System and method for pumping a particle-laden fluid, such as pressurized fracking fluid

Abstract

A system for delivering pressurized fracking fluid to a well includes a high-pressure pump pumping proppant-free fluid, and a double-piston pressure transfer arrangement for transferring pressure from the proppant-free fluid to a fracking fluid. The pressure transfer arrangement includes first and second cylinder assemblies, each having a piston in sliding engagement within a first hollow cylinder so as to define first and second chambers of the first cylinder and third and fourth chambers of the second cylinder. A piston rod interconnects the pistons. A flow selector alternately directs high-pressure proppant-free fluid to the first chamber and the third chamber so as to act on the pistons, thereby applying pressure to fracking fluid within the second and fourth chambers, respectively, for delivery to the well in alternate power strokes. The faces of the pistons facing the first and third chambers have a smaller effective surface area than the faces towards the second and fourth chambers such that pressure in the fracking fluid remains lower than pressure in the proppant-free fluid.

What is claimed is: 
     
         1 . A system for delivering pressurized fracking fluid to a well, the system comprising:
 (a) a source of proppant-laden fracking fluid;   (b) a high-pressure pump connected to a source of proppant-free fluid;   (c) a double-piston pressure transfer arrangement, said pressure transfer arrangement comprising:
 (i) a first cylinder assembly comprising a first hollow cylinder, and a first piston in sliding engagement within said first hollow cylinder so as to at least partially define a first chamber and a second chamber; 
 (ii) a second cylinder assembly comprising a second hollow cylinder, and a second piston in sliding engagement within said second hollow cylinder so as to at least partially define a third chamber and a fourth chamber; and 
 (iii) at least one piston rod interconnecting said first piston and said second piston; and 
   (d) a flow selector associated with said high-pressure pump, said first chamber of said first cylinder and said third chamber of said second cylinder, said flow selector assuming alternately:
 (i) a first selector state in which the proppant-free fluid from said high-pressure pump is directed to said first chamber so as to act on said first piston, thereby applying pressure to a quantity of the fracking fluid within said second chamber for delivery to the well in a first power stroke, said first power stroke also expelling a quantity of the proppant-free fluid from said third chamber and taking in a quantity of the fracking fluid to said fourth chamber; and 
 (ii) a second selector state in which the proppant-free fluid from said high-pressure pump is directed to said third chamber so as to act on said second piston, thereby applying pressure to a quantity of the fracking fluid within said fourth chamber for delivery to the well in a second power stroke, said second power stroke also expelling the quantity of the proppant-free fluid from said first chamber and taking in a quantity of the fracking fluid to said second chamber, 
   
       wherein said first and second pistons have an inner face facing, respectively, said first and third chambers and an outer face facing, respectively, said second and fourth chamber, said outer face having larger effective surface area than said inner face, such that pressure in said fracking fluid remains lower than pressure in said proppant-free fluid. 
     
     
         2 . The system of  claim 1 , wherein said first cylinder arrangement further comprises a pressure vessel enveloping substantially the entirety of said first hollow cylinder, said pressure vessel defining at least one enveloping volume selected from the group consisting of: a first enveloping volume in fluid flow communication so as to form an extension of said first chamber; and a second enveloping volume in fluid flow communication so as to form an extension of said second chamber, and wherein said second cylinder arrangement further comprises a pressure vessel enveloping substantially the entirety of said second hollow cylinder, said pressure vessel defining at least one enveloping volume selected from the group consisting of: a third enveloping volume in fluid flow communication so as to form an extension of said third chamber; and a fourth enveloping volume in fluid flow communication so as to form an extension of said fourth chamber. 
     
     
         3 . The system of  claim 1 , further comprising:
 (a) a bidirectional hydraulic actuator associated with said flow selector for switching said flow selector between said first selector state and said second selector state; and   (b) a hydraulic switch having a switch inlet port for the inflow of a pressurized hydraulic fluid and having two hydraulic connections to said hydraulic actuator for actuating said hydraulic actuator,   
       wherein said hydraulic switch is deployed to be actuated by motion of said first and second pistons to switch said hydraulic connections of said hydraulic switch, thereby subsequently actuating said bidirectional hydraulic actuator to switch said flow selector between said first and second selector states. 
     
     
         4 . The system of  claim 3 , wherein said hydraulic actuator includes an actuator piston displaceable within an actuator cylinder. 
     
     
         5 . The system of  claim 3 , wherein said switch inlet port is connected to receive proppant-free fluid from said high-pressure pump. 
     
     
         6 . The system of  claim 1 , wherein said double-piston pressure transfer arrangement is referred to as a master pressure transfer arrangement, and wherein said flow selector is referred to as a master flow selector, the system further comprising:
 (a) a slave double-piston pressure transfer arrangement, said pressure transfer arrangement comprising:
 (i) a first cylinder assembly comprising a first hollow cylinder, and a first piston in sliding engagement within said first hollow cylinder so as to at least partially define first chamber and a second chamber; 
 (ii) a second cylinder assembly comprising a second hollow cylinder, and a second piston in sliding engagement within said second hollow cylinder so as to at least partially define a third chamber and a fourth chamber; and 
 (iii) at least one piston rod interconnecting said first piston and said second piston; and 
   (b) a slave flow selector associated with said high-pressure pump, said first chamber of said first cylinder and said third chamber of said second cylinder, said flow selector assuming alternately:
 (i) a first selector state in which the proppant-free fluid from said high-pressure pump is directed to said first chamber so as to act on said first piston, thereby applying pressure to a quantity of the fracking fluid within said second chamber for delivery to the well in a first power stroke, said first power stroke also expelling a quantity of the proppant-free fluid from said third chamber and taking in a quantity of the fracking fluid to said fourth chamber; and 
 (ii) a second selector state in which the proppant-free fluid from said high-pressure pump is directed to said third chamber so as to act on said second piston, thereby applying pressure to a quantity of the fracking fluid within said fourth chamber for delivery to the well in a second power stroke, said second power stroke also expelling the quantity of the proppant-free fluid from said first chamber and taking in a quantity of the fracking fluid to said second chamber; and 
   (c) a bidirectional slave hydraulic actuator associated with said slave flow selector for switching said slave flow selector between said first selector state and said second selector state,   
       wherein said slave hydraulic actuator is associated with said master flow selector or said master pressure transfer arrangement such that, during said first power stroke of said master pressure transfer arrangement, proppant-free fluid from said high pressure pump is delivered to said slave hydraulic actuator so as to switch said slave flow selector from said second selector state to said first selector state and, during said second power stroke of said master pressure transfer arrangement, proppant-free fluid from said high pressure pump is delivered to said slave hydraulic actuator so as to switch said slave flow selector from said first selector state to said second selector state. 
     
     
         7 . A method for delivering pressurized fracking fluid to a well, the method comprising the steps of:
 (a) providing a double-piston pressure transfer arrangement, said pressure transfer arrangement comprising:
 (i) a first cylinder assembly comprising a first hollow cylinder, and a first piston in sliding engagement within said first hollow cylinder so as to at least partially define a first chamber and a second chamber; 
 (ii) a second cylinder assembly comprising a second hollow cylinder, and a second piston in sliding engagement within said second hollow cylinder so as to at least partially define a third chamber and a fourth chamber; and 
 (iii) at least one piston rod interconnecting said first piston and said second piston; and 
   (b) directing a proppant-free fluid from a high-pressure pump to said first chamber so as to act on said first piston, thereby applying pressure to a quantity of the fracking fluid within said second chamber for delivery to the well in a first power stroke, said first power stroke also expelling a quantity of the proppant-free fluid from said third chamber and taking in a quantity of the fracking fluid to said fourth chamber; and   (c) directing the proppant-free fluid from the high-pressure pump to said third chamber so as to act on said second piston, thereby applying pressure to a quantity of the fracking fluid within said fourth chamber for delivery to the well in a second power stroke, said second power stroke also expelling the quantity of the proppant-free fluid from said first chamber and taking in a quantity of the fracking fluid to said second chamber,   
       wherein said first and second pistons have an inner face facing, respectively, said first and third chambers and an outer face facing, respectively, said second and fourth chamber, said outer face having larger effective surface area than said inner face, such that pressure in said fracking fluid remains lower than pressure in said proppant-free fluid. 
     
     
         8 . The method of  claim 7 , wherein said first cylinder arrangement further comprises a pressure vessel enveloping substantially the entirety of said first hollow cylinder, said pressure vessel defusing at least one enveloping volume selected from the group consisting of: a first enveloping volume in fluid flow communication so as to form an extension of said first chamber; and a second enveloping volume in fluid flow communication so as to form an extension of said second chamber, and wherein said second cylinder arrangement further comprises a pressure vessel enveloping substantially the entirety of said second hollow cylinder, said pressure vessel defining at least one enveloping volume selected from the group consisting of: a third enveloping volume in fluid flow communication so as to form an extension of said third chamber; and a fourth enveloping volume in fluid flow communication so as to form an extension of said fourth chamber. 
     
     
         9 . A system for pumping a particle-laden fluid from a fluid source, the system comprising:
 (a) a pump connected to a source of clean fluid;   (b) a double-piston pressure transfer arrangement, said pressure transfer arrangement comprising:
 (i) a first cylinder assembly comprising a first hollow cylinder, and a first piston in sliding engagement within said first hollow cylinder so as to at least partially define a first chamber and a second chamber; 
 (ii) a second cylinder assembly comprising a second hollow cylinder, and a second piston in sliding engagement within said second hollow cylinder so as to at least partially define a third chamber and a fourth chamber; and 
 (iii) at least one piston rod interconnecting said first piston and said second piston; and 
   (c) a flow selector associated with said pump, said first chamber of said first cylinder and said third chamber of said second cylinder, said flow selector assuming alternately:
 (i) a first selector state in which the clean fluid from said pump is directed to said first chamber so as to act on said first piston, thereby applying pressure to a quantity of the particle-laden fluid within said second chamber for delivery through an outlet in a first power stroke, said first power stroke also expelling a quantity of the clean fluid from said third chamber and taking in a quantity of the particle-laden fluid to said fourth chamber; and 
 (ii) a second selector state in which the clean fluid from said pump is directed to said third chamber so as to act on said second piston, thereby applying pressure to a quantity of the particle-laden fluid within said fourth chamber for delivery through an outlet in a second power stroke, said second power stroke also expelling the quantity of the clean fluid from said first chamber and taking in a quantity of the particle-laden fluid to said second chamber, 
   
       wherein said first and second pistons have an inner face facing, respectively, said first and third chambers and an outer face facing, respectively, said second and fourth chamber, said outer face having larger effective surface area than said inner face, such that pressure in said particle-laden fluid remains lower than pressure in said clean fluid.