Sand decanter

Abstract

A method for processing hydrocarbons recovered from a subterranean formation is disclosed. The method includes: feeding a stream including water, sand, and heavy hydrocarbons produced from a subterranean formation to a separation vessel; concurrently in the separation vessel: heating the stream components to an elevated temperature to reduce a viscosity of the heavy hydrocarbons; and separating the sand, the heavy hydrocarbon, and the water to form a water fraction, a hydrocarbon fraction, and a sand fraction comprising sand and at least one of water and heavy hydrocarbons; and recovering the water fraction from the separation vessel; recovering the hydrocarbon fraction from the separation vessel; and withdrawing the sand fraction from the separation vessel. Also disclosed are apparatus suitable for performing the above described method.

1 . A method for processing hydrocarbons recovered from a subterranean formation, comprising:
 feeding a stream comprising water, sand, and heavy hydrocarbons produced from a subterranean formation to a separation vessel;   concurrently in the separation vessel:
 heating the stream components to an elevated temperature to reduce a viscosity of the heavy hydrocarbons; and 
 separating the sand, the heavy hydrocarbon, and the water to form a water fraction, a hydrocarbon fraction, and a sand fraction comprising sand and at least one of water and heavy hydrocarbons; and 
   recovering the water fraction from the separation vessel;   recovering the hydrocarbon fraction from the separation vessel; and   withdrawing the sand fraction from the separation vessel.   
     
     
         2 . The method of  claim 1 ,
 wherein the separating comprises separating the sand, the heavy hydrocarbon, and the water by a density separation technique;   wherein the withdrawing comprises:
 feeding the sand fraction to a screw conveyor; and 
 concurrently in the screw conveyor:
 transporting the sand fraction from a screw conveyor inlet to a screw conveyor outlet; and 
 separating the sand fraction from at least a portion of the at least one of water and heavy hydrocarbons; and 
 
 recovering the sand fraction from the screw conveyor outlet. 
   
     
     
         3 . The method of  claim 1 , wherein the heating comprises:
 combusting a fuel to form a flue gas; and   heating the stream components via indirect heat exchange with the flue gas.   
     
     
         4 . The method of  claim 3 , further comprising:
 heating the sand fraction during the withdrawing via indirect heat exchange with at least a portion of the flue gas.   
     
     
         5 . The process of  claim 3 , wherein the fuel comprises at least one of a natural gas and a portion of the recovered hydrocarbon fraction. 
     
     
         6 . The process of  claim 1 , further comprising washing the sand fraction to recover at least a portion of any residual hydrocarbons. 
     
     
         7 . The process of  claim 6 , further comprising at least one of reinjecting at least a portion of the washed sand into a subterranean formation and landfilling at least a portion of the washed sand. 
     
     
         8 . The process of  claim 1 , wherein the separation vessel comprises:
 a vertical portion on top of an angled portion;   at least one inlet nozzle for feeding a stream comprising water, sand, and heavy hydrocarbons produced from a subterranean formation into the vessel for separation into a hydrocarbon fraction, a water fraction, and a sand fraction comprising sand and at least one of water and heavy hydrocarbons;   an indirect heat exchange device disposed within at least one of the vertical portion and the angled portion for heating the water, sand, and heavy hydrocarbons;   at least one outlet nozzle for recovering the hydrocarbon fraction;   a screw conveyor located at a bottom of the angled portion to concurrently transport the sand fraction from the bottom of the angled portion to a screw conveyor outlet and separate the sand fraction from at least a portion of the at least one of water and heavy hydrocarbons   
     
     
         9 . The method of  claim 8 , wherein the separation vessel further comprises at least one outlet nozzle for recovering the water fraction; 
     
     
         10 . The method of  claim 8 , wherein the screw conveyor comprises a drying auger unit comprising:
 a. an inclined housing having side walls joined by a bottom and having an inlet end and an outlet end;   b. at least one inlet fluidly connected to the bottom of the angled portion for feeding the sand fraction comprising sand and at least one of water and heavy hydrocarbons to the inlet end;   c. a helical auger located in the housing for transporting the sand fraction from the inlet end of the housing to the outlet end of the housing, and a drive for rotating the auger,   d. an elevated pan disposed in and extending at least a portion of the length of the housing and having an arcuate cross section with a radius greater than a radius of the helical auger, wherein the pan is disposed proximate at least a lower quadrant of the helical auger;   e. the housing further comprising a liquid recovery zone adjacent to the pan for transporting the at least one of water and heavy hydrocarbons, separated from the sand during transport along the pan by the helical auger, to a liquid collection zone;   f. an outlet for recovering the at least one of water and heavy hydrocarbons from the liquid collection zone; and   g. at least one outlet for recovering sand having a reduced content of the at least one of water and heavy hydrocarbons.   
     
     
         11 . A system for processing hydrocarbons recovered from a subterranean formation, comprising:
 a separation vessel comprising:
 a vertical portion on top of an angled portion; 
 at least one inlet nozzle for feeding a stream comprising water, sand, and heavy hydrocarbons produced from a subterranean formation into the vessel for separation into a hydrocarbon fraction, a water fraction, and a sand fraction comprising sand and at least one of water and heavy hydrocarbons; 
 an indirect heat exchange device disposed within at least one of the vertical portion and the angled portion for heating the water, sand, and heavy hydrocarbons; 
 at least one outlet nozzle for recovering the hydrocarbon fraction; 
 at least one outlet nozzle for recovering the water fraction; 
 a screw conveyor located at a bottom of the angled portion to concurrently transport the sand fraction from the bottom of the angled portion to a screw conveyor outlet and separate the sand fraction from at least a portion of the at least one of water and heavy hydrocarbons; and 
 at least one outlet for recovering the sand fraction from the screw conveyor. 
   
     
     
         12 . The system of  claim 10 , further comprising an indirect heat exchange device disposed at an exterior of at least a portion of the screw conveyor for heating the sand fraction during transport. 
     
     
         13 . The system of  claim 11 , further comprising a combustion system for combusting a fuel to produce a flue gas for use in indirect heat exchange in at least one of the indirect heat exchange device disposed within at least one of the vertical portion and the angled portion and the indirect heat exchange device disposed at an exterior of at least a portion of the screw conveyor. 
     
     
         14 . The system of  claim 10 , further comprising a sand wash system for washing the sand fraction to recover at least a portion of any residual hydrocarbons. 
     
     
         15 . The system of  claim 11 , wherein the screw conveyor comprises a drying auger unit comprising:
 a. an inclined housing having side walls joined by a bottom and having an inlet end and an outlet end;   b. at least one inlet fluidly connected to the bottom of the angled portion for feeding the sand fraction comprising sand and at least one of water and heavy hydrocarbons to the inlet end;   c. a helical auger located in the housing for transporting the sand fraction from the inlet end of the housing to the outlet end of the housing, and a drive for rotating the auger,   d. an elevated pan disposed in and extending at least a portion of the length of the housing and having an arcuate cross section with a radius greater than a radius of the helical auger, wherein the pan is disposed proximate at least a lower quadrant of the helical auger;   e. the housing further comprising a liquid recovery zone adjacent to the pan for transporting the at least one of water and heavy hydrocarbons, separated from the sand during transport along the pan by the helical auger, to a liquid collection zone;   f. an outlet for recovering the at least one of water and heavy hydrocarbons from the liquid collection zone; and   g. at least one outlet for recovering sand having a reduced content of the at least one of water and heavy hydrocarbons.