Adaptive control system and methods for well service pump systems

Abstract

A well service pump system supplies high pressure working fluid to a well. The pump system includes a closed-loop hydraulic circuit for actuating a plurality of working pump assemblies. The pump system is powered by a motor, which transfers mechanical energy to a plurality of pumps, which, in turn, provide hydraulic fluid to operate hydraulic ram cylinders, and thereby operate the working pump assemblies. Each of the polished rods of the hydraulic ram cylinders is connected axially to a plunger rod end of the working fluid end cylinder to operate the working pump assembly.

1 . A well service pump system for delivering fracturing fluid at high pressure to a well, the pump system comprising:
 three or more working fluid pump assemblies, each comprising:
 a working fluid end cylinder having an end cylinder housing, a plunger rod configured to reciprocate in the end cylinder housing; and 
 a hydraulic ram cylinder having a ram cylinder housing, a ram piston configured to reciprocate in the ram cylinder housing, and a piston rod coupled to the ram piston and coupled to the plunger rod of the working fluid end cylinder such that piston of the hydraulic ram cylinder can be actuated to move the plunger rod of the working fluid end cylinder:
 in a first direction to expel working fluid from the end cylinder housing during a forward stroke of the plunger rod, and 
 in a second direction to draw working fluid into the end cylinder housing during a return stroke of the plunger rod; and 
 
 a sensor configured to detect a parameter indicative of the position of the plunger rod of the working fluid end cylinder and/or the position of the ram piston of the hydraulic ram cylinder; 
   one or more sources of hydraulic fluid configured to selectively direct pressurized hydraulic fluid to each of the hydraulic ram cylinders to drive the respective ram piston in at least one of the first and second directions;   a control system coupled to the sensors and configured to sequentially actuate the hydraulic ram cylinders to deliver a continuous output flow of the working fluid from the pump system to the well, the control system further configured to:
 determine how many of the working fluid pump assemblies are operational; and 
 adjust the timing of actuation of each of the operational ones of the working fluid pump assemblies based on the number of operational working fluid pump assemblies. 
   
     
     
         2 . The well service pump system of  claim 1 , where the control system is configured to:
 adjust the timing of actuation of each of the operational ones of the working fluid pump assemblies based on the number of operational working fluid pump assemblies relative to the total number of working fluid pump assemblies.   
     
     
         3 . The well service pump system of  claim 2 , where the control system comprises a processor or programmable logic controller (PLC) configured to sequentially actuate the working fluid pump assemblies such that the hydraulic ram cylinder of a first one of the working fluid pump assemblies is beginning its forward stroke as the hydraulic ram cylinder of a second one of the working fluid pump assemblies is ending its forward stroke. 
     
     
         4 . The well service pump system of  claim 3 , where the processor or PLC is configured to sequentially actuate the working fluid pump assemblies such that the hydraulic ram cylinder of a third one of the working fluid pump assemblies is beginning its forward stroke when the hydraulic ram cylinder of the first one of the working fluid pump assemblies is a fraction of the way through its forward stroke, where the fraction equals 1/(n−1), and n equals the number of operational working fluid end cylinders. 
     
     
         5 . The well service pump system of  claim 1 , where the three or more working fluid pump assemblies comprises six or more of the working fluid pump assemblies, and the control system is configured to control the working fluid pump assemblies in two sets each with three or more working fluid pump assemblies. 
     
     
         6 . The well service pump system of  claim 5 , where the control system is configured to:
 determine how many of the working fluid pump assemblies are operational in each set; and   adjust the timing of actuation of each of the operational ones of the working fluid pump assemblies in each set based on the number of operational working fluid pump assemblies in the respective set, independently of the timing of the other set.   
     
     
         7 . The well service pump system of  claim 5 , where the control system is further configured to, if one of the sets has fewer than a threshold number of operational working fluid pump assemblies, not adjust the timing of the sets independently, and instead treat all operational working fluid pump assemblies as a single set for purposes of adjusting the timing of actuation of the operational ones of the working fluid pump assemblies. 
     
     
         8 - 10 . (cancelled) 
     
     
         11 . The well service pump system of  claim 3 , where the processor or PLC is configured to actuate each of the working fluid pump assemblies, via adjustment of the source of pressurized working fluid, such that the duration of the forward stroke is twice the duration of the return stroke. 
     
     
         12 . The well service pump system of  claim 1 , where the one or more sources of hydraulic fluid comprise:
 a plurality of bi-directional pumps, each coupled to a respective one of the working fluid pump assemblies such that the bi-directional pump is in fluid communication with the first hydraulic port and the second hydraulic port of the hydraulic ram cylinder to pump hydraulic fluid:
 from the second hydraulic port directly into the first hydraulic port to actuate the ram piston to drive the plunger rod in the first direction; and 
 from the first hydraulic port directly into the second hydraulic port to actuate the ram piston to drive the plunger rod in the second direction. 
   
     
     
         13 . The well service pump system of  claim 12 , comprising a fluid reservoir configured to be in fluid communication with each of the plurality of bi-directional pumps to compensate for leakage in the system. 
     
     
         14 . (canceled) 
     
     
         15 . The well service pump system of  claim 12 , comprising a motor configured to drive each of the bi-directional pumps to direct fluid to the first and second ports. 
     
     
         16 . The well service pump system of  claim 15 , comprising a pump drive coupled to the motor and to each of the bi-directional pumps, the pump drive configured to transfer mechanical energy from the motor to each of the bi-directional pumps. 
     
     
         17 . The well service pump system of  claim 16 , wherein at least one of the bi-directional pumps is mounted to the pump drive. 
     
     
         18 - 22 . (canceled) 
     
     
         23 . The well service pump system of  claim 1 , wherein at least one of the sources of hydraulic fluid comprises a fixed-displacement hydraulic pump. 
     
     
         24 . (canceled) 
     
     
         25 . (canceled) 
     
     
         26 . A method comprising:
 delivering a working fluid to a well with a well service pump system comprising:
 at least three working fluid pump assemblies, each comprising:
 a working fluid end cylinder having a plunger rod configured to reciprocate within the fluid end cylinder; and 
 a hydraulic ram cylinder having a ram piston configured to reciprocate within the hydraulic ram cylinder and a piston rod coupled to the ram piston and coupled to the plunger rod of the working fluid end cylinder; 
 wherein the hydraulic ram cylinder includes a first hydraulic port on a first side of the ram piston and second hydraulic port on a second side of the ram piston; 
 
 one or more sources of hydraulic fluid configured to selectively direct pressurized hydraulic fluid to each of the hydraulic ram cylinders to drive the respective ram piston in at least one of the first and second directions; 
   wherein delivering the working fluid comprises, for each operational one of the working fluid pump assemblies:
 actuating the ram piston of the hydraulic ram cylinder to move the plunger rod of the working fluid end cylinder:
 in a first direction to expel working fluid from the fluid end cylinder during a forward stroke of the plunger rod, and 
 in a second direction to draw working fluid into the fluid end cylinder during a return stroke of the plunger rod; and 
 
   determining how many of the working fluid pump assemblies are operational; and   timing actuation of each of the operational ones of the working fluid pump assemblies based on the determined number of operational working fluid pump assemblies.   
     
     
         27 . The method of  claim 26 , further comprising:
 identifying a change in the number of the working fluid pump assemblies that are operational; and   adjusting the timing of actuation of each of the operational ones of the working fluid pump assemblies based on the number of operational working fluid pump assemblies.   
     
     
         28 . The method any of  claim 26 , where the timing of actuation of each of the operational ones of the working fluid pump assemblies is set or adjusted based on the number of operational working fluid pump assemblies relative to the total number of working fluid pump assemblies. 
     
     
         29 . The method of  claim 28 , where the working fluid pump assemblies are actuated such that the hydraulic ram cylinder of a first one of the working fluid pump assemblies is beginning its forward stroke as the hydraulic ram cylinder of a second one of the working fluid pump assemblies is ending its forward stroke. 
     
     
         30 . The method of  claim 29 , where the working fluid pump assemblies are actuated such that the hydraulic ram cylinder of a third one of the working fluid pump assemblies is beginning its forward stroke when the hydraulic ram cylinder of the first one of the working fluid pump assemblies is a fraction of the way through its forward stroke, where the fraction equals 1/(n−1), and n equals the number of operational working fluid end cylinders. 
     
     
         31 . The method of  claim 26 , where the three or more working fluid pump assemblies comprises six or more of the working fluid pump assemblies, the working fluid pump assemblies are actuated in two sets each with three or more working fluid pump assemblies, and determining and setting comprises:
 determining how many of the working fluid pump assemblies are operational in each set; and   timing actuation of each of the operational ones of the working fluid pump assemblies in each set based on the number of operational working fluid pump assemblies in the respective set, independently of the timing of the other set.   
     
     
         32 . The method of  claim 31 , further comprising:
 detecting a change in the number of operational working fluid pump assemblies in each set; and   adjusting the timing actuation of each of the operational ones of the working fluid pump assemblies in each set based on the number of operational working fluid pump assemblies in the respective set, independently of the timing of the other set.   
     
     
         33 . The method of  claim 31 , where, if one of the sets has fewer than a threshold number of operational working fluid pump assemblies, treating all operational working fluid pump assemblies as a single set for purposes of adjusting the timing of actuation of the operational ones of the working fluid pump assemblies. 
     
     
         34 . The method of  claim 33 , where the threshold number is 2. 
     
     
         35 . The method of  claim 32 , where the working fluid pump assemblies in each set are actuated such that the hydraulic ram cylinder of a first one of the operational working fluid pump assemblies is beginning its forward stroke as the hydraulic ram cylinder of a second one of the operational working fluid pump assemblies is ending its forward stroke. 
     
     
         36 . The method of  claim 35 , where the working fluid pump assemblies in each set are actuated such that the hydraulic ram cylinder of a third one of the working fluid pump assemblies is beginning its forward stroke when the hydraulic ram cylinder of the first one of the working fluid pump assemblies is a fraction of the way through its forward stroke, where the fraction equals 1/(n−1), and n equals the number of operational working fluid end cylinders in the set. 
     
     
         37 . The method of  claim 29 , where the working fluid pump assemblies are actuated such that the duration of the forward stroke is twice the duration of the return stroke. 
     
     
         38 . The method of  claim 26 , where the one or more sources of hydraulic fluid comprise a plurality of bi-directional pumps, each fluidly coupled to a respective one of the working fluid pump assemblies, and actuating each ram piston comprises:
 directing hydraulic fluid, via a corresponding bi-directional pump:
 from the second hydraulic port directly into the first hydraulic port to actuate the ram piston to drive the plunger rod in the first direction; and 
 from the first hydraulic port directly into the second hydraulic port to actuate the ram piston to drive the plunger rod in the second direction. 
   
     
     
         39 - 41 . (canceled)