Multiphase pressure boosting pump

Abstract

The invention provides a system for multiphase pumping, preferably for subsea application, distinctive in that it comprises a multiphase pressure boosting pump and a separator, preferably adapted for subsea operation, a multiphase fluid inlet connected to the pump, a multiphase outlet from the separator, an outlet of the pump arranged to an inlet of the separator, a liquid outlet of the separator arranged to a liquid inlet on the pump, and a power recovery turbine arranged between said liquid outlet of the separator and said liquid inlet on the pump. The invention also provides a multiphase pressure boosting pump, preferably adapted for subsea operation, comprising a motor, one or more impellers arranged on a shaft common with a motor shaft or coupled to the motor, a pressure housing, a multiphase fluid inlet and an outlet, distinctive in that the pump further comprises a liquid injection inlet and a power recovery turbine, with the power recovery turbine arranged between the liquid injection inlet and the pump impellers.

1 . A system for multiphase pumping, the system comprising a multiphase pressure boosting pump and a separator, a multiphase fluid inlet connected to the pump, a multiphase outlet from the separator, an outlet of the pump arranged to an inlet of the separator, a liquid outlet of the separator arranged to a liquid inlet on the pump, and a power recovery turbine arranged between said liquid outlet of the separator and said liquid inlet on the pump, where the pressure at the outlet of the turbine is equal to or substantially equal to the pressure at the inlet on the pump. 
     
     
         2 . The system according to  claim 1 , wherein the system is adapted for application subsea. 
     
     
         3 . The system according to  claim 1 , wherein the multiphase inlet is arranged to the pump downstream of the turbine but upstream of the pump impellers, so as to mix lower pressure gas-rich inlet wellstream with equal pressure liquid-rich flow from the turbine, regaining energy of the recycled liquid rich flow in the turbine and compressing gas by rotating liquid in the impellers. 
     
     
         4 . The system according to  claim 1 , wherein the coupling for liquid from the turbine is arranged so as to inject liquid into the pump impellers close to the rotational axis, preferably within two average fluid flow path diameters from the surface of the rotating hub or shaft, more preferably within one, and even more preferably within a half average fluid flow path diameter from the surface of the rotating hub or shaft, such as in an annular turbine liquid delivery flow cross section inside an annular multiphase fluid inlet arrangement. 
     
     
         5 . The system according to  claim 1 , wherein a cooler is arranged in the pipe from the separator liquid outlet to the pump liquid injection inlet, the impeller blades are multiphase fluid impeller blades, the separator is preferably integrated with the pump and turbine into one machine. 
     
     
         6 . A multiphase pressure boosting pump comprising a motor, one or more impellers arranged on a shaft common with a motor shaft or coupled to the motor, a pressure housing, a multiphase fluid inlet and an outlet, the pump further comprises a liquid inlet and a power recovery turbine, with the power recovery turbine arranged between the liquid inlet and the pump impellers. 
     
     
         7 . The multiphase pressure boosting pump according to  claim 6 , wherein the pump is adapted for application subsea. 
     
     
         8 . The multiphase pressure boosting pump according to  claim 6 , wherein the liquid injection inlet is arranged into an upstream side of the power recovery turbine so as to regain energy in the turbine and enhance gas compression by rotation of injected liquid by the impellers. 
     
     
         9 . The multiphase pressure boosting pump according to  claim 6 , wherein the coupling for liquid from the turbine is arranged so as to inject liquid into the pump impellers close to the rotational axis, preferably within two average fluid flow path diameters from the surface of the rotating hub or shaft, more preferably within one, even more preferably within a half average fluid flow path diameter from the surface of the rotating hub or shaft, such as in an annular turbine liquid delivery flow cross section inside an annular multiphase fluid inlet arrangement. 
     
     
         10 . The multiphase pressure boosting pump according to  claim 6 , wherein the impellers comprise multiphase fluid blades, and the injected liquid has a velocity component parallel to the multiphase velocity direction at the coupling from turbine to impellers, preferably coaxial around a rotating shaft common for the motor, impellers and turbine, but coaxial inside multiphase fluid. 
     
     
         11 . A method of boosting the pressure of a multiphase fluid, preferably subsea, by operating the system according to of  claim 1 , wherein liquid recirculates from the separator to the liquid inlet of the recovery turbine, at increasing rate at decreasing liquid contents of the multiphase fluid entering the multiphase pump. 
     
     
         12 . The method according to  claim 11 , wherein the liquid injection or recirculation flow rate comprises 30-50% of the multiphase inlet flow rate. 
     
     
         13 . A method of boosting the pressure of a dry gas, preferably subsea, by operating the pump according to of  claim 6 , comprising supplying a compatible liquid to the liquid inlet of the recovery turbine, at increasing rate at decreasing liquid contents of the multiphase fluid entering the multiphase pump. 
     
     
         14 . (canceled) 
     
     
         15 . (canceled) 
     
     
         16 . The method according to  claim 11 , wherein the GVF ratio of fluid entering the pump impellers is 95% or lower. 
     
     
         17 . The method according to  claim 16 , wherein the GVF ratio of fluid entering the pump impellers is 80% or lower. 
     
     
         18 . The method according to  claim 17 , wherein the GVF ratio of fluid entering the pump impellers is 70% or lower. 
     
     
         19 . The method according to  claim 13 , wherein the GVF ratio of fluid entering the pump impellers is 95% or lower. 
     
     
         20 . The method according to  claim 19 , wherein the GVF ratio of fluid entering the pump impellers is 80% or lower. 
     
     
         21 . The method according to  claim 20 , wherein the GVF ratio of fluid entering the pump impellers is 70% or lower. 
     
     
         22 . The method according to  claim 13 , wherein the liquid is a hydrocarbon liquid that can be pumped further with the boosted gas. 
     
     
         23 . The method according to  claim 13 , wherein the liquid is hydrate inhibited water.