OA12102A - Production valve. - Google Patents

Abstract

A wellbore system formed in an earth formation including at least one hydrocarbon fluid reservoir, the wellbore system comprising a main wellbore and a plurality of branch wellbores, each branch wellbore extending from the main wellbore into the earth formation and providing fluid communication between said at least one hydrocarbon fluid reservoir and the main wellbore, each branch wellbore being provided with a production valve comprising anchoring means for fixedly anchoring the production valve in the branch wellbore and control means for controlling the flow rate of a stream of hydrocarbon fluid flowing from said at least one reservoir via the branch wellbore into the main wellbore.

Description

1210?

Mal*

The présent invention relates to a wellbore Systemcomprising a main wellbore and a plurality of branchwellbores formed in an earth formation. Such wellboreSystem is generally referred to as a branched wellbore 5 System, or a multilatéral wellbore System. It is to be understood that in the context of the présent inventionthe wellbore section extending from surface to the firstwellbore junction below surface is referred to as themain wellbore, and the other wellbore sections are 10 referred to as branch wellbores. For example, if the wellbore System consrsts of a vertical wellbore extendinginto a réservoir and one branch extending from a junctionat the main wellbore into another réservoir, the part ofthe vertical wellbore below the junction is referred to 15 as a branch wellbore, and the part of the vertical wellbore above the junction is referred to as the mainwellbore.

In conventional multilatéral wellbore Systems it hasbeen tried to control fluid production by means of a 20 production valve at the wellhead located on top of the main wellbore. However a problem inhérent to the use of aproduction valve at the wellhead is that sélectiveproduction from the different réservoirs is impossible.Another problem occurs if one of the réservoirs is at a 25 · higher fluid pressure than another réservoir, whereby hydrocarbon fluid flows from the high pressure réservoirinto the low pressure réservoir instead of to thewellhead. 2 12102

The wellbore System according to the preamble ofclaim 1 is known from International patent applicationWO 96/30625. In the known System valves are arranged atthe branch points of a multilatéral well. If the fluid 5 pressures in various well branches are different some of the valves hâve to maintained in a half open positionduring an extensive period of time, which causes highwear and érosion of the valve. International patentapplication WO 97/37102 discloses another controllable 10 downhole valve which is subject to high wear if the valve is maintained half open during a long period of time.

Accordingly, it is an object of the invention toprovide an improved wellbore System which overcomes theproblems of the prior art. 15 In accordance with the invention there is provided a wellbore System formed in an earth formation including atleast one hydrocarbon fluid réservoir, the wellboreSystem comprising a main wellbore and a plurality ofbranch wellbores, which wellbore System is characterised 20 by the characterising features of claim 1.

By the arrangement of the production valves according to the invention in the branch wellbores it isachieved that the flow rate of hydrocarbon fluid producedfrom the different branch wellbores can be individually 25 controlled. Furthermore, the pressure drop across each production valve can be controlled in a manner that thepressure of the stream of fluid in the correspondingbranch wellbore downstream the production valve is suchthat flow from one réservoir into another réservoir is 30 prevented.

The invention will be described hereinafter in moredetail and by way of example with reference to theaccompanying drawings in which 1210 2 2a

Fig. 1 schematically shows an embodiment of aproduction valve applied in the wellbore System accordingto the invention;

Fig. 2 schematically shows a first detail of the5 embodiment of Fig. 1;

Fig. 3 schematically shows a second detail of theembodiment of Fig. 1;

Fig. 4 schematically shows a third detail of theembodiment of Fig. 1; 12102

Fig. 5 schematically shows a detail of an alternativepower generator for use in a modified version of theembodiment of Fig. 1; and

Fig. 6 schematically shows cross-section 6-6 ofFig. 5.

In Fig. 1 is shown a production valve 1 fixedlyarranged within a casing 2 of a wellbore (not shown) bymeans of a lock mandrel 4 which seals the productionvalve 1 to the casing 2 and which is suitable to transmitacoustic signais from the casing 2 to the productionvalve 1. The wellbore forms one of a plurality ofwellbore branches of a branched wellbore System for theproduction of natural gas. The branched wellbore systemis formed of a main wellbore and a plurality of branchwellbores, each branch wellbore extending from the mainwellbore into a natural gas réservoir, whereby thedifferent réservoirs hâve mutually different fluidpressures. The main wellbore is provided with a maincasing, and each branch wellbore is provided with abranch casing similar to casing 2, each branch casingbeing sealed to, and in metallic contact with, the maincasing.

The production valve 1 includes a tubular housing 6provided with a controllable valve A, a valve actuationmodule B, and a power generator C.

Fig. 2 shows in more detail the controllable valve Ahaving axis of symmetry 8, whereby at the upper side ofaxis 8 the controllable valve A is shown in an open modethereof, and at the lower side of axis 8 the controllablevalve is shown in a closed mode thereof. The controllablevalve A includes a flow passage 10 and a closuremember 12 which is movable in axial direction relative tothe flow passage 10 between an open position in which theclosure member 12 leaves the flow passage open and aclosed position in which the closure member 12 closes the 4 12102 flow passage 10. Το this end the closure member 12 isprovided with a frustoconical surface portion 14 which,when the closure member is in the closed position, is insealing contact with a correspondingly shaped seatsurface 16 surrounding the flow passage 10. The flowpassage is in fluid communication with two inletopenings 18 and an outlet 19, the inlet openings 18 beingarranged such that these are gradually covered by theclosure member 12 as the latter moves from the openposition to the closed position thereof. A slottedtube 20 is at one end thereof connected to the end of theclosure member 12 opposite the surface portion 14, whichtube 20 is at the other end thereof provided with anannular shoulder 22. The housing is internally providedwith a stop ring 24 arranged so that the annularshoulder 22 of the tube 20 contacts the stop ring 24 whenthe frustoconical surface portion 14 of the closuremember 12 is only a very short distance away from theseat surface 16. Thus, when the closure member 12 ispushed against the seat surface 16, the tube 20 exerts atensile force to the closure member 12 and thereby actsas a spring. An annular choke 26 is arranged in the flowpassage 10 such that fluid entering the housing 6 via theinlet openings 18 flows via the annular choke 26 to theoutlet 19. A lock ring threadedly connected to thehousing locks the choke 26 in place.

Referring further.to Fig. 3 there is shown in moredetail the actuation module B which includes an electricstepper motor 30 having a drive shaft 32 provided with afirst gear-wheel 34 driving a second gear-wheel 36. Atubular spindle 38 extends in axial direction through thesecond gear-wheel 36, the spindle 38 and the second gear-wheel 36 having co-operating threads (not shown) by sothat when the second gear-wheel 36 is rotated, thespindle 38 moves in axial direction. A guide pin 40 is 1 2102 fixedly arranged in the housing by a fixing dise 42 suchthat the guide pin extends in axial direction through thetubular spindle 38 so as to guide the spindle 38 duringaxial movement thereof. The end of the spindle 38 remotefrom the fixing dise 42 is connected to the closuremember 12 by suitable connecting means (not shown). Theactuation module B furthermore includes a controlSystem 44 provided with a battery (not shown) for drivingthe electric motor and a microprocessor (not shown)having an acoustic sensor. The microprocessor has beenprogrammed to control operation of the stepper motor independence of coded acoustic signais received by theacoustic sensor. The various parts of the drive assembly B are locked in the housing 6 by means of fourlock rings 46a, 46b, 46c, 46d.

Referring further to Fig. 4, the power generator Cincludes a turbine having a housing member 48 fixedlyconnected to the tubular housing 6 by threadconnection 50. A shaft 52 extends concentrically throughthe housing member 48, which shaft is rotatably arrangedin a ceramic bearing 53 and is provided with animpeller 54 arranged at the end of the shaft 52 oppositethe actuation module B. The other end of the shaft 52 isprovided with a thrust bearing 56 preventing axialmovement of the shaft 6 relative to the tubularhousing 6. A plurality of magnets 58 are fixedlyconnected to the shaft 52 at regular angular intervalsalong the circumference of the shaft 52. A glass sealedcoil 60 is fixedly arranged in the housing member 48 andextends around the magnets 58, the coil beingelectrically connected to the control System in a mannerthat the coil 60 charges the battery when the shaft 52rotâtes.

In Figs. 5 and 6 is shown an alternative powergenerator 60 for incorporation in the production valve of 6 1210 2

Fig. 1 instead of the power generator C. The alternativepower generator 60 forms a fluidic electrical generatorcomprising a generator body 62 including an outer bodypart 62a and an inner body part 62b fixedly arranged inthe outer body part 62a. The outer body part 62a isprovided with a thread connection 64 for screwing thepower generator 60 into the housing 6 and with a fluidchamber 66 having a fluid inlet 68 and two fluidoutlets 70, 72 extending in diverging directions. Amagnetic oscillator 74 is arranged in the fluidchamber 66, the oscillator 74 being provided with twosupports 76 of triangular cross-sectional shape, eachsupport having an edge resting in a groove (not shown)provided in the inner body part 62b in a manner allowingangular oscillation of the oscillator 74 relative to saidedge. Thus the oscillator divides the fluid chamber 66 intwo fluid passages 66a, 66b along opposite sides of theoscillator 74. A feed-back conduit 79 provides fluidcommunication between the fluid passages 66a, 66b. Twoelectric coils 80, 82 are arranged in the outer bodypart 62a, which coils extend around the magneticoscillator 74 are provided with electric connections (notshown) for connecting the coils 80, 82 to the controlSystem in a manner that the coils 80, 82 charge thebattery when the oscillator 74 oscillâtes in the fluidchamber 66.

Each one of the branch wellbores is provided with aproduction valve similar to the production valve 1,except that the inner diameters of the annular chokes aredifferent for the different production valves. Thesélection of said different inner diameters is discussedhereinafter in relation to normal operation of theproduction valve 1.

During normal operation of the embodiment of Fig. 1natural gas is produced simultaneously from the different 12102 réservoirs, whereby for each réservoir a stream ofproduced gas flows through the respective branch wellboreinto the main wellbore and from there to a productionfacility (not shown) at surface. Thus the differentstreams commingle in the main wellbore so as to form amain stream of produced gas. The inner diameters of thechokes 26 of the different production valves 1 areselected such that, with each controllable valve A in theopen mode, the gas pressures in the different streamsdownstream the respective chokes 26 are about equal. Itis thereby prevented that gas from a réservoir at arelatively high pressure flows into a réservoir at arelatively low pressure.

As long as it is desired to produce gas at a maximumflow rate from the wellbore System, each controllablevalve A of a respective production valve 1 is kept in theopen mode. In this mode produced gas flows via the inletopenings 18 into the flow passage 10 at maximum flowrate. As the gas flows along the impeller 54 the latteris rotated, resulting in rotation of the shaft 52 and themagnets 58. An electric current is thereby generated inthe coil 60, which current flows via the control Systemto the battery and thereby charges the battery. Sincecritical flow of the gas does not occur at the locationof the closure member 12, but instead in the choke 26,the closure member 12 is not subjected to enhancedérosion as a resuit of gas flowing at critical flow ratealong the closure member.

When it is desired to decrease production of gas fromone or more of the branch wellbores a coded acousticsignal representing an instruction to move the closuremember 12 a selected distance into the flow passage 10,is generated in the main casing. This can be done, forexample, by inducing a sequence of metallic objectimpacts on the main casing. The acoustic signal travels 12102 via the main casing, the branch casing 2 and the lockmandrel 4 to the acoustic sensor which induces themicroprocessor to control the stepper motor 30 so as torotate the drive shaft 32 a selected number ofrévolutions commensurate with the required movement ofthe closure member 12. As a resuit the second gear-wheelrotâtes and thereby moves the spindle 38 and the closuremember 12 over said selected distance into the flowpassage 10. The flow openings 18 are thereby partlycovered so that gas can only flow at a reduced flow ratevia the inlet openings 18 to the outlet 19.

When it is desired to stop production of gas from oneof the branch wellbores, the same procedure as describedwith reference to decreasing production of gas isfollowed, except that the coded acoustic signal nowrepresents an instruction to move the closure member 12against the seat surface 16 of the housing 6. As a resuitthe closure member 12 is moved against the seatsurface 16 so that the controllable valve A is in theclosed mode. In this position the annular shoulder 22 ofthe tube slotted 20 contacts the stop ring 24, and thetube·20 exerts a tensile force to the closure member 12biasing the closure member 12 away from the seatsurface 16.

When it is desired to bring the closure assembly backto the open mode, a coded acoustic signal representing aninstruction to move the closure member 12 to the openposition thereof is generated in the main casing. Initialmovement of the closure member 12 from the closedposition to the open position thereof is promoted by thetensile force from the slotted tube 20.

Normal operation of the modified version of theembodiment of Fig. 1 is similar to normal operation ofthe embodiment of Fig. 1, except that electric current isgenerated by the alternative power generator 60 instead 9 12102 10 of the power generator C. Namely, gas which enters thefluid chamber 66 via fluid inlet 68 flows through thefluid passages 66a, 66b along the oscillator 74 andfurther through the fluid outlets 70, 72. The feed-back5 conduit 79 causes a Coanda effect to occur in the fluid passages 66a, 66b causing flow of gas into theoutlets 70, 72 in an alternating manner. As a resuitangular oscillation of the magnetic oscillator 74 occursaround the support edges of the supports 76. An electriccurrent is thereby generated in the coils 80, 82, whichcurrent flows via the control System to the battery andthereby charges the battery.

Claims (11)

10 7 2102

1. A wellbore System formed in an earth formationincluding at least one hydrocarbon fluid réservoir, thewellbore System comprising a main wellbore and aplurality of branch wellbores, each branch wellboreextending from the main wellbore into the earth formationand providing fluid communication between said at leastone hydrocarbon fluid réservoir and the main wellbore,each branch wellbore being provided with a controllableproduction valve (1) for varying the flow rate of thestream of hydrocarbon fluid, the valve (1) comprisinganchoring means (4) for fixedly anchoring the productionvalve (1) in the branch wellbore and control means (B)for controlling the flow rate of a stream of hydrocarbonfluid flowing from said at least one réservoir via thebranch wellbore into the main wellbore; characterised in that the valve (1) furthermore comprisesa critical flow choke (26) arranged so that the streamflows therethrough.

2. The wellbore System of claim 1, wherein the criticalflow choke (26) is arranged downstream the controllablevalve (1).

3. The wellbore System of claim 1 or 2, wherein thecontrollable valve (1) comprises a flow passage (10)arranged so that the stream flows therethrough and aclosure member (12) movable in a selected directionrelative to the flow passage (10) so as to at leastpartially close the flow passage (10).

4. The wellbore System of claim 3, wherein the closuremember (12) is movable in said selected direction between 12102 11 an open position in which the closure member leaves theflow passage (10) substantially open, and a closedposition in which the closure member (12) closes the flowpassage (10).

5. The wellbore System of claim 3 or 4, furthercomprising an actuation module (B) for controllingmovement of the closure member (12) in the selecteddirection.

6. The wellbore System of claim 5, wherein the actuation module (B) comprises an electric motor (30)arranged tô rotate a spindle (38), the spindle (38) beingarranged so as to induce the closure member (12) to movein the selected direction upon rotation of the spindle (38).

7. The wellbore System of claim 6, wherein the actuation module (B) further comprises a battery fordriving the electric motor and a power generator (C)arranged to be driven by the stream of hydrocarbon fluidand to charge the battery.

8. The wellbore System of claim 7, wherein the powergenerator (C) is selected from a turbine and a fluidicelectrical generator.

9. The wellbore System of any one of daims 5-8,wherein the actuation module (B) comprises an acousticsensor and a microprocessor programmed to controlmovement of the closure member (12) in dependence ofreceipt of a coded acoustic signal by the acousticsensor.

10. The wellbore System of claim 9, wherein the anchoring means (4) comprises a lock mandrel for lockingthe production valve in a casing (2) of the branchwellbore, the lock mandrel being suitable to transmit 12102 12 said coded acoustic signal from the casing (2) to theproduction valve (1).

11. The wellbore System of any one of daims 1-10,wherein the earth formation includes a plurality of said 5 hydrocarbon fluid réservoirs having mutually different fluid pressures, each branch wellbore providing fluidcommunication between a corresponding one of thehydrocarbon fluid réservoirs and the main wellbore.