Geothermal well and tubing apparatus therefor

Abstract

A tubing apparatus is for use in a geothermal well. The tubing apparatus includes a vacuum insulated tubing string describing a conduit and a cooling string received within the conduit. The conduit conveys a working fluid between a surface location and a subsurface location. The cooling string injects a cooling fluid into the conduit so as to adjust the temperature of the working fluid.

1 - 15 . (canceled) 
     
     
         16 . A geothermal well comprising:
 a wellbore within which is received an insulated tubing string defining a conduit configured to convey a working fluid between a surface location and a subsurface location, and a cooling string configured to adjust, in use, the temperature of the working fluid as it is conveyed toward the surface location.   
     
     
         17 . The geothermal well according to  claim 16 , wherein the cooling string is received within the conduit and the geothermal well is configured to convey, in use, the working fluid from the surface location to the subsurface location through an annular space between the wellbore and the insulated tubing string, and from the subsurface location to the surface location through the insulated tubing string. 
     
     
         18 . The geothermal well according to  claim 17 , wherein the cooling string is configured to inject, in use, a cooling fluid into the conduit so as to adjust the temperature of the working fluid. 
     
     
         19 . The geothermal well according to  claim 18 , wherein the cooling string has a smaller flow area than the insulated tubing string. 
     
     
         20 . The geothermal well according to  claim 18 , wherein the cooling string has a smaller diameter than the insulated tubing string. 
     
     
         21 . The geothermal well according to  claim 18 , wherein the cooling string is located adjacent a wall of the insulated tubing string. 
     
     
         22 . The geothermal well according to  claim 18 , wherein a bottom end of the cooling string is located short of the bottom end of the insulated tubing string. 
     
     
         23 . The geothermal well according to  claim 18 , wherein the cooling string is removable from the insulated tubing string. 
     
     
         24 . The geothermal well according to  claim 16 , wherein the well is a closed-loop geothermal well. 
     
     
         25 . A tubing apparatus for use in the geothermal well according to  claim 16 , the apparatus comprising:
 an insulated tubing string defining a conduit configured to convey a working fluid between a surface location and a subsurface location, and a cooling string configured to adjust, in use, the temperature of the working fluid as it is conveyed toward the surface location.   
     
     
         26 . The tubing apparatus according to  claim 25 , further comprising a casing string, wherein the insulated tubing string is located within the casing string such that an annular space is defined therebetween, the cooling string being received within the conduit or within the annular space. 
     
     
         27 . The tubing apparatus according to  claim 26 , wherein the cooling string is received within the conduit and the tubing apparatus is configured to convey, in use, the working fluid from the surface location to the subsurface location through the annular space and from the subsurface location to the surface location through the insulated tubing string. 
     
     
         28 . The tubing apparatus according to  claim 25 , further comprising a controller configured to control the flow rate of working fluid and/or cooling fluid. 
     
     
         29 . A well head control assembly for use with the tubing apparatus according to  claim 25 , the assembly comprising:
 a controller and one or more flow valves, wherein the controller is configured to control the flow rate and/or pressure of a working fluid and the flow rate and/or pressure of cooling fluid through the tubing apparatus.   
     
     
         30 . A method of starting up a geothermal well, the method comprising:
 circulating a working fluid between a surface location and a subsurface location via an insulated tubing string; and   adjusting the temperature of the working fluid as working fluid is circulated toward the surface using a cooling string.