Subsea pump and system and methods for control

Abstract

A subsea or downhole pump includes an inlet and an outlet. A flow of a multiphase fluid entering the inlet can have a variation in a gas volume fraction (GVF). The subsea or downhole pump includes or is operatively coupled to control devices which provide for a control as the GVF varies. The control devices include a first transmitter for an electric pump current, a second transmitter for at least one of a pump speed, a pump frequency, and a pump voltage, and a controller. The controller reduces a speed of the subsea or downhole pump when a measured pump current decreases, and increases the speed of the subsea or downhole pump when the measured pump current increases.

What is claimed is: 
     
         1 - 14 . (canceled) 
     
     
         15 . A subsea or downhole pump comprising:
 an inlet;   an outlet,   wherein,   a flow of a multiphase fluid entering the inlet can have a variation in a gas volume fraction (GVF), and   the subsea or downhole pump comprises or is operatively coupled to control devices which provide for a control as the GVF varies, the control devices consisting of:
 a first transmitter for an electric pump current, 
 a second transmitter for at least one of a pump speed, a pump frequency, and a pump voltage, and 
 a controller which reduces a speed of the subsea or downhole pump when a measured pump current decreases, and which increases the speed of the subsea or downhole pump when the measured pump current increases. 
   
     
     
         16 . The subsea or downhole pump as recited in  claim 15 , wherein the first transmitter and the second transmitter are integrated into or coupled for a real-time measurement at a topsides variable speed drive or at an onshore variable speed drive so as to eliminate a subsea instrumentation or a downhole instrumentation. 
     
     
         17 . The subsea or downhole pump as recited in  claim 15 , wherein the control devices consist of:
 the first transmitter, and   the second transmitter for the pump speed.   
     
     
         18 . The subsea or downhole pump as recited in  claim 15 , wherein,
 the subsea or downhole pump is a subsea pump,   a flow conditioning unit comprising an inlet and an outlet is arranged upstream of the subsea pump, the flow conditioning unit being configured to dampen a variation of the GVF and to reduce a gas bubble size in the multiphase flow entering the inlet of the fluid conditioning unit to allow for a delivery of the multiphase fluid through the outlet of the fluid conditioning unit to the subsea pump,   a liquid collecting unit is arranged downstream of the subsea pump, and   a liquid recirculation line connects the liquid collecting unit to an area which is upstream of the subsea pump, the liquid recirculation line being configured to provide a liquid to decrease the GVF to an acceptable operating level of the subsea pump where the GVF is too high.   
     
     
         19 . The subsea or downhole pump as recited in  claim 15 , wherein the subsea or downhole pump is an electrical submersible pump (ESP) arranged in a subsea flowline jumper. 
     
     
         20 . A method for controlling the subsea pump or downhole pump as recited in  claim 15 , the method comprising:
 measuring or transmitting parameters selected from the group of parameters consisting of:
 the electric pump current, and 
 at least one of the pump speed, the pump frequency, or the pump voltage; 
   reducing the speed of the subsea or downhole pump when the electric pump current measured or transmitted decreases; and   increasing the speed of the subsea or downhole pump when the electric pump current measured or transmitted increases.   
     
     
         21 . The method as recited in  claim 20 , wherein the parameters consist of the electric pump current and the pump speed which are measured or transmitted in real-time at a topsides variable speed drive. 
     
     
         22 . A subsea pump system comprising:
 a subsea pump comprising,
 an inlet, 
 an outlet, 
 wherein, 
 a flow of a multiphase fluid entering the inlet can have a higher gas volume fraction (GVF), a larger variation in the GVF, or larger gas bubbles, than is acceptable for an efficient and reliable operation of the subsea pump; 
   a flow conditioning unit comprising an inlet, the flow condition unit being arranged upstream of the subsea pump;   a liquid collecting unit arranged downstream of the subsea pump; and   a liquid recirculation line arranged to connect the liquid collecting unit with an area which is upstream of the subsea pump,   wherein,   the flow conditioning unit is configured,
 to reduce a variation in the GVF, to mix a gas and a liquid, and to reduce a size of gas bubbles in the multiphase flow entering the inlet of the flow conditioning unit, and 
 to recirculate a liquid from the liquid collection unit so as to reduce the GVF of a flow entering the inlet of the subsea pump so that the subsea pump can operate within an operational window which provides for the efficient and reliable operation of the subsea pump, and 
   the subsea pump comprises or is operatively coupled to control devices which provide for a control as the GVF at the inlet of the subsea pump varies, the control devices consisting of:
 a first transmitter for an electric pump current, 
 a second transmitter for at least one of a pump speed, a pump frequency, and a pump voltage, and 
 a controller which reduces a speed of the subsea pump when a measured pump current decreases, and which increases the pump speed of the subsea pump when the measured pump current increases. 
   
     
     
         23 . The subsea pump system as recited in  claim 22 , wherein,
 the flow conditioning unit further comprises a volume and an outlet which comprises a perforated outlet pipe which extends upwards into the volume,   the liquid collecting unit comprises an inlet, a volume, and an outlet which comprises an outlet pipe which extends upwards into the volume, the outlet pipe comprising perforations only in an upper part of the volume, and   the liquid recirculation line is arranged to connect a lower liquid filled part of the volume of the liquid collecting unit with the flow conditioning unit.   
     
     
         24 . The subsea pump system as recited in  claim 22 , wherein the first transmitter and the second transmitter are integrated into or coupled for a real-time measurement at a topsides variable speed drive or at an onshore variable speed drive so as to eliminate a subsea instrumentation or a downhole instrumentation. 
     
     
         25 . The subsea pump system as recited in  claim 22 , further comprising:
 a line coupled to the flow conditioning unit, the line being configured to export a gas or to import a liquid when an excessive GVF of the multiphase fluid to be pumped exists.   
     
     
         26 . The subsea pump system as recited in  claim 22 , wherein the subsea pump is an electrical submersible pump (ESP) arranged in a flow line jumper. 
     
     
         27 . A method for controlling the subsea pump system as recited in  claim 22 , the method comprising:
 measuring or transmitting parameters selected from the group of parameters consisting of:
 the electric pump current, and 
 at least one of the pump speed, the pump frequency, or the pump voltage; 
   reducing the speed of the subsea pump when the electric pump current measured or transmitted decreases; and   increasing the speed of the subsea pump when the electric pump current measured or transmitted increases.   
     
     
         28 . The method as recited in  claim 27 , whereby the parameters consist of the electric current and the pump speed measured in real-time at a topsides variable speed drive.