Pipe Stuck Prevention

Date : 04/99

Clt : 04-292 Rev : 0 draft

DGEP/DO/FPL/MTH

STUCK PIPE PREVENTIONPage : 1/11

1.1 INTRODUCTION

STUCK PIPE IS NOT INEVITABLE.

More detailed preventive actions are developed according tothe various type of sticking faced; however some basic rulesapply to every sticking hazard:

- Plan ahead: Always know what formations/potential problemsare coming up. Have contingency plans ready in case oftrouble arises ( mud change, application of overpulls,etc…).

- "Listen" to the hole constantly: torque , drag, cuttings,pump pressure are all indicators of hole condition. Recordall information; this will help identifying importanttrends. Change in parameters may indicate hole problems.

- Communicate effectively: Keep the team members regularlyinformed of what the hole is saying; what may seem trivialto someone may be vital for someone else. Ensure holecondition is recorded and handed over at shift change; mostof stuck pipe occurs around shift change.

- Maintain good mud: Keep all mud properties withinspecification, (density, rheology, fluid loss). Analyzereasons for change in any mud properties.

- Keep pipe moving: Whenever possible when in open hole,(reciprocation preferable to rotation).

- Clean the hole as fast as you drill it: Overgauge anddirectional drilling holes require faster circulation toclean them effectively. Always circulate clean beforetripping.

When prevention failed: Take action early to fix stuck pipeproblems. Stuck pipes and hole problems will not curethemselves but will become worse as time goes away. Refer toClt 04-293

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1.2 DIFFERENTIAL STICKING

INDICATION OF DIFFERENTIAL STICKINGDrag Torque Pressure Other

Drilling Possible increase No change No changeConnection Increasing

overpull off slipsNo change

Tripping out Increasingoverpull off slips

Tripping in Increasingoverpull off slips

Back reaming Increasingoverpull off slips

No change No change

Pumping out Increasingoverpull off slips

No change

Shaker trends No changeLogger trends High over balance; permeable formation depth, thickness, permeability

data to estimate sticking potential.Mud trends Increasing mud weight. Increasing PV and low gravity solids, High API

water loss, thick filter cake

The basic prevention is:- to keep a mud weight to the minimum required for hole

stability and well control,- to maintain the fluid loss within the specification,- to minimize the contact length with the well bore:

- minimizing the BHA length- limiting the length of unstabilised drill collar

(i.e., a 12 ¼” string stabilizer inserted in betweendrill collars for 17 ½” drilling)

- reducing the contact area with the well bore withspiraled drill collar,

- Keep the string moving as long as possible, consider torotate the string for connection,

- In zone with high sticking potential, minimize seepage losswith plugging agents,

- Preplan to minimize down time operation that require to staystatic( surveys, minor repairs)

1.3 HOLE PACKING OFF (SETTLED CUTTINGS)

1.3.1. DUE TO INADEQUATE HOLE CLEANING.

Hole cleaning is affected by the following factors:

- Rate of penetration (ROP) determines the volume of cuttings

in the returning mud, (For ERD wells cuttings returns can be

weighed accurately to verify that hole cleaning process is

efficient).

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- Hole instability (further developed in paragraph 1.3.2,

1.3.4) increases the volume of rocks to be removed from the

hole (cavings added to the cuttings),

- Annular velocity lifts the cuttings,

- Mud rheology (gels, YP) suspends and carries cuttings,

- Circulating time allows the transport to the surface,

- Hole angle reduces the ability to clean the hole.

INDICATION OF SETTLED CUTTINGSDrag Torque Pressure Other

Drilling Increasing,erratic Increasing,erratic Increasing Pressure surge,gradual decreasein ROP

Connection Overpull off slips Surge tostartcirculation

Back pressurebefore breakingconnection; backflow

Tripping out Increasing,erratic, overpulloff slips

Swabbing

Tripping in Increasing setdown weight,overpull off slips

Begins with BHAbelow depths of45° angle

Back reaming Overpull offslips, erraticoverpull

Increasing,erratic Increasing Surge to startcirculation,stringpistonning, lossof fluid possible

Pumping out Overpull offslips, Increasing,erratic

Increasing Surge to startcirculation,stringpistonning, lossof fluid possible

Shakertrends

Low cuttings return rate for ROP; Erratic cuttings return, no cuttingreturning while drilling, high cuttings return on fine shaker screens,high solids discharge rate at desilter and mud cleaner.

Loggertrends

Rounded ,re grounded cuttings

Mud trends Increasing plastic viscosity and yield point, increasing low gravitysolid, increasing mud weight.

The basic prevention is:- To maintain the required mud properties- Circulate at maximum recommended flow rate for hole size,

refer to hole clean guide lines table

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Minimum flow rate versus hole size and hole angleHole size 26” 17 ½” – 16” 12 ¼” 8 ½”Angle interval0° - 45° 2600 LPM 1900 LPM 1500 LPM 1100 LPM45° - 60° 4700 LPM 3600 LPM 2500 LPM 1700 LPM60°+ 4200 LPM 2800 LPM 1900 LPM

- Place more emphasis on annular velocity when designing thehydraulics for 12 ¼” and larger hole size; on floaterconsider using the riser booster line when drilling the 8 ½”and smaller section

- Do not allow the ROP to exceed the ability to clean the hole- Record torque and drag trends for symptoms of inadequate

hole cleaning- Consider wiper trip after drilling long section with down

hole motor- Wipe hole at full circulation rate before connection- Maximize string motion when circulating the hole clean; use

maximum practical RPM, raise string slowly and slack off ata safe but fast rate

- Consider pumping high-vis. sweep in low angle wells and low-vis./high density sweep in high angle wells (the borderbetween low and high angle well being around 45°)

- Do not stop pumping until all sweeps return to surface- Circulate until hole is clean. If the last sweep brings up

excessive amount of cuttings, continue with hole cleaningoperation. Several circulations may be necessary.

- Calculate the minimum circulation to clean the hole, referto table for minimum circulation factor

Minimum Circulating Strokes Factor (CSF) to clean holeHole size 26” 17 ½” – 16” 12 ¼” 8 ½”Angle interval0° - 45° 2 1.7 1.4 1.445° - 60° 2.5 2.5 1.8 1.660°+ 3 2 1.7

Procedure:- Separate the hole into section by hole angle from

intervals above- Multiply each hole section length (sect.lth) by the

CSF and sum the corrected length- Calculate the minimum circulating strokes to clean

the hole.

Minimum Circ. Strokes = Corrected Length x Bottom up stksMeasured depth

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1.3.2. UNCONSOLIDATED FORMATION.

INDICATION OF UNCONSOLIDATED FORMATIONDrag Torque Pressure Other

Drilling Increasing ,erratic Increasing,erratic Increasing Pressure surgesConnection Overpull off slips Surge to

startcirculation

Hole fill

Tripping out Increasing ,erratic,Overpull off slips.

Swabbing

Tripping in Increasing setdown weight

Begin at depth ofproblem formation,hole fill on bottom

Back reaming Overpull off slips Increasing,erratic Increasing Surge to startcirculation, Stringpistoning, Loss offluid possible.

Pumping out Increasing ,erratic,Overpull off slips

Increasing Surge to startcirculation, Stringpistoning, Loss offluid possible

Shakertrends

Large volume of sand over shakers. Sand trap and desander overloaded

Loggertrends

Large quantity of sand in samples, Prognosed unconsolidated formation.

Mud trends Increase in mud weight and PV. High % sand content

The basic prevention is:- Provide an effective filter cake for the hydrostatic

overbalance to “push against” and stabilize the formation,- If possible, avoid excessive circulating time with the BHA

opposite to unconsolidated formation to reduce hydraulicerosion,

- Slow down tripping speed when the BHA is opposite tounconsolidated formation to avoid mechanical damage,

- Start and stop the drill string slowly to avoid pressuresurges to unconsolidated formations,

- Control-drill the suspected zone to allow time for filtercake to build up, to minimize annulus loading and tominimize annulus friction pressure,

- Use sweeps to help keeping the hole clean,- Be prepared for shaker, desander, desilter overloads,- Minimize seepage loss with fine LCM (Lost Circulating

Material) through these intervals.

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1.3.3. FRACTURED – FAULTED FORMATION

INDICATION OF FRACTURED - FAULTED FORMATIONDrag Torque Pressure Other

Drilling Sudden, increasing,erratic

Sudden, erratic No change

Connection Overpull off slips No change Hole fillTripping out Increasing, erratic,

Overpull off slipsTripping in Increasing, erratic

set down weightBridging at depthof formationproblem, hole fillon bottom

Back reaming Overpull off slips,Increasing, erratic

Increasing, erratic No change Drag decrease whenpumping

Pumping out Overpull off slips,Increasing, erratic

No change Drag decrease whenpumping

Shaker trends Blocky or angular rock fragmentsLogger trends Same as shaker trends, possible offset well data clues. Prognosed

fractured formationMud trends No change

Note: With the fractured formations, maintaining goodquality filter cake can help to support the formationin some cases. Generally, fractured formations requiretime to stabilize. Prior to this, the problem must becontrolled with adequate mud properties, sweeps andsufficient circulation time to keep the hole clean.

The basic prevention is to:- Circulate the hole before drilling ahead,- Restrict tripping speed when BHA is opposite to fractured

formation, and fault zones,- Start and stop drill string slowly to avoid pressure surges

to the well bore- Anticipate reaming during trips. Ream fractured zone

cautiously- Be prepared for potential lost circulation when drilling

fractured formations- Problem likely to stabilize with time

1.3.4. MECHANICALLY STRESSED FORMATION.

This chapter considers the prevention for all thevarious mechanically stressed formation (Refer tochapter # 1.3.4 of Clt 04-291) and that are overpressured formation (naturally over pressured or undercompacted shale and artificially over pressured shale),

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tectonically stressed formation, overburden stressedformation.

INDICATION OF MECHANICALLY STRESSED FORMATIONDrag Torque Pressure Other

Drilling Increasing, erratic Increasing,erratic Increasing Increase ROPfollowed bygradual decrease,pressure surge

Connection Overpull off slips Surge to startcirculation

Hole fill

Trippingout

Increasing, erraticOverpull off slips

Swabbing

Trippingin

Increase set downweight

Bridges at depthof problemformation. Holefill on bottom

Backreaming

Over pull off slips Increasing,erratic Increasing Surge to startcirculation,string pistoning,loss of fluidpossible

Pumpingout

Increasing, erratic,Over pull off slips

Increasing Surge to startcirculation,string pistoning,loss of fluidpossible

Shakertrends

Large splintery or blocky shale cavings. Large volume of cavings

Loggertrends

Large quantity of splintery or blocky cavings with striations. Possibleindications of increase in formation pressure. Prognosed mechanicallystressed shale.

Mud trends Possible slight increase in mud weight and PV.

The basic prevention is:- Consider offset well data and/or computer models which

simulate failure limits when planning mug weight for holesection,

- Mud weight must increase with hole angle and TVD specific tothe area to maintain hole stability,

- Exploration wells, consult the mud logger for changes information pressure. Increase the mud weight cautiously untilsymptoms are no longer observed.

- If possible, increase the mud weight slowly (1 to 2 pointsper day) until the desired mud weight for a given depth isreached. This will maintain an overbalance againsthydrostatically sensitive shales.

- Avoid mud weight reduction after 1+ day exposure tohydrostatically sensitive shale. If mud weight reduction is

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necessary, reduce mud weight gradually over a time frameequal to the time of exposure.

- Follow up trends of cuttings volume, size and shape onshakers

- Maintain mud properties to ensure hole cleaning- Use sweeps to help cleaning the hole- Stop drilling until the hole is circulated clean- Minimize open hole exposure time- Plan contingency to case off the problem

1.3.5. REACTIVE FORMATION

INDICATION OF DIFFERENTIAL STICKINGDrag Torque Pressure Other

Drilling Increasing, smooth Increasing,smooth Increasing Pressure surge ,mud loss possibledecreasing ROP

Connection Overpull off slips Surge to startcirculation

Tripping out Increasing, smooth,overpull off slips

Swabbing

Tripping in Increase set downweight, Overpulloff slips

Begins at depthof problemformation; mudloss possible

Back reaming Overpull off slips Increasing,smooth

Increasing Surge to startcirculation, mudloss possible,string pistoning

Pumping out Increasing, smoothOverpull off slips

Increasing Surge to startcirculation, mudloss possible,string pistoning

Shakertrends

Soft clay, wet “mushy” clay (Gumbo). Flow line plugging

Loggertrends

Large quantity of hydrated shale cuttings. High value on shale swellingtest.

Mud trends High funnel (or marsh) viscosity and YP. Increasing PV and low gravitysolids. Increasing mud weight. Increasing CEC. Low level or no inhibition

in mud system.

The basic prevention is:- Addition of various salts (potassium, sodium, calcium, etc)

to reduce the chemical attraction of water to the shale- Addition of various encapsulation (coating) polymers (HEC,

PHPA, etc) to reduce the water contact with the shale- Use of oil base mud and synthetic base mud to exclude water

contact with the shale- Minimize the time the open hole is exposed

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- Plan regular wiper trips based on time, footage drilled orwarning signs of reactive shale

- Maintain required mud properties- Ensure adequate hydraulics for bit and hole cleaning- Minimize low gravity solids (LGS)- Be prepared for high swab/surge pressures

1.4 MECHANICAL AND WELL BORE GEOMETRY.This chapter considers the prevention for all thevarious mechanical and well bore geometry linked typeof sticking (Refer to chapter # 1.4 of Clt 04-291) andthat are key seat, under gauge hole, ledges and doglegs, BHA changes, mobile formation and under gaugehole.

The indications of well bore geometry problem areobserved only when BHA is moving in the hole sectionwith geometry problem.

INDICATION OF MECHANICAL AND WELL BORE GEOMETRY PROBLEMDrag Torque Pressure Other

Drilling Increasing, erratic Increasing,erratic No change Momentaryoverpull & setdown

Connection Increasing, erratic No change Momentaryoverpull & setdown

Trippingout

Increasing, erraticoverpull with BHA atzone problem

Momentaryoverpull & setdown

Tripping in Increasing, erraticset down weight

Begins at depthof problemsection

Backreaming

Erratic Increasing,erratic No change Momentaryoverpull

Pumping out Increasing, erraticoverpull

No change Momentaryoverpull

Shakertrends

No change

Loggertrends

No change

Mud trends No change

The basic prevention is:- Optimize BHA design (run only what is required ) and when

possible, minimize BHA stiffness- Plan a reaming trip if the new BHA is lock up and/or hole

geometry problem is suspected- Slow down trip speed before BHA enters kick off or doglegs

depth, micro doglegs and/or ledges, mobile formations

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- Minimize dog leg severity. Minimize rotating hours below asharp dog leg without a wiper or reaming trip

- Consider using key seat wipers or drill string reamers if akey seat is suspected

- Limit the length of casing rathole to avoid key seating thebottom of the casing. Do not start angle build up operationstoo close to the shoe

- Minimize sharp, frequent well bore course changes- Avoid prolonged circulation in suspected micro dog leg

section to prevent hole wash out and forming ledges- With mobile salts consider using slightly undersaturated mud

system to allow a controlled wash out. If necessary ,increase the mud weight to help slow down salt intrusion

- Consider drilling mobile salts with eccentric PDC bits. Planregular wiper trips to keep the hole section open

- Use hard faced stabilizers and select bits with extra gaugeprotection if abrasive formation are drilled

- Gauge the old bit and stabilizers as well as the bit andstabilizer picked up

- Begin reaming 1 stand above cored section. As standardpractice, ream the last stand to bottom on all trips.

1.4.1. JUNK IN HOLE.The basic prevention is:

- Inspect slips and tong dies regularly- Use good house-keeping practices on the rig floor- Install drill string wiper as soon as possible

keep hole covered when out of the hole- Maintain rig floor equipment in good operating

condition

1.4.2. CEMENT BLOCK

The basic prevention is:- Limit casing rate hole to minimize a source of cement

blocks- Several squeeze jobs at the casing shoe increases the

potential for cement blocks- Allow sufficient cement curing time before drilling

ahead- Ream casing rat hole and open hole cement plugs

slowly and thoroughly before drilling ahead- Maintain sufficient distance between the paths of

platform wells to reduce the possibility of cementblocks

- Deduce tripping speed when BHA is entering the casingshoe or opposite open hole cement plugs

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- Start and stop the drilling string slowly to avoidpressure surges to the wellbore

1.4.3. GREEN CEMENT

The basic prevention is:- Know the calculated top of cement before tripping in

hole- Do not rely on the weight indicator to find the top

of cement- Begin washing down 5 stands above the theoretical top

of cement- If set down weight is observed when tripping in hole

after cement operation, pull out at least two standsbefore starting circulation

- Pre-treat the mud system prior drilling out cement- Verify cement compressive strength before drilling

out- Control rate of penetration when cleaning out soft

cement

1.5 ADDITIONAL WAY OF GETTING STUCK.

- Liner hanger, packer, whipstock premature setting.The basic prevention is:- Control running speed in order to reduce surge

pressure,- Land the string on slips and pick up the string off

slips smoothly to reduce mechanical shock extraprecaution are to be taken close to surface whendrill string stretch is reduced,

- When circulation is required to run the liner startcirculation slowly until confirmation of freecirculation is achieved keeping a “safety margin”below setting pressure.

- Junk on sea bed hidden below cuttings from surroundingwells.

- Allow time to inspect and clean sea bed before drillahead,

- Perform a detailed inspection of sea bed after half ameter drilled and crater is formed with thecirculation.

Pipe Stuck Prevention

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