Fluid heating

Abstract

A method and apparatus for providing a working fluid having a desired temperature at a predetermined location are disclosed. The apparatus comprises a downhole casing disposed in a pre-drilled borehole; and at least a portion of at least one flexible pipe comprising flexible pipe body, disposed in the casing, wherein a working fluid is moveable in a first direction in an annular region, between the casing and the flexible pipe body and a bore region of the flexible pipe body, and in a further direction opposite to the first direction via the bore region.

What is claimed is: 
     
         1 . Apparatus for providing a working fluid having a desired temperature at a predetermined location, comprising:
 a downhole casing disposed in a pre-drilled borehole; and   at least a portion of at least one flexible pipe comprising flexible pipe body, disposed in the casing, wherein   a working fluid is moveable in a first direction in an annular region, between the casing and the flexible pipe body and a bore region of the flexible pipe body, and in a further direction opposite to the first direction via the bore region.   
     
     
         2 . The apparatus as claimed in  claim 1 , further comprising:
 the downhole casing is fluidically sealed at a lower casing end region and movement of the working fluid is via a closed loop fluid communication pathway and optionally the downhole casing is fluid tight.   
     
     
         3 . The apparatus as claimed in  claim 1 , further comprising:
 the flexible pipe body comprises a fluid retaining layer having a radially inner surface that defines the bore region, an outer layer, having an outer surface that defines a radially inner surface of the annular region, coaxial with the fluid retaining layer and at least one intermediate layer between the fluid retaining layer and the outer layer.   
     
     
         4 . The apparatus as claimed in  claim 1 , further comprising:
 the casing comprises a hollow elongate wall body that surrounds a region of the borehole in which said a portion of the flexible pipe is located and optionally an end cap that is integrally formed with or is secured to a lower end of the wall body to provide a sealed end to the casing.   
     
     
         5 . The apparatus as claimed in  claim 1 , further comprising:
 said a portion comprises a portion of a single flexible pipe or a portion of a full length of a plurality of flexible pipes disposed in an end-to-end configuration and optionally said a portion extends for more than 60% of a casing length of the downhole casing.   
     
     
         6 . The apparatus as claimed in  claim 4  wherein the wall body is integrally formed or comprises a plurality of elongate wall body elements secured together in an end-to-end configuration and optionally the wall body is cylindrical or has a rectangular or elliptical cross section that optionally is substantially common at all positions along a casing length of the downhole casing. 
     
     
         7 . The apparatus as claimed in  claim 1  wherein the flexible pipe body is disposed in a substantially coaxial spaced apart relationship with the downhole casing. 
     
     
         8 . The apparatus as claimed in  claim 1 , further comprising:
 a lower end of the flexible pipe body is located around 1000 m below an upper terrain surface and working fluid proximate to the lower end is at a temperature that comprises a downhole heated temperature of around 40° C. or a lower end of the flexible pipe body is located around 3000 m below the surface and working fluid proximate to the lower end is at a temperature that comprises a downhole heated temperature of 90° C. or the lower end of the flexible pipe body is located around 5000 m below the surface and working fluid proximate to the lower end is at a temperature that comprises a downhole heated temperature of around 140° C.   
     
     
         9 . The apparatus as claimed in  claim 1 , further comprising:
 at least one pump element in fluid communication with at least one of the annular region and the bore region of the flexible pipe body.   
     
     
         10 . The apparatus as claimed in  claim 1 , further comprising:
 each borehole is a repurposed well or a purpose drilled well and optionally each well is a geothermal well for transferring heat from earth's ground temperature to a predetermined location that comprises a surface location, a heat pump system or a heating system for homes/business or district heating.   
     
     
         11 . The apparatus as claimed in  claim 1 , further comprising:
 providing a working fluid at a predetermined location comprises providing working fluid having a thermal temperature elevated via geothermal heating from a geothermal reservoir to a surface location where heat is extractable for return of the working fluid downhole and optionally the working fluid comprises water or Isobutane or N-butane or Isopentane or N-pentane or Cyclopentane or Propane.   
     
     
         12 . The apparatus as claimed in  claim 1 , further comprising:
 the desired temperature at the predetermined location is within 20% of a downhole heated temperature accumulated by the working fluid at a lower end of the flexible pipe body disposed in the casing and optionally the desired temperature at the predetermined location is within 10% of the downhole heated temperature.   
     
     
         13 . The apparatus as claimed in  claim 1 , further comprising:
 the flexible pipe body comprises multi-layer unbonded Reinforced Thermoplastic Pipe (RTP) body or multi-layer bonded RTP body or single layer RTP body or unbonded flexible pipe body or bonded Thermoplastic Composite Pipe (TCP) body.   
     
     
         14 . A method for providing a working fluid having a desired temperature at a predetermined location, comprising:
 urging a working fluid along an annular region between a downhole casing disposed in a pre-drilled borehole and a portion of at least one flexible pipe that comprises flexible pipe body, disposed in the casing;   heating the working fluid at a lower end region of flexible pipe body; and   urging the heated working fluid along a bore region of the flexible pipe to a predetermined location.   
     
     
         15 . The method as claimed in  claim 14 , further comprising:
 urging the working fluid along the annular region in a first axial flow direction and urging the working fluid along the bore region in a further axial flow direction that is opposite to the first axial flow direction.   
     
     
         16 . The method as claimed in  claim 14 , further comprising:
 urging the working fluid along a closed loop fluid communication pathway that comprises an annular region pathway portion and a bore region pathway portion.   
     
     
         17 . The method as claimed in  claim 14 , wherein the flexible pipe body and casing are disposed in a pipe-in-pipe substantially coaxial relationship and the method further comprises:
 urging working fluid down a borehole via an annular region that surrounds the flexible pipe body and is inside the casing; and   urging working fluid up the borehole towards the predetermined location via the bore region of the flexible pipe body.   
     
     
         18 . The method as claimed in  claim 14 , further comprising:
 providing thermal insulation, between working fluid that moves vertically down away from an upper terrain surface and is relatively cool relative to rising heated working fluid that moves vertically upwards via the bore region, via a layer of the flexible pipe body.   
     
     
         19 . The method as claimed in  claim 18 , further comprising:
 providing the thermal insulation via a fluid retaining layer of the flexible pipe body and/or an outer polymer layer of the flexible pipe body and/or a polymer intermediate layer of the flexible pipe body.   
     
     
         20 . The method as claimed in  claim 14 , further comprising:
 providing geothermal fluid from a geothermal reservoir via at least one feed zone to the downhole casing;   via heat conduction, heating the casing via the geothermal fluid; and   heating the working fluid in a lower region of the annular region via the heated casing and optionally providing heated working fluid to a heat pump system or a heating system for homes/business or district heating of the predetermined location.