CHRISTMAS TREE - European Patent Office - EP 0907821 B1

Note: Within nine months from the publication of the mention of the grant of the European patent, any person may givenotice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed ina written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art.99(1) European Patent Convention).

Printed by Jouve, 75001 PARIS (FR)

Europäisches Patentamt

European Patent Office

Office européen des brevets

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1*EP000907821B1*(11) EP 0 907 821 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mentionof the grant of the patent:20.11.2002 Bulletin 2002/47

(21) Application number: 97927294.5

(22) Date of filing: 20.06.1997

(51) Int Cl.7: E21B 33/035, E21B 34/04

(86) International application number:PCT/GB97/01680

(87) International publication number:WO 97/049892 (31.12.1997 Gazette 1997/57)

(54) CHRISTMAS TREE

ERUPTIONSKREUZ

ARBRE DE NOEL

(84) Designated Contracting States:BE DE DK ES FR GB GR IE IT NL PT SE

(30) Priority: 27.06.1996 GB 9613467

(43) Date of publication of application:14.04.1999 Bulletin 1999/15

(73) Proprietor: Expro North Sea LimitedDyce, Aberdeen AB21 0GU (GB)

(72) Inventors:• EDWARDS, Jeffrey Charles

Aberdeen AB2 0HD (GB)

• MORGAN, Michael GrahamBanff AB4 2NS (GB)

(74) Representative: Naismith, Robert Stewart et alCRUIKSHANK & FAIRWEATHER19 Royal Exchange SquareGlasgow, G1 3AE Scotland (GB)

(56) References cited:WO-A-97/11252 GB-A- 2 267 920US-A- 4 784 225

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Description

[0001] The present invention relates to a xmas treestructure for use in extended well tests. In particular, theinvention relates to a simplified horizontal xmas treestructure for use in such tests and to a method of install-ing such a tree for use in such extended well tests.[0002] Extended well tests (EWTs) are procedureswhich can last up to 180 days and are carried out in orderto assess the viability of a producing reservoir and toobtain accurate reservoir data over a prolonged period.Extended well tests are common for on-shore locationsrequiring little more than a conventional well test pack-age. Off-shore packages are somewhat different due totighter regulatory, product and effluent specifications.Due to the extended flow periods, crude oil is normallyrecovered for commercial sale from the extended welltest. Off-shore systems are highly sensitive to well per-formance because the cost of a rig and export systemhas to be accounted for. It is of considerable importanceto be able to minimise the cost of conducting extendedwell tests and the apparatus used in the tests withoutcomprising the accuracy of reservoir data or compro-mising safety.[0003] Extended well tests are typically conducted us-ing a traditional sub-sea test tree and BOP stack. How-ever, if additional wells are also to be tested, or if aninjectivity test is to be conducted, it will be necessary todeploy a sub-sea xmas tree to provide well pressurecontrol. For applications in which well testing involvestesting more than one well, the term "extended appraisaltest" (EAT) is used in place of the term extended welltest (EWT). Traditional xmas tree are relatively expen-sive and require additional accessories and tools suchas tubing hangers and tubing hanger running tools anda workover system in order to conduct the extended welltest further adding to the rig time and overall cost of con-ducting the well test.[0004] UK Patent Publication No. GB 2267920 (Pe-troleum Engineering Services Limited) discloses a xmastree for use in a variety of well applications and a methodof installing a xmas tree on a wellhead. The disclosureis particularly directed towards a xmas tree and well-head structure of reduced height, whilst still accommo-dating the required valves and pipes to prevent, for ex-ample, fishing trawler nets from catching on the tree, toavoid the requirement of providing expensive protectionstructures or well reinforcing. The disclosed xmas treecomprises a generally cylindrical xmas tree housing de-fining a generally cylindrical bore, a separate xmas treevalve block disposed within the cylindrical bore of saidxmas tree housing, and a xmas tree cap for engagingwith said valve block and/or said xmas tree housing. Thexmas tree cap is coupled to a rig via various flow lineand umbilical services to facilitate control of the xmastree in conveying fluids between a surface mountedprocess facility and a downhole reservoir, and the xmastree valve block has a main production bore having at

least two valves axially spaced therein. The valves areoperable to seal the bore and provide well barriers.[0005] The applicant's earlier International Publica-tion No. WO 97/11252 relates to an improved subseaxmas tree and method of installing the tree on a well-head. The disclosed xmas tree consists of a wellheadconnector, a cylindrical structural housing and a tree capmounted on top of the housing. A dual bore subsea com-pletion test tree is disposed in the housing, and the testtree has a main production bore with series ball valvesfor controlling fluid flow in the production flow path andan annulus bore with a ball valve therein. The ball valvesare independently and remotely actuatable by a remote-ly operated vehicle (ROV) override system to controlcommunication through the xmas tree and to complywith various regulatory standards. A cross-over valve isprovided between the main bore and the annulus boreto allow fluid passage for well kill operations.[0006] An object of the present invention is to providea pressure control system embodied in a simplifiedstructure and a method of its deployment which obviatesor mitigates at least one of the disadvantages associat-ed with existing xmas trees.[0007] This is achieved by providing a simplified xmastree based on a dual bore sub-sea test tree. A separatetubing hanger is not required and the main bore of thesub-sea test tree is used as the production bore. In apreferred embodiment, an axial bore, which includes anisolation valve, is provided for communication with thewell annulus and an additional axial bore is occupied byan electrical power cable for supplying an electrical sub-mersible pump (ESP).[0008] According to a first aspect of the present inven-tion there is provided a xmas tree for use in a variety ofwell applications, said xmas tree comprising:

a generally cylindrical xmas tree housing defining agenerally cylindrical bore, a separate xmas treevalve disposed within the cylindrical bore of saidxmas tree housing and engaged with the xmas treehousing, anda xmas tree cap for engaging with said valve block,or said xmas tree housing, the xmas tree cap beingcoupled to a rig via various flowline and umbilicalservices to facilitate control of the xmas tree in con-veying fluids between surface mounted process fa-cility and a downhole reservoir,the xmas tree valve block having a main productionbore and at least one auxiliary bore, the main pro-duction bore having at least two valves axiallyspaced therein, said valves being operable to sealthe main production bore and provide well barriers,said at least one auxiliary bore providing an annulusaccess bore and containing a single valve operableto seal the access bore and provide a well barrierin the annulus access bore, and wherein the xmastree housing is coupled to a guide frame which isadapted to guide and receive the tree cap when in-

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stalled to facilitate coupling between the tree capand the tree housing and valve block.

[0009] Conveniently, the xmas tree valve block has amain production bore and two auxiliary bores. One aux-iliary bore provides the annulus access bore and has avalve therein and the other auxiliary bore has no valvebut is used for receiving a power cable for driving anelectrical submersible pump.[0010] In the absence of a requirement for an electri-cal submersible pump, no power cable is used and asingle axial bore for the cable is provided or, if two boresare present, the additional bore is blocked and sealed.A single axial annulus access bore is provided for pro-viding annulus control regardless whether or not thereis a power cable disposed in said auxiliary bore.[0011] It will also be appreciated that each of thebores has sealing means to seal the bores so that leak-age of fluid from the bore is prevented when the tree capis made up to the valve block and/or valve housing.[0012] Preferably also, said valves in series withinsaid production bore and the annulus bore are ballvalves. Alternatively, said valves are flapper valves, discvalves or plug valves.[0013] Preferably also, the housing engages with astandard wellhead connector to enable it to be attachedto a subsea wellhead and the valve block is proportionedand dimensioned to fit in within the bore of this housingand the housing is adapted to be received by the treecap so that connection is made between parts of the pro-duction bore, and parts of the two auxiliary bores to pro-vide effective connection for these bores. The connec-tions in the production and annulus bore are hollow pinand socket connections. The connections in the boresfor electrical communication are of a wet mateable con-nection in the power and signal cables. The connectionsin the controls parts are also by hollow pins and sockets.[0014] Conveniently also, locking means are providedbetween the xmas tree housing and the valve block as-sembly which are actuated when the tree cap fits on tothe valve block to lock the valve block to the xmas treehousing, and to provide fine alignment between the treecap and the housing. Conveniently, the locking meansare radially acting dogs which are actuated by axialmovement of a ring within the tree cap locking means.The top surface of the upper end of the valve block,which is level with the top of the housing, is providedwith profiles to accommodate:-

1) the sealing of the production and annulus bores,2) the sealing of the hydraulic ports required for thecontrol of the actuation of xmas tree and other wellfunctions,3) repeatable make and break of connections in thecommunications of electric signals between the sur-face and the electrical equipment located within thewell,4) repeatable make and break of connections in the

communications of electrical power between thesurface and electric submersible pump.

The external surface of the upper end of the valve blockis provided with at least one shaped keyway to ensurecorrect angular alignment between the xmas tree andthe tree cap to facilitate correct engagement of the var-ious connections at the top surface of the tree cap asdescribed above.[0015] Conveniently also, the xmas tree housing maybe coupled to a guide frame which is adapted to guideand receive the tree cap when installed so that there iseffective and efficient coupling between the tree cap andthe tree housing and valve block. The guide base is fittedto the wellhead system, and a protective frame is at-tached to the tree housing which takes the guidancefrom the wellhead, into the tree, and hence into the treecap.[0016] A permanent guide base, attached to the well-head system, including a side guide frame with guide-post spacing of the same dimensions as the guide framecoupled to the wellhead so that when the tree cap is re-moved for workover mode, the tree cap can be movedto one side and parked adjacent to the wellhead.[0017] According to another aspect of the present in-vention there is provided a xmas tree structure compris-ing:

a xmas tree housing coupled to a sub-sea wellhead;a xmas tree valve block located in said xmas treehousing, said xmas tree valve block having a pro-duction bore with at least two valves axially spacedtherein disposed in series and at least one auxiliarybore for facilitating annulus access control, said atleast one auxiliary bore having a valve therein, axmas tree cap coupled to the xmas tree valve blockand to said xmas tree housing, locking means dis-posed in said xmas tree to fasten the xmas treehousing, xmas tree valve block and said xmas treecap together, said respective xmas tree valves be-ing remotely operable to be selectively moved be-tween an open and a closed position to control flowof liquid through said xmas tree structure, andwherein the xmas tree housing is coupled to a guideframe which guides and receives the tree cap wheninstalled to facilitate coupling between the tree capand the tree housing and the valve block.

[0018] Conveniently, there are two auxiliary bores;one annulus access bore and a further auxiliary borewith at least one valve therein and a further auxiliarybore for receiving a power cable for supplying power toa downhole electrical submersible pump (ESP).[0019] According to a further aspect of the present in-vention there is provided a method of installing the xmastree on a wellhead for use in a variety of well tests, ahousing of the xmas tree having a blow-out preventermeans initially coupled thereto in place of a tree cap,

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said method comprising the steps of:

a) providing a xmas tree housing coupled to thewellhead by a guide frame, the xmas tree housinghaving a top part adapted to be coupled to a blow-out preventer connector,b) running a xmas tree valve assembly having avalve block through a blow-out preventer stack ofthe blow-out preventer for engaging with the xmastree housing, the valve block defining a productionbore and at least one auxiliary bore, with at leasttwo valves axially spaced in the production bore anda valve in the auxiliary bore, the xmas tree valveassembly being operable for providing a well barrierto the flow of well fluid,c) closing said valves in the production and annulusbores to provide well isolation once the xmas treevalve assembly is located in said xmas tree hous-ing,d) removing the blow-out preventer stack from thexmas tree housing,e) running in a xmas tree cap, guided and receivedby the guide frame for securing the xmas tree capto the xmas tree housing and xmas tree valve as-semblyto provide coupling from production and an-nulus bores to the surface and from auxiliary portsand bore to the surface, the arrangement beingsuch that said valves in the production and annulusbores can be controlled to provide control of wellfluid and xmas tree functionality.

[0020] Preferably also, the method includes the stepof using the xmas tree in a workover mode, said methodincluding the additional steps of removing the xmas treecap and parking the xmas tree cap on a further guideframe adjacent to the wellhead and xmas tree housing,and coupling a blow-out preventer stack on top of saidxmas tree housing with said xmas tree assembly con-tained therein.[0021] These and other aspects of the invention willbe better understood from the following descriptionwhen taken in combination with the accompanyingdrawings in which:-

Fig. 1 depicts a diagrammatic representation of asemi-submersible rig coupled to two EAT trees (ex-tended appraisal test tree) simplified xmas trees inaccordance with an embodiment of the present in-vention shown mounted on wellheads;Fig. 2 is a sectional elevational view through part ofa simplified horizontal xmas tree housing in accord-ance with an embodiment of the present inventioninstalled on a wellhead with a BOP stack showncoupled to the xmas tree;Fig. 3 is a view similar to Fig. 2 but depicts an inserttree valve block being installed through the BOPstack into the xmas tree housing;Fig. 4 shows the insert tree valve block of Fig. 3

landed within the xmas tree housing;Fig. 5 shows a view similar to Fig. 4 with the BOPstack removed and a simplified xmas tree in accord-ance with the embodiment of the present inventionbeing completed by the installation of a xmas treecap;Figs. 6a and 6b are respective perspective views ofa lockdown assembly and part of a valve block re-spectively for locking down the valve block and pro-viding fine angular alignment from the block to thexmas tree cap;Fig. 6c is an enlarged part section through the lock-down assembly located within the xmas tree hous-ing;Fig. 7 is a view similar to Fig. 5, but drawn to a largerscale, in which the xmas tree cap is shown coupledto the xmas tree housing to define a complete sim-plified xmas tree ready for in production mode withthe flow line controls and umbilical attached to thexmas tree cap;Fig. 8 is a sectional view taken on the line 8-8through the structural housing of Fig. 7;Fig. 9 is a detail of part of the dual bore tree shownin Fig. 7 and taken on the lines 9-9 of Fig. 8 to dem-onstrate the second auxiliary bore, providing com-munication with the annulus and showing the pro-duction and annulus bores with isolation valves,andFig. 10 is a view of the extended well test xmas treein workover mode where the xmas tree cap hasbeen removed and parked adjacent to the perma-nent guide base (PGB) and a BOP stack is connect-ed to the structural housing.

[0022] Reference is first made to Fig. 1 of the draw-ings which is a diagrammatic illustration of an extendedappraisal test (EAT) tree from a semi-submersible rig 10in which there is simultaneous production from two sep-arate wells 12,14.[0023] Wells 12 and 14 have associated extended ap-praisal test (EAT) tree simplified horizontal xmas trees16,18 which are located on respective wellheads 20 and22. A horizontal tree is one in which the completion canbe pulled out of the well without the need to recover thetree. Each xmas tree 12,14 is coupled to the semi-sub-mersible 10 via various lines, generally indicated by ref-erence numeral 24, a flexible production riser 26, anelectrical power cable 28 and a controls umbilical 30.The umbilicals are connected to a respective rig-mount-ed process system 34, control system 36 and electricalpower distribution system 38 via rig-mounted EQDC(Emergency Quick Disconnect/Connect) units. Liquidswhich are produced during the extended well test pass-es through the process system, and oil is pumped to atanker 41 via EQDC 39 and export line 40.[0024] The simplified xmas trees 16,18 on the well-heads, which will be later described in detail, are basedon a dual bore sub-sea test tree and allow an extended

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appraisal test (EAT) to be conducted without the ex-pense and complexity associated with traditional xmastrees.[0025] Reference is now made to Fig. 2 of the draw-ings which is an enlarged scale sectional elevationthrough the wellhead and the EAT xmas tree 16 whichconsists of a xmas tree housing installed on a wellheadwith a blow-out preventer BOP attached to a structuralhousing. For convenience, only the simplified xmas tree16 will be described in detail although it will be under-stood that xmas tree 18 has the same structure and op-erates in the same way. Mounted on the conductorhousing 20 of the wellhead system is a four post perma-nent guide base (PGB) 42 which surrounds 18θ" highpressure wellhead 44. A guide frame 46 fitted with fourfunnels to capture the PGB guide posts 42a is coupledonto the xmas tree housing connector 48 which hasdogs 50 which engage with an exterior profile 52 on thewellhead 44 to securely fasten the guide frame 46 andtree connector 48 to the wellhead 44. The wellhead con-nector 48 has a connection point 55 for receiving a struc-tural xmas tree housing 56 as shown in Fig. 2. An inter-nal cam profile (not shown) is provided at a pre-deter-mined angular orientation with respect to the guideframe 42, to engage a key on the valve block to controlthe angular position of the valve block in relation to thePGB 42, in order to achieve correct landing of the treecap. A BOP stack 60 also having a guide frame 57, withfunnels 58 which receive the posts 46a of frame 46, isshown mounted on the xmas tree housing 56. The ar-rangement of Figs. 2, 3 and 4 depict the installation orworkover mode as compared to extended well testmode.[0026] As mentioned above, a conventional type ofhorizontal tree wellhead is expensive and it also re-quires that the tubing hanger is run prior to use of thewellhead.[0027] This is overcome using the arrangementshown in Fig. 3 in which an insert xmas tree valve block,generally indicated by reference numeral 62 is installedthrough the BOP 60 into the xmas tree housing 56. Inthis case it will be understood that the insert tree valveblock 62 is based on a dual bore sub-sea test tree (sim-ilar to the type disclosed in applicant's co-pending Inter-national Published Application No. PCT/GB96/01115)which carries at its lower end tubing 64 and an electricalcable 66 which is coupled to an electrical submersiblepump (ESP), not shown in the interest of clarity. It willbe noted that in Fig. 3, and in Figs. 4, 5, 7, 9 and 10 ofthe drawings (which will be described below), the valveblock 62, tubing 64 and cable 66 are shown in section,but that these parts have not been sectioned, for clarity,due to the scale of the drawings. The installation proce-dure for the insert xmas tree valve block 62 will be laterdescribed but it is sufficient to note that at present, withreference to Fig. 3, the valve block 62, including the tub-ing 64 and the cable 66 which it is carrying, passesthrough the BOP stack 60 and the xmas tree housing 56.

[0028] Reference is now made to Fig. 4 of the draw-ings which is similar to Fig. 3 except that the insert treevalve block 62 has been landed on an annular landingshoulder 68 within the structural housing 56 whereby itadopts the position shown in Fig. 4; that is, part of thexmas tree valve block 62 extends upwardly from thexmas tree housing 56 inside the BOP stack 60. It will beseen that the main bore 70 of the valve block 62 containstwo 5" ball valves 72,74 in series similar to the sub-seatest tree and, as shown in Figs. 8 and 9, a smaller singlevalve 98 in the annulus bore 96, and an auxiliary 2" an-nulus bore 76 provides a pathway for the electrical sub-mersible cable 66. The ball valves 72,74 are qualified toa relevant xmas tree design standard, for example AP117D. It will be understood that the xmas tree ball valvesare uni-directional sealing valves which may be used ina bi-directional application if required. Each ball valve72,74 is "failsafe closed" fitted with a spring package75,77 respectively to return the valve to the closed po-sition on loss of control pressure. This is designed togive a valve closure time of approximately 30 seconds.Each ball valve has a double acting hydraulic actuator(not shown in the interest of clarity) whose axis is coin-cident with the axis of flow through the valve. Thismeans that pressurised hydraulic control fluid can beapplied to either the open or the closed side of the ac-tuator. For a uni-directional sealing application, a singlecontrol line conveys pressurised control fluid to the openside of the actuator. This opens the valve against springforce, which spring force returns the valves to the closedposition, on cessation of the application of pressuremaintaining the valve in the open position. It will also beappreciated from Fig. 4 that the xmas tree valve block62 is run on a casing riser 78 and the electrical cableconnection is made via a power cable 80. An umbilical(not shown in the interest of clarity) contains a bundleof tubular conduits for the conveyance of control fluids,and for communication with the well annulus. The xmastree housing 56 has the annular landing shoulder 68 forreceiving the xmas tree valve block 62 as shown andwhen the valve block 62 is in the position as shown inFig. 4, it is then in the correct position. Once the xmastree valve block is installed, the ball valves 72,74 and98 can be actuated to a closed position to provide wellcontrol barriers in the main bore 70, and the annulusbore 96 also as shown in Fig. 4, and the BOP stack 60can then be removed.[0029] Reference is now made to Figs. 5 and 6a, band c of the drawings; Fig. 5 depicts installation of thexmas tree cap, generally indicated by reference numeral84, after the BOP stack 60 has been removed, and Figs.6a,6b depict the separate parts of a lockdown assemblyby which the tree cap 84 is accurately aligned orienta-tionally to the valve block 62 and xmas tree housing 56and Fig. 6c depicts the lockdown assembly located with-in the xmas tree housing 56.[0030] The EAT tree cap connector 83 is mounted ina tree cap guide frame 85 which has four guide frame

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funnels 86 (only two of which are shown) so that whenit is run, as shown in Fig. 5, the funnels 86 mate with theguide posts 46a of guide frame 46, thereby providingcoarse alignment between the tree cap connector 83and the xmas tree housing 56 and tree valve block 62.It will be seen that the tree cap connector 83 is a centralperforated cylindrical block within a conventional exter-nally attached wellhead connector, and which is of asimilar structure to the wellhead connector 48, and locksto the structural housing 56 in the same way as the well-head connector 48 connects to the wellhead 44. Oncethe valve block 62 has been landed within the housing56 a lockdown assembly 161, shown in Fig. 6a, is in-stalled. This has an expanding profile which engages asuitable internal profile 162 in the housing and, whenset, locks the valve block 62 in the housing 56 in orderto prevent its upwards movement due to well pressureacting on closed valves 72,74 within the valve block 62.The lockdown assembly 161 has an outer body 161aand a rotatable and axially movable, via engagement ofthreads 166a,b (Fig. 6b), inner ring 169 for locking theassembly to the housing 56, as will be later described,outer body 161a has lower keys 163 (one of which isshown) which engage shaped keyways 165 on the ex-ternal surface 167 at the upper end of the valve block,and similar upper keys 167 engage corresponding key-ways 159 in the tree cap 84, to provide fine alignmentto ensure the engagement of the hollow pins and sock-ets, in the connections in the halves of the productionand annulus bores, the power and the signal electricalconnectors and the controls connections, between thetree cap 84 and the insert valve block 62 as will be de-scribed below. The assembly is run in and landed withthe lower protruding keys 163 engaged with the keyway165 in the valve block 62. As best seen in Fig. 6c, rota-tion of the inner body 169 expands dogs 171 to lock intoa housing groove 162. With the dogs 171 engaged, fur-ther downward travel of the inner body 169 contacts thevalve block 62 to rigidise it in place within the tree hous-ing 56. As shown in Fig. 5, the tree cap connector 83has parts which mate with the valve block including theupper part of wet mateable connectors, generally shownby numeral 88, for making the connections in the electricsignals and power to downhole equipment, generallyshown by numeral 89, and hollow pins, generally indi-cated by numeral 90, for connection with the sockets inthe production, annulus and controls ports bores gener-ally shown by numeral 92. It will be seen that the top 90of the tree cap 84 contains a termination 93 for the flowline and controls umbilical. It will also be seen from Fig.5 that the permanent guide base 42 has a side exten-sion, generally indicated by reference numeral 99, of thesame configuration as the guide base 42 for receivingthe xmas tree cap 84 from the xmas tree housing 56 inorder to accommodate a workover operation which re-quires a BOP stack to be installed on the tree housing.[0031] Reference is now made to Figs. 7 and 9 of theaccompanying drawings which depicts the assembled

simplified xmas tree 16 based on the xmas tree valveblock 62 for providing control of reservoir fluids. The treecap 84 is mounted on the xmas tree housing 56 withdogs 91 engaging the exterior profile 93 in the same wayas the BOP stack 60 was connected. When xmas treeis assembled there is connection between the parts ofthe main production bore 70, the annulus bore 96 andauxiliary bore 76. In this arrangement, which is the pro-duction mode, it can be seen that the flow line and um-bilicals, generally indicated by reference numeral 94,are attached to the tree cap 84. It will also be seen inFig. 7 and 9 that the 5" ball valves 72,74, and 1υ" valve98 are shown in the closed position. However, it will alsobe appreciated that they may be actuated via the umbil-ical 94 from surface to open positions to permit reservoirfluid to flow through the main production bore 70, andto monitor pressure in the annulus bore 96. The electri-cal power cable 66, which passes through the auxiliarybore 76, allows power to be supplied from the surfaceto the downhole electrical submersible pump.[0032] Fig. 8 depicts a section through the xmas treehousing 56 on line 8-8 of Fig. 7 and it will be seen thatthere are three principal axial bores in the insert valveblock (control axial bores have been omitted for clarity) ;the main 5" production bore 70 which has the two ballvalves 72,74 in series, the 1υ" annulus access bore 96,and the 2" auxiliary bore 76, which receives the electri-cal power cable 66 coupled to the downhole electricalsubmersible pump.[0033] Reference is also made to Fig. 9 of the draw-ings which is a sectional view taken along the lines 9-9of Fig. 8 and shows a partial sectional elevation of thetree showing through a detail 98 (shown in broken out-line) of the xmas tree 16 of Fig. 7, depicting the produc-tion and annulus access bores 70,96 each with an iso-lation valve 74,98 (with the tubing omitted for clarity). Itwill be appreciated that with this structure, control of theannulus line 96 will be carried out in the same way asusing the dual bore sub-sea test tree with the resultingadvantages also being present in this arrangement.[0034] Reference is now made to Fig. 10 of the draw-ings which shows the xmas tree 16 in workover modewith the tree cap 84 removed and the flow line and um-bilicals part 94 parked on the extended guide base 99disposed adjacent to the permanent guide base 42 andwith the BOP stack 60 run to again mate with the xmastree housing 56 in the same way as shown in Fig. 4 ofthe drawings.[0035] It will be appreciated that the xmas tree valveblock 62 is run on the riser 78 as if it were a sub-sea testtree and landed on the annular landing seat 68 withinthe xmas tree housing 56. It will also be appreciated thatbecause the xmas tree valve block 62 interfaces with itsdeployment tool 121, and the xmas tree cap 84 havingmultiple axial penetrations, it must be installed in aknown orientation to the permanent guide base guideposts 46 in order to ensure correct engagement with thetree cap 84 and the electrical power connector and the

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usual seal subs. The orientation alignment between thetree 16 and the tree cap 84 is achieved in step-like fash-ion with each successive step controlling more closelythe alignment.[0036] As described above, rough alignment is estab-lished between the tree guide frame funnels 58 and thepost on the PGB guide frame posts 46a, and immediatealignment is established with the installation of the xmastree valve insert block 62 into the housing 56. Fine align-ment is set up with the installation of the lock-down as-sembly (161) in preparation for the alignment requiredfor the installation of the tree cap 84.[0037] The insert valve block 62 is provided withmeans of achieving correct alignment. As describedabove with reference to Figs 6a and 6b, the keyways165 on the external diameter of block 62 facilitates en-gagement with keys 167 and orientational alignment ofthe latch/running tool. Similarly, at the bottom end, anorientational alignment key (not shown) is fitted to thexmas tree insert valve block 62 which interacts with aninternal bi-directional cam profile (not shown) within thelower end of the cylindrical xmas tree housing 56. Theangular relationship between the orientational aids ormain set valve block 62, the keys at the top and the ori-entation key at the bottom are controlled.[0038] The lock-down mechanism, or assembly 161is run in to rigidise the valve block 62 in place and alsoprovides a fine orientational alignment. As describedabove, with reference to Figs. 6a to 6c, the underside ofthe lockdown mechanism 161 carries the same key pro-file 163 as the valve block 62, whereas an upward facingkey 167 at the top of the lock-down mechanism 161 pro-vides a precision location for a matching keyway withinthe tree cap 84.[0039] The aforementioned structure and overview ofinstallation and operation will give the reader an under-standing of the structure and the installation procedure.However, for a better and more complete understandingregarding the running of the EAT xmas tree 16, it will beunderstood that prior to and during the running of thecompletion, the tree components are tested for function,orientation and pressure integrity using a tree stump/shipping skip. It is anticipated that drilling is carried outconventionally with the BOP stack 60 located directly onthe wellhead 44 which may be of a conventional type,for example Vetco SG-5 H-4.[0040] A brief summary of the sequence of events re-garding the running of the EAT simplified xmas trees16,18 is as follows:

a) At the end of the drilling phase, the well is sus-pended conventionally with the appropriate plugs/suspension string. The BOP 60 is pulled and a well-head corrosion cap (not shown) installed and thePGB guidelines are disconnected and retrieved.b) In the event that a rig and completion equipmentare available for installation of the completion im-mediately after drilling, it will be understood that the

trip to run the corrosion cap may be eliminated.c) The xmas tree housing 56 is then run using therunning tool available from the drilling phase and islocked on the wellhead 44 using either a workover(W/O) umbilical attached to the hydraulically oper-ated wellhead connector by using a ROV "hot stab"connection system stabbed into a suitable recepta-cle on the guide frame of the xmas tree spool hous-ing 56. The workover umbilical may then be discon-nected using the ROV.d) The BOP stack 60 is then run in the conventionalway on marine riser.e) Once the BOP stack 60 is run and is in position,as shown in Fig. 2, the running tool is used to runin the hole and test the VX seal, the running toolbeing available from the drilling phase and being fit-ted with a cup tester which seals the top of the pro-duction casing or the casing hanger in the wellhead.f) Once the VX seal has been tested, the runningtool and cup tester is pulled from the hole.g) On surface the electrical submersible pump(ESP) is made up to the completion tubing andpacker, the downhole chemical controls line ismade up and the ESP is then run in the hole on7" tubing/casing with the electrical power cable andcontrols line being unreeled and strapped to theproduction tubing as necessary until the correctlength of production tubing has been run in the hole.h) The xmas tree valve block 62 will already havebeen made up to its running tool 121, Fig. 10, onthe surface and will have been stored (racked) backin the derrick. This valve block 62, the running tool121 and the umbilical 80 are now made up to thestring 78. The downhole electrical cable 66 cut andterminated at the termination point 130,131, Fig. 3,to tails from the wet mate connector halves 88,89at the tree cap 84 and the xmas tree valve block 62and tested for continuity and function.i) Assuming that the continuity and function is ac-ceptable, the xmas tree valve block 62 is run in thehole and production tubing and landed in the xmastree housing 56 as shown in Fig. 4. In this positionthe ESP can be tested as required.j) The xmas tree valve block running tool 121, therunning string and umbilical 80 are then retrievedfrom the hole.k) The lockdown assembly 161 and running tool notshown are picked up and run in the hole on tubingor drill pipe and the valve block 62 is then rigidisedwithin the xmas tree housing 56 by turns of righthand rotation of the lockdown assembly runningtool and thereafter the lock-down assembly runningtool is retrieved from the hole.

[0041] As described above, the tree cap 84 is run withthe flow line, the umbilical and the electrical power cableattached to the tree cap, which all need to be pulled outfrom storage drums located on the rig deck or on an ad-

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jacent vessel. Once these "flexible members" havebeen unreeled from the respective storage drums, thefree ends are delivered and connected to the EQDC sys-tem. It is necessary to have installed "keel haul" linesfrom the storage reel locations into the moonpool areain order to deliver the ends of the flexible members tothe moonpool for attachment to the xmas tree cap 84.[0042] The xmas tree cap 84 is positioned on the spi-der beams (not shown in the interests of clarity) in themoonpool of the vessel and the respective connectionsof the flow line, umbilical and electrical power cable 94are made up to the xmas tree cap 84 with the requiredbend restrictors, strapping and buoyancy modules be-ing installed as required.[0043] Thereafter, the connection is made up to thetree cap running tool 104, the spider beams are spreadand the xmas tree cap 84 picked up and run in to landit on the xmas tree housing 56 as shown in Fig. 7 withthe flexible members being strapped together at the var-ious locations along their length as necessary.[0044] Once in the position shown in Fig. 7, the treecap connector 84 is locked in place using alternativeprocedures described above for running the structuralhousing 56 and the system is tested. The tree cap run-ning tool 104 is then retrieved.[0045] It will be appreciated that the tree may be re-trieved using steps which are basically the reversal ofthe running in steps.[0046] The workover procedures are similar to the re-trieval procedures except that the tree cap 84 is not re-covered to the surface provided that it is still functional.The tree cap running tool 121 is run, the tree cap con-nector is released and the tree cap 84 lifted off the tree62. A ROV is mobilised to disconnect the guidelineswhich are fitted with ROV releasable post tops of a pro-prietary manufacturer (such as Regan GL4).[0047] As best seen in Fig. 10, the tree cap 84 is skid-ded to one side, similar to running the BOP stack 60,and the guidelines are reconnected to a second set ofposts of guide frame 92 adjacent to the normal sideposts 46, thereby forming a "parking bay" adjacent tothe well attached to the existing permanent guide base46. The tree cap 84 is set down over the posts of theparking bay and the tree cap running tool 104 discon-nected and retrieved to the surface. The ROV is remo-bilised to effect reconnection of the guidelines back tothe well guide post tops.[0048] This allows the BOP stack 60 to be re-run toland on the structural housing 56 of the tree, as shownin Fig. 10, and the completion and ESP can be pulledas a normal retrieval operation. It will also be appreciat-ed that the tree cap can be replaced as a reversal of theforegoing steps.[0049] Various modifications may be made to the sim-plified xmas tree hereinbefore described without depart-ing from the scope of the invention. For example, thepreferred embodiment describes a xmas tree with anauxiliary channel which receives a cable for use with an

electrical submersible pump. However, it will be under-stood that the system could equally well be used in awell with natural drive in which case a conventional sub-sea test tree may be used as a valve block with the an-nulus line performing its normal annulus path function.It will also be understood that the ball valves may bereplaced by any other type of suitable valves, such asflapper valves, which are sufficient to provide a sealingfunction in the production bore and the annulus bore.It will be understood that a single valve may be used inthe xmas tree bore but, for safety reasons, two valvesin series are preferred in the production bore, althougha single valve in the annulus bore is adequate.[0050] It will also be understood that various diame-ters of xmas tree housings and xmas tree valve blocksmay be used. However, it will be understood that thexmas housing of 18θ" nominal bore diameter which isthe same as that of the wellhead is particularly conven-ient and is designed to receive a valve block assemblyand machined in accordance with the diameter of a typ-ical 5" x 2" sub-sea test tree. It will be appreciated thatthe dimensions of the bore and length of the tools maybe varied in accordance with specific requirements andthat the dimensions hereinbefore described are exem-plary only.[0051] The connection between the xmas tree capand the xmas tree housing may be other than using awellhead type of connector as hereinbefore described.Any other suitable connector may be used which givesan appropriate sealing function which is sufficient tocomply with the safety requirements and it will be un-derstood that the tree cap connector and structuralhousing connection which simulates the wellhead andwellhead connector arrangement is particularly conven-ient as these products already exist and have been welltested.[0052] In the event of a requirement to test the treevalves from above, a second control line is required toconvey pressurised control fluid to the closed side of theactuator. This creates an upward force which counter-acts the hydrostatic pressure acting downward on theball from above, and maintains contact between the balland the seat to prevent leakage, thus facilitating the testof the valve from above, if so required.[0053] It will also be understood that although the pre-ferred used of the simplified xmas tree structure is anextended well test, it will nevertheless be understoodthat the xmas tree may be used in an early productionfacility or even a permanent production facility and alsofor water and gas injection operations where relativelyquick and straightforward access to a well is requiredwithout requiring the considerable expense of a tradi-tional xmas tree.[0054] Advantages of the simplified xmas tree in ac-cordance with the present invention are that the struc-ture can be readily and quickly installed and is capableof being used in a variety of well applications, such asextended well tests, extended appraisal tests and early

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production facility and gas and water injection. Thexmas tree uses many existing well components therebyminimising the cost and also utilises a dual bore sub-sea test tree to provide dual valve protection in the pro-duction bore, whereas the annulus bore is used to pro-vide access into the well annulus and an auxiliary boreis used to provide a facility for receiving an electricalpower cable for driving a electrical submersible pump.In the situation where a power cable is provided through,an additional bore is necessary to allow the installationof the electric power cable for an ESP. This enables thesimplified xmas tree to provide all of the functions of atraditional xmas tree. In addition, the xmas tree can bereadily assembled or the tree cap removed from thexmas tree to receive a BOP stack for use in the workovermode. A further advantage is that the dual valve xmastree insert provides well barriers in accordance with stat-utory offshore requirements.

Claims

1. A xmas tree (16) for use in a variety of well applica-tions, said xmas tree (16) comprising:

a generally cylindrical xmas tree housing (56)defining a generally cylindrical bore, a separatexmas tree valve block (62) disposed within thecylindrical bore of said xmas tree housing (56)and engaged with the xmas tree housing (56),anda xmas tree cap (84) for engaging with saidvalve block (62), and/or said xmas tree housing(56), the xmas tree cap (84) being coupled to arig (10) via various flowline and umbilical serv-ices (94) to facilitate control of the xmas tree(16) in conveying fluids between surfacemounted process facility and a downhole res-ervoir,the xmas tree valve block (62) having a mainproduction bore (70) and at least one auxiliarybore (76;96), the main production bore (70)having at least two valves axially spaced there-in, said valves (72,74) being operable to sealthe main production bore (70) and provide wellbarriers, said at least one auxiliary bore provid-ing an annulus access bore and containing asingle valve (98) operable to seal the accessbore (76;96) and provide a well barrier in theannulus access bore (76;96) and wherein thexmas tree housing (56) is coupled to a guideframe (46) which is adapted to guide and re-ceive the tree cap (84) when installed to facili-tate coupling between the tree cap (84) and thetree housing (56) and valve block (62).

2. A xmas tree (16) as claimed in claim 1 wherein thexmas tree valve block (62) has a main production

bore (70) and two auxiliary bores (76,96).

3. A xmas tree (16) as claimed in claim 2 wherein oneauxiliary bore (96) provides the annulus accessbore and has a valve (98) therein and the other aux-iliary bore (76) has no valve but is used for receivinga power cable for driving an electrical submersiblepump.

4. A xmas tree (16) as claimed in claim 2 wherein if nopower cable is used one auxiliary bore (76) isblocked and the other auxiliary bore (96) is providedwith a valve (98) for annulus control.

5. A xmas tree (16) as claimed in any preceding claimwherein said at least two axially spaced valves(72,74) in the production bore are ball valves.

6. A xmas tree (16) as claimed in any one of claims 1to 4 wherein said valves (72,74) are flapper valves,disc valves or plug valves.

7. A xmas tree (16) as claimed in any preceding claimwherein the housing (56) engages with a standardwellhead connector (48) to enable it to be attachedto a sub-sea wellhead (44) and the valve block (62)is proportioned and dimensioned to fit in within thebore of this housing (56) and the housing (56) isadapted to be received by the tree cap (84) so thatconnection is made between parts of the productionbore (70), and parts of the two auxiliary bores (76;96) to provide effective connection for these bores.

8. A xmas tree (16) as claimed in claim 7 wherein theconnections in the production and the auxiliary bore(70;96) providing the annulus access bore are pro-vided by hollow pin and the auxiliary connections.

9. A xmas tree (16) as provided in any preceding claimwherein separate locking means (161) are providedbetween the xmas tree housing (56) and the valveblock assembly (62) which are actuated when thetree cap (84) fits on to the valve block (62) to lockthe valve block (62) to the xmas tree housing (56),and to provide fine alignment between the tree cap(84) and the housing (56).

10. A xmas tree (16) as claimed in claim 9 wherein thelocking means (161) are radially acting dogs (171)which are actuated by axial movement of a ring(169) within the locking means (161).

11. A xmas tree (16) as claimed in any preceding claimwherein an external surface of an upper end of thevalve block (62) is provided with at least one shapedkeyway (165) to ensure correct angular alignmentbetween the xmas tree (16) and the tree cap (84)to facilitate correct engagement of various connec-

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tions (93) at the top surface of the tree cap (84).

12. A xmas tree (16) as claimed in any preceding claimwherein there is provided a permanent guide base(42), attached to a wellhead system (20,44), includ-ing a side guide frame (99) with guidepost spacingof the same dimensions as the guide frame (42)coupled to a wellhead (44) of the wellhead system(20,44), so that when the tree cap (84) is removedfor workover mode, the tree cap (84) can be movedto one side and parked adjacent to the wellhead(44).

13. A xmas tree structure (16) comprising:

a xmas tree housing (56) coupled to a sub-seawellhead (44);a xmas tree valve block (62) located in saidxmas tree housing (56), said xmas tree valveblock (62) having a production bore (70) with atleast two valves (72,74) axially spaced thereinand at least one auxiliary bore (76;96) for facil-itating annulus access control, said at least oneauxiliary bore (96) having a valve (98) therein,a xmas tree cap (84) coupled to the xmas treevalve block (62) and to said xmas tree housing(56), locking means (161) disposed in saidxmas tree (16) to fasten the xmas tree housing(56), xmas tree valve block (62) and said xmastree cap (84) together, said respective xmastree valves (72,74;98) being remotely operableto be selectively moved between an open anda closed position to control flow of liquidthrough said xmas tree structure (16); andwherein the xmas tree housing (56) is coupledto a guide frame (46) which guides and receivesthe tree cap (84) when installed to facilitate cou-pling between the tree cap (84) and the treehousing (56) and the valve block (62).

14. A xmas tree structure (16) as claimed in claim 13wherein there are two auxiliary bores (76;96) beingone annulus access bore (96) with at least onevalve (98) therein and an auxiliary bore (76) for re-ceiving a power cable for supplying power to adownhole electrical submersible pump (ESP).

15. A method of installing the xmas tree (16) on a well-head (44) for use in a variety of well tests, a housing(56) of the xmas tree (16) having a blow-out pre-venter means (60) initially coupled thereto in placeof a tree cap (84), said method comprising the stepsof:

a) providing a xmas tree housing (56) coupledto the wellhead (44) by a guide frame (46), thexmas tree housing (56) having a top part adapt-ed to be coupled to a blow-out preventer con-

nector,b) running a xmas tree valve assembly havinga valve block (62) through a blow-out preventerstack of the blow-out preventer (60) for engag-ing with the xmas tree housing (56), the valveblock (62) defining a production bore (70) andat least one auxiliary bore (76;96), with at leasttwo valves (72,74) axially spaced in the produc-tion bore (70) and a valve (98) in the auxiliarybore (96), the xmas tree valve assembly beingoperable for providing a well barrier to the flowof well fluid,c) closing said valves (72,74;98) in the produc-tion (70) and annulus bores (96) to provide wellisolation once the xmas tree valve assembly islocated in said xmas tree housing (56),d) removing the blow-out preventer stack fromthe xmas tree housing,e) running in a xmas tree cap (84), guided andreceived by the guide frame (46) for securingthe xmas tree cap (84) to the xmas tree housing(56) and xmas tree valve assembly (62) to pro-vide coupling from production and annulusbores (70;96) to the surface and from auxiliaryports and bore (76) to the surface, the arrange-ment being such that said valves (72,74;98) inthe production (70) and annulus bores (96) canbe controlled to provide control of well fluid andxmas tree functionality.

16. A method as claimed in claim 15 wherein the meth-od includes the step of using the xmas tree (16) ina workover mode, said method including the addi-tional steps of removing the xmas tree cap (84) andparking the xmas tree cap (84) on a further guideframe (99) adjacent to the wellhead (44) and xmastree valve housing (56) , and coupling a blow-outpreventer stack on top of said xmas tree housing(56) with said xmas tree assembly contained there-in.

Patentansprüche

1. Eruptionskreuz ("xmas tree") (16) für die Verwen-dung bei einer Vielzahl von Bohrlochanwendungen,wobei das Eruptionskreuz (16) folgendes umfaßt:

ein allgemein zylindrisches Eruptionskreuz-Gehäuse (56), das eine allgemein zylindrischeBohrung definiert, einen gesonderten Erupti-onskreuz-Ventilblock (62), der sich innerhalbder zylindrischen Bohrung des Eruptionskreuz-Gehäuses (56) befindet und mit dem Eruptions-kreuz-Gehäuse (56) im Eingriff ist, und

einen Eruptionskreuz-Aufsatz (84) zum Inein-andergreifen mit dem Ventilblock (62) und/oder

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dem Eruptionskreuz-Gehäuse (56), wobei derEruptionskreuz-Aufsatz (84) über verschiede-ne Feldleitungs- und Versorgungsleitungsan-schlüsse (94) an eine Bohranlage (10) gekop-pelt ist, um eine Steuerung des Eruptionskreu-zes (16) beim Befördern von Fluids zwischeneiner an der Oberfläche montierten Verarbei-tungseinrichtung und einem Untertage-Reser-voir zu erleichtern,

wobei der Eruptionskreuz-Ventilblock (62) ei-ne Haupt-Förderbohrung (70) und wenigstens eineHilfsbohrung (76; 96) hat, wobei die Haupt-Förder-bohrung (70) wenigstens zwei in Axialrichtung mitZwischenraum in derselben angeordnete Ventilehat, wobei die Ventile (72, 74) betätigt werden kön-nen, um die Haupt-Förderbohrung (70) abzudich-ten und Bohrlochsperren bereitzustellen, wobei diewenigstens eine Hilfsbohrung eine Ringspalt-Zu-gangsbohrung bereitstellt und ein einzelnes Ventil(98) enthält, das betätigt werden kann, um die Zu-gangsbohrung (76; 96) abzudichten und eine Bohr-lochsperre in der Ringspalt-Zugangsbohrung (76;96) bereitzustellen, und bei dem das Eruptions-kreuz-Gehäuse (56) an einen Führungsrahmen(46) gekoppelt ist, der dafür geeignet ist, den Erup-tionskreuz-Aufsatz (84) zu führen und aufzuneh-men, wenn er installiert wird, um das Koppeln zwi-schen dem Eruptionskreuz-Aufsatz (84) und demEruptionskreuz-Gehäuse (56) und dem Ventilblock(62) zu erleichtern.

2. Eruptionskreuz (16) nach Anspruch 1, bei dem derEruptionskreuz-Ventilblock (62) eine Haupt-Förder-bohrung (70) und zwei Hilfsbohrungen (76, 96) hat.

3. Eruptionskreuz (16) nach Anspruch 2, bei dem dieeine Hilfsbohrung (96) die Ringspalt-Zugangsboh-rung bereitstellt und ein Ventil (98) in derselben hatund die andere Hilfsbohrung (76) kein Ventil hat,sondern verwendet wird, um ein Stromkabel zumAntreiben einer elektrischen Tauchpumpe aufzu-nehmen.

4. Eruptionskreuz (16) nach Anspruch 2, bei dem dieeine Hilfsbohrung (76) blockiert wird und die andereHilfsbohrung (96) mit einem Ventil (98) zur Rings-paltsteuerung versehen ist, wenn kein Stromkabelverwendet wird.

5. Eruptionskreuz (16) nach einem der vorhergehen-den Ansprüche, bei dem die wenigstens zwei in Axi-alrichtung mit Zwischenraum angeordneten Ventile(72, 74) in der Förderbohrung Kugelventile sind.

6. Eruptionskreuz (16) nach einem der Ansprüche 1bis 4, bei dem die Ventile (72, 74) Klappenventile,Scheibenventile oder Stopfenventile sind.

7. Eruptionskreuz (16) nach einem der vorhergehen-den Ansprüche, bei dem das Gehäuse (56) mit ei-nem standardmäßigen Bohrlochkopf-Verbinder(48) ineinandergreift, um zu ermöglichen, daß es aneinem Unterwasser-Bohrlochkopf (44) befestigtwird, und der Ventilblock (62) proportioniert und be-messen ist, um in die Bohrung dieses Gehäuses(56) zu passen, und das Gehäuse (56) dafür geeig-net ist, durch den Eruptionskreuz-Aufsatz (84) auf-genommen zu werden, so daß zwischen Teilen derFörderbohrung (70) und Teilen der zwei Hilfsboh-rungen (76; 96) eine Verbindung hergestellt wird,um eine wirksame Verbindung für diese Bohrungenzu gewährleisten.

8. Eruptionskreuz (16) nach Anspruch 7, bei dem dieVerbindungen in der Förderund der Hilfsbohrung(70; 96), welche die Ringspalt-Zugangsbohrung be-reitstellt, durch einen Hohlstift und die Hilfsverbin-dungen bereitgestellt werden.

9. Eruptionskreuz (16) nach einem der vorhergehen-den Ansprüche, bei dem gesonderte Arretiermittel(161) zwischen dem Eruptionskreuz-Gehäuse (56)und der Ventilblock-Baugruppe (62) bereitgestelltwerden, die betätigt werden, wenn der Eruptions-kreuz-Aufsatz (84) auf dem Ventilblock (62) sitzt,um den Ventilblock (62) am Eruptionskreuz-Gehäu-se (56) zu arretieren und eine Feinausrichtung zwi-schen dem Eruptionskreuz-Aufsatz (84) und demGehäuse (56) zu gewährleisten.

10. Eruptionskreuz (16) nach Anspruch 9, bei dem dieArretiermittel (161) in Radialrichtung wirkende Mit-nehmer (171) sind, die durch eine Axialbewegungeines Rings (169) innerhalb der Arretiermittel (161)betätigt werden.

11. Eruptionskreuz (16) nach einem der vorhergehen-den Ansprüche, bei dem eine Außenfläche einesoberen Endes des Ventilblocks (62) mit wenigstenseiner geformten Keilnut (165) versehen ist, um einerichtige Winkelausrichtung zwischen dem Erupti-onskreuz (16) und dem Eruptionskreuz-Aufsatz(84) zu sichern, um einen richtigen Eingriff der ver-schiedenen Verbindungen (93) an der oberen Flä-che des Eruptionskreuz-Aufsatzes (84) zu erleich-tern.

12. Eruptionskreuz (16) nach einem der vorhergehen-den Ansprüche, bei dem eine dauerhafte Führungs-basis (42) bereitgestellt wird, die an einem Bohr-lochkopf-System (20, 44) befestigt ist,einschließlich eines seitlichen Führungsrahmens(99) mit einem Leitpfostenabstand der gleichen Ab-messungen wie der an einen Bohrlochkopf (44) desBohrlochkopf-Systems (20, 44) gekoppelte Füh-rungsrahmen (42), so daß der Eruptionskreuz-Auf-

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satz (84) nach einer Seite bewegt und angrenzendan den Bohrlochkopf (44) geparkt werden kann,wenn der Eruptionskreuz-Aufsatz (84) für den Wie-deraufwältigungsbetrieb abgenommen wird.

13. Eruptionskreuzstruktur (16), die folgendes umfaßt:

ein Eruptionskreuz-Gehäuse (56), das an ei-nen Unterwasser-Bohrlochkopf (44) gekoppeltist,einen Eruptionskreuz-Ventilblock (62), der sichim Eruptionskreuz-Gehäuse (56) befindet, wo-bei der Eruptionskreuz-Ventilblock (62) eineFörderbohrung (70) mit wenigstens zwei in Axi-alrichtung mit Zwischenraum in derselben an-geordneten Ventilen (72, 74) und wenigstenseine Hilfsbohrung (76; 96) hat, um eine Rings-palt-Zugangssteuerung zu erleichtern, wobeidie wenigstens eine Hilfsbohrung (96) ein Ventil(98) in derselben hat, einen Eruptionskreuz-Aufsatz (84), der an den Eruptionskreuz-Ven-tilblock (62) und an das Eruptionskreuz-Gehäu-se (56) gekoppelt ist, im Eruptionskreuz (16)bereitgestellte Arretiermittel (161), um dasEruptionskreuz-Gehäuse (56), den Eruptions-kreuz-Ventilblock (62) und den Eruptionskreuz-Aufsatz (84) aneinander zu befestigen, wobeidie jeweiligen Eruptionskreuz-Ventile (72, 74;98) fernbetätigt werden können, um selektivzwischen einer offenen und einer geschlosse-nen Position bewegt zu werden, um den Flüs-sigkeitsstrom durch die Eruptionskreuzstruktur(16) zu steuern, und bei der das Eruptions-kreuz-Gehäuse (56) an einen Führungsrah-men (46) gekoppelt ist, der den Eruptions-kreuz-Aufsatz (84) führt und aufnimmt, wenn erinstalliert wird, um das Koppeln zwischen demEruptionskreuz-Aufsatz (84) und dem Erupti-onskreuz-Gehäuse (56) und dem Ventilblock(62) zu erleichtern.

14. Eruptionskreuzstruktur (16) nach Anspruch 13, beider zwei Hilfsbohrungen (76; 96) vorhanden sind,die eine Ringspalt-Zugangsbohrung (96) mit wenig-stens einem Ventil (98) in derselben und eine Hilfs-bohrung (76) zum Aufnehmen eines Stromkabelsfür die Stromversorgung einer elektrischen Unter-tage-Tauchpumpe (ESP - electrical submersiblepump) sind.

15. Verfahren zum Installieren des Eruptionskreuzes(16) auf einem Bohrlochkopf (44) für die Verwen-dung bei einer Vielzahl von Bohrlochuntersuchun-gen, wobei ein Gehäuse (56) des Eruptionskreuzes(16) ein Ausbruchssicherungsmittel (60) hat, dasanfangs anstelle eines Eruptionskreuz-Aufsatzes(84) an dasselbe gekoppelt wird, wobei das Verfah-ren die folgenden Schritte umfaßt:

a) Bereitstellen eines Eruptionskreuz-Gehäu-ses (56), das durch einen Führungsrahmen(46) an den Bohrlochkopf (44) gekoppelt wird,wobei das Eruptionskreuz-Gehäuse (56) einenoberen Teil hat, der dafür geeignet ist, an einenAusbruchssicherungsverbinder gekoppelt zuwerden,

b) Verlegen einer Eruptionskreuz-Ventilbau-gruppe mit einem Ventilblock (62) durch einenAusbruchssicherungsschacht der Ausbruchs-sicherung (60) zum Ineinandergreifen mit demEruptionskreuz-Gehäuse (56), wobei der Ven-tilblock (62) eine Förderbohrung (70) und we-nigstens eine Hilfsbohrung (76; 96) definiert,mit wenigstens zwei Ventilen (72, 74), die inAxialrichtung mit Zwischenraum in der Förder-bohrung (70) angeordnet sind, und einem Ven-til (98) in der Hilfsbohrung (96), wobei die Erup-tionskreuz-Ventilbaugruppe betätigt werdenkann, um eine Bohrlochsperre für den Stromvon Fördermedium bereitzustellen,

c) Schließen der Ventile (72, 74; 98) in der För-der- (70) und der Ringspaltbohrung (96), um ei-ne Bohrlochtrennung zu gewährleisten, sobalddie Eruptionskreuz-Ventilbaugruppe sich imEruptionskreuz-Gehäuse (56) befindet,

d) Abnehmen des Ausbruchssicherungs-schachts vom Eruptionskreuz-Gehäuse,

e) Einfahren eines Eruptionskreuz-Aufsatzes(84), geführt und aufgenommen durch denFührungsrahmen (46), um den Eruptionskreuz-Aufsatz (84) am Eruptionskreuz-Gehäuse (56)und der Eruptionskreuz-Ventilbaugruppe (62)zu befestigen, um eine Kopplung von der För-der- und der Ringspaltbohrung (70; 96) zurOberfläche und von Hilfsöffnungen und -boh-rung (76) zur Oberfläche zu gewährleisten,

wobei die Anordnung derart ist, daß die Ventile (72,74, 98) in der Förder- (70) und der Ringspaltboh-rung (96) gesteuert werden können, um eine Steue-rung der Funktionalität des Fördermediums und desEruptionskreuzes zu gewährleisten.

16. Verfahren nach Anspruch 15, bei dem das Verfah-ren den Schritt einschließt, das Eruptionskreuz (16)in einem Wiederaufwältigungsbetrieb zu verwen-den, wobei das Verfahren die zusätzlichen Schritteeinschließt, den Eruptionskreuz-Aufsatz (84) abzu-nehmen und den Eruptionskreuz-Aufsatz (84) aufeinem weiteren Führungsrahmen (99) angrenzendan den Bohrlochkopf (44) und das Eruptionskreuz-Gehäuse (56) zu parken und einen Ausbruchssi-cherungsschacht oben auf das Eruptionskreuz-Ge-

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häuse (56) zu koppeln, wobei die Eruptionskreuz-Baugruppe in derselben enthalten ist.

Revendications

1. Arbre de Noël (16) destine à être utilisé dans diffé-rentes applications de puits, ledit arbre de Noël (16)comprenant:

un boîtier de l'arbre de Noël généralement cy-lindrique (56) définissant un alésage générale-ment cylindrique, un bloc de vannes séparé del'arbre de Noël (62) agencé dans l'alésage cy-lindrique dudit boîtier de l'arbre de Noël (56) etengagé dans le boîtier de l'arbre de Noël (56),et

une couronne d'arbre de Noël (84) destinée às'engager dans ledit bloc de vannes (62) et/ouledit boîtier de l'arbre de Noël (56), la couronnede l'arbre de Noël (84) étant couplée à une ins-tallation de forage (10) par l'intermédiaire dedifférentes lignes de conduite et de câbles om-bilicaux (94) pour faciliter la commande de l'ar-bre de Noël (16) lors du transfert de fluides en-tre une installation de traitement montée ensurface et un réservoir de fond,

le bloc de vannes de l'arbre de Noël (62) com-portant un alésage de production principal (70)et au moins un alésage auxiliaire (76; 96), l'alé-sage de production principal (70) comportantau moins deux vannes qui y sont espacéesaxialement, lesdites vannes (72, 74) étant des-tinées à assurer l'étanchéité de l'alésage deproduction principal (70) et à établir des barriè-res de puits, ledit au moins un alésage auxiliai-re établissant un alésage d'accès à l'espaceannulaire et contenant une seule vanne (96)destinée à assurer l'étanchéité de l'alésaged'accès (76; 96) et à établir une barrière depuits dans l'alésage d'accès à l'espace annu-laire (76; 96), le boîtier de l'arbre de Noël (56)étant couplé à un cadre de guidage (46) destinéà guider et à recevoir la couronne de l'arbre (84)après l'installation pour faciliter le couplage en-tre la couronne de l'arbre (84), le boîtier de l'ar-bre (56) et le bloc de vannes (62).

2. Arbre de Noël (16) selon la revendication 1, danslequel le bloc de vannes de l'arbre de Noël (62)comporte un alésage de production principal (70)et deux alésages auxiliaires (76, 96).

3. Arbre de Noël (16) selon la revendication 2, danslequel un alésage auxiliaire (96) établit l'alésaged'accès à l'espace annulaire et comporte une vanne

(98), l'autre alésage auxiliaire (76) ne comportantpas de vanne mais servant à recevoir un câble d'ali-mentation pour entraîner une pompe électriquesubmersible.

4. Arbre de Noël (16) selon la revendication 2, danslequel, si on n'utilise pas de câble d'alimentation,un alésage auxiliaire (76) est bloqué, l'autre alésa-ge auxiliaire (96) étant équipé d'une vanne (98) envue de la commande de l'espace annulaire.

5. Arbre de Noël (16) selon l'une quelconque des re-vendications précédentes, dans lequel lesdites aumoins deux vannes à espacement axial (72, 74)dans l'alésage de production sont des vannes àboulet.

6. Arbre de Noël (16) selon l'une quelconque des re-vendications 1 à 4; dans lequel lesdites vannes (72,74) sont des vannes à clapet, des vannes à disqueou des vannes à boisseau.

7. Arbre de Noël (16) selon l'une quelconque des re-vendications précédentes, dans lequel le boîtier(56) s'engage dans un connecteur de tête de puitsstandard (48) pour permettre sa fixation à une têtede puits sous-marine (44), le bloc de vannes (62)ayant des proportions et des dimensions telles àpermettre son ajustement dans l'alésage de ce boî-tier (56), le boîtier (56) pouvant être reçu par la cou-ronne de l'arbre (84), de sorte à établir une con-nexion entre les parties de l'alésage de production(70) et les parties des deux alésages auxiliaires (76;96) pour assurer une connexion efficace de ces alé-sages.

8. Arbre de Noël (16) selon la revendication 7, danslequel les connexions dans l'alésage de productionet l'alésage auxiliaire (70; 96) établissant l'alésaged'accès à l'espace annulaire sont assurées par unegoupille creuse et les connexions auxiliaires.

9. Arbre de Noël (16) selon l'une quelconque des re-vendications précédentes, dans lequel des moyensde verrouillage séparés (161) sont agencés entrele boîtier de l'arbre de Noël (56) et l'assemblage debloc de vannes (62), actionnés lors de l'ajustementde la couronne de l'arbre (84) sur le bloc de vannes(62) pour verrouiller le bloc de vannes (62) sur leboîtier de l'arbre de Noël (56), en vue d'assurer unalignement de précision entre la couronne de l'arbre(84) et le boîtier (56).

10. Arbre de Noël (16) selon la revendication 9, danslequel les moyens de verrouillage (161) sont destaquets à actionnement radial (171), actionnés parle déplacement axial d'une bague (169) dans lesmoyens de verrouillage (161).

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11. Arbre de Noël (16) selon l'une quelconque des re-vendications précédentes, dans lequel une surfaceexterne d'une extrémité supérieure du bloc de van-nes (62) comporte au moins une rainure de clavettefaçonnée (165) pour assurer l'alignement angulairecorrect entre l'arbre de Noël (16) et la couronne del'arbre (84), pour faciliter l'engagement correct desdifférentes connexions (93) au niveau de la surfacesupérieure de la couronne de l'arbre (84).

12. Arbre de Noël (16) selon l'une quelconque des re-vendications précédentes, comportant une base deguidage permanente (42) fixée à un système de tê-te de puits (20, 44), englobant un cadre de guidagelatéral (99) avec des colonnes de guidage espa-cées à dimensions identiques à celles du cadre deguidage (42), couplé à une tête de puits (44) du sys-tème de la tête de puits (20, 44), de sorte que lorsdu retrait de la couronne de l'arbre (84) pour un mo-de de reconditionnement, la couronne de l'arbre(84) peut être déplacée vers un côté et bloquée prèsde la tête de puits (44).

13. Structure d'arbre de Noël (16), comprenant:

un boîtier d'arbre de Noël (56) couplé à la têtede puits sous-marine (44);un bloc de vannes de l'arbre de Noël (62) agen-cé dans le boîtier de l'arbre de Noël (56), leditbloc de vannes de l'arbre de Noël (62) compor-tant un alésage de production (70) avec aumoins deux vannes (72, 74) qui y sont espa-cées axialement et au moins un alésage auxi-liaire (76; 96) pour faciliter la commande d'ac-cès à l'espace annulaire, ledit au moins un alé-sage auxiliaire (96) comporte une vanne (98),une couronne d'arbre de Noël (84) couplée aubloc de vannes de l'arbre de Noël (62) et auditboîtier de l'arbre de Noël (56), des moyens deverrouillage (161) agencés dans ledit arbre deNoël (16) pour assembler le boîtier de l'arbrede Noël (56), le bloc de vannes de l'arbre deNoël (62) et ladite couronne de l'arbre de Noël(84), lesdites vannes respectives de l'arbre deNoël (72, 74; 98) pouvant être actionnées à dis-tance en vue d'un déplacement sélectif entreune position ouverte et une position ferméepour assurer la commande de l'écoulement deliquide à travers ladite structure de l'arbre deNoël (16); ledit boîtier de l'arbre de Noël (56)étant couplé à un cadre de guidage (46) guidantla couronne de l'arbre (84) et la recevant lorsde l'installation pour faciliter le couplage entrela couronne de l'arbre (84), le boîtier de l'arbre(56) et le bloc de vannes (62).

14. Structure d'arbre de Noël (16) selon la revendica-tion 13, comportant deux alésages auxiliaires (76;

96), un alésage d'accès à l'espace annulaire (96)avec au moins une vanne (98), et un alésage auxi-liaire (76) pour recevoir un câble d'alimentation pourfournir de l'énergie à une pompe électrique submer-sible de fond (ESP).

15. Procédé d'installation d'un arbre de Noël (16) surune tête de puits (44) en vue d'une utilisation dansdifférents tests de puits, un boîtier (56) de l'arbre deNoël (16) comportant un moyen d'obturation dupuits (60) qui y est initialement couplé à la placed'une couronne de l'arbre (84), ledit procédé com-prenant les étapes ci-dessous:

a) fourniture d'un boîtier de l'arbre de Noël (56)couplé à la tête du puits (44) par un cadre deguidage (46), le boîtier de l'arbre de Noël (56)comportant une partie supérieure destinée àêtre couplée à un connecteur d'obturation dupuits,

b) passage de l'assemblage de vannes de l'ar-bre de Noël comportant un bloc de vannes (62)à travers le bloc d'obturation du puits du moyend'obturation du puits (60) en vue d'un engage-ment dans le boîtier de l'arbre de Noël (56), lebloc de vannes (62) définissant un alésage deproduction (70) et au moins un alésage auxiliai-re (76; 96), au moins deux vannes (72, 74) étantespacées axialement dans l'alésage de pro-duction (70) et une vanne (98) étant agencéedans l'alésage auxiliaire (96), l'assemblage devannes de l'arbre de Noël pouvant être action-né pour établir une barrière du puits contrel'écoulement du fluide du puits,

c) fermeture desdites vannes (72, 74; 98) dansles alésages de production (70) et de l'espaceannulaire (96) pour assurer l'isolation du puitsaprès le positionnement de l'assemblage devannes de l'arbre de Noël dans ledit boîtier del'arbre de Noël (56),

d) retrait du bloc d'obturation du puits du boîtierde l'arbre de Noël,

e) descente d'une couronne de l'arbre de Noël(84), guidée et reçue par le cadre de guidage(46) pour fixer la couronne de l'arbre de Noël(84) sur le boîtier de l'arbre de Noël (56) et l'as-semblage de vannes de l'arbre de Noël (62)pour établir le couplage des alésages de pro-duction et de l'espace annulaire (70; 96) sur lasurface et d'orifices auxiliaires et de l'alésage(76) à la surface, l'agencement étant tel quelesdites vannes (73, 74; 98) dans les alésagesde production (70) et de l'espace annulaire (96)peuvent être commandées pour assurer la

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commande du fluide du puits et de la capacitéde fonctionnement de l'arbre de Noël.

16. Procédé selon la revendication 15, le procédé en-globant l'étape d'utilisation de l'arbre de Noël (16)dans un mode de reconditionnement, ledit procédéenglobant les étapes additionnelles de retrait de lacouronne de l'arbre de Noël (84) et du blocage dela couronne de l'arbre de Noël (84) sur un cadre deguidage additionnel (99) adjacent à la tête du puits(44) et au boîtier de l'arbre de Noël (56) et de cou-plage d'un bloc d'obturation du puits sur la partiesupérieure dudit boîtier de l'arbre de Noël (56), leditassemblage de l'arbre de Noël y étant contenu.

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