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22 D R I L L I N G CONTRACTOR March/April 2006

Hydril tubular connection finds perfect harmony with Weatherford MPD system

In 2004 and2005,Unocalteamedupwith Weatherford International andHydril on a managed pressure drillingprogram in the Gulf of Mexico. For thefirsttime,theoperatordecidedtocoupleWeatherfordsMPDsystemwithatubingconnection. The combination, accordingto Hydril Technical Services ManagerBen Kelly III, was a technological suc-cessthatshowcasedthepotentialofthetwosystemsworkingtogether.

P r o j e c t b a c k g r o u n dThe drilling was targeted for the EastBreaks160CervezaPlatform,whichwasset in 1981 and had 25 wells. The plat-form is located in 940 ft of water andhastwo20-slotwellbays.ThePride1502Platform Rig was used to complete theproject.Theprogramplannedforatotalofeightwells105milesfromtheGalves-tonshorebase.Intheend,however,only1 new well was drilled, followed by 2sidetracks.

Duetohistoricaldrillingchallengesasso-ciated with wells in the area, Unocallooked at managed pressure drilling asawayforre-entry.SomeofthebenefitofMPDconsideredwere:

Narrow pore pressure and fracturegradientwindows;

Highpermeabilityzones;

More precise control over wellborepressures;

Ability to lighten the mud in zoneswherelostcirculationisexpected;

Allowsbettercontrolofwellboresta-bility;and

When conventional practice of mud-weight is greater than pore pressure,lost circulation occurs when the pumpsare turned on at planned circulatingrates.Assoonasthepumpsarestarted,theresapressurespikeatthebit,which

translates into bottomhole pressure.That means you may be exceeding thefracturegradientoftheformationbeingdrilledinto,MrKellyexplained.

When the initial wells were drilled,Unocal encountered many challenges,includingwellboreballooningandlosses,stuckpipe,hole-cleaningissues,difficultyobtaininglogdataand,ofcourse,logisticsanddeckspacelimitationduetoitbeingaremoteplatform.Unocaltookthoseles-sonslearnedandsoughttousetheinno-vationsofMPDandtubulartechnologytoimproveitsnewdrillingcampaign.

OnceUnocaldecidedonusingMPDtech-nology,ithadtopickamanagedpressuredrilling system. The system chosen wasa rotating head system. WeatherfordsModel 7100 was utilized. It was 5 -ft tall and could handle up to 6 -in. tooljoints, withdualsealingelementsandaworkingpressureofabout2,500psiwhilerotating.

P i c k i n g t h e c o n n e c t i o nAfter theMPDsystemwasselected, theconnection had to be chosen. Unocalbeganreviewingmorethanadozencon-nections,mostofthemconventionaldrill-pipeconfigurations.Keepinginmindthe

ThisarticlecontainsadditionalcontentnotfoundwithinthepagesoftheprintedversionofDrilling Contractor magazinevexclusive to the online version of the magazine.

this Fea animation models 18-degrees and 30-degrees on a tooljoint, showing it going through the stripping rubber at different stages. this was the marrying of the Weatherford Model 7100 MPd system with hydril's 522 tubing connection. the Fea show that these two systems can work together in harmony. Provided courtesy of Weatherford international.

Web-exclusive content: Click on image to view animation.

historicaldifficulties indrillingtheEastBreak wells, a connection that wouldallow much improved hydraulics wouldbe required. The companies narrowedtheirfielddowntothreechoices:

3 -in. 13.30-lb S-135 NC38;

4-in.14.00-lbS-135NC40;

4 -in. 15.50-lb P-110 Hydril Type 533, theonethatwasultimatelychosen.

Three other criteria were considered inthe selection: The connection had to bereadilyavailable,usableonall8plannedwells, and Unocal wanted to use theconnection as a completion string afterworkoveroperationswerecompleted.

HydrilalreadyhadseveralhundredrunsinMexicowheretheType533connectionis used as a drillstring, then buried onevery third well as a completion stringafteritsfatiguelifewasdrilledoutonthefirsttwowells.Wevehadabsolutelynoproblemswiththat,MrKellysaid.

Basedontheabovecriteria, thecompa-niescomparedtheirtopthreecandidates(see Table 1). Because the 533s tubingjoints are cut on an integral IEU upset,thestrengthof thetubing ismaintainedso that it has the same strength all thewaythrough.

Mr Kelly pointed out that the tubularconnectioncanprovideamuchlargerIDthanitscompetitionalongwithasmallerOD.Thatwouldcomeinhandybecausethe companies knew that equivalentcirculatingdensitiesweregoingtogivethem a lot of challenges, he said, andoneofthemainwaystoimproveECDsistohavealargeIDandasmallerOD.

Healsoemphasizedthebenignfailureaspect of the connection. Whereas pinstendtotwistoffonrotaryshouldercon-nections, the Wedge Thread connectionwill plastically deform the box, giving awarningbeforeitfails.Thiswillbeseenoninspectionduringtrippingoperationsinstead of having to fish downhole. Theconnectionalsodidnotrequireanyhardbanding,hepointedout.

Benefits also were identified with theWedge Thread used with the 533 con-nection. Aside from high torsional yieldstrengths and good fatigue characteris-tics, a smooth bore for cementing andmetal-to-metalsealfordrillstemtesting(DST) and completion, it also had 100percentpipe-bodytension,compression,burstandcollapse,whichmeantthattheconnectionwasnottheweaklink.Itsasstrongasthepipebody.

Based on all considerations, Unocalselected the Hydril connection, whichhad never been used with the Weather-ford Model 7100 MPD system before. Itturnedouttobeagreatcombination,MrKellysaid.

t h e d r i l l i n gAlthough8wellswereoriginallyplanned,theprojectendedupdrilling1newwelland2sidetracks.

On the new well, workers drilled out totheirfirsttargetusingWeatherfordsMPDsystem, set a 7 -in. liner and cemented it in place. They then drilled out the floatcollar and the shoe before drilling outto the second target and setting a 5 -in. expandable liner. Workers cleanedout the hole and circulated completion

fluid.Thentheyperforatedusingtubing-conveyed perforating (TCP) and flowedthe well back. The zone of interest wasgravel-packed and frac-packed. On thiswell, a total of 20 full tripsand27 shorttripsweremadeonthedrillstring.

Onthenextwell,asidetrack,workerspicked up and ran a bit and scraperto the bottom before setting a sumppacker and whipstock and milling outa window. They drilled out to thetarget zone and set a 7 5/8-in. liner. Afloat collar and shoe were drilled outand cemented before drilling to thesecond target. A 5 -in. liner was set, a scraperwasrun,andcompletion fluiddisplaced.They thenagainperforatedthezoneofinterestwithTCPandgrav-el-packedand frac-packedthezoneofinterest.Atotalof17full tripsand18additional short trips were made onthesamestring.

So far, if all this sounds a little mun-dane, thenyouvegotten thepoint thatMrKelly is tryingtoconvey.Iwanttoemphasizethatnosurpriseshappened.Thecombinationof theconnectionandtheMPDsystemdidnotcauseanyprob-lemsatall.Theyworkedasanticipatedtogether,hesaid.

On the second sidetrack well, theyraninwithbitandscraper,setwhip-stock and milled out the window.They made a clean-out trip and ranintodressthewindow.Atthispoint,there was an occurrence of stuckpipe.Afteritsretrieval,theydressedthe window and drilled out to thetargetzone.A5-in.linerwasrun,butthelinerstuck.

Atthispoint,theprojectwasterminated.Abridgeplugwasset,andtheypluggedand abandoned the well. For this thirdwell,atotalof12fulltripsand15shorttripsweremade.

t o t a l u s a g e s u M M a r yOnthetotalusagesummaryofthestring,atotalof49fulltripsand60shorttripswere made. This equates to about 109make and breaks on each connection.Operationalextremeswere:

10,000-lb.weightonthebottom(WOB)settingpackers

80kipsoverpullwithjarsduringfish-ing

35kipssetdownduringfishing

13,000 ft-lbs maximum torque duringdrilling.

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March/April 2006 D R I L L I N G CONTRACTOR 23

c o M P l e t i o nFromtheoutset,thestringhadbeenengi-neeredanddesignedtomeettherequire-ments of completion, because Unocalhad planned on using the drill stringas a completion string once it nearedtheendofitsfatiguelife.Oncethedrill-ingstarted,however,Unocaldecided toinstall gas lift mandrels. A 4 -in. gas lift mandrelwouldnotfitinsidetheproduc-tioncasingstring.Therewerealsomate-rial changes to the completion stringthat dictated using 13 percent Chrometubing instead of the P-110. Therefore,it was not used as a completion stringasplanned.

The conclusion of the project, accord-ingtoMrKelly,wasthat thestringandthe MPD system performed flawlesslythroughout all operations drilling,reaming, washing, perforating, fracing,gravelpacking,cementing,settingpack-ersandmillingwindows.

These are worth noting because theyarent common operations for a tubing

string,hepointedout.Theyrecommonforadrillpipestring.

Other advantages identified during theprojectwere:

The use of one string allowed moreflexibilityondeckspace;

The upset tubing in harmony withWeatherfords MPD system proved todecreasewearonstrippingrubberalongwithmaintainingseal;

Using tubulars provided increasedhydraulics over conventional drillpipe(small OD vs. large ID) and allowed forbetterperformanceatthebit;

Overall,lessthan1percentrecutswillbe required to repair the string. Thatmeansoutofatotalof400joints,about4recutswillberequired.

Will tubular connections ever replacedrillpipe? Probably not, Mr Kelly said.But this project proved that there arecertainapplicationswhereatubularcon-nectionwillworkbetter.

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this project proved that there are certain applications where a

tubular connection will work better (than drill-

pipe).hydril technical services

Manager Ben Kelly III

24 D R I L L I N G CONTRACTOR March/April 2006

Specification NC38 IF (S) Type 533 NC40 FH (S)

Wall Thickness 0.368 in. 0.337 in. 0.330 in.

Pipe ID 2.764 in. 3.826 in. 3.340 in.

Drift 2.000 in. 3.701 in. 1.875 in.

Box OD 5.000 in. 4.992 in. 5.500 in.

Pin OD 5.000 in. 4.868 in. 5.500 in.

Box and Pin ID 2.125 in. 3.776 in. 2.000 in.

Minimum Make-up Torque 13,000 ft-lbs 5,800 ft-lbs 18,000 ft-lbs

Yield Torque 18,100 ft-lbs 29,000 ft-lbs 36,000 ft-lbs

Pipe Body Yield Strength 489 kips 485 kips 515 kips

Collapse Pressure 12,000 psi 14,340 psi 20,140 psi

Internal Yield Pressure 13,800 psi 14,420 psi 19,490 psi

Hard banding Yes No Yes

Table 1: Comparing the 3 connection candidates