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