Work Over

Workover

Workover Workover

1

Workover Course Aim

•• To To introduce introduce the the candidate candidate to to the the various various methods methods of of killing killing aa production production well well safely safely with withminimum minimumformation formationdamage. damage.

2

Workover Course Objectives

At Atthe theend endof ofthe thecourse coursethe thecandidate candidateshould shouldbe beable ableto: to: •• State State the the various various reasons reasons for for killing killing aa producing producing well well prior priortotoworkover. workover. •• Identify Identify the the common common methods methods of of killing killing aa producing producing well. well. •• Identify Identify the the most most appropriate appropriate method method of of killing killing aa producing producingwell. well.

•• List List the the well well and and reservoir reservoir parameters, parameters, and and the the various variousstages stagesnecessary necessarytotogenerate generateaawell wellkill killplan. plan. •• •• •• ••

Perform Performhydrostatic hydrostaticcalculations. calculations. Construct Constructaawell wellkill killgraph. graph. Generate Generateaaprocedure procedurefor forkilling killingaaproduction productionwell. well. Knowledgeably Knowledgeably discuss discuss problems problems inin production production well well kill killand andidentify identifyappropriate appropriatesolutions. solutions. 3

Workover Reasons for Workover

The Themain mainreasons reasonsfor forperforming performingaaworkover workoverare: are: •• Increase Increase production production by by bringing bringing other other productive productivezones zoneson onstream. stream. •• Eliminate Eliminateexcessive excessivewater wateror orgas gasproduction. production. •• Maintain Maintain control control of of oil, oil, water, water, and and gas gas in in various variouszones zonesor orlayers layersin instratified stratifiedreservoirs. reservoirs. •• Remove Remove obstructions obstructions to to flow flow e.g. e.g. blockage blockage with withsand, sand,wax, wax,or orasphaltene. asphaltene. •• Enhance Enhanceproduction productionthrough throughwell wellstimulation. stimulation. •• Repair Repair mechanical mechanical failure failure of of the the completion completion components. components.

4

Workover Reasons for Workover

Some Somemechanical mechanicalfailures failuresof ofthe thecompletion completioncan canbe be repaired repairedby byWireline Wirelineor orCoiled CoiledTubing Tubingtechniques. techniques.

Failures Failuresthat thatrequire requireaafull fullworkover workoverprogram programare: are: ••TRSV TRSVfailure failureor orleak. leak. ••Casing, Casing,Tubing, Tubing,or orPacker Packerleak. leak. ••Casing Casingor orTubing Tubingcollapse. collapse. ••Cement Cementfailure. failure. ••Gas Gaslift liftsystem systemfailure failureor orinefficiency. inefficiency. ••ESP ESPor orHydraulic HydraulicPump Pumpfailure. failure. ••Recovery Recovery of of Fish Fish unable unable to to be be recovered recovered by by conventional conventionalmethods. methods. 5

Workover Definition of Barrier

Define Define the the term term “Well “Well Barrier”. Barrier”.

6

Workover Well Barriers

Closed Barriers Production Side

Annulus Side

Wireline Stuffing Box/Riser Envelope

Packer-Tubing System

Grease Injection Head/Riser Envelope

Tubing Hanger – Tubing Head Spool

Coiled Tubing Strippers/Riser Envelope Coiled Tubing Check Valves Snubbing Strippers/Riser Envelope Snubbing String Check Valves

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Workover Well Barriers

Closeable Barriers Production Side

Annulus Side

Xmas Tree Valves

Casing Head Spool Outlet valves

BOP Rams

Tubing Hanger Outlet Valves

Annular Preventers Shear-Seal Valves Sub-Surface Safety Valves (?????)

Annulus Safety Valves (?????)

8

Workover Well Barriers

Additional Barriers Production Side

Annulus Side

Wireline Plugs Tubing Hanger Plugs Packer Plugs Bridge Plugs Cement Plugs Ice Plugs

Ice Plugs

Additional Additional downhole downhole barriers barriers may may be be installed installed either either as as aa backup backup to to aa failed failed mechanical mechanical barrier barrier or or for for the the removal removal of of the theXmas XmasTree. Tree. 9

Workover Additional Barrier

10

Workover Additional Barrier

11

Workover Additional Barrier

12

Workover Barrier Philosophy

During During well well operations operations when when surface surface primary primary pressure pressure control control equipment equipment (Xmas (Xmas Tree, Tree, BOPs, BOPs, LMV LMV repairs) repairs) isis to to be be removed removed itit will will be be Operating Operating Company’s Company’s policy policy to to isolate isolate the the reservoir reservoir or or formation formation with with atat least least two two independently independentlytested testedbarriers. barriers. Where Wherepossible possiblemore morethan thantwo twobarriers barriers are arepreferred. preferred. The Thesame samepolicy policywill willapply applyto toboth boththe the tubing tubingand andthe theannulus. annulus. More Morethan thanone onebarrier barrierof ofeach eachtype typeisisacceptable. acceptable. At Atleast leastone onebarrier barrierbelow belowthe thesea seabed. bed. 13

Workover Barrier Philosophy

Barriers Barriers •• Unperforated, Unperforated,cemented cementedand andpressure pressuretested testedcasing. casing. •• Unperforated Unperforatedcemented cementedand andtested testedliner linerwith withliner linerlap laptested. tested. •• Wireline Wirelineplug plugintegrity integritytested testedusing usingwell wellpressure pressurefrom frombelow below ororpressure pressuretested testedfrom fromabove. above. •• Permanent Permanent oror retrievable retrievable bridge bridge plug plug integrity integrity tested tested using using well wellpressure pressurefrom frombelow belowororpressure pressuretested testedfrom fromabove. above. •• Cement Cementplug plugverified verifiedby bypressure pressureororintegrity integritytesting. testing. •• Pressure Pressuretested testedtubing tubinghanger hangerseals seals(annulus (annulusbarrier). barrier). •• Pressure Pressure tested tested packer/PBR packer/PBR seals seals and and tubing tubing string string (annulus (annulus barrier). barrier). •• Kill Killweight weightfluid fluidwith withwell wellmonitored, monitored,confirmed confirmedtotobe befull fullofof fluid, fluid,and andstatic. static. Possible PossibleAdditional AdditionalBarriers Barriers •• Newly Newly integrity integrity tested tested SCSSV SCSSV which which will will remain remain closed closed throughout. throughout. •• BPV. BPV. •• Integrity Integritytested testedannulus annulussafety safetyvalve valve(annulus (annulusbarrier). barrier). 14

Workover Barrier Philosophy

During Duringwell welloperations operationswhen whenpart partof ofthe the surface surface pressure pressure control control equipment equipment isis temporarily temporarily removed removed (e.g. (e.g. wireline wireline stuffing stuffingbox, box,coiled coiledtubing tubingstuffing stuffingbox, box, braided braided line line grease grease tubes) tubes) atat least least two two barriers barriers will will be be in in place place or or one one barrier barrier and and the the facility facility for for closure closure of of an an additional additional containment containment device device in in the the event eventof ofan anemergency. emergency. Barriers Barrierswill willbe beintegrity integritytested testedbefore beforeremoval removalof of any anyequipment. equipment. On OnSub-Sea Sub-SeaWells, Wells,the thefacility facilitymust mustexist existto tobleed bleed off offsub-sea sub-seariser riserpressure pressurebelow belowaasurface surfacebarrier barrier in inthe theevent eventof ofan anemergency, emergency,after afterclosure closureof ofaa sub-sea sub-seavalve. valve. 15

Workover Barrier Philosophy

Barriers Barriers (in (in addition addition toto relevant relevant barriers barriers specified specified previously) previously) •• Closed Closedwireline wirelineBOP BOPrams. rams. •• Closed Closedcoiled coiledtubing tubingBOP BOPrams. rams. •• Double Double coiled coiled tubing tubing check check valves valves previously previously pressure pressure tested. tested. •• Closed Closeddrilling drillingBOP BOPrams. rams. •• Closed Closedshear-seal shear-sealBOPs. BOPs. Possible PossibleContainment ContainmentDevices Devices •• Cutting CuttingXmas XmasTree Treefor forwireline. wireline. •• Cutting CuttingLRP LRPvalve valvefor forwireline wirelineor orcoiled coiledtubing tubing(sub-sea (sub-sea operations). operations). •• Coiled Coiled Tubing TubingBOPs. BOPs. •• Shear ShearSeal SealBOPs. BOPs. •• Drilling DrillingBOPs. BOPs. •• Wireline WirelineBOPs BOPs(extra (extraset). set).

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Workover Testing Barriers

All Alldevices deviceswhich whichremain remainin inplace placeduring during well welloperations operationsand andwhich whichmay maythen thenbe beused used as asbarriers barriersor orcontainment containmentdevices devices(e.g. (e.g. drilling drillingBOPs, BOPs,wireline wirelineBOPs) BOPs)will willbe be pressure pressuretested testedbefore beforeuse useas asdirected directedby by Operating OperatingCompany CompanyPhilosophy. Philosophy.

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Workover Testing Barriers

The The lowermost lowermost mechanical mechanical barrier barrier in in aa live live well well will will always always be be integrity integrity tested tested against against the thewell wellpressure pressureititisisdesigned designedto tohold holdback. back. Testing Testing under under these these circumstances circumstances will will be be to to bleed bleed off off the the pressure pressure in in the the tubing tubing and and then then monitor monitorfor forpressure pressurebuild buildup upfor for30 30minutes. minutes.

This This lowermost lowermost barrier barrier may may also also be be tested tested “from “from above” above” to to some some pressure pressure above above the the wellbore wellborepressure pressureunderneath. underneath.

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Workover Testing Barriers

The Thenext nextbarrier barriershould shouldbe betested testedfrom fromabove above to to avoid avoid trapping trapping pressure pressure underneath underneath with with no nomeans meansof ofbleeding bleedingoff. off.

Note: Note: Pressure Pressure testing testing Pump Pump Open Open Plugs Plugs from from above above may may be be limited limited by by the the shear shear pin pin rating. rating. Note: Note: Pressure Pressure testing testing may may also also be be limited limited by by the the pressure pressure rating rating of of aa wireline wireline lock lock mandrel mandrelto topressure pressurefrom fromabove. above. 19

Workover Workover

AA typical typical completion completion string string has has many many components components and and sometimes sometimes isis designed designed with with an an incomplete incomplete knowledge knowledge of of the the likely likely conditions conditions for for the the full full life life of ofthe thewell. well. Equipment Equipment may may fail fail for for aa number number of of reasons reasons including: including: ••Effects Effectsof ofpressure. pressure. ••Effects Effectsof ofthermal thermalstress. stress. ••Applied Appliedand andinduced inducedmechanical mechanicalloading. loading. ••Corrosion Corrosionfailure failure(O (O22, ,CO CO22, ,HH22S, S,Acids). Acids). ••Erosion. Erosion.

ItItisisalso alsoimportant importanttotodistinguish distinguishtwo twotypes typesofoffailure: failure: •• Catastrophic Catastrophic failure failure implying implying aa safety safety concern, concern, e.g. e.g. aa tubing tubing leak. leak. •• Inability Inability toto function function with with no no immediate immediate safety safety concerns, concerns, e.g. e.g. gas gaslift liftvalve valvefailure. failure.

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Workover Workover

Failure Failure of of completion completion equipment equipment may may dictate dictate two two courses coursesof ofaction: action: 1) 1)Repair Repairor orremoval removaland andreplacement. replacement. 2) 2) Abandon Abandon the the well well inin cases cases where where due due toto safety safety implications implicationsthe thewell wellisisnot notsalvageable. salvageable.

The The consequences consequences of of aa component component failure failure depends depends upon uponits itsintegration integrationwith withthe thecompletion completionstring stringand andits its replacement replacementmay mayrequire: require: ••Removal Removaland andreplacement replacementby bymeans meansof ofwireline wirelineor or

coiled coiledtubing tubingwithout withouthaving havingtotokill killthe thewell. well.

••Removal Removaland andreplacement replacementof ofthe theXmas XmasTree. Tree. ••Partial Partialor orfull fullremoval removaland andreplacement replacementof ofthe the completion completionstring. string. ••Other Otherremedial remedialwork. work.

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Workover Workover

ItIt may may not not always always be be possible, possible, or or desireable, desireable, toto perform performaaworkover workoverimmediately, immediately,ififfor forexample, example,the the means meansare arenot notreadily readilyavailable. available.In Inthis thiscase casethe thewell well may maybe: be: ••Shut Shutin, in,ififthere thereisisno nosafety safetyproblem; problem;e.g. e.g.this thismay may

be bethe thecase caseof ofhigh highwater watercut. cut.

••Temporarily Temporarilysuspended, suspended,ififthere thereisisaasafety safetyproblem, problem, such such as as aa tubing tubing leak. leak. This This involves involves installing installing the the required required number number of of fluid fluid and and mechanical mechanical barriers barriers so so that thatthe thewell wellisisrendered renderedsafe. safe. ••Abandoned, Abandoned,ififthe theproblem problemisisso sosevere severethat thatititisisnot not safe safeor oreconomical economicaltotoperform performaaworkover. workover.This Thismay may occur occur ifif there there are are major major well well performance performance problems problems or or irretrievable irretrievable junk junk inin the the well. well. In In this this case case permanent permanent barriers barriers such such as as cement cement plugs plugs will will be be placed placedininthe thewell. well.

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Workover Workover Programs

Typical TypicalWorkover WorkoverProgram ProgramContents Contents 1) 1)Well Wellhistory. history. 2) 2)Current Currentstatus statusof ofthe thewell. well. 3) 3)Completion Completiondetails. details. 4) 4)Proposed Proposedworkover workoverprocedure, procedure,including: including: ••Well WellKill. Kill. ••Installation Installationof ofbarriers. barriers. ••Removal Removalof ofXmas XmasTree Treeand andcompletion. completion. ••Installation Installationof ofBOPs. BOPs. ••Cleaning Cleaningthe thewell. well. ••Running Runningnew newcompletion. completion. ••Removing Removingthe theBOPs. BOPs. ••Re-Installing Re-Installingthe theXmas XmasTree. Tree. 23

Workover Workover Programs

From Fromaawell wellcontrol controlperspective perspectivewe wewould wouldwant wanttoto have havespecific specificinformation informationon onthe thefollowing: following:

Information

Reason

Pore pressure of exposed formations

Kill fluid requirements

Fracture pressure of the exposed formations

Bullheading Requirements

Permeability of exposed formations

Kill fluid specifications

Accessibility of tailpipe landing nipples

Barriers considerations

Integrity of packer and tubing hanger

Procedures to control the well

Current wellhead annuli Procedures to control pressure info the well Hydrate formation

Procedures to control the well

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Workover Workover Programs

From From an an operational operational point point of of view view the the following followingshould shouldbe beconsidered: considered: ••Disposal Disposalof ofcontaminants. contaminants. ••Prevalence/likelihood Prevalence/likelihoodof ofHH22SSand andLSA LSAscale. scale. ••Personnel Personnelprotection. protection. All Allpressure pressurecontrol controlequipment, equipment,i.e. i.e.risers, risers,BOPs, BOPs, etc etcshould: should: ••Be Berated ratedtotoatatleast leastthe themaximum maximumanticipated anticipated surface surfacepressure. pressure. ••Be Besuited suitedtotothe theworking workingenvironment. environment. ••Allow Allowpassage passageof ofall alltoolstrings. toolstrings.

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Workover Well Control Problems During Workover

The The following following are are typical typical causes causes of of well well control controlproblems problemsduring duringworkover. workover. 1) 1) Different Different workover workover philosophies philosophies within within the the same same company company for for different different fields fields can can lead lead toto subtle subtle changes changes inin procedures, procedures, which which inin turn turn can can lead leadtotoerrors. errors. 2) 2) In In some some cases cases there there isis no no test test of of mechanical mechanical barriers barriersfrom frombelow belowthe thebarrier. barrier. 3) 3) Attempting Attempting toto remove remove aa toolstring toolstring from from aa well well having having insufficient insufficient length length or or riser riser toto isolate isolate the the formation formationtotodepressurise depressurisethe thesystem. system. 4) 4)Brine Brinedensities densitiescan canbe beaffected affectedconsiderably considerablyby by downhole downhole pressures pressures and and temperatures; temperatures; this this isis particularly particularly hazardous hazardous where where aa low low overbalance overbalance margin marginexists. exists.

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Workover Workover Example

Object Object--to toremove removeaapermanent permanentpacker packer from fromaawell well

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Workover Normal Production

BARRIER ENVELOPE IN PLACE • Casing • Packer • Tubing • Hanger • Xmas Tree

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Workover Well Killed and Barriers In Place for Tree Removal

WELL CONTROL CONSIDERATIONS • Check for gas migration • Check annulus dead • Cause of surface pressure, thermal effects or well not dead • Do not exceed tubing or csg specs

BARRIERS IN PLACE • Kill wt brine in tubing and annulus • Plug in tailpipe • BPV in tubing hanger

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Workover Tree Removal, BOP Installed

BARRIERS IN PLACE • Kill wt brine in tubing and annulus • Plug in tailpipe • BPV in tubing hanger

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Workover Prepare to Pull Tubing Plugs removed Tubing hanger lockdown Bolts removed

WELL CONTROL CONSIDERATIONS • Check for trapped pressure before removing tbg hanger lockdown bolts • Consider the SCSSV • Make final checks for annulus pressure • Enough kill wt material on board

BARRIERS IN PLACE • Kill wt brine in tubing and annulus

WHILST PULLING • Perform regular flow checks • Keep the hole full • Trapped pressure

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Workover Tubing Removed, Wearbushing Installed

WELL CONTROL CONSIDERATIONS • Perform regular flow checks • Monitor hole fill on trip tank • Minimise ‘time on the bank’

BARRIERS IN PLACE • Kill wt brine

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Workover Milling the Packer

WELL CONTROL CONSIDERATIONS • Keep accurate trip record • Gains or losses after packer broken through • Surging whilst RIH with mill • Swabbing whilst POOH • Run wearbushing prior to RIH with mill

BARRIERS IN PLACE • Kill wt brine in tubing

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Workover Running New Completion RU wireline on THROT Install plug in tailpipe Set packer Test tubing Set hanger Test annulus between packer and hanger

WELL CONTROL CONSIDERATIONS WHILST RUNNING TUBING • Perform regular flow checks • Keep the hole full • Surging – RIH slowly • Check tubing burst pressure before testing • Test hanger seal integrity

BARRIERS IN PLACE WHEN RUNNING TUBING • Kill wt brine in tubing and annulus

BEFORE RUNNING • Consider the SCSSV • Enough kill wt material on board

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Workover Plugs Run Prior to Nipple Down BOP

WELL CONTROL CONSIDERATIONS PRIOR TO ND BOP • Leak-off test tubing • Check annulus pressures

BARRIERS IN PLACE • Kill wt brine in tubing and annulus • Plug in tailpipe • BPV in tubing hanger

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Workover BOP Removed and Tree Replaced

RU wireline, pull plugs Return well to production

BARRIERS IN PLACE • Kill wt brine in tubing and annulus • Plug in tailpipe • BPV in tubing hanger

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Workover Sub-Sea Well Normal Production

BARRIER ENVELOPE IN PLACE • Casing • Packer • Tubing • Hanger • Xmas Tree

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Workover Tree Cap Pulled, Sub-Sea Workover Riser Installed

BARRIERS IN PLACE WHILST RUNNING WORKOVER PACKAGE • Tree valves

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Workover Well Killed and Barriers in Place Prior to Removing Tree

WELL CONTROL CONSIDERATIONS DURING KILL • Check for gas migration • Check annulus dead • Source of surface pressure • Thermal effects or well not dead • Do not exceed tubing or csg specs

BARRIERS IN PLACE • Kill wt brine in tubing and annulus • Plug in tailpipe • 2 x BPV in tubing hanger

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Workover Tree Removed and BOP Riser Installed - THROT Engaged

BARRIERS IN PLACE • Kill wt brine in tubing and annulus • Plug in tailpipe • 2 x BPV in tubing hanger

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Workover Plugs Removed, Prepare to Pull Tubing on THROT

WELL CONTROL CONSIDERATIONS PRIOR TO PULLING • Check for trapped pressure before removing tbg hgr lockdown bolts • Consider the SCSSV • Make final checks for annulus pressure • Enough kill wt material on board

BARRIERS IN PLACE • Kill wt brine in tubing and annulus

DURING PULLING • Perform regular flow checks • Keep the hole full • Trapped pressure

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Workover Tubing Removed

WELL CONTROL CONSIDERATIONS • Perform regular flow checks • Monitor hole on trip tank

BARRIERS IN PLACE • Kill wt brine

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Workover Milling the Packer

WELL CONTROL CONSIDERATIONS • Keep accurate trip record • Gains or losses after packer breakthrough • Surging whilst RIH with mill • Swabbing whilst POOH • Run wearbushing prior to RIH

BARRIERS IN PLACE • Kill wt brine

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Workover New Tubing Run on THROT RU wireline on dual running string Install plug in tailpipe Set packer Test tubing Set and test hanger

WELL CONTROL CONSIDERATIONS WHILST RUNNING TUBING • Perform regular flow checks • Keep hole full monitor on trip tank • Surging – RIH slowly • Check tubing burst pressure before testing

BARRIERS IN PLACE WHEN RUNNING TUBING • Kill wt brine in tubing and annulus

BEFORE RUNNING TUBING • Pull wearbushing • Consider the SCSSV • Enough kill wt material on board

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Workover Plugs Run Prior to ND BOP

WELL CONTROL CONSIDERATIONS • Leak-off test tubing

BARRIERS IN PLACE • Kill wt brine in tubing and annulus • Plug in tailpipe • 2 x BPV in tubing hanger

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Workover BOP and Drilling Riser Pulled, Tree Run on Workover Package

RU wireline Pull plugs Pull workover package Return well to production

BARRIERS IN PLACE • Kill wt brine in tubing and annulus • Plug in tailpipe • 2 x BPV in tubing hanger

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Workover Hydrostatic Pressure (Liquids)

In Interms termsof ofpressure pressuregradient: gradient: P = G × D TV G − Pr essure Gradient ( psi / ft ) D TV − True Vertical Depth ( ft )

In Interms termsof ofspecific specificgravity: gravity: P = SG × 0.433 × D TV SG − Specific gravity

In Interms termsof ofdensity densityin inlbs/gal: lbs/gal: P = ρ × 0.052 × D TV ρ − density ( lb / gal) 47

Workover Hydrostatic Pressure (Liquids)

Conversion Conversionof ofAPI APIgravity gravityto tospecific specificgravity: gravity:

141.5 SG = 131.5 + APIο

48

Workover Hydrostatic Pressure (Gases)

In Interms termsof ofpressure pressuregradient: gradient: P = G × D TV G − Gas Pr essure Gradient ( psi / ft ) D TV − True Vertical Depth ( ft )

In Interms termsof ofgas gascorrection correctionfactors: factors:

 γ D TV  P = PS exp   53 . 4 z T   P − Surface Pr essure ( psia ) S γ − Gas Specific Gravity D TV − True Vertical Depth ( ft ) z − Gas Deviation Factor ο T − Absolute Temperatrure ( F)

49

Workover Hydrostatic Pressure (Gases)

In Interms termsof ofthe thegas gascorrection correctionfactor factorCCf:f:

 γ D TV  P = PS exp    53.4 z T  P = PS × Cf C − Correction Factor f

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Workover Gas Correction Factors

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Workover Methods of Well Kill Kill Method

Description

Bullheading

Kill fluid pumped into the tubing at surface. Tubing contents displaced into the formation.

Forward Circulation

Kill fluid pumped into tubing at surface. Tubing contents displaced into the annulus through a deep set circulation point. Annulus contents displaced to disposal system.

Lubricate and Bleed

A controlled volume of kill fluid pumped into the tubing at surface. After an appropriate time, pressure is bled off at surface down to a predetermined value.

Reverse Circulation Kill fluid pumped into the annulus. Annulus contents displaced into the tubing through a deep set circulation point. Tubing contents displaced to disposal system at surface.

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Workover

Surface Tubing Pressure (psi)

Bullheading Well Kill

Volume Pumped into Tubing (bbls)

53

Workover Forward Circulation Well Kill

Delayed Delayedtill tilllater later!!!!!!

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Workover Lubricate and Bleed Well Kill

55

Workover Reverse Circulation Well Kill

Well Status before SSD is open. 56

Workover

Well Status after SSD is open. 57

Workover

Well Status with SSD open and THP bled down.

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Workover

Well Status when THP reaches zero.

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Workover

Well Status with gas out of tubing, oil at surface.

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Workover

Well Status when annulus is full.

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Workover

Well Status when tubing is full of heavy brine.

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Workover

Well Status when annulus is full of kill brine.

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Workover

Surface Tubing Pressure (psi)

Reverse Circulation Well Kill Graph Example

Volume Pumped into Annulus (bbls)

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Workover Forward Circulation/Reverse Circulation Comparison

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Workover Bullheading

Advantages Advantages--as ascompared comparedtotoreverse reversecirculation. circulation.

••Duration Durationof ofpumping pumpingoperation operationshort. short. ••Lower Lowercost. cost. ••Easier Easiertotoperform performwith withless lesspersonnel. personnel. ••No Noenvironmental environmentalpollution. pollution.

Disadvantages Disadvantages

••No Noprotection protectionfrom fromdamaging damagingfluids fluidsand anddebris. debris. ••Higher Highertubing tubingpressures. pressures. ••Pumping Pumping operations operations may may cause cause accidental accidental fracture fractureof ofthe theformation. formation. ••Cannot Cannotkill killall allwells wells(especially (especiallytight tightformations formations and andsome somegas gaswells). wells). 66

Workover Reverse Circulation

Advantages Advantages

••Reservoir Reservoirfluids fluidsare areexcluded excludedfrom fromthe the“A” “A”annulus. annulus. ••Fluid Fluid densities densities should should keep keep reservoir reservoir fluids fluids segregated segregatedininthe thetubing tubingduring duringpumping pumpingoperations. operations. ••Formation Formationmay maybe beprotected. protected. ••Tubing Tubing and and casing casing pressures pressures are are lower lower during during pumping pumpingoperations. operations. ••Can Cankill killall allwells wellsififthe themechanical mechanicalcondition conditionof ofthe the tubing tubingand andcasing casingisisappropriate. appropriate.

Disadvantages Disadvantages

••“A” “A”annulus annulusdebris debrismay maymake makeaatailpipe tailpipetubing tubingplug plug irretrievable. irretrievable.

••Duration Durationof ofpumping pumpingoperations operationsmay maybe belong. long. ••Higher Highercost. cost. 67

Workover Well Preparation

••Well Well must must be be closed closed in in to to stabilise stabilise bottomhole bottomholepressure. pressure. ••Inspect Inspectand andservice servicethe theXmas XmasTree. Tree. ••Consider Considerthe theSub-Surface Sub-SurfaceSafety SafetyValve. Valve. ••Isolate Isolate well well control control from from all all external external sources sources(except (exceptPSD). PSD). ••Stress Stressanalysis. analysis.

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Workover Information Required for a Well Kill

Reservoir Parameters Completion Parameters Static Reservoir Pressure

Survey Data

TVD Formation

Annulus Volume

Permeability

Tubing Volume

Skin Factor

TVD Circulation Ports

Injection Pressure

MAASP

Fracture Pressure

Static Fluid Gradients TVD Fluid Interfaces Annulus Fluid Gradient Kill Fluid Gradient SITHP SIAHP

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Workover Methods of Equalisation of Pressure

All Allwells wellsand andwell wellcompletions completionsare areunique uniqueand andhence hence there thereisisno nostandard standardmethod methodfor forkilling killingaaproduction production well well. .

The The following following identifies identifies some some ofof the the techniques techniques that that may may be be used used for for pressure pressure equalisation equalisation atat the the depth depth ofof aa circulation circulation device deviceprior priortotopumping pumpingoperations: operations: 1)1)Pressurise Pressurisethe thetubing tubingororannulus annulusby bypumping pumpingaacompatible compatible fluid. fluid. 2)2) Pressurise Pressurise the the tubing tubing by by utilising utilising pressure pressure from from another another well. well. 3)3)Lubricate Lubricateand andbleed bleedthe thetubing tubingororthe theannulus. annulus. Note: Note: The The method method used used will will be be dependent dependent on on the the fluids fluids present presentin inthe thetubing tubingor orthe theannulus. annulus. Note: Note:The Theconditions conditionsofofconstant constantbottomhole bottomholeconditions conditionsmay may still stillbe beapplicable. applicable. 70

Workover Equipment Required for Well Kill Operations

Pump(s) Pump(s)

pump pumpstroke stroke

appropriately appropriatelypressure pressurerated rated known known output output volume volume per per relief reliefvalve valve

Surface SurfaceLines Lines Choke Choke Check CheckValves Valves Pressure PressureGauges Gauges Fluid FluidDisposal DisposalSystem System

appropriately appropriatelypressure pressurerated rated adjustable adjustable appropriately appropriatelycalibrated calibrated

Mixing MixingTanks Tanks Reserve ReserveTanks Tanks Kill KillFluid Fluid Chemical ChemicalAdditives Additives Well WellIntervention InterventionEquipment Equipment 71

Workover Equipment Required for Well Kill Operations

72

Workover Golden Rules for Planning a Well Kill

1) 1)Obtain Obtainrelevant relevantwell welland andreservoir reservoirdata. data. 2) 2)Decide Decideon onthe thebest bestmethod methodto tokill killthe thewell. well. 3) 3) Determine Determine the the kill kill fluid fluid density density appropriate appropriate to tothe theformation formationpressure pressureto tokill killthe thewell. well. 4) 4)Generate Generateaakill killgraph. graph. 5) 5)IfIfpossible, possible,simulate simulatethe thewell wellkill. kill. 6) 6) Generate Generate aa well well kill kill procedure procedure identifying identifying fluid, equipment, and personnel fluid, equipment, and personnel requirements, requirements, expected expected pressures, pressures, and and safety safetyrequirements requirements(barriers). (barriers).

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Workover Golden Rules When Performing a Well Kill

1) 1)Conduct Conductan anawareness awarenessand andsafety safetymeeting meeting for forall allpersonnel personnelinvolved. involved. 2) 2)Prepare Preparethe thewell. well. 3) 3)Pressure Pressuretest testall allsurface surfaceequipment. equipment. 4) 4)Check Checkfluid fluiddensity densityand andvolume. volume. 5) 5)Commence Commenceoperations operationsas asper perthe thekill kill procedure. procedure. •• •• •• •• ••

IfIfReverse ReverseCirculation Circulationisisused: used: equalise equaliseover overcirculation circulationdevice device increase increasepump pumprate rateslowly slowlytotothe therate. rate. surface surfacechoke chokemust mustbe beadjusted adjustedtotoregulate regulatethe theTHP. THP. returns returnstotobe bemonitored. monitored. pump pumpthe theappropriate appropriatevolume volumeof ofkill killfluid. fluid.

6) 6)Check Checkthat thatthe thewell wellisis“dead”. “dead”.

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