Pressure controlled test valve system for offshore wells

Abstract

Methods and apparatus for performing a drill stem test of an offshore well utilizing a pressure controlled test valve. The test valve includes a valve element having a transverse pressure area with the high pressure side exposed to the pressure of fluids in the well annulus and the low pressure side subject to the pressure of a compressible fluid medium contained within a chamber in the test valve. The pressure in the chamber is equalized with the hydrostatic head of the well fluids so that at test depth the same pressure is acting on both sides of the transverse pressure area, whereupon this pressure is confined within the chamber. Then a fluid pressure in excess of the hydrostatic head is applied to the well fluids externally of the test valve to develop a pressure difference across the valve element which causes it to shift from closed to open position.

I claim: 
     
       1. A fluid pressure controlled well tester apparatus comprising: housing means adapted for connection to a pipe string and having a flow passage extending therethrough for conducting formation fluids from an isolated formation interval; valve means movable from a position closing said flow passage to a position opening said flow passage in response to a change in the pressure of fluids in the well annulus externally of said housing means; chamber means containing a compressible fluid medium, said valve means having a transverse, pressure area with one side thereof subject to the pressure of fluids in said well annulus and the other side subject to the pressure of said fluid medium; means for equalizing the pressure of said fluid medium with the hydrostatic head of the well fluids externally of said housing means; and selectively operable means for closing said equalizing means, so that pressure applied to the fluids externally of said housing means subsequent to the closing of said equalizing means can act on said one side of said pressure area to move said valve means from closed to open position. 
     
     
       2. The tester apparatus of claim 1 further including biasing means for continuously urging said valve means toward closed position. 
     
     
       3. The well tester apparatus of claim 1 wherein said equalizing means includes a port through which the hydrostatic head of the well fluids is communicated to said compressible fluid medium, said closing means including a valve operable in response to manipulation of said pipe string for closing off said port. 
     
     
       4. The well tester apparatus of claim 1 wherein said valve means comprises an annular element that is slidable with respect to said housing means between longitudinally spaced positions, said annular element having a piston section providing said transverse pressure area. 
     
     
       5. The well tester apparatus of claim further including a tube that is concentrically disposed within said housing means, said chamber means being defined between an inner wall of said housing means and an outer wall of said tube, said tube providing a portion of said flow passage. 
     
     
       6. The well tester apparatus of claim 5 further including a partition movably mounted at one end of said chamber for providing a separation between said compressible fluid medium and the well fluids present in said equalizing means and for transmitting the pressure of the well fluids to said fluid medium. 
     
     
       7. The well tester apparatus of claim 1 further including a transverse barrier formed in said housing means, a portion of said flow passage being formed to extend past said barrier, said valve means being movably disposed adjacent to said barrier. 
     
     
       8. The well tester apparatus of claim 7 wherein said barrier is provided by an annular member having a closed upper end and flow ports extending laterally through the wall thereof, said valve means being movably received within said annular member and having a valve head that engages a valve seat located on said annular member below said flow ports, disengagement of said valve head and valve seat enabling fluid flow through said flow ports and past said barrier. 
     
     
       9. The well tester apparatus of claim 7 further including a flow tube disposed longitudinally of said housing means, said barrier being formed intermediate the ends of said flow tube, said flow tube having transverse flow ports extending through the wall thereof above and below said barrier, said valve means being constituted by an annular sleeve member that is slidably disposed on said flow tube adjacent said barrier for movement between one position closing off said flow ports and another position enabling communication between said flow ports. 
     
     
       10. A well tester apparatus comprising: upper and lower housing members adapted to be connected in a pipe string, said housing members each having a flow passage extending upwardly therein; pressure responsive first valve means in said upper housing and movable between positions for opening and closing said flow passages; chamber means containing a compressible fluid medium, said first valve means having a transverse pressure area with one side thereof subject to the pressure of fluids in the well annulus externally of said upper housing member and the other side thereof subject to the pressure of said fluid medium; port means for applying the hydrostatic head of well fluids to said fluid medium as the apparatus is lowered into a well bore to equalize the pressures acting on said sides of said transverse pressure area; and second valve means operable in response to downward movement of said upper housing member with respect to said lower housing member for closing off said port means to trap a value of pressure in said chamber means substantially equal to said hydrostatic head, so that pressure applied to the fluids externally of said housing members subsequent to the closing of said port means by said second valve means can act to develop a pressure differential across said transverse pressure area to move said first valve means from closed to open position. 
     
     
       11. The well tester apparatus of claim 10 further including third valve means operable in response to vertical movement of said upper housing member with respect to said lower housing member for opening and closing said flow passage in said lower housing member. 
     
     
       12. The well tester apparatus of claim 10 further including spring means for continuously urging said first valve means toward closed position, and functioning to return said first valve means from open to closed position upon the release of pressure applied to the fluids externally of said housing members. 
     
     
       13. The well tester apparatus of claim 10 wherein said first valve means comprises a tubular mandrel open from one end to the other and having a piston section presenting said transverse pressure area, said valve mandrel having further transverse cross-sectional areas sized so that the pressure of fluids within said flow passages act with equal force in opposite longitudinal directions. 
     
     
       14. The well tester of claim 13 further including a barrier sleeve within said first housing member, said barrier sleeve having a closed upper end and flow ports through the side walls thereof, an upper portion of said tubular mandrel being sealingly and slidably received within said barrier sleeve and having a valve head that is coengageable with a valve seat on said upper housing member below said flow ports. 
     
     
       15. The well tester apparatus of claim 14 further including a second valve head on said tubular mandrel below said first mentioned valve head, said second valve head being coengageable with a second valve seat on said upper housing member, the annular space externally of said tubular mandrel between said valve seats defining a flow-through sample chamber adapted to confine a sample of formation fluids upon simultaneous engagement of said valve heads with said valve seats. 
     
     
       16. The well tester apparatus of claim 10 wherein said compressible fluid medium is nitrogen gas, and further including a movable partition sealingly received at one end of said chamber means for providing separation between said nitrogen gas and the well fluids entering said port means, said partition additionally functioning to transmit the hydrostatic head of the well fluids to said compressible fluid medium. 
     
     
       17. The well tester apparatus of claim 16 wherein said port means opens outwardly to the well annulus intermediate the ends of a reduced diameter section of the lower end portion of said upper housing member, said second valve means being formed in part by a valve seat inside the upper end of said lower housing member adapted to receive said reduced diameter section. 
     
     
       18. A pressure controlled well tester apparatus comprising: an elongated tubular housing member adapted for connection to a pipe string and to be lowered into a fluid filled well bore; said housing member having at its upper portion an internal annular valve seat; barrier means located above said valve seat, said barrier means being an annular member with a closed upper end and having flow ports extending laterally through the wall thereof; a valve mandrel having its upper end portion slidably received within said barrier means and including an annular valve head engageable with said valve seat to prohibit fluid flow through said flow ports; said valve member being movable downwardly to a position where said valve head is disengaged from said valve seat to enable fluid flow through said flow ports; said valve mandrel having a piston section that is sealingly slidable with respect to said housing member and provides a transverse pressure area with an upper side and a lower side; first port means for subjecting the upper side of said piston section to the pressure of fluids in the well annulus externally of said housing member; spring means pressing upwardly on the lower side of said piston section; a chamber of substantial volume defined between an inner wall of said housing member and the outer wall of a flow tube concentrically disposed within said housing member, said chamber containing a compressible fluid medium, the lower side of said piston section being subjected to the pressure of said fluid medium; second port means for applying the hydrostatic head of the well fluids externally of said housing member to said compressible fluid medium so that pressure of said fluid medium is substantially equal to said hydrostatic head; and a valve selectively operable at test depth for closing off said second port means, so that pressure applied to the well fluids externally of said housing can act via said first port means on said upper side of said piston section to develop a pressure difference thereacross and force said valve mandrel downwardly to a position where said valve head is disengaged from said valve seat. 
     
     
       19. The well tester apparatus of claim 18 further including a second valve seat on said housing member and a second valve head on said valve mandrel located below said first mentioned valve head and seat, the space between said housing member and said valve mandrel and between said valve seats providing a flow through sample chamber adapted to trap a sample of formation fluids when said valve heads are simultaneously engaged with said valve seats. 
     
     
       20. The well tester apparatus of claim 19 further including separable coupling means in said housing member below said lower valve seat and in said valve mandrel below said lower valve head, separation of said coupling means enabling that portion of the apparatus defining the sample chamber to be disconnected from the balance of the apparatus. 
     
     
       21. The well tester apparatus of claim 18 wherein said second port means extends between the lower end of said chamber and a side opening in the wall of reduced diameter lower section of said housing member, said lower section being adapted for telescopic reception within the upper end of a second housing member located therebelow, said second housing member having an inner wall surface adapted to span and close off said side opening. 
     
     
       22. The well tester apparatus of claim 21 further including a movable partition sealingly received in the lower end of said chamber and functioning to separate said compressible fluid medium from the well fluids entering said second port means and to transmit the hydrostatic head of said well fluids to said fluid medium. 
     
     
       23. A pressure controlled well tester apparatus comprising: an elongated housing member having a flow tube disposed concentrically therein, said flow tube having a transverse barrier intermediate the ends thereof; port means through the wall of said flow tube above and below said barrier, said port means and the bores in said flow tube extending respectively above and below said barrier providing a flow passage; sleeve valve means slidable on said flow tube adjacent said barrier between a closed position blocking communication between said port means and an open position permitting communication between said port means; chamber means within said housing member and containing a compressible fluid medium, a portion of said sleeve valve means providing a piston section having a transverse pressure area with one side subject to the pressure of fluids in the well annulus externally of said housing member and the opposite side subject to the pressure of said fluid medium; a pressure transmitting channel for applying the hydrostatic head of the fluids in a well bore to said fluid medium as the apparatus is lowered into a well bore so that substantially the same fluid pressure acts on both sides of said transverse pressure area; and a valve structure operable at test depth for closing off said channel to trap the hydrostatic head of the well fluids within said chamber means, so that pressure applied to the well fluids externally of said housing member subsequent to the closing of said channel by said valve structure can act on said one side of said pressure area and develop a pressure differential thereacross to move said sleeve valve means from closed to open position. 
     
     
       24. The well tester apparatus of claim 23 further including spring means pressing between one end of said sleeve valve means and an outwardly directed shoulder on said flow tube for continuously urging said sleeve valve means toward closed position. 
     
     
       25. The well tester apparatus of claim 24 wherein said sleeve valve means comprises a sleeve member having an internal recess for communicating said port means with one another in the open position of said valve means and a valve head section for closing off at least one of said port means in the closed position of said valve means. 
     
     
       26. The well tester apparatus of claim 24 wherein said chamber means is located within said housing member above said sleeve valve means, said spring means being located within said chamber means, and further including a movable partition at the upper end of said chamber means for transmitting the pressure of fluids in said channel to said fluid medium. 
     
     
       27. The well tester apparatus of claim 23 wherein said valve structure includes an annular member adapted for connection to a pipe string and telescopically received over an upper reduced diameter section of said housing member, said pressure transmitting channel having an opening to the exterior of said housing member intermediate the ends of said reduced diameter section, said annular member being selectively movable with respect to said section to a position closing off said opening. 
     
     
       28. A method of operating a test valve that is positioned in a fluid-filled well bore in order selectively to conduct fluids from an isolated formation interval, said test valve including a normally closed valve element having pressure responsive areas one of which is subject to the pressure of fluids in the well bore externally of said test valve and the other of which is subject to the pressure of a compressible fluid medium contained within a chamber in said test valve, comprising the steps of: equalizing the pressure of said fluid medium with the hydrostatic head of the well fluids externally of said test valve to establish within said chamber a value of pressure peculiar to the depth of the well bore where said test valve is positioned; closing said chamber to confine therein said value of pressure; and then while maintaining said chamber in a closed condition, moving the valve element from said normally closed position to an open position by applying pressure to the well bore at the surface to increase the pressure of the well fluids externally of said test valve to a value in excess of the value of pressure confined within said chamber, the difference in pressure acting across said areas to develop a force that is effective to move said valve element to said open position to permit a flow of formation fluids from said isolated formation interval through said test valve. 
     
     
       29. The method of claim 28 including the further steps of releasing the increase in pressure and returning the valve element from open position to closed position while continuing to maintain said chamber in a closed condition. 
     
     
       30. The method of claim 28 including the further steps of precharging the chamber containing said fluid medium to an intial pressure that is less than the hydrostatic head of the well fluids at test depth, and then lowering the test valve into the well bore. 
     
     
       31. The method of claim 30 wherein the precharge pressure is approximately 500 psi less than the hydrostatic head of the well fluids at test depth. 
     
     
       32. A method of operating a pressure controlled test valve that is disposed in a fluid-filled well bore in order selectively to conduct formation fluids from an isolated formation interval, said test valve having a normally closed valve element with a transverse pressure area that is subject on one side to the pressure of fluids in a well bore and on the other side to the pressure of a compressible fluid medium contained within a chamber in the test valve, the application of pressure to said one side shifting the valve element from closed to open position, comprising the steps of: charging the chamber containing said fluid medium to an initial pressure that is less than the hydrostatic head of the well fluids at test depth; lowering the test valve into the well bore; from the point in the well bore where the hydrostatic head is equal to the charge pressure in said chamber on downward to test depth, equalizing the pressure of said fluid medium with the hydrostatic head of the well fluids so that the same pressure acts on both sides of said transverse area; closing the chamber at test depth in order to confine therein a value of pressure substantially equal to the hydrostatic head at test depth; and then while maintaining said chamber in a closed condition, applying pressure to the well fluids externally of said test valve to increase the external pressure to a value in excess of said hydrostatic head so that a pressure difference is developed across said transverse area effective to shift the valve element from closed to open position, thereby to permit a flow of formation fluids from an isolated formation interval. .Iadd. 33. A fluid pressure controlled well apparatus comprising: housing means adapted to be connected to a pipe string and having a flow passage extending therethrough for conducting formation fluids from an isolated formation interval; valve actuator means including a tubular member defining a portion of said flow passage and movable with respect to said housing means between longitudinally spaced positions in response to a change in the pressure of fluids in the well annulus externally of said housing means; chamber means for containing a compressible fluid medium, said tubular member having a transverse pressure area with one said thereof subject to the pressure of fluids in said well annulus and the other side thereof subject to the pressure of said fluid medium; means for equalizing the pressure of said fluid medium with the pressure of well fluids externally of said housing means; and selectively operable means for closing said equalizing means, so that pressure applied to the fluids externally of said housing means subsequent to the closing of said equalizing means can act on said one side of said pressure area to move said valve actuator means from one of said longitudinally spaced positions to another of said longitudinally spaced positions. .Iaddend. .Iadd. 34. The apparatus of claim 33 further including spring means reacting between said housing means and said tubular member for continuously urging said tubular member toward said one longitudinally spaced position. .Iaddend..Iadd. 35. The apparatus of claim 34 further including a partition movably mounted at one end of said chamber means for providing a separation between said compressible fluid medium and the well fluids present in said equalizing means and for transmitting the pressure of the well fluids to said fluid medium. .Iaddend. .Iadd. 36. The apparatus of claim 33 wherein said tubular member has an outwardly directed shoulder defining a piston section which provides said transverse pressure area, said piston section being sealingly slidable with respect to said housing means. .Iaddend..Iadd. 37. The apparatus of claim 33 wherein said equalizing means includes fluid inlet means through which the pressure of the well fluids is communicated to said compressible fluid medium, said closing means including a valve element movable relative to said housing means for opening and closing said fluid inlet means. .Iaddend. .Iadd. 38. A fluid pressure controlled well apparatus comprising: housing means adapted to be connected to a pipe string, said housing means having an inwardly directed shoulder and cylinder means adjacent said shoulder; valve actuator means including a tubular mandrel having a reduced diameter portion sealingly slidable with respect to said shoulder and an enlarged diameter piston section sealingly slidable with respect to said cylinder means, said mandrel being movable with respect to said housing means between longitudinally spaced positions in response to a change in the pressure of fluids in the well annulus externally of said housing means; chamber means within said housing means for containing a compressible fluid medium, said piston section having one side thereof subject to the pressure of fluids in said well annulus and the other side thereof subject to the pressure of said fluid medium; means for transmitting the pressure of fluids in said well annulus to said compressible fluid medium whereby said pressure initially acts on both sides of said piston section; and selectively operable valve means for preventing transmission of the pressure of fluids in said well annulus to said compressible fluid medium, so that pressure subsequently applied to the fluids in the well annulus externally of said housing means can act on said one side of said piston section to move said tubular mandrel from one to another of said longitudinally spaced positions. .Iaddend. .Iadd. 39. The apparatus of claim 38 further including spring means reacting between said housing means and said valve actuator means for continuously urging said valve actuator means toward said one position. .Iaddend..Iadd. 40. The apparatus of claim 38 wherein said transmitting means includes a partition movably mounted at one end of said chamber means for providing a separation between said compressible fluid medium and fluids in said well annulus. .Iaddend. .Iadd. 41. The apparatus of claim 40 wherein said transmitting means further includes fluid inlet means through which the pressure of well fluids is communicated to the interior of said housing means, said valve means including a valve element movable relative to said housing means for opening and closing said fluid inlet means. .Iaddend..Iadd. 42. The apparatus of claim 40 wherein said transmitting means includes a port through which the pressure of well fluids in said annulus is communicated to said compressible fluid medium, said valve means including a valve element that is operable in response to manipulation of the pipe string for closing off said port. .Iaddend. .Iadd. 43. The apparatus of claim 38 further including a tube that is concentrically disposed within said housing means, said chamber means being defined in part between an inner wall of said housing means and an outer wall of said tube, said tube providing a portion of said flow passage. .Iaddend.