Liquefaction of Associated Gas at Moderate Conditions

Abstract

A method is proposed for converting a portion of associated gas generated during crude oil production into a liquid form which permits the transport of a large amount of methane at moderate temperatures.

1 . A method for producing a methane containing liquid at moderate temperature, the method comprising the steps of:
 a. recovering an associated gas from a crude oil production process;   b. drying the associated gas to remove water;   c. chilling the dried associated gas;   d. separating the chilled dried associated gas at a target temperature and target pressure in a vapor-liquid separator into a methane lean liquid stream and a methane rich vapor stream, the methane lean liquid stream containing at least 30% C 2 −; and   e. storing the methane lean liquid stream.   
     
     
         2 . The method of  claim 1  wherein the target temperature is between 5° F. and −55° F. and the target pressure is less than 750 psia. 
     
     
         3 . The method of  claim 2  wherein the target temperature is greater than −55° F. 
     
     
         4 . The method of  claim 2  wherein the pressure is less than 500 psia; 
     
     
         5 . The method of  claim 2  wherein the pressure is in the range of between 220 psia to 450 psia. 
     
     
         6 . The method of  claim 1 , wherein the methane lean liquid stream contains between 30% and 70% C 2 − components. 
     
     
         7 . The method of  claim 6 , wherein the methane lean liquid stream contains between 40 and 60% C 2 − components. 
     
     
         8 . The method of  claim 1  wherein the methane rich vapor stream comprises less than 30% C 2 + hydrocarbons. 
     
     
         9 . The method of  claim 6  wherein the methane rich vapor stream comprises less than 15% C 2 + hydrocarbons. 
     
     
         10 . The method of  claim 1  wherein the associated feed gas comprises greater than 30% C 2 + hydrocarbons. 
     
     
         11 . The method of  claim 8 , wherein the associated feed gas comprises greater than 40% C 2 + hydrocarbons. 
     
     
         12 . The method of  claim 1  wherein the dew point of the dried associated gas is less than the target temperature. 
     
     
         13 . The method of  claim 1 , further comprising using the methane rich vapor as a utility fuel for the uses selected from the group consisting of to drive gas turbine generators, to supply power requirements for living quarters and other utilities and to energize process support equipment and gas fired heaters 
     
     
         14 . The method of  claim 1 , further comprising using the methane rich vapor as a utility fuel to provide power for dynamic position thrusters installed on a dynamically positioned FPSO.