OA11887A

OA11887A - Method of creating a weld in a wellbore.

Info

Publication number: OA11887A
Application number: OA1200200022A
Authority: OA
Inventors: Wilhelmus Hubertus Pau Heijnen; Djurre Hans Zijsling
Original assignee: Shell Int Research
Priority date: 1999-07-27
Filing date: 2000-07-25
Publication date: 2006-03-28
Also published as: MXPA01013432A; EG22607A; DE60007134T2; CA2376963C; CA2376963A1; DZ3158A1; CN1365418A; AU6829100A; GC0000134A; EA200200201A1; AU763587B2; EA003227B1; DE60007134D1

Description

1188 7 1

METHOD OF CREATING A WELD IN A WELLBORE

The présent invention relates to a method of creatinga weld to connect a first element to a second element.

For a variety of applications it would be désirable toprovide a method of creating a weld in a wellbore formedin an earth formation, the wellbore containing a wellborefluid. Such applications include, for example, forming ofmetal-to-metal seals, providing structural integrity towellbore components or repairing corrosion damage.

However welding in a liquid environment (the wellborefluid) at high pressures generally encountered inwellbores, is not feasible. An analogous situation existsfor underwater welding, e.g. at offshore platforms,whereby the depth at which such welding is feasible islimited by the hydrostatic pressure of the water.

It is an object of the invention to provide a methodof creating a weld to connect a first element to a secondelement, said éléments being arranged in a wellborecontaining a wellbore fluid.

The method according to the invention comprises a) selecting a welding path along which the weld is tobe created; b) selecting a volume portion of the wellbore, in whichvolume portion said path is located, and sealing saidselected volume portion from the remainder of thewellbore volume; c) providing pressure control means for controlling thefluid pressure in said selected volume portion; d) operating the pressure control means so as to reducethe fluid pressure in said selected volume portion- to aselected pressure at which the weld can be created; and 1138 7 e) creating the weld along the selected welding path.

By sealing the volume portion in which the weld is tobe created from the remainder of the wellbore, andsubsequently reducing the pressure in the volume portion,the fluid pressure no longer prevents the création of theweld.

Suitably the first element is an upper wellborecasing and the second element is a lower wellbore casinghaving an upper part extending into a lower part of theupper wellbore casing. In this manner metal-to-metalsealed casings are obtained allowing gas at high pressureto be produced through the wellbore casing rather thanthrough a conventional production tube extending throughthe wellbore casing.

In a preferred embodiment said upper part has anouter diameter substantially equal to the inner diameterof said lower part, and step e) comprises welding theupper edge of the lower casing to the upper casing.

In another preferred embodiment said upper part hasan outer diameter smaller than the inner diameter of thelower part, and wherein the method further comprisesinserting a filler tube in the annular space between saidupper part and said lower part, and wherein step e)comprises welding the upper edge of the lower casing tothe filler tube and welding the upper edge of the fillertube to the upper casing.

To allow high pressure gas production from amultilatéral wellbore System, suitably the wellbore is amain wellbore provided with a branch wellbore, said firstelement being a branch of a branch casing member whichconnects a main casing extending through the mainwellbore to a branch casing extending through the branchwellbore, said second element being the branch casing. 3 1138 7

The invention will be c'escribed hereinafter in moredetail and by way of example with reference to theaccompanying drawings in wfcich

Fig. 1 schematically shows a longitudinal cross-section of a system used ii> conjunction with a firstembodiment of the method of the invention;

Fig. 2 schematically shows a longitudinal cross-section of a system used i® conjunction with a secondembodiment of the method of. the invention;

Fig. 3 schematically shows detail A of Fig. 2.

In the Figures like reference numerals relate to likecomponents.

The system shown in Fiç. 1 includes a wellbore 1formed in an earth formation 3, the wellbore beingprovided with a first element in the form of upperwellbore casing 5 extendinç in an upper part la of thewellbore and a second element in the form of lowerwellbore casing 7 extendinç in a lower part lb of thewellbore 1. The lower casing 7 has an outer diametersubstantially equal to the inner diameter of the uppercasing 5 and extends partly into the upper casing 5. Alayer of cernent 9 is arrançed in the annular spacebetween the two casings on one hand and the wellbore wallon the other hand. A welding system 10 is arranged in the wellbore 1,the welding system comprising a radially expandable upperpacker 12 arranged in the upper casing 5 above the upperedge 14 of the lower casing 7 and a radially expandablelower packer 16 arranged in the lower casing 7. Thepacker 12, 16 are interconnected by a tubular element 18provided with a plurality of openings 20 in the wallthereof. Each packer 12, 16 is internally provided withan contractible memory métal element (not shown) forradially expanding the packer against the respectivecasing 5, 7 and with an electric heating coil (not shown) 4 1188 7 for activating the raemory métal element. The packers 12,16 are provided with suitable seals 21 for sealing thepackers 12, 16 in their expanded position against therespective casing 5, 7.

The upper packer 12 is internally provided with aremotely controlled welding unit 22 (shown in dottedUnes) having a welding electrode 24 and a tube 25. Theelectrode 24 and tube 25 are movable between a retractedposition and an expanded position. In the retractedposition the electrode 24 and tube 25 are located in achamber (not shown) arranged within the upper packer 12,which chamber is sealed by a removable annular sealingmember 26 fitting in a corresponding annular recess 28(shown in dotted lines) provided in the upper packer 12at the side facing the lower packer 16. The annularsealing member 26 is removable from the upper packer bythe operation of a solenoid coil (not shown) which iscapable of inducing the sealing member to drop down fromthe packer 12. In Fig. 1 the annular sealing member isshown removed from the upper packer 12. In the expandedposition the electrode 24 and tube 25 extend throughannular recess 28 into a volume portion 30 of thewellbore 1 defined by the space enclosed by thepackers 12, 16 and the casings 5, 7. The welding unit isfurtherraore provided with means (not shown) for movingthe electrode 24 and tube 25 in circumferential directionalong the corner formed by the upper edge 14 of the lowercasing 7 and the inner surface of the upper casing 5. A tubular conduit 33 is connected to the weldingunit 10 at upper packer 12 and extends through thewellbore 1 to a control unit (not shown) at surface, theconduit 33 being in fluid communication with the interiorof the tubular element 18 and being provided with acontrol valve (not shown) at surface which, in open 5 118 8 7 position, provides fluid communication of the conduit 33to the atmosphère.

An electric cable 34 extends from the control unittrough the tubular conduit 33 to the welding System 10and from there to the heating coils and to the solenoidcoil. A fibre optical cable 35 extends from a monitoringunit (not shown) at surface trough the tubular conduit 33to the welding System 10 and from there into the tube 25so as to provide optical signais to the monitoring unit.

The control unit is adapted to selectively provideelectric power and/or electric control signais via thecable 34 to the welding System 10, the heating coils, thesolenoid coil and the caméra.

An outlet conduit 36 extends from the lower packer 16through the tubular element 18 and through the upperpacker 12, which outlet conduit provides fluidcommunication between the volume portion 30 and theinterior of the wellbore 1 above the welding unit 10. Anon-return valve 38 prevents flow of fluid from theoutlet conduit 36 into the volume portion 30.

During normal operation of the System used in thefirst embodiment, the wellbore 1 contains a wellborefluid of selected density. The welding électrodes 24 arein their retracted position and the annular sealingmember is located in the annular recess 28 so as to sealthe electrode.s. from. the wellbore fluid. The weldingSystem 10 is suspended from the tubular conduit 33 andlowered through the wellbore to the location shown inFig. 1 whereby the upper edge 14 of the lower casing 7 islocated between the packers 12, 17. Electric power isthen provided by the control unit via the cable 34 to theheating coils which thereby provide heat to the memorymétal éléments. Upon reaching their transitiontempérature the memory métal éléments contract andthereby radially expand the packers 12, 16 which become - 6 - 1 1 3 B 7 engaged to the respective casings 5, 7 in a sealingmanner.

The control valve at surface is closed and compressedinert gas, for example nitrogen, is pumped from surfacetrough the tubular conduit 33 and from there via thetubular element 18 and the openings 20 into the volumeportion 30. By pumping the gas into the volumeportion 30, wellbore fluid is evacuated from the volumeportion 30 through the outlet conduit into the interiorof the wellbore 1 above the welding unit 10. When thecompressed gas has displaced substantially ail wellborefluid from the volume portion 30 pumping is stopped. Thecontrol valve is then opened to bleed off the gaspressure in the volume portion 30 and the tubularconduit 33 so that thereby the gas pressure is reduced tosubstantially atmospheric pressure. The non-return-valve 36 prevents return flow of wellbore fluid from theoutlet conduit 36 into the volume portion 30.

The control unit is induced to provide electric powerto the solenoid coil which thereby induces the annularsealing meniber 26 to drop down from the upper packer 12onto the lower packer 16 (as shown in Fig. 1). Thecontrol unit is induced to provide electric power andelectric control signais to the welding system 10 so thatthe welding électrodes 24 assume their expanded positionat which the tips of the welding électrodes arepositioned near the upper edge 14 of the lower casing 7.The control unit then induces the électrodes 24 to createa weld extending in circumferential direction along thecorner formed by the upper edge 14 of the lower casing 7and the inner surface of the upper casing 5. The weldseals the lower casing 7 to the upper casing 5. Duringthe welding process the caméra is operated by the’controlunit in order to monitor the welding process at surface. 7 - 1188 7

When the welding process is completed the weldingSystem 10 is retrieved to surface by retrieval of thetubular conduit 33 from the wellbore 1.

The system used in the second embodiment is shown inFig. 2, and includes a branch casing member 40 arrangedin a main wellbore (not shown) provided with a branchwellbore (not shown), which branch casing member 40 islocated at the branch point of the two wellbores andconnects a main casing 42 extending through the mainwellbore to a branch casing 44 extending into the branchwellbore. The branch casing 44 has an upper part 46extending into a branch 48 of the branch casingmember 40, which upper part has an outer diameter smallerthan the inner diameter of the branch 48 and wherein afiller tube 50 is arranged in the annular space betweensaid upper part 46 and said branch 48. The upper edge ofthe branch casing 44 has been welded to the fillertube 50 and the upper edge of the filler tube 50 has beenwelded to the branch 48 using the method of theinvention.

Referring to Fig. 3, like reference numerals hâvebeen used for like components indicated in Fig. 1,therefore reference is made to Fig. 1 for a descriptionof such components in Fig. 3. The embodiment shown inFig. 3 differs from the embodiment of Fig. 1 in that thefirst element is formed by branch casing 44 and thesecond element is formed by branch casing 44. The outerdiameter of upper part 46 is smaller than the innerdiameter of branch 48.

Normal operation of the System of the secondembodiment is largely similar to normal operation of theSystem of the first embodiment', except that the upperedge of branch casing 44 is welded to the filler tube 50by weld 52 using the welding System 10, and the upper 8 118 8 7 edge of the filler tube 50 is welded to the branch 4 8 byweld 54 using the welding System 10.

The second embodiment of the method of the inventionis of particular interest if during running of the branchcasing 4 6 into the branch wellbore the branch casingbecomes stuck in the branch wellbore before havingreached planned depth. The branch casing 46 is then eutat a level such that the upper 4 6 part of the branchcasing remains in the branch 48, whereafter the fillertube 50 is installed and the welds 52, 54 are createdusing welding System 10. The eut upper section of thebranch casing is removed from the wellbore. 10

Claims

9 - 118 8 7 C L A I M S

1. A method of creating a weld at an element arranged ina wellbore containing a wellbore fluid, the methodcomprising a) selecting a welding path along which the weld is tobe created; b) selecting a volume portion of the wellbore, in whichvolume portion said path is located, and sealing saidselected volume portion from the remainder of thewellbore volume; c) providing pressure control means for controlling thefluid pressure in said selected volume portion; d) operating the pressure control means so as to reducethe fluid pressure in said selected volume portion to aselected pressure at which the weld can be created; and e) creating the weld along the selected welding path.
2. The method of claim 1, wherein step b) comprisesinstalling a first packer and a second packer in thewellbore, said selected volume portion being locatedbetween the packers.
3. The method of claim 2, wherein the first packer isprovided with a remotely controlled welding unit forcreating said weld.
4. The method of claim 3, wherein the welding unit hasat least one welding electrode sealed from the selectedvolume portion by removable sealing means.
5. The method of any one of daims 1-4, wherein saidelement is a first element and said weld connects thefirst element to a second element arranged in thewellbore.
6. The method of claim 5, wherein the first element isan upper wellbore casing and the second element is a 113 8 7 10 lower wellbore casing havinc an upper part extending intoa lower part of the upper wellbore casing.
7. The method of daim 6, wherein said upper part has anouter diameter substantially equal to the inner diameterof said lower part, and step e) comprises welding theupper edge of the lower casing to the upper casing.
8. The method of claim 6, wherein said upper part has anouter diameter smaller than the inner diameter of thelower part, and wherein the method further comprisesinserting a filler tube in the annular space between saidupper part and said lower part, and wherein step e)comprises welding the upper edge of the lower casing tothe filler tube and welding the upper edge of the fillertube to the upper casing.
9. The method of any one of daims 5-8, wherein thewellbore is a main wellbore provided with a branchwellbore, said first element being a branch of a branchcasing member which connects a main casing extendingthrough the main wellbore to a branch casing extendingthrough the branch wellbore, said second element beingthe branch casing.
10. The method of any one of daims 1-9, wherein thepressure control means comprises a conduit provided witha control valve and being in fluid communication withsaid selected volume portion, the conduit extendingthrough the wellbore to surface, and wherein step c)comprises opening the control valve so as to allow thefluid pressure in said selected volume portion todecrease.
11. The method of any one of daims 1-10, furthercomprising providing fluid évacuation means forevacuating drilling fluid from said selected volumeportion, and prior to step d) operating the fluidévacuation means so as to evacuate wellbore fluid fromthe selected volume portion. 11 118 8 7
12. The method of claim 11, wherein the fluid évacuationmeans comprises an outlet conduit providing fluidcommunication between the selected volume portion and theremainder of the wellbore volume, and wherein the step of 5 evacuating wellbore fluid comprises inducing a selected gas to flow into the selected volume portion so as toinduce wellbore fluid to flow from the selected volumeportion via the outlet conduit into the remainder of thewellbore volume.
13. The method of claim 12 when dépendent on claim 10, wherein the selected gas is induced to flow into saidvolume portion via said conduit.
14. The method of claim 12 or 13, wherein the outletconduit is provided with a non-return valve preventing 15 flow of wellbore fluid from the remainder of the wellbore volume into the selected volume portion.
15. The method substantially as described hereinbeforewith reference to the drawings.