Method of cooling a multiphase well effluent stream

Abstract

A method of cooling a multiphase well effluent stream comprises: separating the multiphase well effluent stream (G+L) into gas enriched and liquid enriched fractions in a gas liquid separator ( 2, 22 ); cooling the liquid enriched fraction in a heat exchanger ( 6,26 ); reinjecting the cooled liquid enriched fraction into the well effluent stream (G+L) at a location upstream of the gas liquid separator ( 2, 22 ), thereby cooling the well effluent stream without requiring a gas-liquid heat exchanger to directly cool the multiphase well effluent stream, which may be ten times larger than the liquid-liquid heat exchanger ( 6, 26 ) for cooling the recycled liquid enriched fraction (L cold ).

1 . A self-controlling subsea system for cooling a multiphase well stream from a subsea production well where a multiphase conduit ( 3 ,  23 ) is led into a separator ( 2 ) for separating gas and liquid, and where a liquid recycling conduit ( 5 ) extends from the separator ( 2 ), and where the system furthermore includes a sea water cooled heat exchanger ( 6 ),
 characterized in that   the liquid recycling conduit ( 5 ) extends directly into the heat exchanger ( 6 ) and further directly into the multiphase conduit ( 3 ,  23 ) upstream of the separator ( 2 ), such that the equipment exclusively includes static equipment.   
   
   
       2 . The self-controlling subsea system as defined in  claim 1 , further including a jet pump ( 28 ), allowing the multiphase well flow to suck liquid from the separator ( 2 ), placed inside the multiphase conduit ( 3 ,  23 ). 
   
   
       3 . The self-controlling subsea system as defined in  claim 1 , further comprising that the separator ( 2 ) includes a vertically orientated tubular separation vessel ( 22 ) with a liquid outlet near the bottom of the vessel and a gas outlet near the top of the vessel, said vessel being supplied with the multiphase well stream through a substantially tangential multiphase fluid inlet ( 20 ) from the multiphase conduit ( 3 ,  23 ). 
   
   
       4 . A method of cooling a multiphase well effluent stream, the method comprising:
 separating the multiphase well effluent stream into gas enriched and liquid enriched fractions in a gas liquid separator;   
     characterized in leading the liquid enriched fraction directly to a heat exchanger ( 6 ),
 cooling the liquid enriched fraction in the heat exchanger ( 6 ), 
 lead the liquid enriched fraction from the heat exchanger ( 6 ) directly into the multiphase well stream, 
 injection the cooled liquid enriched fraction into the well effluent stream at a location upstream of the gas liquid separator. 
 
   
   
       5 . The method of  claim 4 , wherein the gas liquid separator and heat exchanger are immersed in water and the heat exchanger is cooled by the surrounding water. 
   
   
       6 . The method of  claim 4 , wherein the multiphase well effluent stream is transported from one or more gas an/or crude oil production wells to the gas liquid separator via a multiphase well effluent transportation conduit ad the cooled liquid enriched fraction is reinjected into the multiphase well effluent transportation conduit by means of a jet pump. 
   
   
       7 . The method of  claim 6 , wherein the gas liquid separator is a hybrid cyclonic and gravity separator comprising a substantially vertically orientated tubular separation vessel with a liquid outlet near the bottom of the vessel and a gas outlet near the top of the vessel and a substantially tangential multiphase fluid inlet which is connected to the multiphase well effluent transportation conduit.