Fluid Heating

The present invention relates to a method and apparatus for providing a working fluid having a desired temperature at a predetermined location. In particular, but not exclusively, the present invention relates to using flexible pipes in a Down Bore Heat Exchanger (DBHX) to transport thermal energy extracted from the ground via the working fluid upwards to a surface level heat exchanger.

Flexible pipes are widely used in the oil and gas industry in both onshore and offshore applications for the transportation of oil, gas, water, or other fluids from one location to another. Offshore flexible pipe is particularly useful in connecting sea-level supporting structures and subsea locations (which may be deep underwater, say 1000 metres or more), where the pipe may act as a riser. Onshore flexible pipe is typically arranged underground or on the surface of the ground to connect two onshore structures, and to transport a fluid from one of these structures to another. Due to their location in use, flexible pipes are exposed to a range of challenging conditions that may have high pressures, seawater, high tensile strain, and corrosive environments, for example. Flexible pipe body is therefore often composed of several concentric polymeric, metallic, and/or composite layers. For example, pipe body may include polymer and metal layers, or polymer and composite layers, or polymer, metal and composite layers. Layers may be formed from a single piece such as an extruded tube or by helically winding one or more wires or tapes at a desired pitch or by connecting together multiple discrete hoops that are arranged concentrically side-by-side. Depending upon the layers of flexible pipe used and the type of flexible pipe some of the pipe layers may be bonded together or remain unbonded. The polymeric layers generally provide sealing from fluids and/or dirt ingress and the composite and/or metallic layers provide structural rigidity.

Examples of types of non-metallic flexible pipe include Reinforced Thermoplastic Pipe (RTP), Thermoplastic Composite Pipe (TCP), and the like. Reinforced thermoplastic pipe (RTP) may either be of an unbonded construction, where the layers of the pipe are unbonded to each other, i.e. the inner fluid containing polymer liner layer is not bonded to the reinforcement layer, which is in turn not bonded to the outer protective sheath polymer layer, or of a bonded construction, i.e. all layers are bonded to each other as part of the pipe manufacturing resulting in a pipe which is in effect a single, consolidated layer comprising sub-layers. Non-metallic flexible pipe may be suitable for use in transporting and/or distributing oilfield fluids, such as water, gas (methane, ethane, COetc.) and/or the transport and distribution of hydrocarbon liquids, or other fluids such as hydrogen may be used onshore (over land) or in very shallow water applications (for instance less than 50 m water depth).

Structurally, non-metallic flexible pipe body may have a non-complex construction, comprising two or more polymer layers each of which may be similar or different polymer types and/or composite material(s). See also American Petroleum Institute Specification 15S as a reference for an example of these types of pipes. The inner and outer polymer layers (often termed a liner and protective sheath respectively) are non-porous tubes usually consisting of at least one type of polymer. Aptly for some applications the inner polymer layer may comprise sub-layers similar or different polymer compositions which are co-extruded to form a liner.

It is known that down bore heat exchangers (DBHXs) can harness geothermal heat from the ground for a number of applications. For example, geothermal heat is sometimes utilised to heat a working fluid for heating buildings, district heating, and the like. Additionally, geothermal heat is sometimes utilised to heat a working fluid and this heat can be utilised to generate electricity. In some cases, the geothermal heat is used directly or indirectly to drive a turbine that converts mechanical energy into electrical energy. DBHXs can be installed in newly-drilled wells, used to repurpose existing end of life wells, or the like. Typically DBHXs consist of an outer metallic casing located in a borehole that extends downwardly into the ground and a concentric inner insulated tubing separated from the casing by an annulus region. Cool working fluid is pumped downwards in the annulus region where it is heated by contact with the outer metallic casing, reaching a closed bottom end of the casing and then is driven upwards through the inner insulated tubing.

Conventionally the inner insulated tubing is provided by Vacuum Insulated Tubing (VIT). VIT often includes an inner tubing concentric with an outer tubing with a vacuum provided therebetween to help reduce heat loss of geothermically heated fluid in the inner tubing of the VIT. Manufacturing and/or assembly VIT can thus be a costly process. Installing VIT in a bore (for use in a DBHX) often requires many rigid sections of VIT to be welded together. Also, VIT is heavy, requiring significant support when suspended from a support at surface level. As such, the installation of VIT in a DBHX is a time consuming and costly process. Furthermore, it is known that problems associated with VIT use in DBHX systems occur should the VIT annulus region (the region between the inner and outer VIT tubing) become damaged, flooded, or the like. For example, flooding of the annular region can result in a significant loss of insulation of the VIT. This can limit the overall performance of the DBHX, for example by limiting the heat that can be utilised from working fluid provided in the VIT.

It is an aim of certain embodiments disclosed herein to at least partly mitigate one or more of the above-mentioned problems.

It is an aim of certain embodiments disclosed herein to transfer heat from an existing location to a desired location (e.g., a heat exchange surface or the like) through circulation of working fluid in a geothermal bore (well).

It is an aim of certain embodiments disclosed herein to use a closed loop geothermal well to transfer heat from an underground source to an above-ground interface for providing district heating, power generation, or the like.

It is an aim of certain embodiments disclosed herein to increase the commercial viability of existing end of life wells as closed loop geothermal wells through the use of a Down Bore Heat Exchanger (DBHX).

It is an aim of certain embodiments disclosed herein to provide a method for reducing the time required to install a DBHX compared to conventional techniques.

It is an aim of certain embodiments disclosed herein to provide apparatus that facilitates more rapid and economic installation of a DBHX compared to conventional techniques.

It is an aim of certain embodiments disclosed herein to provide apparatus for repurposing end of life wells as a DBHX even when the bore of the well is angled.

It is an aim of certain embodiments disclosed herein to provide apparatus for increasing the reliability and/or decreasing maintenance requirements for a DBHX.

According to a first aspect there is provided apparatus for providing a working fluid having a desired temperature at a predetermined location, comprising:

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According to a second aspect, there is provided a method for providing a working fluid having a desired temperature at a predetermined location, comprising:

In certain embodiments, the method further comprises:

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In certain embodiments, the flexible pipe body and casing are disposed in a pipe-in-pipe substantially coaxial relationship and the method further comprises:

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According to a third aspect there is provided apparatus for providing a working fluid having a desired temperature at a predetermined location, comprising:

According to a fourth aspect, there is provided a method for providing a working fluid having a desired temperature at a predetermined location, comprising:

Certain embodiments provide a transfer of heat to a predetermined location using the circulation of a working fluid through flexible pipe body from an underground heat source.

Certain embodiments provide apparatus for repurposing an end of life bore as a Down Bore Heat Exchanger (DBHX) using flexible pipe to transfer working fluid heated in the bore by geothermal energy to a heat exchanger. The heat exchanger may transfer heat to a district heating system, a second working fluid of an Organic Rankine Cycle (ORC) power plant, or the like.

Certain embodiments provide a DBHX that utilises low-grade heat emitted by a newly drilled or end of life well for district heating.

Certain embodiments a method for installing flexible pipe in an angled downhole bore from ground level.