On completion of this module you will be able to:

Understand the main stuck pipe mechanisms causes

Explain the preventive actions to avoid sticking

Indentify the stuck pipe mechanism

Describe the first actions to free the pipe

Solids Induced Packoff

Differential Sticking

Wellbore Geometry

Cause

Occurrence

Rig Site Warnings

Preventative Action

Freeing Guidelines

Hole CleaningUnconsolidated FormationsReactive ShalesNaturally & Induced Over-Pressured ShalesFractured and Faulted FormationsTectonically Stressed FormationsOverburden StressJunk in the HoleGreen Cement and LCM TreatmentCement Blocks

Cuttings

PDC Roller Cone

Cavings

Blocky/Platy

Splintery Angular

Cause:Low annular velocityPoor mud propertiesInsufficient rotation

Occurrence:All the time but critical between 30-60

degrees.

Rig Site Warnings:Increase in Torque and Drag Increase in Pump Pressure / ECD

Preventative Action:Maximize Annular velocity Maximize Pipe Rotation Pumping adequate pillsEnsure circulation times are adequate Optimize mud properties (YP, LSRYP)

HOLE MAX GPM MIN GPM BEST RPM MINSIZE RPM

17½” 900 – 1200 800 gpm, with ROP at 20 120 – 180 120m/hr (65’ / hr)

12¼” 800 – 1100 650-700 gpm, with ROP at 150 – 180 12010-15m/hr (30-50’/ hr)800 gpm, with ROP at 20-30m/hr (65-100’ / hr)

9⅞” 700 – 900 500 gpm, with ROP at 10-20 120 – 150 100m/hr (33-65’ / hr)

8½” 450 – 600 350-400 gpm, with ROP at 70 – 100 6010-20 m/hr (33-65’ / hr)

These are Ideal Parameters and may not be achievable in every condition

Diam

eter

Angl

e

Torq

ue

and

Drag

Mud

Typ

e

Hole H o l e

VERY IMPORTANT ! Define the box size and what it will allow us to do………

Apply a systems approach. Parameters cannot be singled out and optimized separately

Box dimensions determined by various factors (Rig equipment, Solid control equipment, well design, BHA, design, drilling practices and most importantly personnel competency.

Cause:The formation can not be supported by the hydrostatic overbalance as the fluid simply flows into the formation

Occurrence:While drilling shallower unconsolidated formations

Rig Site Warnings:Increase in Torque and DragIncrease in Pump Pressure / ECDFill on bottomShaker blinding

Preventative Actions:Control-drill the suspected zone to allow time for the filter cake to build up.Avoid unnecessary reaming and backreaming Use sweeps to help keep the hole clean Slowdown trip speed across those formations

Cause:Water sensitive shale /clays drilled with

less inhibition than required

Occurrence:Poor shale inhibition (Occurs more often

w/WBM and less often with OBM)The reaction is time dependent, from hours

to days depending on mud and formation interaction

Rig Site Warnings:Increase in LGS, filter cake thickness, PV, YP, MBT Increase in T&D / Pump Pressure / ECDShale Shakers blind off

Preventative Actions:Use inhibitive mud systemPerform wiper trips regularlyMonitor MBT

Barbados Shale Dry SampleBarbados Shale in 10.8 ppg CaCl2 (24 hrs)

Fortune Bay Dry Sample Fortune Bay 24 hrs in Fresh water

Cause:commonly caused by geological phenomena ( under-

compaction, naturally removed overburden and uplift).

Occurrence:Using insufficient MWRemoval of ECD

Rig Site Warnings:Cavings (splintery) at shakersIncrease in T&D / Pump Pressure / ECD / Gas level An increase in ROP

Preventative Actions:Use sufficient mud weightMinimize hole exposureAfter exposing shale, do not reduce MW

Cause:Shale pore pressure becomes charged

by hydrostatic overbalance

Occurrence:After a reduction in MW or a long exposure time

with constant MWHigh ECD (small hole size) / While surgingIn casing “rat hole”

Rig Site Warnings:Cavings at shakersIncrease in T&D / Pump Pressure / Hole fill Ballooning effect

Preventative Actions:Control ECD properly to minimize ballooning and

inducing over pressure to sensitive formationsDo not reduce MW

Cause:Rock near faults can be broken into small or

large pieces, and if lose can fall into the hole and jam the drill string

Occurrence:In tectonically active zonesFractured limestone

Rig Site Warnings:Possible losses or gains (or ballooning)Fault damaged cavings at shakersHole fill on connectionsSticking can be instantaneous

Preventative Actions:Limit the rotary speed and tripping speeds Monitor ECDs

E. Folding and faulting associated with Salt dome diapirism

Cause:Due to the movement of earth’s crust, natural lateral

stresses are present

Occurrence:In mountainous locations / tectonic active zones

Rig Site Warnings:Cavings at shakersIncrease in T&D / Pump Pressure

Preventative Actions:Maintain mud weight and ECD within planned mud

weight windowIf possible drill these formations in smaller hole sizes Plan to case off these formations as quickly as

possible

Cause:The overburden or vertical stress, sV , is usually a

principal stress. MW is insufficient to support the overburden and is not adjusted as hole angle increases.

Occurrence:In deviated wells mainly

Rig Site Warnings:Increase in Torque and DragIncrease in Pump Pressure / ECDFill on bottom

Preventative Actions:Maintain mud weight and ECD within planned

mud weight window

Cause:Down hole equipment failurePoor housekeeping on the rig floorHole cover not being installedInattention

Occurrence:Any time!!

Rig Site Warnings:Sudden erratic torqueInability to drill aheadCirculation not restricted

Preventative Actions:Inspect all handling tools regularly, especially

rig tongs and slips.Practice good housekeeping Install drill pipe wiper

Cause:Circulation attempted with the bottom of the drill string

in soft cement which dehydrates the cement due to differential pressure

Cleaning LCM treatment with insufficient flow rate and high penetration rates.

Occurrence:When using LCM or cement (Dress cement plug)

Rig Site Warnings:Increase in pump pressure leading to inability to circulate Loss of string weightGreen cement in mud returns, discoloration of mud

Preventative Actions:Give cement enough time to set and estimate the TOCStart circulation several joints above the TOC and run

down slowly. Do not rely on WOB to show TOC.Drill out cement with low WOB and high flow rate

Cause:Hard cement chunks fall into the well bore and jam

the drill string

Occurrence:Around the casing shoeOpen hole squeeze plugsKick-off plugs

Rig Site Warnings:Large Cement fragments at the shakersRotation and downward movement may be possible. Erratic torque

Preventative Actions:Limit casing rat hole length to minimize a source

of cement blocks.Slow the trip speed down before the BHA enters

the casing shoe or the plug depth.

Filter cake

Overbalance

pressure Mud

Drill pipe

Sticking Force = DP x A x CDP = Overbalance (kg/cm2)Ph= Hydrostatic Pressure

Pf= Formation Pressure

A = Contact Area (m2)C = Friction Factor

FF WBM = 0.2 - 0.4 FF

OBM = 0.15 - 0.25

Porous and

PermeablePorous andzonePermeable zone

70 kg/cm2 Overbalance (997.5 psi)1) Contact Area (A) = Wall contact x Length of Permeable Formation

= 5 in x 0.0254m/in x 10 m =1.27 m2 (1968.5in2)

2) Sticking Force = 70 kg/cm2x 1.27m2x(100 cm/m)2 x 0.15= 133 Tons=294,500 lbf approx.

Cause:High overbalance applies a differential sticking force to the drill string contact area Drill string contacts a permeable zoneWhen motion stops, static filter cake develops

Occurrence:With a stationary or very slow moving drill stringWhen contact exists between the drill string and the well boreWhen an overbalance is present across a permeable formationIn a thick filter cake or cuttings bed

Rig Site Warnings:Increasing over pull on connections and after surveysFull unrestricted circulationHigh overbalance (losses, MW..)

Porous and Permeable zone

Other Preventative Actions :

Well designOptimize casing setting depths to minimize overbalance

across potential sticking zonesDesign for adequate overbalance for hole stability and well control

MudUse OBM where possible. Keep fluid loss to a minimumUtilize bridging agents such as sized CaCO3 and asphalts/gilsonite Maintain a low concentration of LGS. Keep gels low

Operations

KEEP THE STRING MOVING. Pre-plan to minimize operational downtime that requires static drill string (connections, surveys, minor repairs, etc.)

Consider rotating the drill string during drilling, tripping and connections while BHA is opposite to high risk zones (CAUTION)

Preventative Action :Well bore contact

Minimize BHA length when possibleMaximize BHA stand off. Use spiral drill collars and HWDPs

Porous Rig team awarenessThe rig team should be made aware of the depth ofand

Permeable permeable formations and the estimated overbalance inzone those zones.

Ledges & Doglegs

Under gauge hole

Mobile formation

Stiff Assembly

Key Seating

Cause:Ledges at interface hard/soft formationsToo high doglegs

Occurrence:Hard/soft interbedded layersFaulted/fractured formationsFrequent angle/direction changes

Rig Site Warnings:Sudden erratic over pull or set downProblems are at reoccurring fixed depths

Preventative Actions:Minimize excessive directional changes in the

well bore.Slow trip speeds before BHA enters the

suspected ledge zone or dogleg.Avoid prolonged circulation across soft inter

bedded formations

Cause:Hard abrasive rock wears bit gauge and results in

an under gauge hole

Occurrence:After running a new bitRunning a PDC after a triconeDrilling abrasive formationsAfter coring

Rig Site Warnings:Pulled bit or stabilizers are under gaugeOccurs only when RIHSudden set down weightCirculation not restricted

Preventative Actions:Slow the trip speedGauge all BHA components when RIH and POOH Ream suspected under gauge sections

OVE

RPU

LL!!

Cause:Overburden weight squeezes formation out

because the mud weight is not sufficient

Occurrence:Salt or plastic shale formation

Rig Site Warnings:Over pull when moving up, takes weight

when running inSticking occurs with BHA at mobile formation depth

Preventative Actions:Maintain sufficient mud weight.With mobile salts consider using a slightly under-

saturated mud system to allow a controlled washout

Minimize the open hole exposure time of these formations

Cause:Stiffer BHA is run into a previously drilled hole

and can not negotiate hole angle and directional changes

Occurrence:Where doglegs are presentWith a different BHA and stabilizer design Most likely while tripping in hole

Rig Site Warnings:Erratic over pull / set down and torque

Preventative Actions:Consider running same or similar BHA configurations Slow the trip speed down before the new BHA

enters a problematic zoneConsider reaming tight spots with sufficient flow

rate and rotation

Cause:By the drill pipe rotating against the wellbore wall atthe same point and wearing a groove or “keyseat”

Occurrence:At abrupt changes in angle or directionAfter long drilling hours with no wiper trips in dogleg

section

Rig Site Warnings:Cyclic over pull at tool joint intervals on trips Sudden over-pull when BHA reaches DL depthFree string movement below key seat depth

possible if not already stuck in key seat

Preventative Actions:Minimize dogleg severityPerform reaming and/or wiper trips if a dogleg

is presentConsider running reamers or a key seat wiper if a

key seat is likely to be a problem

Instructions:Answer the questions by circling all the numbers in the row with the correct answerAdd the columnsThe one with the highest total is the sticking mechanism

BackPressure

Back

Pressure

Jar!

Freeing:

Initial Action:1. Establish that Differential Sticking is the mechanism2. Initially circulate at the maximum allowable flow rate.

This may erode the filter cake. In slim hole conditions this might not be possible due to ECD constraints. It may not be effective in directional wells.

3. Slack off the string weight while holding 50% of make-up torque of surface pipe

4. Use an action similar to what would be used with a bumper sub

5. Pick up to just above the up weight and perform step 4 again.

6. Repeat 4. & 5. Increasing to 100% make-up torque Allow sufficient time for hydraulic jars to trip

7. If the string does not come free hold torque in the string and continue jarring with the maximum trip load while preparing the pipe releasing pill

Overbalancepressure

Porous and Permeable zone

Filter cake

Mud

Drill pipe

Filter cakeOverbalance Mud

pressure

Drill pipe

Differentially Work/ YesWork Free ?Stuck Jar Pipe

No

Select alternate Is U TubingmethodNo Spotting Possible?

fluid at rig? Yes

YesYes Is over balance No Prepare U Tube

Mix Spot & Spacer needed forWell control/

U Tubestability

Pump Spot & SpacerNo

U Tube second Time Pipe Free??Pipe Free?? Yes

YesNo

No YesCut pipe/Fish/ Cond MudSidetrack/P&A Pipe Free??

& Drill Ahead

200

100300

0

200

100300

0

Backreaming Bit