Pumping device

Abstract

A fluid pumping device for placing inside a casing extending into a drilling well in order to pump a fluid present in a lower zone of the casing and delivering it to an upper zone of the casing. The fluid pumping device comprises an assembly of cylindrical elements placed end to end, the cylindrical elements of this assembly comprising: a seal to cooperate with the casing to ensure a tight seal between the lower zone and the upper zone; a hydraulic pump; an electric motor for driving the hydraulic pump, lubricated by a hydraulic fluid; and a compensator to balance the pressure of the hydraulic fluid lubricating the electric motor with the pressure of the fluid in the lower zone of the casing.

1 . A fluid pumping device for placing inside a casing extending into a drilling well to pump a fluid from a lower zone of the casing to an upper zone of the casing, the pumping device comprising an assembly of cylindrical elements placed end to end, the cylindrical elements of this assembly comprising:
 a seal that cooperates with the casing to ensure a tight seal between the lower zone and the upper zone;   a hydraulic pump;   an electric motor lubricated by hydraulic fluid for driving the hydraulic pump; and   a pressure compensator that balances the pressure of the hydraulic fluid lubricating the electric motor with the pressure of the fluid in the lower zone of the casing.   
     
     
         2 . The pumping device according to  claim 1 , wherein
 the seal is situated at the base of said assembly;   the pressure compensator comprises a cylindrical chamber in which a free piston slides counterheld by a spring, said free piston being in contact with the fluid to be pumped and with the hydraulic fluid lubricating the electric motor, so as to balance the pressure of the fluid to be pumped and of the hydraulic fluid; and   the hydraulic pump comprises two symmetrical and opposing inclined plates mobile in rotation, and two sets of hollow axial pistons resting against the two inclined plates, the hollow axial pistons being
 able to be displaced axially by the rotational movement of the two inclined plates, 
 housed in cylindrical chambers able to communicate with the lower zone of the casing and cooperating with a delivery pipeline able to communicate with the upper zone of the casing, and 
 arranged to draw in the fluid from the cylindrical chambers and deliver it to the delivery pipeline on a rotational movement of the two inclined plates. 
   
     
     
         3 . The pumping device according to  claim 2 , wherein the pressure compensator, the hydraulic pump and the electric motor are housed in a cylindrical envelope, and the delivery pipeline opens to the outside of the cylindrical envelope into a space between the casing and the cylindrical envelope. 
     
     
         4 . The pumping device according to  claim 3 , wherein the pressure compensator comprises a cylindrical tube defining the cylindrical chamber in which the free piston slides, and the cylindrical chambers accommodating the hollow axial pistons communicate with the lower zone of the casing via a cylindrical space lying between the tube of the pressure compensator and the cylindrical envelope, said tube of the pressure compensator comprising drillings allowing the fluid to be pumped to mix between the tube of the pressure compensator and the cylindrical envelope. 
     
     
         5 . The pumping device according to  claim 2 , wherein the two inclined plates are fixed to a plate drive shaft, the plate drive shaft comprising two ends each cooperating with support bearings arranged in housings, the pumping device comprising a hydraulic fluid housing space in which the pressure is balanced by the pressure compensator, the hydraulic fluid housing space comprising the support bearing housings of the drive shaft and a drilled conduit in the drive shaft connecting the support bearing housings. 
     
     
         6 . The pumping device according to  claim 5 , wherein the electric motor comprises a housing, a stator and a motor shaft carrying a rotor, the motor shaft being connected in rotation to the plate drive shaft and comprising two ends each cooperating with support bearings of the motor shaft arranged in housings, the hydraulic fluid housing space further comprising the support bearing housings of the motor shaft and the housing of the electric motor. 
     
     
         7 . The pumping device according to  claim 1 , further comprising:
 an element anchoring the pumping device inside the casing; and   a transfer pump comprising mobile pumping elements, each cooperating with a suction pipeline that communicates with the lower zone, and with a delivery pipeline that communicates with the upper zone, in order to draw in fluid from the suction pipeline and delivering it to the delivery pipeline;   wherein the hydraulic pump is a hydraulic pump with a double slope cam comprising an internal hydraulic fluid circuit, a double slope cam mobile in rotation, and two sets of pistons able to be displaced axially on a rotational movement of the double slope cam, the two sets of axial pistons extending axially on either side of the double slope cam; the hydraulic pump being associated with the transfer pump such that a displacement of the axial pistons of the hydraulic pump causes pressurization of the hydraulic fluid that drives the pumping elements of the transfer pump;   wherein the electric motor driving the hydraulic pump drives the double slope cam in rotation; and   wherein the pressure compensator balances the pressure of the fluid in the lower zone of the casing and the pressure in the internal hydraulic fluid circuit of the hydraulic pump.   
     
     
         8 . The pumping device according to  claim 7 , wherein the double slope cam comprises two identical and symmetrical inclined faces against which rest respectively one or the other of the two sets of axial pistons arranged symmetrically on either side of the double slope cam. 
     
     
         9 . The pumping device according to  claim 8 , wherein the axial pistons are hollow, each able to slide in a cylinder, the hollow axial pistons drawing in hydraulic fluid during a suction phase and delivering hydraulic fluid during a delivery phase, each inclined face of the double slope cam having an intake passage arranged so as to cooperate with at least one of the hollow axial pistons during the suction phase. 
     
     
         10 . The pumping device according to  claim 9 , wherein the pumping elements of the transfer pump are supports which are each counterheld by a spring and each comprise a head resting against a flexible membrane under the effect of the spring, each of the supports being associated with a cylinder in which a piston slides so as to be displaced against the spring when said support is subjected, via the flexible membrane, to a pressure of the hydraulic fluid delivered into said cylinder by the piston during the delivery phase. 
     
     
         11 . The pumping device according to  claim 9 , wherein the double slope cam comprises a plurality of drillings arranged in the body of the double slope cam, the drillings arranged so as to cooperate with two hollow axial pistons arranged axially on either side of the double slope cam during a delivery phase, so as to connect the cylinders in which the two hollow axial pistons slide through the double slope cam. 
     
     
         12 . The pumping device according to  claim 11 , wherein the hollow axial pistons each cooperate with one of the two inclined faces of the double slope cam via a hollow stud, the diameter of each hollow stud being greater than the distance separating two adjacent drillings. 
     
     
         13 . The pumping device according to  claim 10 , wherein the hydraulic pump has a housing comprising pipelines arranged to bring the cylinders of a first hollow axial piston into communication with the cylinders of a second hollow axial piston. 
     
     
         14 . The pumping device according to  claim 7 , wherein the hydraulic pump comprises a housing and the transfer pump comprises an upper pumping stage and a lower pumping stage extending respectively on either side of the hydraulic pump housing, each of the upper and lower pumping stages comprising pumping elements associated with a respective piston, the delivery pipelines opening into a common pipeline, and the suction pipelines of the lower pumping unit communicating with the common pipeline via a pipeline arranged along the casing of the hydraulic pump. 
     
     
         15 . The pumping device according to  claim 7 , wherein the pressure compensator comprises:
 a tube with an inner space communicating with the internal hydraulic circuit of the hydraulic pump and equipped with a base through which passes a drilling communicating with the lower zone; and   a flexible separator or free piston counterheld by a spring and receiving firstly the pressure predominating in the drilling and secondly the pressure predominating in the internal hydraulic circuit of the hydraulic pump.   
     
     
         16 . The Pumping device according to  claim 15 , wherein the electric motor has a housing comprising firstly a cover through which passes a bore communicating with the inner space of the tube, and secondly a cap through which passes a bore communicating with the internal hydraulic circuit of the hydraulic pump. 
     
     
         17 . The pumping device according to  claim 16 , wherein the electric motor comprises a stator and a rotor carried by a motor shaft, the cover being provided with a bearing carrying one of the ends of the motor shaft, and the cap being provided with a bearing carrying the other end of the motor shaft, the motor shaft being connected to a shaft of the hydraulic pump carrying the double slope cam. 
     
     
         18 . The pumping device according to  claim 7 , wherein the seal is a compressible seal and the anchoring element comprises catches able to be spaced apart, the pumping device comprising a control mechanism for the seal and the anchoring element that is mobile between a released position and an engaged position, in which firstly the control mechanism axially compresses the seal such that when the pumping device is placed inside the casing, the seal is pressed radially against the inner wall of the casing, and secondly the control mechanism exerts a force on the anchoring element spacing the catches apart, such that when the pumping device is placed inside the casing, the catches come to rest against the inner wall of the casing. 
     
     
         19 . The pumping device according to  claim 18 , wherein the control mechanism is a hydraulic control mechanism and the pumping device comprises a hydropneumatic accumulator and a distributor linked to the hydropneumatic accumulator and to the hydraulic control mechanism, the distributor comprising a closed position in which communication between the hydropneumatic accumulator and the hydraulic control mechanism is interrupted, and an open position in which communication between the hydropneumatic accumulator and the hydraulic control mechanism is established, in order to move the control mechanism between its released position and its engaged position. 
     
     
         20 . The pumping device according to  claim 19 , wherein the hydraulic control mechanism is provided with a return means able to return the control mechanism to its released position, and is linked to the distributor such that the latter is able to move the control mechanism into its engaged position. 
     
     
         21 . The pumping device according to  claim 19 , wherein the hydraulic control mechanism is provided with a return means able to return and hold the hydraulic control mechanism in its engaged position, and is connected to the distributor such that the latter is able to move the control mechanism into its released position. 
     
     
         22 . The pumping device according to  claim 18 , wherein the control mechanism comprises a shaft carrying a guide piston and a cylinder mounted sliding on the guide piston against a spring. 
     
     
         23 . The pumping device according to  claim 22 , wherein the cylinder comprises a first moveable stop surface and the shaft comprises a second fixed stop surface, the anchoring element being a deformable liner mounted on the shaft between the first movable stop surface and the second fixed stop surface, the seal being mounted on the shaft between the first movable stop surface and the second fixed stop surface, the control mechanism comprising an intermediate element arranged between the seal and the anchoring element, the intermediate element comprising a flat surface facing the seal and a conical surface facing the deformable liner such that when the first movable stop surface is moved in the direction of the second fixed stop surface, the flat surface of the intermediate element compresses the seal and spaces the deformable liner from the anchoring element such that its catches are able to come into engagement against the inner wall of the casing.