PRODUCTION VALVE

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: _ ± _ PRODUCTION VALVE The present invention relates to a wellbore system comprising a main wellbore and a plurality of branch wellbores formed in an earth formation. Such wellbore system is generally referred to as a branched wellbore system, or a multilateral wellbore system. It is to be understood that in the context of the present invention the wellbore section extending from surface to the first wellbore junction below surface is referred to as the main wellbore, and the other wellbore sections are referred to as branch wellbores. For example, if the wellbore system consists of a vertical wellbore extending into a reservoir and one branch extending from a junction at the main wellbore into another reservoir, the part of the vertical wellbore below the junction is referred to as a branch wellbore, and the part of the vertical wellbore above the junction is referred to as the main wellbore . In conventional multilateral wellbore systems it has been tried to control fluid production by means of a production valve at the wellhead located on top of the main wellbore. However a problem inherent to the use of a production valve at the wellhead is that selective production from the different reservoirs is impossible. Another problem occurs if one of the reservoirs is at a higher fluid pressure than another reservoir, whereby hydrocarbon fluid flows from the high pressure reservoir into the low pressure reservoir instead of to the wellhead. Accordingly, it is an object of the invention to provide an improved wellbore system which overcomes the problems of the prior art . In accordance with the invention there is provided 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. By the arrangement of the production valves in the branch wellbores it is achieved that the flow rate of hydrocarbon fluid produced from the different branch wellbores can be individually controlled. Furthermore, the pressure drop across each production valve can be controlled in a manner that the pressure of the stream of fluid in the corresponding branch wellbore downstream the production valve is such that flow from one reservoir into another reservoir is prevented. The invention will be described hereinafter in more detail and by way of example with reference to the accompanying drawings in which Fig. 1 schematically shows an embodiment of a production valve applied in the wellbore system according to the invention; Fig. 2 schematically shows a first detail of the embodiment of Fig. 1; Fig. 3 schematically shows a second detail of the embodiment of Fig. 1; Fig. 4 schematically shows a third detail of the embodiment of Fig. 1; Fig. 5 schematically shows a detail of an alternative power generator for use in a modified version of the embodiment of Fig. 1; and Fig. 6 schematically shows cross-section 6-6 of Fig. 5. In Fig. 1 is shown a production valve 1 fixedly arranged within a casing 2 of a wellbore (not shown) by means of a lock mandrel 4 which seals the production valve 1 to the casing 2 and which is suitable to transmit acoustic signals from the casing 2 to the production valve 1. The wellbore forms one of a plurality of wellbore branches of a branched wellbore system for the production of natural gas. The branched wellbore system is formed of a main wellbore and a plurality of branch wellbores, each branch wellbore extending from the main wellbore into a natural gas reservoir, whereby the different reservoirs have mutually different fluid pressures. The main wellbore is provided with a main casing, and each branch wellbore is provided with a branch casing similar to casing 2, each branch casing being sealed to, and in metallic contact with, the main casing. The production valve 1 includes a tubular housing 6 provided with a controllable valve A, a valve actuation module B, and a power generator C. Fig. 2 shows in more detail the controllable valve A having axis of symmetry 8, whereby at the upper side of axis 8 the controllable valve A is shown in an open mode thereof, and at the lower side of axis 8 the controllable valve is shown in a closed mode thereof. The controllable valve A includes a flow passage 10 and a closure member 12 which is movable in axial direction relative to the flow passage 10 between an open position in which the closure member 12 leaves the flow passage open and a closed position in which the closure member 12 closes the flow passage 10. To this end the closure member 12 is provided with a frustoconical surface portion 14 which, when the closure member is in the closed position, is in sealing contact with a correspondingly shaped seat surface 16 surrounding the flow passage 10. The flow passage is in fluid communication with two inlet openings 18 and an outlet 19, the inlet openings 18 being arranged such that these are gradually covered by the closure member 12 as the latter moves from the open position to the closed position thereof. A slotted tube 20 is at one end thereof connected to the end of the closure member 12 opposite the surface portion 14, which tube 20 is at the other end thereof provided with an annular shoulder 22. The housing is internally provided with a stop ring 24 arranged so that the annular shoulder 22 of the tube 20 contacts the stop ring 24 when the frustoconical surface portion 14 of the closure member 12 is only a very short distance away from the seat surface 16. Thus, when the closure member 12 is pushed against the seat surface 16, the tube 20 exerts a tensile force to the closure member 12 and thereby acts as a spring. An annular choke 26 is arranged in the flow passage 10 such that fluid entering the housing 6 via the inlet openings 18 flows via the annular choke 26 to the outlet 19. A lock ring 28 threadedly connected to the housing locks the choke 26 in place. Referring further to Fig. 3 there is shown in more detail the actuation module B which includes an electric stepper motor 30 having a drive shaft 32 provided with a first gear-wheel 34 driving a second gear-wheel 36. A tubular spindle 38 extends in axial direction through the second gear-wheel 36, the spindle 38 and the second gearwheel 36 having co-operating threads (not shown) by so that when the second gear-wheel 36 is rotated, the spindle 38 moves in axial direction. A guide pin 40 is fixedly arranged in the housing by a fixing disc 42 such that the guide pin extends in axial direction through the tubular spindle 38 so as to guide the spindle 38 during axial movement thereof. The end of the spindle 38 remote from the fixing disc 42 is connected to the closure member 12 by suitable connecting means (not shown) . The actuation module B furthermore includes a control system 44 provided with a battery (not shown) for driving the electric motor and a microprocessor (not shown) having an acoustic sensor. The microprocessor has been programmed to control operation of the stepper motor in dependence of coded acoustic signals received by the acoustic sensor. The various parts of the drive assembly B are locked in the housing 6 by means of four lock rings 46a, 46b, 46c, 46d. Referring further to Fig. 4, the power generator C includes a turbine having a housing member 48 fixedly connected to the tubular housing 6 by thread connection 50. A shaft 52 extends concentrically through the housing member 48, which shaft is rotatably arranged in a ceramic bearing 53 and is provided with an impeller 54 arranged at the end of the shaft 52 opposite the actuation module B. The other end of the shaft 52 is provided with a thrust bearing 56 preventing axial movement of the shaft 6 relative to the tubular housing 6. A plurality of magnets 58 are fixedly connected to the shaft 52 at regular angular intervals along the circumference of the shaft 52. A glass sealed coil 60 is fixedly arranged in the housing member 48 and extends around the magnets 58, the coil being electrically connected to the control system in a manner that the coil 60 charges the battery when the shaft 52 rotates . In Figs. 5 and 6 is shown an alternative power generator 60 for incorporation in the production valve of Fig. 1 instead of the power generator C. The alternative power generator 60 forms a fluidic electrical generator comprising a generator body 62 including an outer body part 62a and an inner body part 62b fixedly arranged in the outer body part 62a. The outer body part 62a is provided with a thread connection 64 for screwing the power generator 60 into the housing 6 and with a fluid chamber 66 having a fluid inlet 68 and two fluid outlets 70, 72 extending in diverging directions. A magnetic oscillator 74 is arranged in the fluid chamber 66, the oscillator 74 being provided with two supports 76 of triangular cross-sectional shape, each support having an edge resting in a groove (not shown) provided in the inner body part 62b in a manner allowing angular oscillation of the oscillator 74 relative to said edge. Thus the oscillator divides the fluid chamber 66 in two fluid passages 66a, 66b along opposite sides of the oscillator 74. A feed-back conduit 79 provides fluid communication between the fluid passages 66a, 66b. Two electric coils 80, 82 are arranged in the outer body part 62a, which coils extend around the magnetic oscillator 74 are provided with electric connections (not shown) for connecting the coils 80, 82 to the control system in a manner that the coils 80, 82 charge the battery when the oscillator 74 oscillates in the fluid chamber 66. Each one of the branch wellbores is provided with a production valve similar to the production valve 1, except that the inner diameters of the annular chokes are different for the different production valves. The selection of said different inner diameters is discussed hereinafter in relation to normal operation of the production valve 1. During normal operation of the embodiment of Fig. 1 natural gas is produced simultaneously from the different reservoirs, whereby for each reservoir a stream of produced gas flows through the respective branch wellbore into the main wellbore and from there to a production facility (not shown) at surface. Thus the different streams commingle in the main wellbore so as to form a main stream of produced gas. The inner diameters of the chokes 26 of the different production valves 1 are selected such that, with each controllable valve A in the open mode, the gas pressures in the different streams downstream the respective chokes 26 are about equal. It is thereby prevented that gas from a reservoir at a relatively high pressure flows into a reservoir at a relatively low pressure. As long as it is desired to produce gas at a maximum flow rate from the wellbore system, each controllable valve A of a respective production valve 1 is kept in the open mode. In this mode produced gas flows via the inlet openings 18 into the flow passage 10 at maximum flow rate. As the gas flows along the impeller 54 the latter is rotated, resulting in rotation of the shaft 52 and the magnets 58. An electric current is thereby generated in the coil 60, which current flows via the control system to the battery and thereby charges the battery. Since critical flow of the gas does not occur at the location of the closure member 12, but instead in the choke 26, the closure member 12 is not subjected to enhanced erosion as a result of gas flowing at critical flow rate along the closure member. When it is desired to decrease production of gas from one or more of the branch wellbores a coded acoustic signal representing an instruction to move the closure member 12 a selected distance into the flow passage 10, is generated in the main casing. This can be done, for example, by inducing a sequence of metallic object impacts on the main casing. The acoustic signal travels via the main casing, the branch casing 2 and the lock mandrel 4 to the acoustic sensor which induces the microprocessor to control the stepper motor 30 so as to rotate the drive shaft 32 a selected number of revolutions commensurate with the required movement of the closure member 12. As a result the second gear-wheel rotates and thereby moves the spindle 38 and the closure member 12 over said selected distance into the flow passage 10. The flow openings 18 are thereby partly covered so that gas can only flow at a reduced flow rate via the inlet openings 18 to the outlet 19. When it is desired to stop production of gas from one of the branch wellbores, the same procedure as described with reference to decreasing production of gas is followed, except that the coded acoustic signal now represents an instruction to move the closure member 12 against the seat surface 16 of the housing 6. As a result the closure member 12 is moved against the seat surface 16 so that the controllable valve A is in the closed mode. In this position the annular shoulder 22 of the tube slotted 20 contacts the stop ring 24, and the tube 20 exerts a tensile force to the closure member 12 biasing the closure member 12 away from the seat surface 16. When it is desired to bring the closure assembly back to the open mode, a coded acoustic signal representing an instruction to move the closure member 12 to the open position thereof is generated in the main casing. Initial movement of the closure member 12 from the closed position to the open position thereof is promoted by the tensile force from the slotted tube 20. Normal operation of the modified version of the embodiment of Fig. 1 is similar to normal operation of the embodiment of Fig. 1, except that electric current is generated by the alternative power generator 60 instead of the power generator C. Namely, gas which enters the fluid chamber 66 via fluid inlet 68 flows through the fluid passages 66a, 66b along the oscillator 74 and further through the fluid outlets 70, 72. The feed-back conduit 79 causes a Coanda effect to occur in the fluid passages 66a, 66b causing flow of gas into the outlets 70, 72 in an alternating manner. As a result angular oscillation of the magnetic oscillator 74 occurs around the support edges of the supports 76. An electric current is thereby generated in the coils 80, 82, which current flows via the control system to the battery and thereby charges the battery.

Claims: C L A I M S 1. 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. 2. The wellbore system of claim 1, wherein the production valve comprises a controllable valve for varying the flow rate of the stream of hydrocarbon fluid and a critical flow nozzle arranged so that the stream flows therethrough. 3. The wellbore system of claim 2, wherein the critical flow nozzle is arranged downstream the controllable valve . 4. The wellbore system of claim 2 or 3, wherein the controllable valve comprises a flow passage arranged so that the stream flows therethrough and a closure member movable in a selected direction relative to the flow passage so as to at least partially close the flow passage . 5. The wellbore system of claim 4, wherein the closure member is movable in said selected direction between an open position in which the closure member leaves the flow passage substantially open, and a closed position in which the closure member closes the flow passage. 6. The wellbore system of claim 4 or 5, further comprising an actuation module for controlling movement of the closure member in the selected direction. 7. The wellbore system of claim 6, wherein the actuation module comprises an electric motor arranged to rotate a spindle, the spindle being arranged so as to induce the closure member to move in the selected direction upon rotation of the spindle. 8. The wellbore system of claim 7, wherein the actuation module further comprises a battery for driving the electric motor and a power generator arranged to be driven by the stream of hydrocarbon fluid and to charge the battery. 9. The wellbore system of claim 8, wherein the power generator is selected from a turbine and a fluidic electrical generator. 10. The wellbore system of any one of claims 6-9, wherein the actuation module comprises an acoustic sensor and a microprocessor programmed to control movement of the closure member in dependence of receipt of a coded acoustic signal by the acoustic sensor. 11. The wellbore system of claim 10, wherein the anchoring means comprises a lock mandrel for locking the production valve in a casing of the branch wellbore, the lock mandrel being suitable to transmit said coded acoustic signal from the casing to the production valve. 12. The wellbore system of any one of claims 1-11, wherein the earth formation includes a plurality of said hydrocarbon fluid reservoirs having mutually different fluid pressures, each branch wellbore providing fluid communication between a corresponding one of the hydrocarbon fluid reservoirs and the main wellbore. 13. The wellbore system substantially as described hereinbefore with reference to the drawings.

Inventors: HEIJNEN WILHELMUS HUBERTUS PAU, HEIJNEN, WILHELMUS, HUBERTUS, PAULUS, MARIA
Applicants: SHELL CANADA LTD, SHELL INT RESEARCH, SHELL CANADA LIMITED, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 2000
Main classification: E21B43
IPC codes: E21B34, E21B41, E21B43