Thermoelectric energy generation system

Abstract

The present invention provides a riser system (10) or a production tubing (36) designed for generating electrical energy for downhole applications. Within this system, one or more thermoelectric modules / elements (24) are integrated into either the riser system (10) or the production tubing (36). The thermoelectric modules / elements (24) harness the temperature difference between a hot side and a cold side to generate electrical energy. The produced electrical energy serves multiple purposes, including the operation and control of valves (47), sensors, and various monitoring systems. Furthermore, this electrical energy is utilized to power functions on remote rigs through cables, or to operate local gas or gasoline turbines for local electricity generation.

Description

Title: Thermoelectric Energy Generation SystemTechnical Field

[0001] The invention pertains to the field of offshore oil and gas production facilities, specifically within the domain of riser systems and production tubing. More specifically, it relates to the implementation of thermoelectric modules within the riser system or production tubing, with the objective of harnessing electrical energy by exploiting the temperature differential between the flowing oil or gas inside the riser system or production tubing and the surrounding liquid or fluids within the annulus formed between the riser system or production tubing and the outer casing.Background

[0002] Offshore oil and gas production facilities rely on a complex network of pipes and tubing systems to extract and transport hydrocarbons from beneath the seabed to the surface. This infrastructure includes various components such as riser systems (also known as riser flexible tubing or riser tubing) used for pumping up produced oil or gas, as well as other pipelines for the delivery of chemicals to reduce crude oil viscosity, facilitating efficient pumping. Additionally, power cables and flow lines connect the underwater operations to the surface facilities situated vertically above the seafloor.

[0003] The riser system, often referred to as a subsea riser or marine riser, plays a critical role in offshore oil and gas production by conveying hydrocarbons from subsea wells to topside production platforms or vessels. Similarly, the production tubing, comprised of multiple tubular elements assembled together, is used to drill subsea wells. This production tubing is lowered into the water depths until it reaches the wellhead located on the seafloor.

[0004] Within the realm of downhole applications for oil and gas production, various essential components are present inside the well, including downhole electrical systems, electronic systems, valves, sensors, and monitoring systems. These components are typically powered by battery packs, which, due to the relatively high discharge rates required, often result in short battery life spans. Consequently, larger battery packs become necessary, but their installation in downhole operations ischallenging, requiring frequent replacements that disrupt operations, increase costs, and demand additional labor resources.

[0005] An alternative to battery packs is the use of conventional power cables. However, cables are vulnerable to failure in the harsh downhole environment and may even break under their own weight, leading to further operational complications.

[0006] In light of increasing power costs, unwanted interventions, and various other considerations, researchers have turned their attention to enhancing power systems through energy harvesting. Thermoelectric generators (TEGs) have emerged as a promising solution, capable of directly converting thermal energy into electricity via the Seebeck effect. TEGs offer numerous advantages, including environmental friendliness, quiet operation without mechanical components, and adaptability to various substrates such as silicon, polymers, and ceramics. These solid-state semiconductor devices exploit temperature differences and heat flow to generate a useful DC power source by leveraging the Seebeck effect to induce voltage and generate electrical current, thereby providing valuable power to connected loads.

[0007] The DC / DC converter could be connected to a battery as an option. Then any short-term high-power needs can be covered by the battery. This means that the TEG installation is dimensioned according to a mean power requirement, and not to the maximum demand.

[0008] Notably, GB2336943A discloses a method and apparatus for generating electric power in downhole environments using a thermoelectric device, converting temperature gradients into electric power. The generated electric power can recharge battery packs and thereafter provides power to the control valves, the signal receivers and the control circuits.

[0009] Riser systems exhibit diverse shapes and designs depending on factors such as platform type and water depth. In shallow waters with fixed platforms, solid pipes are commonly used, while in deeper waters with floating platforms, flexible tubing is preferred. Despite these differences, most riser systems share a common feature, comprising inner and outer housing that extend from the production tubing and casing within the well.

[0010] The present invention aims to harness the potential of thermoelectric devices integrated into riser systems or production tubing to generate electricity, utilizing the temperature disparity between the flowing oil or gas inside the riser system or production tubing and the surrounding liquid in the annulus between the riser system or production tubing and the outer casing.

[0011] The annulus between the inner and outer tubing contains cables and smaller pipes. However, they are significantly thinner and offer less room than down hole environments. Consequently, the annulus in riser systems is well-suited for the installation of thermoelectric devices.

[0012] As riser systems are typically prefabricated as complete units and there is no access to install thermoelectric devices during field installation. Therefore, the integration of thermoelectric devices must be done at the manufacturing plant and be adaptable to various types and applications.Summary of the invention

[0013] Aspects of the present invention provide innovative methods for generating electrical energy in downhole applications, specifically for operating and controlling essential functions such as valves, sensors, and monitoring systems. Additionally, it enables the supply of electric energy via cables to facilitate control functions on remote rigs or the operation of local gas or gasoline turbines for local electricity needs.

[0014] In one aspect of the present invention provides a riser system comprising inner housing and outer housing separated by an annulus, where one or more thermoelectric modules / elements are installed within the inner housing of the riser system. These modules harness the temperature difference between the inner and outer housing to produce electrical energy.

[0015] The temperature of fluid flow in the riser system is close to the temperature at the well head and the cold sea water will provide more efficient cooling than the surroundings downhole. The distance between the two tubing’s is the annulus, so thethermoelectric material can be mounted in direct contact with the hot inner housing and the cold outer housing,

[0016] Another aspect of the invention pertains to production tubing, where one or more thermoelectric modules / elements are integrated. Here, the temperature difference between the production tubing and an outer casing is exploited by the thermoelectric modules / elements to generate electrical energy.

[0017] Noteworthy advantages of this invention include its ability to operate effectively with smaller temperature differentials (as low as 10°C) and its absence of moving parts, as it lacks mechanical mechanisms or rotating elements. This characteristic reduces mechanical wear, fatigue, and fracture due to mechanical vibration and stress, thereby extending the system's lifespan while minimizing maintenance requirements.

[0018] The primary utility of this invention lies in the production of electrical energy to control functions and operate valves in oil and gas production wells. Since oil companies have remote producing wells in a distance from other oil rigs (control centers and main producing rigs), the alternative can be used to send electric energy through cables to the necessary control functions on remote rigs or operate local gas or gasoline turbines for local electric use.

[0019] Additionally, the invention finds application in providing electricity to support sensors and other monitoring systems employed in downhole applications, enhancing efficiency and reliability in the field.

[0020] Other aspects and advantages of the invention will be apparent from the following description and the appended claims.Brief description of the drawings

[0021] The detailed description will be better understood in conjunction with the accompanying drawings as follows:

[0022] Fig.1 a shows an example of a riser system with thermoelectric modules / elements to generate electricity according to an embodiment of the present invention.

[0023] Fig.1 b shows another example of a riser system with thermoelectric modules to generate electricity according to an embodiment of the present invention.

[0024] Fig.2 is a cross-sectional view of the riser system of Fig. 1 a according to an embodiment of the present invention.

[0025] Fig.3 shows mounting of the thermoelectric modules / elements in a production tubing to generate electricity according to an embodiment of the present invention.

[0026] Fig.4 illustrates a block diagram representing a principle of powering downhole valves and sensors.

[0027] Fig.5 shows a vertical section through the center of a production tube, according to an embodiment of the present invention.

[0028] Fig.6 shows a horizontal section of a production tube, according to an embodiment of the present invention.

[0029] Fig.7 is a semi-exploded view showing two halves of the thermoelectric modules / elements in the production tube, according to an embodiment of the present invention.

[0030] Fig.8 shows an alternative cross section of a riser tube, where in every second sections the TEG elements can be replaced by insulation elements.Detailed description of the invention

[0031] The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, the embodiments are provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.

[0032] Embodiments of the invention provide mounting thermoelectric devices in a riser system or a production tubing to generate electricity based on the temperature difference between the flowing oil / gas in a riser system or a production tubing and the liquid in an annulus between the riser system or the production tubing and the outer casing.

[0033] As it is known that the riser systems come in many shapes and designs depending on the platform type, water depth etc. In the shallow water with fixed platforms, the riser systems are commonly solid pipes / tubes, while in deeper waters with floating platform riser systems are flexible tubes.

[0034] Fig.1a and Fig.1b illustrates downhole conversion from thermal energy (heat) to electrical energy (electricity) in a riser system 10 that comprises an inner housing 12 and an outer housing 14 that may be in a continuation of a production tubing (described later in the document) in a well, where a plurality of springs 16 are placed in between the inner housing 12 and the outer housing 14. The springs as shown must be able to distantly trigger. It will be difficult to thread the inner tube in with the springs out. The springs can be locked in with a so-called ‘rupture disk’. The springs can be triggered remotely with a calibrated pressure pulse. An annulus 18 between the inner housing 12 and outer housing 14 contains one or more power cables 20 and also houses smaller pipes / tubes 22, which is exemplary shown in the cross-sectional view in Fig. 2. According to an embodiment of the present invention as shown in Fig.1a, Fig.1b and Fig.2, one or more thermoelectric modules / elements 24 are mounted in the annulus 18 of the riser system 10. These thermoelectric modules / elements 24 are thermoelectric generators (tegs). After mounting / installation of the thermoelectric modules / elements 24 in the riser system 10, insulation 26 is done with suitablematerials. Where the inner housing 12 being a hot side and the liquid / fluid in the annulus 18 being a cold side. The temperature difference between the hot side and the cold side is being used by the thermoelectric modules / elements 24 to produce electricity.

[0035] Similarly in an embodiment, Fig.3 illustrates a well pipe installation 30 for downhole operation, where the thermoelectric modules / elements 24 are mounted in a production tubing 36 to generate electricity based on the temperature difference between the flowing oil / gas in the production tubing 36 and the liquid / fluid in the annulus 18 between the production tubing 36 and the outer casing 32. Where the production tubing 36 being a hot side and the liquid / fluid in the annulus 18 being a cold side. The temperature difference between the hot side and the cold side is being used by the thermoelectric modules / elements 24 to produce electricity. The thermoelectric modules / elements 24 are mounted on the production tubing 36 on the fly while installing the production tubing 36. Hence, mounting of the thermoelectric modules / elements 24 between hot side and cold side a temperature differential or gradient, is produced across the thermoelectric modules / elements 24. Further conductors (not shown) are coupled to the thermoelectric modules / elements 24 to access the electrical power generated by applying the temperature differential or gradient.

[0036] As shown in the Fig.3, the well pipe installation 30 comprises interconnected tubular sections and having an outer casing (surface casing) 32, production casing 34 and an innermost is the production tubing 36 through which oil or gas are conveyed / pumped 19 toward topsides production platform or vessel on the sea surface. The outer casing 32 is further enclosed within a conductor casing 31 extends from the wellhead installation to the workstation 40 above the sea surface 41. The conductor casing 31 provides a conduit (not shown) for fluids from the wellhead to the workstation 40. The Inner part of the outer casing 32 is provided with a casing liner 33. Similarly, the inner part of the production casing 34 is also provided with a production liner 35.

[0037] The well pipe installation 30 includes a workstation 40 stationed over a sea surface 41 with a submerged well 45. The submerged well 45 may include a well bore (not shown), the well bore extends from the surface of the submerged well 45 to alower zone toward a subterranean formation. As will be appreciated, the formation contains the fluid, such as oil or gas, to be produced by a well system.

[0038] As shown in the Fig.3, a valve 47 is placed near the lower end of each casing. The valve 47 is a flow control valve that selectively allows fluids or oil / gas to flow from the formation. The valve 47 may be remotely actuated. Further a plurality of sensors are installed in the production tube 36 for measuring the various data that relates to the field of drilling, completing, servicing, and treating a subterranean well such as a hydrocarbon recovery well. In particular, the present invention describes the methods for detecting and / or monitoring the position and / or condition of wellbore servicing compositions, integrity and performance of wellbore servicing compositions over the life of the well using sensor data.

[0039] According to an embodiment, one important use of the present invention is to produce electricity for control function and operating valves 47 in producing oil / gas wells. Since oil companies have remote producing wells in a distance from other oil rigs (control centers and main producing rigs), the alternative will be used to send electric energy through cables to the necessary control functions on remote rigs or operate local gas or gasoline turbines for local electric use.

[0040] Another use of the invention is to produce electricity for powering the sensors and other monitoring systems used in the downhole application.

[0041] In another embodiment of the present invention, Fig.4 shows a block diagram representing a principle of powering downhole valves 47, sensors and other electrical monitoring systems. As shown in Fig.4, a thermoelectric generators (tegs) system 50 that comprises a plurality of thermoelectric modules / elements 24 is regulated by a DC / DC power regulator 52, where electricity produced by the teg system 50 is regulated by the DC / DC power regulator 52 and thereafter a power 53 is supplied to the valves 47, sensors and other electrical monitoring systems and further as shown data acquisition is performed through a bus system 54, which is controlled form the surface.

[0042] In an embodiment, Fig.5 shows vertical sections through the center of a production tube 36, the production tube 36 comprises an outer casing 32. The production tube 36 can be several meters long, where a plurality of tubes is joinedtogether. For the understanding of the person skilled in the art, a joint between two tubes is referred herein as a tubing joint 62. As shown in Fig.5, a clamp 64 holds a TEG-element 24 to the tubing joint 64. It will be appreciated that the thermoelectric modules / elements 24 are anchored on the tubing joint 62 while forming the production tubing 36. It can be appreciated that each joint 62 in the production tube 36 follows a new series of thermoelectric modules / elements 24.

[0043] Fig.6 shows horizontal section through the center of a production tube 36, the production tube 36 comprises an outer casing 32, a plurality of clamps 64 holding a number of the thermoelectric modules / elements 24. Though one half of the thermoelectric modules / elements 24 is shown, it will be appreciated that without limiting the scope of the present invention, the thermoelectric modules / elements 24 is mounted on the whole outer peripheral of the production tube 36.

[0044] Fig.7 shows both halves of a complete thermoelectric modules / elements 24, where the clamp 64 holding thermoelectric modules / elements 24 of a first half 72 and a second half 74 is shown outside of the production tube 36. It should be appreciated that it is shown for illustrative purpose only, while both halves should be joined together on the production tube 36 with the clam 64. Further it should be noted that both halves may have different thermoelectric modules / elements 24

[0045] Fig.8 shows an alternative configuration of the cross-section of the riser tube without springs, where the tube may be configured in alternating sections, where in every second section the TEG elements 24 are replaced by insulation elements. We need to minimize the heat flow from the inner tubing to the fluid in the annulus. By installing insulation elements wherever the inner piping is directly exposed to the annulus in the near environment to the TEG elements. The spaces between the TEG elements leaving room for power cables 20 and smaller pipes / tubes.

[0046] It is appreciated that there are different types of the materials are available for production of the thermoelectric modules / elements 24 and commonly used for conversion between thermal energy and electrical energy. This conversion process involves charge and heat transport, with electrons and phonons mainly being the carriers. These materials are bismuth (Bi2Te3) telluride, lead telluride (PbTe) andSilicon germanium (SiGe). Use of these materials depends on the characteristics of the heat source, cold sink and the design of the thermoelectric modules / elements 24.

[0047] But it will be appreciated that Bismuth telluride and its alloys are widely used as materials for the thermoelectric modules / elements 24. They are also the best materials for use in thermoelectric generators (tegs) when the temperature of the heat source is moderate. Further works with smaller temperature differences (10°C).

[0048] Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing from the spirit and scope of the invention as hereinafter claimed.

[0049] Other variants should therefore be obvious to a person of skill in the arts. For example, there may be a production tube 36 in combination with a casing string that includes one or more perforations at the lower interior zone. The perforations provide flow communication between the formation and the lower interior zone of the well bore.

[0050] The foregoing description of embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention without departing from the scope of the invention. The embodiments were chosen and described to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.

Claims

AMENDED CLAIMS received by the International Bureau on 20 January 2025 (20.01.2025).What is claimed is:1 . A method of generating electoral energy for a downhole application comprises interconnected tubular sections having an outer casing (32), a production casing (34), and an innermost production tubing 36 through which oil or gas are conveyed / pumped (19) toward a topside production platform or vessel on a sea surface; characterized in that, mounting one or more thermoelectric modules / elements (24) in the production tubing (36), where a production tube (36) extends several meters in length and is formed by a plurality of joined tubes making a continuous assembly, a clamp (64) attached at each tubing joint (62), and the thermoelectric modules / elements (24) secured by the clamp (64) at the each tubing joint (62), where a plurality of release springs (16) are incorporated to ensure the thermoelectric modules / elements (24) maintain full contact with a cold side where a temperature difference between the hot side and the cold side is being used by the thermoelectric modules / elements (24) to generate electrical energy, where the production tubing (36) is being the hot side and liquid / fluids following in an annulus (18) between the production tubing (36) and outer casing (32) is being the cold side, a DC / DC power regulator (52) is configured for regulating the generated electrical energy and charging a battery that supplies power to valves (47) installed at the lower end of the outer casing (32), the production casing (34), and the production tubing (36).

2. The method according to claim 1 , wherein the electrical energy is further used to supply power to sensors and other monitoring systems employed within the downhole application.13AMENDED SHEET (ARTICLE 19)3. The method according to claim 1 , wherein the electrical energy is further supplied to facilitate the control of functions on remote rigs or the operation of local gas or gasoline turbines for localized electricity consumption.

4. An apparatus for providing electrical energy for downhole application, the apparatus comprising: a riser system (10) and / or a production tubing (36), where the riser system (10) comprises an inner housing (12), an outer housing (14) and an annulus (18) between the inner housing (12) and the outer housing (14), the riser system (10) is in continuation of the production tubing (36) in a well, where the production tubing (36) comprises an outer casing (32), a production casing (34), and an annulus (18) between the production tubing (36) and the outer casing (32), characterized by, one or more thermoelectric modules / elements (24) are mounted in the riser system (10) and / or the production tubing (36), where a plurality of release springs (16) are incorporated between the inner housing (12) and the outer housing (14) to ensure the thermoelectric modules / elements (24) maintain full contact with a cold side, where a temperature difference between the hot side and the cold side is used by the thermoelectric modules / elements (24) to generate electrical energy, where the riser system (10) and / or the production tubing (36) is being the hot side and liquid / fluids following in the annulus (18) is being the cold side and a DC / DC power regulator (52) is configured for regulating the generated electrical energy and charging a battery that supplies power to valves (47) installed at the lower end of the outer casing (32), the production casing (34), and the production tubing (36).

5. The apparatus according to claim 4, wherein the electrical energy is used to supply power to sensors and other monitoring systems employed within the downhole application.14AMENDED SHEET (ARTICLE 19)he apparatus according to claim 4, wherein the electrical energy is further supplied to facilitate the control of functions on remote rigs or the operation of local gas or gasoline turbines for localized electricity consumption.15AMENDED SHEET (ARTICLE 19)

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