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Copyright 2000, IADC/SPE Asia Pacific Drilling Technology

This paper was prepared for presentation at the 2000 IADC/SPE Asia Pacific DrillingTechnology held in Kuala Lumpur, Malaysia, 1113 September 2000.

This paper was selected for presentation by an IADC/SPE Program Committee followingreview of information contained in an abstract submitted by the author(s). Contents of thepaper, as presented, have not been reviewed by the International Association of DrillingContractors or the Society of Petroleum Engineers and are subject to correction by the

author(s). The material, as presented, does not necessarily reflect any position of the IADC orSPE, their officers, or members. Papers presented at the IADC/SPE meetings are subject topublication review by Editorial Committees of the IADC and SPE. Electronic reproduction,

distribution, or storage of any part of this paper for commercial purposes without the writtenconsent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print isrestricted to an abstract of not more than 300 words; illustrations may not be copied. Theabstract must contain conspicuous acknowledgment of where and by whom the paper waspresented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax01-972-952-9435.

Abstract

During a recent revisit (October 1999) to DuyongField, Offshore Peninsular Malaysia, the operatorPetronas Carigali Sdn Bhd (PCSB) was able to drillthrough the troublesome Terengganu Shale and

successfully completed a well in the productive TapisGas Sands. The well, Duyong A-4 STR4D (DYA-4STR4D) was drilled and completed under approvedbudget with minimal lost time. DYA-4STR4D was thefirst 3-1/2 monobore completion by PCSB in PeninsularMalaysia, paving the way for future application of thetechnology especially for the development of marginal oiland gas fields. This paper will summarize the design,planning and execution of this milestone achievement forPCSB.

Background

Duyong Gas Field located about 236 kmsoutheast of Kuala Terengganu in Block PM-12 and wasdiscovered by Conoco in 1970. The field developmentwas started in 1983 by PCSB and a total of 13 wellswere drilled by 1985 from the 3 platforms; DYDP-A, Band C using the jack-up rig Parameswara in waterdepths of about 76-78 meters (Fig.1, 2, 3). All thesewells were completed in the S reservoir sands locatedbetween 1650 to 1827 mss.

Out of these 13 wells, well DY-A4 was initiallyplanned to develop the T reservoir sands which requirepenetrating the approximately 250 meters thick highlyreactive Terengganu Shale overlying it. This well wasdrilled down to the top of the Terengganu Shale without

problems and the 9-5/8" production casing was set andcemented casing-off the S sands. Several attemptswere made below the 9-5/8" casing to pass theTerengganu Shale failed. Severe bore hole problemswere encountered resulting the well to be sidetrackedthree times without success. A water based sea watepolymer mud used failed to inhibit the TerengganuShale. Finally, further drilling into the T sands wasterminated and the well was completed as a single gasproducer in the S sands. A new 9-5/8 inches casingstring had to be run inside a sidetrack hole due to a leakin the old casing string resulting from extended drillingbelow it.

In 1995, during the Revisit-I Campaign, anotherattempt was made to develop the "T" sands from a newwell DY-A7 drilled from the Duyong-A platform. This welalso failed to be drilled to the objective T sands. Thistime the failure was due to the differential pipe stickingproblems encountered in the depleted "S" sands whichwas further aggravated by the higher equivalent mudweight required to drill through the shallower "R" sands("R" sands are being produced from the Duyong B & Cplatforms). Like in the DY-A4 well, a water based mudwas used. This well failed even to penetrate theTerengganu Shale. After premature running of the 133/8" casing set at shallower depth, the well was pluggedand abandoned. Further attempts to make progress in

drilling to the S sands failed, due to the repeateddifferential pipe stuck problems encountered.

With potential viable reserves still remaininguntapped at this location, a third attempt was planned todevelop the "T sands during the Revisit-II Campaignfrom Duyong-A platform in Q4, 1999. For this Revisit-Icampaign, the jack-up rig Harvey H. Ward owned andoperated by R & B Falcon was contracted for the project.

IADC/SPE 62773

THE DRILLING AND COMPLETION OF THE FIRSTMONOBORE WELL IN PENINSULAR MALAYSIAAminuddin Mohammad & U Mya Maung, PETRONAS CARIGALI SDN. BHD.


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2 AMINUDDIN MOHAMMAD & U MYA MAUNG, PETRONAS CARIGALI SDN. BHD. IADC/SPE 62773

Operation Planning

Side-scan Sonar. Suspecting poor primary cementingas observed from the high annuli pressures in all thewells, a shallow seismic survey was conducted prior tothe Revisit - I campaign in 1993 / 1994. The resultsshowed severe gas migration resulting from channeling

effects in most of the shallow unconsolidated sandylayers beneath the platforms to be gas charged. Forsafety in using the jack-up rig, a shallow seismic surveywas run again prior to this campaign.. As part of theprocedure in positioning a jack-up at a platform, a ROVsurvey will be conducted to check for any seabedconstruction debris. An opportunity will be taken tocheck for any gas breaking to the seabed which alsoindicated no active gas bubbling at the seabed.

In addition, to check for shallow gas a dedicatedpilot hole drilling will be carried out in each of the footprint areas by drilling 8-1/2 inches pilot holes to 18meters below the seabed.

Swiss Cheesing. As stated earlier, the jack-upParameswara, a BMC 300C independent leg type jack -up rig was used during the initial development stage in1983 / 1985. For the Revisit - I campaign in 1994/1995,the rig Randolph Yost a MLT 116 C also an independentleg jack-up design was used. Thus, these campaignsleft two different foot -prints having different spud candiameters as well as spud can center distances.Thus to alleviate this foot print in-compatibility problemwhen bringing in the jackup rig Harvey H. Ward (Friede& Goldman L 780 - MOD II C design) this time, the rigowner R & B Falcon formulated a novel procedure calledSwiss Cheesing drilling (Fig. 4). Basically this involvesdrilling a number of 26 inches diameter pilot holes ineach of the foot print overlapping areas of the three spudcans to soften and disturb the soils significantly so thatthe leg of Harvey H. Ward rig will not slide into the oldspud can holes left behind in the previous campaigns.This will be carried out with the rig in floating mode withthe rotary table positioned 1.5 feet off from the transomof the rig hull.

Well Planning

Well Plan Change. Initial planning called for drilling a

new well DY-A8 from an empty conductor on theDuyong-A platform. However, after thorough re-studytaking into account the deterioration in the shallow gassituation, the need to pass through the highly depleted"S" sands (as low as 3.79 ppg EMW) and lessons learntfrom the previous two failures, the team decided to abortdrilling the new well DY-A8 and instead of decided intothe option of sidetracking and deepening the existingDY-A4 well from below the existing 9-5/8" productioncasing to the prospective "T" sands. The existing 5-1/2

by 5 single completion string need to be pulled outincluding the permanent packer. After remediasqueezing and establishing the integrity of the S sandperforations in this 9-5/8 casing, the 8-1/2 hole to bedrilled from below this 9-5/8" casing shoe and 7" liner tobe run to case-off the Terengganu Shale. This entailsdrilling a 6" hole below the 7" liner penetrating the

prospective "T" reservoir sands. At total depth, a smal3-1/2 liner to be run, cemented, tieback and completedas monobore (Fig. 5). Deepening of the DY - A4 will noonly save well cost but also it will increase the chance ofsuccessful drilling as all the shallow hazards are alreadyisolated behind this casing. This decision eliminatedmost of the problems present in the upper hole sectionsabove the Terengganu Shale. Since there was nocontingent hole size available, the drilling operation wasvery carefully planned and executed.

Synthetic Oil Based Mud. Terengganu Shale is astressed swelling shale that is sensitive to water based

mud system with an exposure time window of 3-1/2 to 5days. This evidence not only happened in Duyong bualso in other fields e.g. Bekok. In these fields the shaleis about 250 meters thick and situated 1700 metersbelow vertical depth. In this campaign, the team usedthe newly formulated synthetic LTOBM to tackle thisswelling shale. Prior to the Duyong revisit campaign, thenew synthetic mud was tried in a nearby Bekok-B10where it proved very effective in mitigating thetroublesome Terengganu Shale.

The mud system used was Ancovert 2000 (Low-Toxic Oil Based Mud) with Escaid 110 as the base oilThe advantages observed in using this systemcomparing to the previous campaign which used Salpolymer and KCI/PHPA polymer muds are:

LTOBM provided better hole stabilityOne of the main cause of shale (K-shale) instabilityin Malay Basin is water absorption. LTOBM utilizesoil as the external phase, thereby eliminating theeffect of shale swelling. Moreover, increasedinhibition is obtained by balancing the internal brinephase with that of the formation water, thuspreventing waters transfer.

LTOBM provided better lubricity while drillingLow torque and drags were observed while drilling

using LTOBM compared to the Salt and KCI / PHPApolymer muds that were used in the previouscampaign. The base oil as well as the extremelytough, thin and slick filter cake formed by theLTOBM provided the lubricating properties whichwould help in drilling DY-A4STR4D which is a 68well.


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IADC/SPE 62773 THE DRILLING AND COMPLETION OF THE FIRST MONOBORE WELLS IN PENINSULAR MALAYSIA 3

High Pressure Tapis Sand. Based on pressure datafrom exploration well, the "T" sand (Tapis sand) isoverpressured with an anticipated maximum surfacepressures exceeding 6000 psi with a dry gas columnfrom the T-10.2 and T-11 sands. The drilling andcompletion of this sand require high mud weight up to14.3 ppg and wellhead equipment was subsequently

rated to 10,000 psi WP. During the DY-A4 original welldrilling program, the drill string got stuck several timesand at TD, it failed to be freed. The string was cut abovefree point and abandoned without cement plugs leavingthe T sands in potential communication with eachother. As such, cross flow was anticipated anddetermining the mud weight became a critical planningfactor.

Completion Strategies

Well DY-A4STR4D will access new productionfrom the prolific Northern Tapis T-sand at about 2870 to

3400 meters. Based on data obtained from explorationand appraisal wells, the team determined that thereservoir was composed of heterogeneous sandstonelayers with some of the layers having potential for waterbreakthrough. It was necessary that the completion bedesigned to allow eventual segregating the differentzones as they water-out in order to maximize productionand recovery. It was determined that the well life for DY-A4STR4D would be 4 - 5 years. Production from the Tsands is expected to be highly corrosive (CO2content of6 to 10 mole percent and no H2S). Because of this, theteam chose to go with 13% chrome tubulars andaccessories to minimize sweet corrosion that may occurafter water breakthrough. Premium connections wereselected for all tubulars to minimize potential leak paths.

In deepening the well, the hole size is limited bythe drilling interval from the kick-off point to reach targetreservoir. After setting the 7 liner at base ofTerengganu Shale, the next available hole size is 6inches. This limits the size of liner available to completethe well. Completing with standard 4-1/2" liner cannotalleviate the problem of potential early water cut from theupper "T" sands (T2, T4 sands). The last and bestoption is to complete well inside the 3-1/2" monobore setacross the "T" sands. This would not only achieveeffective co-mingled production from the different sandmembers namely ; T-2 , T-4, T-10, T-11.1 and T-11.2

but most importantly will minimize cost well interventionand maintenance during the producing life (Fig. 7).Future wellbore intervention, if required for zone charge,water shut-off etc., could be easily achieved at minimalcost using wireline only.

Completion Components. The liner hanger will includeintegral pack-off packer. A polished bore receptacle(PBR) and retrievable hydraulic packer are included inthe monobore completion. The hydraulic packer is used

to ensure annular pack-off above the liner. The wet flowparts of the packer were enhanced to accommodate anypotential erosion or corrosion problems that may occurdownhole.

A key driver in the DY-A4STR4D completionstrategy was to minimize well intervention andmaintenance. This was done in the individual component

designs. An example of this, was the using of standardHalliburton (Otis) X line flow control equipment with a2.813 inch bore which is commonly available. Thisallows the use of Petroleum Engineering Services (PSE)plugs and straddles which was designed to pass througha 2.813 inch bore ID. Further, both wireline and coiledtubing set retrievable bridge plugs are available to passthrough a 2.813 inch seal bore.Three locations were chosen for landing nipples:

Above the formation liner, which allows for work tobe done on the upper wellbore components withoua dynamic kill and for setting the hydraulic packer.

Above the retrievable hydraulic, which allows work todone on the upper wellbore without a dynamic kill.

Below the safety valves, which allows for leakdetection, and work to be done on the SSSVstubing hanger and Christmas Tree components.

The use of a monobore completion design forDY-A4STR4D was driven to minimize well installationtimes and costs. This is in line with PCSBs drive forapplication of slim well engineering to achieve cosoptimization

Deepening The Well

Positioning The Rig. As planned, the shallow seismicsurvey conducted confirmed that the shallow gassituation had deteriorated and has encroachedunderneath the platform area at three different layers 36 meters, 26 meters and as shallow as 13 metersbelow the sea bed. The boundary of this shallow layebeing close to the rigs bow leg spud-can needed furtherconfirmation due to safety implication. A confirmationwith a dedicated pilot hole drilled using a soil boringvessel before the rig move in and an earlier ROV surveyshowed it has not effected the spud can foot print area.

The planned swiss cheesing was alsoconducted with the Harvey H. Ward in floating mode. Atotal of 101 numbers of 26 diameter pilot holes weredrilled in the three (3) spud can foot print areas toweaken and to disturb the soils in the foot printoverlapping area. The rig was then pulled intopositioned. After successfully preloading to full 40.7MN(9132 kips) it was jacked up to operating air gap andrigged up for operations.


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Drilling of DYA-4STR4D. After retrieveing the old 5 x 5 completion assembly, the inside of the casing wascleaned down past the S sand perforations to PBTD.The well was displaced to 12.0 ppg LTOBM mud. Thenthe mud weight was increased to 13.9 ppg required todrill the next 8 hole section penetrating theTerengganu Shale. There were no losses of mud

confirming the integrity of the squeeze cementing acrossthe perforations. A 14.3 ppg PIT was performed afterdrilling 3 meters of new formation to 2365m, below theshoe. This 14.6 ppg PIT was considered more thansufficient to drill the next hole section.

An 8-1/2 rock bit with directional BHA was ranand successfully steered the well away from the old fishleft behind in the initial campaign. This section wascontinued drilled through the Terengganu Shale withoutproblems to the section TD of 2726 m MD. The 13.9ppg Escaid-110 synthetic based drilling fluid systemproved very successful in mitigating the shale. There

was no shale breakout observed at 13.9 ppg mudweight. No borehole problems were also encountered.At TD, no logging was carried out to reduce timeexposure of the mud to the shale. The 7 liner was setand cemented as planned.

For the production section, a 6 BHA was runand the well displaced with 15.6 ppg mud. The 15.6 ppgmud weight was used in anticipation of cross flow andand potential charging of the shallower T sands i.e. T-1,T-2, and T-4 from the deeper T-11.2, T-11.1 sands.However, the drill string got differentially stuck at 2940 mwhile setting the tool face. The pipe was freed by slowlyreducing the mud weight in stages down to 14.3 ppgconfirming that the pressure charging of the upper Tsands were not as severe as earlier predicted. The wellwas drilled ahead without anymore problem reaching TDat 3480m. Drilling was slow probably due to the heavymud weight and low GPM limited by the small nozzleflow area attainable even with the jets removed for the6 bit selected.

At total depth, two wiper trips were made andthe hole cleaned but failed to log the hole successfullyfrom TD. TLC run also failed and further attempts to logthe hole was terminated. The hole was conditioned andthe planned 3-1/2 monobore was run and cemented.The ESCAID 110 based OBM also proved quitesuccessful and there was no major mud related

problems encountered. Overall drilling of this holesection went quite well with only minor problems only.The well was completed by running the 3 completionassembly as planned. A 1 Coil Tubing Unit ( CTU )was rigged up and the 3 monobore was cleaneddown to PBTD and the well was perforated in the T-10Sands. Estimated savings in well cost was about 30%as compared to drilling a new well.

Conclusion

Team work and proper planning was the maincontribution factor in the successful drilling of thiscomplicated well.

Use of this monobore technology also helped in thesuccessful drilling by allowing the well to be drilled to

TD in a small 6 hole interval. However, due to smalhole size, no more contingent hole size will beavailable in case of any problem prior to reach TD.

Monobore completion has proven successful in thiswell and can be recommended for consideration inthe development of marginal oil and gas fields in thefuture. Most importantly, it paves the way for theapplication of slim well design for future fielddevelopment.

The Escaid 110 based LTOBM proved verysuccessful in mitigating the borehole stabilityproblems in the Terengganu Shale

Acknowledgement

The authors wish to express out thanks to themanagement of Petroliam Nasional Berhad andPetronas Carigali Sdn Bhd for giving their permission topublish this paper, and those who have contributed tothis paper.


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PM 306PM 306

PM 307PM 307

PM 10PM 10

PM 2PM 2PM 3PM 3

PM 5PM 5

PM 8PM 8

1976 PSC1976 PSC

KUALA

TERENGGANU

KualaDungun

Marang

Pulau Redang

Pulau Perhentian Besar

MALONG

ANDING

SOTONG DUYONGBARAT

BESAR

ANGSI

TEMBIKAI

BERANTAIBEKOK

OPHR

BAYONG

LEDANGBARAT

LEDANG

PULAI

BELANGA

TINGGI

SELIGI

N.WSELIGI

TIONGBARAT

TIONGKEPONG

EAST RAYA

PALASTAPISIRONG

IRONGBARAT

T ABU G UNTO NG

SOUTH RAYAW.BELUMUT

BELUMUT

CAHAYA

CHERMINGATPETA

PETAKIRI

YONG

NORTH RAYA

BANGGOL

SERUDONLAWANG PANTAI

PALUHBERUANG

LEREK

DIWANGSA

BUBU

ABU KECIL

ABU

RABUNG

PENARA

NORTH LUKUT

DELAH

LIANG

JAMBU 1

JAMBU 2

KETUMBAR

BERANANG

MERANTI

KAPAL

SEMANGKOK

DULANG

TANGGA

TANGGABARAT

BUJANG

MELOR

LAHO

TUJOH

INASGULING

BEDONG

SEPATNORING

JERNEH

JERNEH BARAT

LAWIT

BINTANG

DAMAR

S. BUNDI

BUNDI

LARUT

LARUT-LIKU

EASTLARUT

NORTHLARUT

PIATU

MESAH

TELOK

TELOK

BARATSEROK

LABA

LABA BARAT

600,000 N

700,000 N

400,

000

E

500,

000E

600,000 N

700,000 N

DUYONG

1: 1,000,000

0 10 20Miles

0 50KM

FIGURE 1 : LOCATION MAP

JKT-A

ProposedA4 Sdtr

FIGURE 2 : TOP T RESERVOIR MAP

5.6 KM (14 " 0)

48.7 km (24 "0)

Gas/condensate

to Onshore Gas Terminal

80KM(18"0)

156KM(30"0)

Duyong Drilling Platform (DDP-A)

o 9 slots

o 3 production wells

o current prod @ 60 MMscf/d

o 1 emergency generator

o 1 firewater pump

o 1 12 ton crane

Duyong Drilling Platform (DDP-C)

o 9 slotso current production @ 155 MMscf/d

o 8 producing strings


o 1 fire water pump

o 1 12 ton crane

Flare tripod

o capacity @ 250 MMscf/d

5 km (14")

Living Quarters Platform (LQ)

o 122 men living quarters


o 1 fire water pump

o 1 12 ton crane

Central Processing Platform (CPP)

o 3 trains capacity @ 300 MMscf/d

o 4 gas (solar saturn) turbines for generation

o 1 fire water pump

o 1 18 ton crane

o 2 screw air compressor

Gas Compressor Platform (GCP)

o 3 unit Dresser Rand compressor

o Compression @ 300 MMscf/d

o 1 30 ton crane

Sotong Collector Platform (SCP)

o Pig receiving/launching facilities

o 4 men living quarters

o 2 generator sets for power generation

o 1 fire water pump

o 1 19 ton crane

o 1 32 men survival craft

Duyong Drilling Platform (DDP-B)

o 9 slots

o 8 production strings

o current prod @ 140 MMscf/d

o 1 12 ton craneGas/condensate from EPMI operated Bekokfield

FIGURE 3 : DUYONG FACILITIES

FIGURE 4 : PILOT HOLE DRILLING AND SWISS CHEESING

Drill 8-1/2" pilot hole to 18 m below seabed

Swiss cheesing with 26" bit to 15 m below seabed

Individual leg pre-loading procedure

Old footprint depressionsleft over from previouscampaign

Harvey H.Ward

footprint

50 NOs X 26"hole X 15marea to swiss cheese

DUYONG

DP-A

8-1/2" pilothole

to check on shallow gas

15

m

18m

seabed

footprint area afterswiss cheesing

old footprintdepression

Shallow gas layer @ 26m BSB


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26"conductor

20" casing

13-3/8" casing

9-5/8" casing

7" liner

3-1/2" liner

158

390.1

1175.9

1777

1993

2330

158

391

1529

2361

2725

3480

BEFORE AND AFTER REVISIT mTVD m M D

FIGURE 5: DYA-ASTR4D CASING SCHEME

TERENGGANU

SHALE

TAPIS SANDS

estimatedbase

at 20 29mTVD

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

DAYS

(3,500)

(3,000)

(2,500)

(2,000)

(1 ,500)

(1 ,000)

(500)

0

MEA

SUREDD

EPTH(

M-RKB)

P L A N A C T U A L

1

10

11

13

12

2

4 5 6 7

8

9

3

8

9

10

11-13

14

FIGURE 6 : DY-A4STR4D - DEPTH vs DAYS

15 16 17 18

D AY # C M. DA YNO . ACTIVITIES CUM.DAY DAY #

0.27

0.71

1.10

1.52

1.83

3.96

4.65

6.00

12.21

14.08

24.08

26.54

29.86

31.72

33.02

35.17

0.27

0.44

0.39

0.42

0.31

2.13

0.69

1.35

6.21

1.87

10.00

2.46

3.21

1.86

1.30

2.15

SKID RIG TO DYA-4

KILL WELL/ CUT TBG

INSTALL BPV, R/U, TEST BOP

POOH COMPLETION

ND BOP, C/OUT THS

MILL & RETRIEVE PKR

PRESSURE TEST BOP

CLEAN-OUT & LOT

DRILL 8-1/2" HOLE TO 2726M

RUN, CMT & TEST 7"LINER

DRILL 6"HOLE TO T-4 SAND

RUN INT.LOG

DRILL 6"HOLE TO TD

LOGGING & WIPER TRIP

RUN, CMT & TEST 3-1/2" LINER

RUN COMPLETION

N/D BOP, N/U XMAS TREE

RIG DOWN

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

PLAN ACTUAL

0.50

1.00

1.00

1.00

1.00

2.00

1.50

2.00

2.25

1.50

2.25

1.50

2.25

3.00

1.75

3.00

1.00

1.50

0.50

1.50

2.50

3.50

4.50

6.50

8.00

10.00

12.25

13.75

16.00

17.50

19.75

22.75

24.50

27.50

28.50

30.00

DYA - 4STR4D CASING SCHEME


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FIGURE 7 : COMPLETION DIAGRAM BEFORE AND AFTER REVISIT - II


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FIGURE 8 : DYA-A4STR4D WELL PROFILE

00062773- completamiento angsi

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