids

are pumped into the for-

mation at pressure great

enough to fracture the

surrounding rock. A prop-

pant slurry follows, biode-

grading to sand proppant

that holds the fractures

open, allowing free pas-

sage of fluids to the well-

head. So successful has

this technology been that

the industry currently

spends a billion dollars

annually on hydraulic

fracturing.

Stimulating wells

to deliver more

F I RS T I NT RO DU C ED I N, hydraulic fracturingquickly became the mostcommonly used technique tostimulate oil and gas wells,ultimately enabling produc-tion of an additional eightbillion barrels of NorthAmerican oil reserves thatwould otherwise have beenunrecovered. By, fracturing

had already been appliednearly a million times. Eachyear, approximately,gas and oil wells are hydrauli-cally fractured.

Fracturing is generally used toregain productivity after thefirst flow of resources dimin-ishes. It is also applied to ini-tiate the production processin unconventional forma-

tions, such as coalbedmethane, tight gas sands, andshale deposits. Improvementsin fracturing design and qual-ity control have enabled oper-ators to successfully applyfracturing techniques in morecomplex reservoirs, hostileenvironments, and otherunique production settings.

New advances

The DOE-led Natural

Gas and Oil TechnologyPartnership has promotedmany of this decades fractur-ing advances. These includethe use of air, underbalanceddrilling, and new fracturingfluids to reduce formationdamage and speed well clean-up. Improved log interpreta-tion has improved identifica-tion of productive pay zones.Improved borehole tools help

map microseismic events andpredict the direction andshape of fractures. New-Dfracture simulators withrevised designs and real-timefeedback capabilities improveprediction of results.

Advanced breakers andenzymes that minimize therisk of formation pluggingfrom large-volume hydraulicstimulations are the latest

advances to protect the envi-ronment and increase ultimaterecovery. In addition, emerg-ing technologies developed byDOE and the Gas ResearchInstitute, such as microseismicfracture mapping and down-hole tiltmeter fracture map-ping, offer the promise ofmore effective fracture diag-nostics and greater ultimateresource recovery.

Hydraulic FracturingLocations: Worldwide, onshore and offshore


T E C H N O L O G Y

S U M M A R Y

Optimized recovery of valuable oil and

gas resources

Protection of groundwater resources

Fewer wells drilled, resulting in less waste

requiring disposal


Increased well productivity and ultimate recovery

Significant additions to recoverable reserves

Greatly facilitated production from marginal

and mature fields

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C O N T A C T

The CER Corporation. Using theRifle, CO, Test Site to Improve

Fracturing Technology,

apollo.osti.gov/html/fe/cer.html

Diffusion of Advanced

Stimulation Technology in the

Petroleum Industry: A Case

History. Journal of Petroleum

Technology, 3/98.

Dual-Hydraulic-Fracturing

Technique Minimizes Proppant

Convection and Increases

Hydrocarbon Production. Journal

of Petroleum Technology, 3/97.

Ellis, R. An Overview of FracPacks: A Technical Revolution

(Evolution) Process. Journal of

Petroleum Technology, 1/98.

Jennings, A., Jr. Fracturing

FluidsThen and Now. Journal


Longitudinally Fractured

Horizontal Wells Add Value in

Alaska. Journal of Petroleum

Technology, 3/97.

Stewart, Stewart, and Gaona.Fracturing Alliance Improves

Profitability of Lost Hills Field.

Oil & Gas Journal, 11/21/94.

Swift, T., and P. Mladenka.

Technology Tackles Low-

Permeability Sand in South

Texas. Oil & Gas Journal,

9/29/97.

Wolhart, S. New Initiatives in

Hydraulic Fracture Diagnostics.

GasTIPS, Fall 1998.




Increased profits from the once

declining Lost Hills field

Refined fracturing methods and improved quality control havebrought increased productivity and profitability to a field that onceresisted development. The Lost Hills field in California contains anestimated two billion barrels of oil-in-place, but since its discoveryin it has produced only a fraction of its potential. The fieldhas very low permeability and it lacks a strong natural fracture net-

work, which restricts the flow of resources. This makes the field dif-

ficult to produce at acceptable rates without fracture stimulation.

Although hydraulic fracturing began in Lost Hills during the and , completion results were poor because of small prop-pant volumes and inefficient fracture fluids. Between and, Chevron initiated massive hydraulic fracture stimulation.

Although productivity increased significantly, costs were high andthe work was not as profitable as anticipated.

In , Chevron and Schlumberger Dowell formed a partner-ship aimed at improving fracturing efficiency, reducing costs,and increasing productivity. One result is that multiple wells arenow stimulated from fixed equipment locations. Since itsimplementation in late , this central site strategy has beenused to fracture more than wells, using some millionpounds of proppant. The strategy has lowered costs by reducing

personnel, well completion time, and equipment mobilization,while improving environmental management and safetycontrols. Along with fracture design changes, this has reducedoverall fracturing costs by percent since . These effortsplayed a large part in the fields percent production increasebetween and from , barrels to more than, barrels of oil per day.

SPE, 1993





Elena S. Melchert

(202) 586-5095

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]


and gas potential

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High-tech tools that deliver real-time bottomhole data

prevent excessive formation damage and make drillingsignificantly more precise and cost-effective


Measurement-while-drilling

(MWD) systems measure

downhole and formation

parameters to allow more

efficient, safer, and more

accurate drilling. These

measurements can other-

wise be obtained only by

extrapolation from surface

measurements. MWD sys-

tems calculate and transmit

real-time data from the drill

bit to the surface, avoiding

the time-lag between

occurrence and surface

assessment and significantly

improving drilling safety

and efficiency. Without this

analysis of bottomhole con-

ditions, it is sometimes

necessary to abandon a

hole for a new start. MWD

reduces both costs and

environmental impacts

because measurements and

formation evaluation occurbefore formation damage,

alteration, or fluid displace-

ment have occurred. Of par-

ticular use in navigating

hostile drilling environ-

ments, MWD is most fre-

quently used in expensive

exploratory wells, and in

offshore, horizontal, and

highly deviated wells.

More information for

better drilling

MW D T E CH N OLO GYis critical as operatorsseek to reach deeper and far-ther for new hydrocarbonresources. A real-time bit nav-igation and formation evalua-tion aid, MWD uses toolssuch as triaxial magnetome-ters, accelerometers, and pres-

sure sensors to provide vitaldownhole data concerningdirectional measurements,pore pressures, porosity, andvibration. This provides formore effective geosteeringand trajectory control, andsafer rig operations. Novelequipment transmits bottom-hole information to the sur-face by encoding data as aseries of pressure pulses in thewellbores mud column or by

electromagnetic telemetry.Surface sensors and computersystems then decode thetransmitted information andpresent it as real-time data.

In normal drilling environ-ments, MWD is used to keepthe drill bit on course. MWDis also valuable in more chal-lenging drilling environments,

including underbalanced,extended-reach, deviated, andhigh-pressure, high-tempera-ture drilling. In underbal-anced directional drilling,MWD monitors the use ofgas injected to maintain safeoperating pressure. In deviat-ed and horizontal wells,MWD can be used to geolog-ically steer the well for maxi-mum exposure in the reser-voirs most productive zones.

Evaluating the formation

Prior to the spread of MWDsystems in the late , bot-tomhole conditions weremonitored by time-consum-ing analysis of cuttings andgas intrusion, and by after-the-fact wireline steering mea-surement that necessitated fre-quent interruptions for piperemoval. Today, the continu-

ous flow of MWD informa-tion improves formationevaluation efforts as well asdrilling progress. Over succes-sive periods, MWD data canreveal dynamic invasioneffects, yielding informationon hydrocarbon mobility, gas-oil-water contact points, andformation porosity. Futureadvances in MWD technology,such as MWD acousticaliperswith digital signal processing

Measurement-While-DrillingLocations: Worldwide, onshore and offshore


T E C H N O L O G Y

S U M M A R Y

Less formation damage

Reduced possibility of well blowouts and

improved overall rig safety

Reduced volume of drilling waste as fewer

wells drilled overall

Better wellbore control


Improved drilling efficiency and accuracy

Timely formation evaluation

Reduced operating costs and financial risks

Improved rig safety

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Evolving bit technology allows operators to drill wellboresmore quickly and with less environmental impact


Dramatic advances in drill

bit technology have

improved drilling perfor-

mance significantly whilecutting wastes and envi-

ronmental impacts.

Although the choice of bit

represents only 3 percent

of the cost of well con-

struction, bit performance

indirectly affects up to 75

percent of total well cost.

Faster rates of penetration

and greatly extended bit

life, the result of advancesin materials technology,

hydraulic efficiency, cutter

design, and bit stability,

now allow wells to be

drilled more quickly, more

profitably, and with less

environmental impact. The

improvement to an opera-

tors cost-efficiency from

these advances is striking.

Today, selection of the

appropriate bit has

become critical both in

establishing the overall

economics of field devel-

opment and in minimizing

the environmental impacts

of drilling.

The diamond success story

F ROM US E IN ON Epercent of total world-wide drilling in , to anestimated percent in ,diamond drill bits, which usecutters consisting of a thicklayer of tungsten carbide per-meated with bonded dia-mond particles, have beenone of the success stories ofthe last years. Natural dia-monds, synthetic diamonds,

and diamond composites arenow routinely used within

insert-bit cutting structures,and, although originallydeveloped for hard forma-tions, polycrystalline dia-mond compact (PDC) bitshave proved their value insoft- and medium-hard for-mations too. Today, PDC bitsare most applicable in areaswith relatively soft formationsor where drilling is expensive,such as offshore locations andremote wells. In parallel with

PDC development, rollercone bits have also been

improved. TheNational PetroleumCouncil estimatesthat improvementsin drilling efficiencyfrom advances suchas those in bit tech-nology have reducedunderlying drillingcosts by about3 percent annually

over the last years. Asmaterials technology,hydraulics, and bit stabilitycontinue to improve, so willdrilling performance and envi-ronmental protection.

Matching the bit to the

formation

By helping operators choosethe best bit for the job,computerized drill bit opti-mization systems have

improved the way bits arebeing selected and used.These systems match an indi-vidual formation to the mosteffective milled-tooth, tung-sten carbide insert and PDCbit to complete the job for theleast cost per foot. They alsoprescribe other design para-meters such as hole gauge andhydraulic requirements tohelp determine optimalcutting structure.

Modern Drilling BitsLocations: Worldwide, onshore and offshore


T E C H N O L O G Y

S U M M A R Y

Reduced power use and resultant emissions

Less drilling waste

Reduced equipment mobilization and fewer rigs

Less noise pollution

Better wellbore control and less formation

damage


Increased rates of penetration

Fewer drilling trips due to greater bit life

Reduced power consumption

Improved drilling efficiency and hence viability

of marginal resources

Carbide substrate

Carbide

substrate

PDC layer

PDC layer

Carbide cylinder

Carbide stub

PDC wafer

Braze joint

PDC Cutter Components

Source: Petroleum Engineer International, 1993

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C O N T A C T

Bit Design Key to ImprovedPerformance. Journal of


Diamond Enhanced Inserts

Improve Roller-Cone Bits.


Technology, 2/97.

Drill-Bit Solutions for

Operational Constraints. Journal


Lee, M. New Bits Drill Faster,

Cheaper, Better. The American


Locke, S. Advances Reduce TotalDrilling Costs. The American Oil


Mensa-Wilmot, G. New PDC

Cutters Improve Drilling

Efficiency. Oil & Gas Journal,

10/27/97.

New Polycrystalline-Diamond-

Compact-Bit Technology Proves

Cost-Effective. Journal of


Rappold, K. Industry Pushes Useof PDC Bits to Speed Drilling,

Cut Costs. Oil & Gas Journal,

8/14/95.

The Role of Bit Performance in

Drilling Efficiency. Supplement

to Petroleum Engineer

International.




Switching to new drill bits saves time and moneyUsing a specialized bit optimization system, Anadarko Petroleumhas demonstrated significant efficiency improvements. For exam-

ple, drilling time was reduced by to days in Algeria, with sav-ings of, to ,; and a Mississippi project saved days and ,. Ultimately, impacts on the environment wereappreciably lessened.

Petroleum Development Oman found that rates of penetrationdropped from feet per hour to under feet per hour when drillsusing tungsten carbide inserts hit the hard Khuff Formation.Switching to a new generation PDC bit with carbide-supported edgecutters resulted in a new rate of. feet per hour in the Khuff. Theentire section was drilled in one run, at half the cost of the same sec-tion in a similar well. Another well drilled in the comparableZauliayah field resulted in a rate of feet per hour at a cost ofper foot, nearly half the cost of drilling a comparable well in the area

with an earlier-generation bit.

When Chevron switched to new generation polycrystalline bits at itsArrowhead Greyburg field in New Mexico, the rate of penetrationincreased more than percent. Chevron had been experiencingproblems using-cone bits and thermally stabilized diamond bits.Switching to PDC bits with curved cutters significantly increaseddrilling efficiency, while reducing environmental impacts.

Increases in diamond bit drillingIn 1978, approximately 1 percent of the total footage drilled worldwide was drilled

with diamond bits; in 1985, it was approximately 10 percent; by 1997, that figure

was an estimated 25 percent. Also, between 1988 and 1994, advances in PDC

technology increased the average footage drilled by over 260 percent, from

approximately 1,600 feet to 4,200 feet per PDC bit.

100%0%

1978

1985

1997

1%

10%

25%

M E T R I C S





Elena S. Melchert

(202) 586-5095

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]

Source: Rappold, Oil & Gas Journal, 8/14/95

Indian Ocean

Arabian Sea

Somalia

Gulf of Aden

Yemen

Iran Pakistan

India

U.A.E.

Persian

Gulf Gulf of

Oman

Oman

Saudi

Arabia

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New lateral drilling developments provide dramatic returns

for operators, with less waste, smaller footprints, and

increased site protection


Multilateral drilling

creates an interconnected

network of separate, pres-

sure-isolated, and reentry-accessible horizontal or

high-angle wellbores sur-

rounding a single major

wellbore, enabling

drainage of multiple target

zones. In many cases, this

approach can be more

effective than simple hori-

zontal drilling in increas-

ing productivity and

enlarging recoverablereserves. Often multi-

lateral drilling can restore

economic life to an aging

field. It also reduces

drilling and waste disposal

costs. Today, in a wide

variety of drilling environ-

ments, both onshore and

offshore, from the Middle

East to the North Sea

and from the North Slope

to the Austin Chalk, multi-

lateral completions are

providing dramatic returns

for operators.

Multilateral DrillingLocations: Worldwide, onshore and offshore


T E C H N O L O G Y

S U M M A R Y

Fewer drilling sites and footprints

Less drilling fluids and cuttings

Protection of sensitive habitats and wildlife

E N VI R O N M E N T A L B E N E F IT SE C ON O M I C B E NE F I T S

Improved production per platform

Increased productivity per well and greater ulti-

mate recovery efficiency

New life for marginally economic fields in

danger of abandonment

Reduced drilling and waste disposal costs

Reduced field development costs

Improved reservoir drainage and management

More efficient use of platform, facility, and crew

From horizontal to

multilateral branching

wellbores

HO R IZ O NTA L D R IL L-ing provoked a surgeof interest in the as away to contact more oilreserves, penetrating a greatercross-section of the oil-bear-ing rock with a single well-bore and intersecting repeat-edly the fractures that carry

oil to a producing well.Today, declining production,flat prices, and heightenedenvironmental awarenesshave led the exploration andproduction industry to devel-op advanced drilling andcompletion technologies that

permit wells to branch outmultilaterally, in certain casessaving both time and moneycompared to horizontaldrilling. In many cases, suchas deep reservoir production,it is more efficient to create aconnected network than todrill multiple individual hori-zontal wellbores.

Multilateral drilling is ofgreatest value in reservoirsthat:

Have small or isolatedaccumulations inmultiple zones

Accumulate oil above thehighest existing perforations

Have pay zones that arearranged in lens-shapedpockets

Are strongly directional

Contain distinct sets ofnatural fractures

Are vertically segregated,with low transmissibility

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[With advanced re-entry

multilateral technology] we

are seeing the potential to

reduce by half the costs

associated with subsea

developments. In some

cases, this will make what

were previously marginal or

non-economic discoveries

economical.

ALI DAN ES HY

Vice President, Halliburton


C O N T A C T

Boone, L., F. Clausen, T.Birmingham, and N. Schappert.

Horizontal Branches Reach Out

to Drain Reserves: Slim Hole

Laterals Put New Twist on Field

Development. The American Oil


DeLuca, M. Multilateral

Completions on the Verge of

Mainstream. Offshore Magazine,

1/97.

Halliburton Energy Services.

First Subsea Multilateral with

Re-Entry Access. Press Release,

7/21/97.

Halliburton Energy Services.Multilateral Technology (MLT)

Overview.

Taylor, R.W., and R. Russell.

Multilateral Technologies

Increase Operational Efficiencies

in Middle East. Oil & Gas

Journal, 3/16/98.




Norsk demonstrates the future

of offshore drilling

A highly successful offshore project in Norway is showcasing thereduced environmental impacts and increased economic benefits ofmultilateral completions. In March , Norsk Hydro a.s. and

Halliburton Energy Services drilled the worlds first subsea multilat-eral with reentry access in Norsks Troll field. The companies esti-mate that the economic benefits will be percent greater thanthose from fixed platforms. By reducing the systems required toaccess the subsea reservoir, the project cuts both costs and impacton the environment and leads the way for subsequent offshoredrilling operations.

New life for old wells:

pentalateral drilling in the Middle East

Mounting evidence demonstrates that multilaterial drilling canbring new life to old wells. In the Arabian Gulf recently, a signifi-cant reduction in production that may have spelled well closure in

the past was instead the stimulus to drill five lateral branches intonew pay zones. The lateral wells were drilled in only days,reaching some , feet of new producing formations. Since thenew zones consisted of relatively soft limestone layers separatedfrom each other by dolomites, drilling presented few problems.Dramatically increased production rates covered costs in just sixdays. In all, production increased . times as a result of the mul-tilateral completions.





Elena S. Melchert

(202) 586-5095

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]

North

Sea

United

KingdomNetherlands

Germany

Norway

Denmark

Indian Ocean

Arabian Sea

Somalia

Gulf of Aden

Yemen

Iran Pakistan

India

U.A.E.

Persian

Gulf Gulf of

Oman

Oman

Saudi

Arabia

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Technology advances in dynamic positioning expand

opportunities for deepwater drilling with reduced

environmental impact


Recent exploration success-

es in deepwater plays in the

Gulf of Mexico are of crucial

importance in providing avital new domestic

resource. Technological

advances are increasing

operators ability to take

advantage of these finds,

while reducing the dangers

and uncertainty inherent in

deepwater operations.

Without such progress,

much of the Gulfs

resources may remainundeveloped. A major con-

cern for operators is the

safety of deepwater

exploratory operations,

especially as the industry

moves toward depths of

10,000 feet. To ensure

stability and efficiency at

such depths, advanced

dynamic positioning

technology is now being

used. This includes thruster

units and sophisticated

computer and navigation

systems to hold a new

generation of drillships,

floating production, stor-

age, and offloading sys-

tems, and survey vessels on

location without anchors or

mooring lines.

Deepwater opportunities

TH E GULF OF MEXIC OSdeepwater reservoirshave become Americas newfrontier for oil and gas explo-ration. Production potentialfrom proved and unprovedreserves in deepwater areas isestimated to be roughly.billion barrels of oil and .trillion cubic feet of naturalgas. Consequently, drilling in

the Gulfs Outer ContinentalShelf has increased greatlyover the last 10 years. Today,deepwater drilling from per-manent structures and wild-cat wells is at an all-timehigh. In October , arecord temporary andpermanent deepwater rigswere drilling in water depthsgreater than , feet, ascompared to only nine in.

Production from deepwaterwells is increasing too. In, for example, less than percent of the Gulfs total oilproduction was from deepwaterwells. By, over percentof the Gulfs oil productioncame from deepwater wells.Natural gas production fromdeepwater areas in the Gulfhas also increasedfrom lessthan percent of total pro-

duction in to nearlypercent in .

Improving station keeping

Dynamic positioning systemscompensate for the effects ofwind, waves, and current,enabling mobile offshoredrilling units to hold positionover the borehole, maintain-ing within operational limitslateral loads on the drill stemand marine riser. Improved

dynamic positioning systems,in combination withimproved onboard motioncompensation systems, areexpanding the range of waterdepths and environmentalconditions within whichdrilling operations can besafely conducted.

Azimuthing thruster units,often retractable so as to enable

shallow water maneuvers, arethe backbone of the dynamicpositioning system. Ship-basedcomputers and satellite-linkednavigation units control thevessels rudder, propellers, andthrusters using input fromvarious monitoring systems,such as gyrocompass windsensors, real-time differentialglobal positioning systems,micro-wave positioningsystems, underwater sonar

Offshore Drilling

Locations: DeepwaterGulf of Mexico, West Africa, North Sea, Brazil, others


T E C H N O L O G Y

S U M M A R Y

Less disruption to seafloor ecosystem

Reduced environmental impacts due to

increased operational stability

Enhanced deepwater operational safety


Minimized positioning and transit times for

deepwater exploration

Reduced operating costs in deepwater explo-

ration operations

Improved access to deepwater and ultra-deep-

water resources that might otherwise have

remained undeveloped

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Unlike conventional mud-based drilling, air drilling

significantly reduces or eliminates drilling fluid additives

and prevents formation damage


Pneumatic drilling is an

underbalanced drilling

technique in which bore-

holes are drilled using airor other gases as the cir-

culating agent. In certain

cases this air drilling tech-

nique offers the promise

of mudless drilling. By

using nitrogen, air, or

natural gas in place of

oil- or water-based muds,

producers can both elimi-

nate drilling fluids that

need disposal and ensurethat drill cuttings are not

tainted by chemicals or

oil. Although it is suitable

only for certain formation

types and lithologies and

can create potentially

explosive downhole condi-

tionsand is not therefore

likely to become wide-

spreadthis technique is

a very attractive environ-

mental prospect, offering

significant operational

benefits.

Protecting low-pressure

formations and maximizing

production

U N D E R B A L A N CE Ddrilling offers signifi-cant advantages over conven-tional systems in low-pres-sure or pressure-depleted for-mations. Pressure overbal-ances in conventionaldrilling can cause significantfluid filtrate invasion, and

lost circulation in the forma-tion. Expensive completions,decreased productivity, andhigh mud and mud-removalcosts can then plague drillingoperations, but these can beavoided by using underbal-anced conditions. By lower-ing downhole pressure using

a noncondensable gas in thecirculating fluid system,underbalanced pneumaticdrilling can prevent difficul-ties commonly encounteredwhen reservoir pressures arelower than the hydrostaticpressure exerted by tradition-al water-based drilling fluids.Depending on the environ-ment, gas may be used aloneor with water and additives.

When drilling fluid is need-ed for well control, gas ismixed with lightweightdrilling fluids.

In general, pneumaticdrilling is used in maturefields and formations withlow downhole pressures, in

open-hole completions, andin fluid-sensitive formations.It is an important tool indrilling horizontal wells,which must expose a largeamount of reservoir face tobe productive, and haveminimum damage from flu-ids invasion. As horizontaldrilling increases in popular-ity, underbalanced pneumat-ic drilling will become more

widespread, because it canpenetrate the reservoir with-out damaging the formationor its productive capacity.

Air drilling techniques to suit

Air dust drillingis a drytechnique that relies on theannular velocity of air to

Pneumatic DrillingLocations: Worldwide, onshore and offshore


T E C H N O L O G Y

S U M M A R Y

Greatly reduced drilling fluids and chemical-tainted cuttings

Decreased power consumption and emissions

Better wellbore control and less damage to

formations

Fewer workover and stimulation operations

needed

Potential for smaller drilling footprints and less

impact on habitats, wildlife, and cultural

resources


Substantially less fluid and waste requiringdisposal

Increased rates of penetration and longer

drill bit life

Indication and evaluation of productive zones

and more effective geosteering of the well by

monitoring flow of produced fluids

Potential elimination of waste pits gives access

to restricted areas

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C O N T A C T

Baker, L. Underbalanced Drillingwith Air Offers Many Pluses. Oil

& Gas Journal, 6/26/95.

Bennion, D. Underbalanced

Operations Offer Pluses and

Minuses. Oil & Gas Journal,

1/1/96.

Carden, R. Air Drilling Has Some

Pluses for Horizontal Wells. Oil

& Gas Journal, 4/8/91.

A Closed Circulating System for

Air Drilling. Journal of


Downey, R. On-Site GeneratedNitrogen Cuts Costs of

Underbalanced Drilling. Oil &

Gas Journal, 2/24/97.

Elrod, J. Horizontal Air Drilling

Increases Gas Recovery in

Depleted Zone. Oil & Gas

Journal, 6/30/97.

LeBlanc, L. Underbalanced

Drilling Solution for Wells with

Long Exposure. Offshore

Magazine, 8/1/95.

Rusnak, J. Apparatus EliminatesEarthen Pits in Air-Drilling

Operations. Oil & Gas Journal,

8/17/98.

Teichrob, R. Low-Pressure

Reservoir Drilled with Air/N2 in

a Closed System. Oil & Gas

Journal, 3/21/94.




Accessing new supplies in the Carthage field

Selected as the most viable technique to prevent damage to anextremely low-pressure reservoir, pneumatic drilling made historyas the first air-drilled horizontal well in the Carthage field inTexas. Air drilling successfully increased gas recovery fromdepleted zones without wellbore skin damage, which would haverestricted the reservoirs productive flow. Drilled in December, the Pirkle well had by the end of April produced

million cubic feet of gas at a rate of. million cubic feet perday. The well was drilled with compressed nitrogen into theCretaceous Frost A zone at , feet true vertical depth; itproduces through a,-foot lateral well with bottomholepressure of psi. The operation successfully met the economiccriteria of producer OXY USA Inc., which had determined thatthe wells production rate would have to at least double that of astandard vertical well to be economically viable.

transport cuttings. It is

typically employed indrilling dry formations, orwhen any water influx islow enough to be adsorbedby the air stream. If exces-sive water influx precludesits use, air-mist drillingisemployed instead, using anair-injected mud thatreturns to the surface asmist. Sometimesfoam-drillingis required, using astable mixture of water andcompressed air with deter-gent and chemicals. Whenthe water influx is too greatto be removed throughmist or foam, aerated muddrilling, a technique inwhich air is injected intoviscosified fluid or mud inorder to reduce the weightof the fluid column on theformation, combines thebest properties of conven-

tional and air drilling toprovide an effective solution.

A new waste management

technology enables opera-tors to eliminate the earth-en waste pits used to catcheffluent created whiledrilling with an air- or air-mist system. Liquids andsolids in the effluent areseparated and treated, andgases are exhausted. Byeliminating the environ-mental risks associated withpits, drillers can operate inotherwise restricted areas,such as State parks andwithin city limits. Initialfield tests indicate that thistechnology can handle con-tinuous liquid volumes of barrels per hour andsolid volumes of barrelsper hour.





Elena S. Melchert

(202) 586-5095

[email protected]

Trudy A. Transtrum

(202) 586-7253

[email protected]


and gas potential

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S U M M A R Y

Technology advances in less invasive slimhole drillingincreasingly valuable in exploration and production


Improved slimhole drilling

technology brings the twin

advantages of environ-

mental protection and eco-nomical results to oil and

gas exploration and pro-

duction. (For example, a

conventional well drilled

with a 12.25-inch bit and a

5-inch drill pipe becomes a

slimhole when using a

4-inch bit and a 3.7-inch

drill pipe.) Slimhole rigs

are defined as wells in

which at least 90 percentof the hole has been

drilled with a bit six inches

or less in diameter.

Slimhole rigs not only

boast a far smaller foot-

print and less waste gen-

eration than conventional

operations, they can also

reduce operating costs by

up to 50 percent. The tech-

nique is proving a low-

cost, efficient tool with

which to explore new

regions, tap undepleted

zones in maturing fields,

and test deeper zones in

existing fields.

Narrow boreholes prove

highly effective

P OTENTIALLY APPLICABLEto more than percentof all wells drilled, slimholedrilling holds promise forimproving the efficiency andcosts of both exploration andproduction. Although thetechnique was first used inthe oil and gas industry in the, its acceptance has beenhampered until recently by

concerns that smaller bore-holes would limit stimulationopportunities, productionrates, and multiple completions.Advances in technology,coupled with a growingrecord of success, have

dispelled these concerns,making slimhole an increas-ingly attractive option forreservoir development. Today,slimhole drilling is emplo

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