Synchronized dual well variable stroke and variable speed pump down control with regenerative assist

Abstract

A dual well pumping unit ( 12 ) has two hydraulic ram units ( 26 ), one for each well (preferably with each ram unit ( 26 ) having three hydraulic rams). Each hydraulic ram units is connected to first ram pump ( 18 ) and a second ram pump ( 20 ). The drive shaft ( 40 ) of the first ram pump ( 18 ) is coupled to the drive shaft ( 38 ) of the second ram pump ( 20 ) and to a rotor of a drive motor ( 16 ). The ram pump ( 18 ) and the ram pump ( 20 ) are preferably variable displacement piston pumps which are controlled by a microprocessor based controller ( 44 ), such that during the downstroke of the hydraulic ram ( 26 ) the ram pump ( 18 ) operates as an hydraulic motor powering the ram pump ( 20 ) and during the up stroke of the hydraulic ram ( 26 ) the ram pump ( 20 ) operates as a hydraulic motor to provide assist to the ram pump ( 18 ).

What is claimed is: 
     
         1 . A dual hydraulic pumping units for removing well fluids from a first well and a second well, comprising:
 a drive motor having a rotary drive shaft for turning in first angular direction;   a reservoir for a hydraulic fluid;   an accumulator for storing potential energy in response to receiving the hydraulic fluid;   a first sucker rod assembly disposed in the first well for removing the well fluids from the first well;   a first ram connected said first sucker rod assembly for moving in an up-stroke from a retracted position to an extended position and moving said first sucker rod assembly from a lowered position to a raised position, and moving in a down-stroke from said extended position to said retracted position with said first sucker rod assembly moving from said raised position to said lowered position;   a second sucker rod assembly disposed in the second well for removing the well fluids from the second well;   a second ram connected said second sucker rod assembly for moving in an up-stroke from a retracted position to an extended position and moving said second sucker rod assembly from a lowered position to a raised position, and moving in a down-stroke from said extended position to said retracted position with said second sucker rod assembly moving from said raised position to said lowered position;   a ram pump connected to said rotary drive shaft, said ram pump having a ram pump suction port connected to said reservoir and a ram pump discharge port connected to said accumulator and said first ram for during the up-stroke of said first ram transferring the hydraulic fluid into said first ram and moving said first ram from said retracted position to said extended position, and during the down-stroke transferring the hydraulic fluid into said reservoir;   an accumulator pump connected to said rotary drive shaft, said accumulator pump having a accumulator pump suction port connected to said reservoir and an accumulator pump discharge port connected to said accumulator and said second ram for during the up-stroke of said second ram transferring the hydraulic fluid into said second ram and moving said second ram from said retracted position to said extended position, and during the down-stroke transferring the hydraulic fluid into said reservoir;   said ram pump discharge port and said accumulator pump discharge port are connected to said accumulator with a selector valve disposed there-between, for selectively transferring the hydraulic fluid into said hydraulic accumulator and storing potential energy in said hydraulic accumulator during the down-stroke of said ram, and during the up-stroke transferring the hydraulic fluid into said reservoir, wherein hydraulic fluid is transferred to said accumulator when one of said first and second wells are not operated such that said accumulator is connected to allow single ram operation when one of said first and second wells are shut in; and   at least one control unit adapted for controlling flow rates of the hydraulic fluid through said ram pump and said accumulator pump, and adapting said ram pump for pumping the hydraulic fluid into said first ram during the up-stroke and during the down-stroke passing the hydraulic from said first ram into said reservoir and turning said rotary shaft in said first angular direction to power said accumulator pump in response to pressures within said first ram provided by the weight of said first sucker rod assembly in combination with said drive motor, and adapting said accumulator pump for pumping the hydraulic fluid into said second ram during the down-stroke of said first ram and the up-stroke of said second ram and turning said rotary shaft in said first angular direction to power said accumulator pump in response to pressure within said second ram provided by the weight of said second sucker rods in combination with said drive motor.   
     
     
         2 . The dual hydraulic pumping units according to  claim 1 , wherein said ram and accumulator pumps each further comprise:
 a motor housing;   a drive shaft rotatably mounted in said motor housing;   a cylinder block mounted to said drive shaft for rotating with said drive shaft, said cylinder block having a plurality of cylinders formed therein, and a plurality of flow ports in fluid communication with respective ones of said cylinders;   a plurality of pistons mounted in respective ones of said cylinders formed into said cylinder block, wherein said pistons are moveable within respective ones of said cylinders for pulling fluid into and pushing fluid out of said cylinders through respective ones of said flow ports; and   a port plate for engaging said cylinder block and passing the hydraulic fluid from respective ones of said fluid flow ports to a pump suction port and to a pump discharge port corresponding to angular positions of said cylinder block rotating with said drive shaft.   
     
     
         3 . The dual hydraulic pumping units according to  claim 2 , wherein each of said ram and accumulator pumps further comprise a swash plate adapted to engage said plurality of pistons and move said pistons within said cylinders in response to said cylinder block rotating with said drive shaft, wherein said swash plate urges said pistons to press the hydraulic fluid from within said cylinder block when respective ones of said pistons are disposed in proximity to said pump suction port, and to draw hydraulic fluid into said cylinder block when respective ones of said pistons are disposed in proximity to said pump suction port. 
     
     
         4 . The dual hydraulic pumping units according to  claim 3 , wherein said swash plate is pivotally mounted within said pump housing for angularly moving about an axis to vary lengths of stroke for said pistons within said cylinder block to determine displacements for said pump. 
     
     
         5 . The dual hydraulic pumping unit according to  claim 4 , wherein said swash plate is angularly movable over a neutral, center line position to operate said pump in a reverse flow direction in which the hydraulic fluid passes through said pump discharge port, into said cylinder block, and then through said pump suction port to power said pump to drive said drive motor. 
     
     
         6 . The dual hydraulic pumping units according to  claim 4 , further comprising a control member mounted in said pump housing and adapted for angularly moving said swash plate about said axis. 
     
     
         7 . The dual hydraulic pumping units according to  claim 5 , wherein said control member comprises a control piston, and said control piston is actuated by the hydraulic fluid. 
     
     
         8 . The dual hydraulic pumping units according to  claim 5 , further comprising a bias member for urging said swash plate into a first angular position respective to said drive shaft; and
 wherein said neutral, centerline position for said swash plate is a plane of said swash plate for engaging said pistons disposed generally perpendicular to a longitudinal axis of said drive shaft about which said drive shaft rotates.   
     
     
         9 . The dual hydraulic pumping unit according to  claim 1 , further comprising a positioning system which includes proximity sensors for determining when said first ram and said second ram are disposed in a selected reference positions, a sensor disposed within said ram pump for determining angles at which said swash plate is disposed for determining corresponding displacements for said ram pump, and wherein said swash plate is turned at a known angular speed and said controllers are configured for calculating positioning of said ram from the selected reference position and a determined total flow through the ram pump. 
     
     
         10 . The dual pumping unit according to  claim 1 , wherein should pump down be encountered in one of the wells, the controllers reduce the speed and stroke of the ram for pumped-down well by the same percentage, such that ram unit the pumped down well will remain synchronized with the ram unit other well, with the speed and stroke of the ram of the pumped down well will be decreased by 1.5% per stroke when pump down is detected, and will be increased by 3% per stroke until a constant fluid level is reached. 
     
     
         11 . The dual pumping unit according to  claim 1 , wherein should pump down be encountered in one of the wells, the controllers will provide pump down control, changing the stroke length an stroke rate by the same percentage for a well being pumped down so that it remains synchronized with a paired well to end and begin each stroke simultaneously with the paired well. 
     
     
         12 . A method for operating the dual hydraulic pump units of  claims 1 - 10 . 
     
     
         13 . The method according to  claim 11 , wherein should pump down be encountered in one of the wells, the controllers reduce the speed and stroke of the ram unit for pumped-down well by the same percentage, such that ram unit of the pumped down well will remain synchronized with the ram unit of other well. 
     
     
         14 . The method according to  claim 12 , wherein the speed and stroke of the ram of the pumped down well will be decreased by 1.5% per stroke when pump down is detected, and will be increased by 3% per stroke until a constant fluid level is reached.