Extraction of heat energy from active hydrocarbon wells

Abstract

A method of extracting heat from hydrocarbon production or injection wells involves passing heat exchanger tubing ( 6 ) down an active production or injection well and securing it. Heat from the formation or from fluids in the production tubing or annulus is extracted and returned to the surface to be used in various ways on a platform, e.g. heating accommodation or water supplies. The heat exchanger tubing ( 6 ) may be delivered on coil tubing ( 13 ) into the production tubing ( 8 ) and anchored above the DHSV, in a retro-fit operation. Alternatively it may be installed in a sidetrack well ( 126 ) via a dedicated kick-off ( 124, 125 ). If installed at the completion of the well, the heat exchanger tubing ( 206 ) may be located in the annulus, mounted on the outside of the production tubing ( 208 ); in this event, the heat exchanger tubing may extend further into the well (beyond the DHSV) to, or even beyond, the production packer ( 231 ).

1 . A process for extracting thermal energy from an active hydrocarbon production or injection well, wherein the process comprises:
 a) running a loop of heat exchanger tubing into the active well;   b) securing the heat exchanger tubing;   c) circulating heat exchange fluid through the heat exchanger tubing; and   d) extracting thermal energy from the heat exchange fluid at the surface.   
     
     
         2 . The process according to  claim 1 , wherein the heat exchanger tubing is run into the well using coil tubing. 
     
     
         3 . The process according to  claim 2 , wherein the coil tubing is run into production tubing of a production well, and the coil tubing also carries the loop of heat exchanger tubing. 
     
     
         4 . The process according to  claim 1 , wherein a packer or anchor device is run into the well to secure the heat exchanger tubing in the production tubing, above a downhole safety valve. 
     
     
         5 . The process according to  claim 4 , wherein the packer is a flow through packer. 
     
     
         6 . The process according to  claim 4 , wherein running the heat exchanger tubing loop into the well, running the packer or anchor device into the well and the operation related to hydrocarbon production are all performed on the same run of coil tubing. 
     
     
         7 . The process according to  claim 1 , wherein the active well is an injector well and wherein a kickoff is made in the well prior to delivery of heat exchanger tubing through the kickoff and then anchored in a sidetrack well. 
     
     
         8 . The process according to  claim 1 , wherein the heat exchanger tubing is anchored outside production tubing and is run into the well with the production tubing. 
     
     
         9 . The process according to  claim 8 , wherein the heat exchanger tubing is run to a point in the well deeper than a downhole safety valve in the production tubing. 
     
     
         10 . The process according to  claim 8 , wherein the heat exchanger tubing is run into the well during completion of the well. 
     
     
         11 . The process according to  claim 1 , wherein a heat pump is used to transfer thermal energy from the heat exchange fluid at the surface. 
     
     
         12 . The process according to  claim 1 , wherein differences in density of the heat exchange fluid as it is heated and cooled create circulation or assist circulation of the heat exchange fluid. 
     
     
         13 . The process according to  claim 1 , wherein the active well is a subsea well having a wellhead located on the seafloor, and wherein the heat exchanger tubing is brought to the surface at a location remote from the subsea well. 
     
     
         14 . The process according to  claim 13 , wherein the remote location is a marine installation such as a marine platform or an onshore location, and wherein produced hydrocarbons are transported by pipeline to the location and the heat exchanger tubing is run along the pipeline. 
     
     
         15 . The process according to  claim 14 , wherein the pipeline is a heated pipeline. 
     
     
         16 . A system for extracting thermal energy from an active hydrocarbon production or injection well, wherein the system comprises:
 a) a coil tubing delivery system including a length of coil tubing;   b) a length of heat exchanger tubing of smaller diameter than the coil tubing;   c) an assembly mounted on the coil tubing, the assembly including a packer and a fastener for securing the heat exchanger tubing to the packer;   whereby a loop of the heat exchanger tubing is capable of being run into a well on the coil tubing, the packer anchored in the well and the coil tubing then withdrawn.   
     
     
         17 . The system according to  claim 16 , wherein the packer is a flow-through packer. 
     
     
         18 . The system according to  claim 16 , wherein the loop of the heat exchanger tubing is mounted in the coiled tubing, adjacent the coiled tubing, or in the annulus of the casing. 
     
     
         19 . The system according to  claim 16 , wherein the active well is a subsea well having a wellhead located on the seafloor, and wherein the heat exchange tubing is brought to the surface at a location remote from the subsea well. 
     
     
         20 . The system according to  claim 19 , wherein the remote location is a marine installation such as a marine platform or an onshore location, and wherein produced hydrocarbons are transported by pipeline to the location and the heat exchange tubing is run along the pipeline, optionally wherein the pipeline is a heated pipeline.