超深水钻井隔水管设计与相关工艺

1、Oil & Gas Science and Technology Rev. IFP, Vol. 57 (2002), No. 1, pp. 39-57Copyright 2002, ditions TechnipUltra Deep Water Drilling Riser Designand Relative TechnologyJ. Guesnon1, Ch. Gaillard1and F. Richard11 Institut franais du ptrole, 1 et 4, avenue de Bois-Prau, 92852 Rueil-Malmaison Cedex - Fra

2、ncee-mail: jean.guesnonifp.fr - christian.gaillardifp.fr - florence.richardifp.frRsum Risers de forage en offshore profond et technologies associes LIFPa dvelopp desoutils et des technologies rpondant aux attentes des contracteurs de forage qui veulent forer en offshoreprofond, dans des conditions d

3、environnement svres avec des densits de boue leves. La mtho-dologie propose vise optimiser le dimensionnement des risers de forage en proposant des rglespratiques de design et un logiciel appropri.Pour rduire les temps morts en opration, un connecteur de riser de forage, le Clip Riser, a t dvelopp.I

4、l permet la connexion rapide des joints de riser. Cette technologie est unique car elle ne comporte aucuncrou ni filetage et ne requiert pas de prcontrainte dans le connecteur lors de lassemblage.Pour rduire la masse des quipements sur les bateaux de forage ainsi que la tension en tte du riser, lIFP

5、a mis au point une technologie appele tubes fretts (tubes acier/composite). Ces tubes fretts pourronttre utiliss pour remplacer les lignes de scurit du riser de grand diamtre (kill and choke lines114,3mm) par des lignes deux fois plus lgres.Afin damliorer le comportement axial du riser, lintgration

6、hyperstatique des lignes de scurit a tenvisage. Cette intgration consiste solidariser les lignes aux extrmits de chaque connecteur si bienquelles participent la rsistance axiale du riser. Les avantages de ce systme seront prsents dans cet article.Finalement, toutes ces technologies et tous ces outil

7、s devront rpondre aux attentes des contracteurs deforage et permettre ainsi de repousser les limites des risers des profondeurs plus grandes et desconditions oprationnelles plus svres.Mots-cls : riser, forage, offshore profond, dimensionnement.Abstract Ultra Deep Water Drilling Riser Design and Rela

8、tive Technology IFPhas developedtools and technology to answer the waiting of contractors that wish to drill in deeper water depths, inharsher environment with higher mud weight. The methodology aims to optimise the riser design by proposing practical guidelines implemented by a software.To reduce u

9、nproductive time on the rig during the drilling, the Clip Riserhas been developed. The mainfeature of the Clip Riser is the coupling which allows quick make-up of the riser. The clip technology is aunique design which does not require bolts, threads or any preloading in operation.To reduce drillship

10、 deckload and required tensioning capacity, the hybrid tubes have been developed toreplace the existing 41/2 ID (114.3 mm) steel kill and choke lines by lighter tubes. The hybrid tubes are50% lighter than equivalent all steel lines. Advantages of this technology will be presented in this paper.To im

11、prove axial behavior of the riser and riser architecture, hyperstatic integration of choke and killlines have been studied. This consists in fixing the auxiliary lines at each riser joint so that they canparticipate to the axial resistance of the riser. Advantages of this system will be presented in

12、 this paper.40Oil & Gas Science and Technology Rev. IFP, Vol. 57 (2002), No. 1Finally, the technological developments should answer the waiting of contractors and will further expandthe range of application of standard riser systems and make them well suited for ultra deep drilling invery harsh oper

13、ational and oceanographic environments.Keywords: drilling riser, ultra deep water, design.NOTATIONSRiser foot angle for unit rig offset (zero current)cRiser foot angle due to current (with zero rig offset)Rig offsetBMApparent weight of the buoyancy modules (negativesign)Riser foot angleDensity of th

14、e sea waterarwaternNormal wave accelerationarrtTangential wave accelerationxrNormal structure accelerationxnotoTangential structure accelerationvrNormal fluid velocityvrntTangential fluid velocityCdnNormal drag coefficientCdtTangential drag coefficientCmnNormal added mass coefficientCmtTangential ad

15、ded mass coefficientdDiameter of the structureEYoungs modulus of the materialF(wave)nNormal inertia force due to waveF(wave)tTangential inertia force due to waveFdnNormal drag forceFdtTangential drag forceFinNormal inertia forceFitTangential inertia forceIInertia of the riserPeExternal pressurePiInt

16、ernal pressureq(z)Lateral loads induced by the currentSeExternal or displaced aeraSiInternal sectional areaSsealSeal sectional areaTALTension in the auxiliary linesTbottomResidual effective tension at the riser lower endTconnectorTension in the connectorTeffectiveEffective tensionTMPTension in the m

17、ain pipeTTopTop tension of the riserTtwTrue wall tension - axial tension in the pipeWALApparent weight of the auxiliary linesWmiscApparent weight of the other miscellaneouscomponentsWMPApparent weight of the main pipeWmudApparent weight of the riser internal fluidWriserApparent weight of the riseryL

18、ateral static displacementzHeight above the riser foot.SuperscriptsALAuxiliary linesMPMain pipe.INTRODUCTIONThe riser is the key element for drilling in ultra-deep water.Its architecture for deepwater drilling depends on numerousdifferent factors related to operational and environmentalconditions. T

19、hese include water depth, mud weight, auxiliaryline diameters and working pressures, sea states and currentprofiles, and maximum rig offset. All of the aboveparameters have to be taken into account in the design of thevarious riser system components including the main tube, theauxiliary lines, the c

20、onnectors, the distribution of buoyancymodules, and the tensioning system. Major concerns of drilling contractors are to run andretrieve the riser fast and to operate it safely in ultra-deepwater.Thus, to answer these queries, the Institut franais duptrole (IFP)has developed methodology and newtechn

21、ology for expanding the range of application of riserssystems and make them well suited for ultra-deep drilling invery harsh operational and oceanographic environments.The main purpose of the methodology is to optimise theriser design to determine the working envelopes. The Clip Riser has been devel

22、oped to allow very fast andsafe make up and break out of the riser joints during runningand retrieving. Two systems have been already built for PrideInternational.They are at present being operated for PrideInternational on the drillships Pride Africaand Pride Angola. The use of light weight hybrid

23、steel/composite kill andchoke lines in order to reduce riser mass and weight on deckJ Guesnon et al./ Ultra Deep Water Drilling Riser Design and Relative Technology4142Oil & Gas Science and Technology Rev. IFP, Vol. 57 (2002), No. 11.1.3Tension in Auxiliary Lines under PressureThe auxiliary lines ar

24、e relatively small-diameter tubes whichare fixed to the connector at one extremity of each riser jointand are free to slide at the other end (stab-in connections).Therefore assuming the sealing diameter is equal to theexternal diameter of the tube, the true wall “tension” in theline is:TtwALPi(SeSi)

25、Hence from Equation (1):TeffectiveAL=(PiPe)SsealALWhen under pressure, the tubes are in effective com-pression. Intermediate collars are therefore needed to preventbuckling.1.1.4Influence of Auxiliary Line Pressureson the Main Tube TensionFrom Equation (3) it can be seen that internal pressure in on

26、eor more of the tubes that make up the riser has no influenceon the global riser effective tension. However it doesinfluence the distribution of tension(effective and true wall)between the different tubes that make up the riser.As has been seen above, an increase in the internal pressurein an auxili

27、ary line causes the effective tension (TALeffective) inthat line to decrease (to a negative value). But as the globaleffective tension in the riser remains unchanged (Eq.(3)itfollows from Equation (4) that the effective tensionin themain pipe must increase. Hence from Equation (1) the truewall tensi

28、on of the main pipe also increases. If the pressure inthe main tube is unchanged, then:(TtwMP)+(TeffectiveAL)=0(8)For real risers, pressure in the auxiliary lines can causesignificant additional axial loads in the main pipe of the orderof 500 kips (225 t), per line for 15000 psi (103.4 MPa)working p

29、ressure and 4 1/2 (114.3 mm) diameter sealing.These additional loads must be taken into account whendesigning the riser.1.1.5Tensile Loads in the ConnectorsThe effective tensionin the riser connectors is given as beforeby Equation (3). When deducing the true axial force in theconnector lugs, dogs, f

30、lange bolts or other connectingelements, it is the “seal” sectional area (Sseal)within theconnector that must be used in the effective tension equation.Hence that equation becomes:Ttrueconnector=TeffectiveMP+(PiPe)*Sseal(9)THowever the effective MPis normally a maximum at the riser top end.effective

31、 tensiondoes not generally varylinearly with depth because of two factors. Firstly the maintube wall section is not of constant thickness. It tends to bethinner in the mid-height region than at the upper end, wheretension is greatest, and the lower end where bursting stressesare greatest. Secondly b

32、uoyancy units tend to be concentratedin the upper section of a riser. Thus Tconnectortends to have itsgreatest value at an intermediate point along the riser. true1.2Drilling-Riser Design ProcedureDesign CriteriaThe riser has to be designed according to API RP 16Q,Table3.11 requirements and in parti

33、cular:maximum von Mises stresses must be limited to less than2/3 of yield;mean angle at the riser foot has to be less than 2.No other quantified specification is listed in this recom-mendation concerning the riser design. In particular, norecommendations are given concerning corrosion, fatigue,and p

34、ressure in the auxiliary lines. IFPhas proposed apractical methodology for designing drilling risers to meetparticular specifications considering riser behaviour in theconnected (drilling mode) and disconnected (hung off mode). 1.2.1Connected Drilling ModeThis is the operating mode for which von Mis

35、es stresses mustbe kept below 2/3 of yield. The following situation should beconsidered:riser connected to the floating vessel through the slip jointand the tensioner system;riser full of mud with the maximum density;all the auxiliary lines under maximum pressure simul-taneously;the wall thickness o

36、f the main pipe 5% less than nominal(due to tolerances); 1/16 (1.588 mm) decrease of the wall thickness due tocorrosion;3% buoyancy loss of the flotation modules due to waterabsorption. 1.2.2Disconnected Hung off ModeIn this situation the fluctuating axial tension should remainpositive when the vess

37、el heaves in order to avoid anyslackening or dynamic buckling of the riser. To meet thesecriteria, the apparent weight of the hanging riser must begreater than the maximum amplitude of variation of thetension in any point. In this mode, the calculation should takeinto account the following:riser dis

38、connected from the wellhead with the LMRPsuspended at the riser lower end;J Guesnon et al./ Ultra Deep Water Drilling Riser Design and Relative Technology43Figure 1Methodology to optimise the riser design.44Oil & Gas Science and Technology Rev. IFP, Vol. 57 (2002), No. 1Main factors:the environmenta

39、l conditions and the water depth arefixed by the drill site;the maximum density is imposed by the reservoirengineering studies;the auxiliary lines are set by the BOP class 10000 psi (69 MPa) or 15000 psi (103.4 MPa);the diameter of the riser 21 (533.4 mm) or less is dictatedby the drilling program;t

40、he buoyancy modules, with their maximum depth charac-teristics, determine the different sections of the riser architecture. These sections are often about 2000 ft long(610 m).With these elements a preliminary design (i.e.wallthickness for each section) of the riser can be easily made. Tooptimise thi

41、s architecture, iterations on the wall thickness ofeach section have to be performed.First of all, the criterion in disconnected mode (hard hangoff) has to be checked (see design procedure in 1.2.2). Thesafety with respect to the dynamic tension has to bedetermined considering 10-year or 100-year wa

42、ve returnperiods. If the safety margin is negative, that means the risermay be subjected to dangerous dynamic buckling, so thebuoyancy ratio may have to be decreased. If the safetymargin is too high, the buoyancy ratio may be increased. Once the buoyancy ratio has been adjusted for thedisconnected m

43、ode, calculations have to be performed tocheck the operating mode (see design procedure in 1.2.1).The von Mises stress criteria have to be checked for eachriser section. If the von Mises stresses exceed 2/3 of the yieldstrength, the wall thickness of this section should beincreased by 1/16 (1.588 mm

44、). Conversely, if the stressesare less than 2/3 of yield strength, the wall thickness can bedecreased by 1/16 (1.588 mm). After modification of thewall thickness, the safety margin in disconnected modeshould be checked again in order to adjust the buoyancyratio.This iterative procedure leads to the

45、final design of thecomplete riser. The maximum top tension can then bededuced in operating mode considering nominal wallthickness of each section, no corrosion and an increasingbuoyancy module weight of 3%. This top tension has to becompatible with the tensioner capacity according to the API16Q reco

46、mmendation(Section 3.3.2) 1. Moreover, the classof the connector has to be compatible with the maximumtension calculated according to Equation (9) (including theeffect of pressure in the auxiliary lines).Moreover, each riser joint has to be check with respect tothe collapse. In this methodology, it

47、is assumed that a fill upvalve is efficient.Finally, the last stage of the design is the dynamiccalculation. The influence of dynamic motions, currentprofiles, wave conditions on the riser bending, on the bottomangle have to be checked. IFPhas developed a finite elementsoftware called “Deeplines” 3

48、to calculate all theparameters in the dynamic mode.1.4Influence of Main Operational and Environmental ParametersIn the final stages of the design, sensitivity to operational orenvironmental parameters has to be examined. Theirinfluence on the riser behavior and on the top tension, whichis the most i

49、mportant factor with respect to the tensionercapacity, has to be checked. The main parameters, which actdirectly on the riser, are dealt with below. 1.4.1Operational ParametersMud DensityAccording to Equation (1), the top tension depends directlyon the apparent weight of the mud (as the bottom tensi

50、on isgenerally about 200 kips ( 100 t), and the apparent weightof the riser may exceed 600 kips (275 t) in very severeconditions to meet the disconnected mode specifications).Risers must be designed with the maximum mud density thatmay be encountered. The range is from 14 ppg (1.6) to 17 ppg (2.04)

51、in the GOM (Gulf of Mexico) conditions. For a typical riser in 10 000 ft (3048 m) water depth, anincrease of 1 ppg (0.12) of the mud density induces thefollowing:an increase in wall thickness of the main pipe of 1/16(1.588 mm);an increase in buoyancy module diameter of 1/2 (12.7 mm);an increase in t

52、op tension of 175 000 lbs (80 t).Similarly a water depth increase of 1000 ft (305m)requires 150 000 lbs (70 t) of additional top tension becauseof the increase in mud volume considering 17 ppg (2.04)mud density.Hence it may be possible to upgrade the water depth of theriser by reducing the mud densi

53、ty range. For example, thewater depth of a riser may be increased by 1000 ft (305 m)just by reducing the maximum mud density by 1 ppg (0.12).It should be noted that the maximum von Mises stresses mustalso be checked, as well as the no dynamic compressioncriterion, in the disconnected mode.Pressure i

54、n the Choke and Kill LinesThe service pressure of choke and kill lines influences riserarchitecture. The difference between 4ID (101.6 mm) 10 000 psi (69 MPa) and 4 1/2ID (114.3 mm) 15 000 psi(103.4 MPa) working pressure is significant. For example, inGOM configuration, 10 000 ft (3050 m) water dept

55、h and15 ppg (1.8) mud density:the wall thickness of the main pipe has to be increased by2/16 (3.175 mm);J Guesnon et al./ Ultra Deep Water Drilling Riser Design and Relative Technology4546Oil & Gas Science and Technology Rev. IFP, Vol. 57 (2002), No. 1Furthermore the hydrodynamic load is directlypro

56、portional to the drag coefficient (Cd) used in thenumerical model. The choice of the drag coefficient toconsider depends on the flow regime (Reynolds number andKeulegan and Carpenter number).TABLE 2Hydrodynamic loads on the riser () + cSometimes in strong currents, a residual bottom endtension great

57、er than standard 200 kips (90 t) may be requiredto keep the bottom angle within the acceptable range. Theoperational procedure may be to offset the DP rig upstreamto reduce the riser foot angle.WavesWave action influences riser design in two ways:* GOG: Gulf of Guinea, GOM: Gulf of Mexico.J Guesnon

58、et al./ Ultra Deep Water Drilling Riser Design and Relative Technology4748Oil & Gas Science and Technology Rev. IFP, Vol. 57 (2002), No. 1Figure 4Tensions in the main pipe (kN) versus water depth (m)(Mud density 17.0 ppg | Top tension 1172 t | Pressure:KCl 10 ksi - B&H 1 ksi).Figure 6Stresses in the main pipe (MPa) versus water depth (m)(Mud densit