Subsea bop control system

Abstract

An activatable choke assembly is arranged in communication with a BOP function manifold. The choke assembly may be placed before a point of distribution (POD). The choke assembly can be activated to dampen acceleration or deceleration of the hydraulic fluid in the BOP function manifold.

We claim: 
     
         1 . A subsea BOP control system for a hydraulic blowout preventer, comprising:
 a BOP function manifold comprising a source side connectable to a hydraulic power unit for powering a BOP function;   at least one main valve connected to said BOP function manifold on one side of the at least one main valve and on the other side of the at least one main valve connectable to the BOP function, to selectively connect or isolate the BOP function from the BOP function manifold;   a computer device functionally coupled to a main actuator of the at least one main valve and arranged to control activation and deactivation of the main actuator;   an activatable choke assembly arranged at the source side of the BOP function manifold and upstream of the main valve.   
     
     
         2 . The subsea control system of  claim 1 , wherein the choke assembly comprises choke actuator functionally coupled to the computer device to control activation and deactivation of the choke actuator. 
     
     
         3 . The subsea control system of  claim 1 , wherein the computer device is programmed to activate the choke actuator prior to shifting the main actuator. 
     
     
         4 . The subsea control system of  claim 3 , wherein the computer device is programmed to subsequently deactivate the choke actuator to fully open the BOP function manifold based on a criterion. 
     
     
         5 . The subsea control system of  claim 1 , further comprising a flow meter configured in the BOP function manifold. 
     
     
         6 . The subsea control system of  claim 6 , wherein the flow meter is functionally coupled to the computer device to provide flow data to the computer device, and wherein said flow data is used in the computer logic to control activation and deactivation of the choke actuator. 
     
     
         7 . The subsea control system of  claim 1 , wherein the computer device is programmed with self-learning logic to regulate activation and deactivation of the activatable choke assembly. 
     
     
         8 . A method of shifting a main valve in a subsea BOP control system for a hydraulic blowout preventer, comprising:
 providing a BOP function manifold connected to a hydraulic power unit for powering a BOP function, and at least one main valve connected to said BOP function manifold on one side of the at least one main valve and on the other side of the at least one main valve connectable to the BOP function, to selectively connect or isolate the BOP function from the BOP function manifold;   shifting the at least one main valve comprising activating or deactivating a main actuator of the main valve, and activating a choke assembly, which is arranged at the source side of the BOP function manifold and upstream of the at least one main valve, prior to shifting the at least one main valve.   
     
     
         9 . The method of  claim 8 , further comprising deactivating the choke assembly to fully open the BOP function manifold based on a criterion. 
     
     
         10 . The method of  claim 8 , wherein the choke assembly is activated and deactivated automatically by means of a computer device functionally coupled to a choke actuator. 
     
     
         11 . The method of  claim 8 , further comprising retrofitting the choke assembly on a pre-existing BOP control system after the pre-existing BOP control system has been operated devoid of said choke assembly. 
     
     
         12 . The system for a hydraulic blowout preventer comprises:
 a hydraulic BOP function comprising a piston having a stroke;   a BOP function manifold comprising a source side connectable to a hydraulic power unit for powering the BOP function;   at least one main valve connected to said BOP function manifold on one side of the at least one main valve and on the other side of the at least one main valve connected to the BOP function, to selectively connect or isolate the BOP function from the BOP function manifold;   an activatable choke assembly arranged at the source side of the BOP function manifold;   a computer device functionally coupled to a choke actuator of the choke assembly, programmed to automatically activate the choke actuator prior to the piston of the BOP function reaching an end of its stroke.   
     
     
         13 . The subsea control system of  claim 12 , further comprising a sensor functionally coupled to the computer device to provide information to the computer device about how far the piston is removed from the end of its stroke, and wherein the LC device is programmed to activate the choke assembly based on the information. 
     
     
         14 . The subsea control system of  claim 14 , and wherein said sensor comprises a flow meter configured in the BOP function manifold, said flow data is used in the computer logic to estimate how far the piston is removed from the end of its stroke. 
     
     
         15 . The subsea control system of  claim 12 , wherein the computer device is programmed with self-learning logic to regulate activation and deactivation of the activatable choke assembly.