Offshore wellhead platform power supply method utilizing high-pressure natural gas

Abstract

The invention discloses an offshore wellhead platform power supply method utilizing high-pressure natural gas, which relates to the technical field of wellhead platform power supply, and comprises the following steps: the high-pressure natural gas exploited by an offshore platform is connected into a production manifold after being subjected to pressure regulation by an oil nozzle and metering by a flow meter, and a part of natural gas is led out from the production manifold to an ETG double-rotor expansion generator; natural gas differential pressure energy power generation and energy storage systems are used for cooperative operation, power supply of a small-load offshore wellhead platform is achieved, and self-generation and self-use are achieved. Differential pressure energy is used for power generation, the problem of wellhead pressure energy waste is solved, and the environmental influence caused by the fact that differential pressure energy is converted into heat energy to be transmitted to the ocean is avoided; a power supply mode of cooperative operation of natural gas differential pressure energy power generation and an energy storage system is adopted to replace a power transmission mode of long-distance submarine cable laying of a central platform, submarine cable laying and installation are not needed, and the investment and construction cost of an offshore platform is greatly reduced; and in the instinct power generation process, no emission is generated, high environmental friendliness is achieved, and the marine ecological environment can be protected easily.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply for wellhead platforms, and particularly to a method for power supply of an offshore wellhead platform using high-pressure natural gas. Background Art

[0002] The power supply system of traditional offshore wellhead platforms usually relies on gas turbine power generation of the central processing platform. Gas turbine power generation by burning natural gas will produce a large amount of greenhouse gas emissions, causing serious impacts on the environment. While new energy power generation methods relying on wind and solar power are restricted by weather conditions and have poor stability, unable to meet the long-term operation requirements of offshore platforms.

[0003] In the traditional offshore platform development mode, the offshore wellhead platform mainly supplies power to the wellhead platform by laying submarine cables from the central platform. The transmission cost of laying submarine cables is high. Moreover, the natural gas of offshore natural gas wellhead platforms has the characteristics of high temperature and high pressure and contains a large amount of energy. Calculated according to the current annual output of marine natural gas in the country of 23 billion cubic meters, if recycled, the total annual power generation can reach more than 600 million kWh, and 340,000 tons of carbon dioxide can be reduced annually.

[0004] The total urine volume of an adult at one time is about 150 - 250 ml. Using the above-mentioned patented product, it has a relatively large volume. For pregnant women, it is necessary to move the above-mentioned patented product or conduct sampling in a dedicated indoor area, which is not convenient for use. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for power supply of an offshore wellhead platform using high-pressure natural gas to solve the problems raised in the above background art.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A method for power supply of an offshore wellhead platform using high-pressure natural gas, including high-pressure natural gas extracted from an offshore platform, which after passing through a choke valve for pressure regulation and being metered by a flowmeter, is connected to a production manifold. A part of the natural gas is taken out from the production manifold and connected to an ETG dual-rotor expansion generator, and another part of the natural gas is connected to the inlet of an external transmission cooler after being depressurized by a PV valve for external transmission. The ETG dual-rotor expansion generator generates electricity by using the pressure reduction and expansion of natural gas. The natural gas after being generated electricity by the ETG dual-rotor expansion generator enters the inlet of the external transmission cooler for external transmission. A flowmeter and a flow control valve are provided at the inlet of the ETG dual-rotor expansion generator for flow regulation.

[0007] As a preferred embodiment of the power supply method for an offshore wellhead platform utilizing high-pressure natural gas in the present invention, the following is provided: A combined method of using a dual-rotor pressure-difference energy generator and a battery energy storage system for power supply is adopted. When intermittent equipment and loads are started, the battery energy storage system responds and supplements power, combining pressure-difference energy generation with an electrochemical energy storage system to supply power to the wellhead platform. An electric energy management system (PMS) is used to automatically control the pressure-difference energy generator and the energy storage.

[0008] As a preferred embodiment of the power supply method for an offshore wellhead platform utilizing high-pressure natural gas in the present invention, the following is provided: The specific cooperative control process of the pressure-difference generator and the battery energy storage system is as follows:

[0009] A. During the startup stage of the platform power grid, for the two energy storage systems ESS1 and ESS2, the state of charge should be greater than 90%. One of them is selected by the PMS to be put into operation, and the other is in a hot standby state. After the PMS instructs ESS1 to establish the power grid and carry the load, the pressure-difference generator is softly started and connected to the grid. The PMS instructs ESS1 to gradually reduce the output power to low-load operation and maintain parallel operation with the pressure-difference generator. ESS1 maintains stable control of the grid voltage and frequency.

[0010] B. Energy storage system switching: When ESS1 has been operating for a period of time and the state of charge < 20%, the PMS receives the status information and sends a startup instruction to ESS2. ESS2 changes from hot standby to synchronous operation with ESS1. After achieving stable synchronous operation, the PMS system instructs ESS2 to take over the grid control, and ESS1 exits the control, completing the control switchover. ESS1 and ESS2 continue to maintain synchronous operation. Subsequently, the PMS system sends an instruction to the pressure-difference generator control cabinet to increase the pressure-difference power generation. The PMS instructs ESS1 to enter the charging mode, and the charging power is the same as the increased power of the pressure-difference generator. When the state of charge of ESS1 reaches 95%, the PMS instructs ESS1 to change to the hot standby state and stop charging and discharging.

[0011] C. When the pressure-difference generator fails and shuts down, the operating energy storage system quickly supplements power to maintain the operation of the power grid. When the state of charge of the energy storage reaches 20%, the PMS sends an instruction to the platform production control system to shut down production.

[0012] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The combined operation of a natural gas pressure difference energy power generation and energy storage system is utilized to solve the power supply problem of small-load offshore wellhead platforms and achieve self-generation and self-use; the pressure difference energy is used for power generation to solve the problem of waste of wellhead pressure energy and avoid the environmental impact caused by the conversion of pressure difference energy into heat energy and transfer to the ocean; the power supply mode of the combined operation of a natural gas pressure difference energy power generation and energy storage system is adopted to replace the power transmission mode of laying long-distance submarine cables from the central platform, eliminating the need for submarine cable laying and installation, and greatly reducing the investment and construction costs of offshore platforms; during the power generation process of the present invention, there is no emission, which is highly environmentally friendly and conducive to protecting the marine ecological environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used in conjunction with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0014] Figure 1 is a system diagram of a power supply method for an offshore wellhead platform using high-pressure natural gas in this invention patent;

[0015] Figure 2 is a system diagram of an ETG dual-rotor expansion generator for a power supply method for an offshore wellhead platform using high-pressure natural gas in this invention patent;

[0016] Figure 3 is a control block diagram of a PMS system for a power supply method for an offshore wellhead platform using high-pressure natural gas in this invention patent. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0018] Please refer to Figure 1 、 Figure 2 and Figure 3, the present invention provides a technical solution: a method for supplying power to an offshore wellhead platform using high-pressure natural gas, a power generation solution using wellhead pressure difference energy. The high-pressure natural gas produced from the offshore platform is adjusted in pressure through a choke valve, and then metered by a flowmeter and connected to the production manifold; a part of the natural gas is taken out from the production manifold and connected to an ETG dual-rotor expansion generator; another part of the natural gas is connected to the inlet of the export cooler after being depressurized by a PV valve for export; the ETG dual-rotor expansion generator uses the depressurization and expansion of natural gas to generate electricity. The pressure difference of the ETG dual-rotor expansion generator is 3.6 - 4.1 MPa. The natural gas after being generated by the ETG dual-rotor expansion generator enters the inlet of the export cooler for export; the design pressure of the ETG dual-rotor expansion generator is 10 MPaG, and the design temperature is 153 °C; a flowmeter and a flow control valve are provided at the inlet of the ETG dual-rotor expansion generator for the adjustment of flow and pressure; the differential pressure generator is provided with an independent unit control system, and the inlet pipeline control valve can be adjusted through the unit control system to reach the set power generation power.

[0019] The power supply system of the wellhead platform adopts a combination of a dual-rotor differential pressure energy generator and a battery energy storage system for power supply; the power generation power of the differential pressure energy generator meets the stable power consumption requirements of the platform. When intermittent equipment and loads start, the battery energy storage system responds and supplements power to ensure the power supply stability of the platform; for the first time, this technology combines differential pressure energy power generation with an electrochemical energy storage system to supply power to the wellhead platform, and uses an electric energy management system (PMS) to automatically control the differential pressure energy generator and the energy storage.

[0020] The battery energy storage system adopts a grid-forming energy storage, which has the function of independently establishing a power grid; two sets of energy storage systems are switched and used with each other, and always keep one set of energy storage system working in the power supply state; the specific cooperative control process of the differential pressure generator and the battery energy storage system is as follows:

[0021] A. During the start-up stage of the platform power grid, for the two sets of energy storage systems ESS1 and ESS2, the state of charge should be greater than 90%. One set is selected through the PMS to be put into operation, and the other set is in the hot standby state; after the PMS commands ESS1 to establish the power grid and operate with load, the differential pressure generator is softly started and connected to the grid. The PMS commands ESS1 to gradually reduce the output power to low-load operation and keep it connected to the grid with the differential pressure generator. ESS1 maintains the stable control of the grid voltage and frequency.

[0022] B. Energy storage system switching: When ESS1 has been operating for some time and its state of charge is < 20%, the PMS receives the status information and sends a start command to ESS2. ESS2 switches from the standby mode to synchronous operation with ESS1. After achieving stable synchronous operation, the PMS system commands ESS2 to take over the grid control, and ESS1 exits the control, completing the control switching. ESS1 and ESS2 continue to operate synchronously. Subsequently, the PMS system issues a command to the differential generator control cabinet to increase the differential generation power. The PMS commands ESS1 to enter the charging mode, and the charging power is the same as the increased power of the differential generator. When the state of charge of ESS1 reaches 95%, the PMS commands ESS1 to switch to the standby state and stop charging and discharging.

[0023] C. When the differential generator fails and shuts down, the operating energy storage system quickly supplements power to maintain the grid operation. When the state of charge of the energy storage reaches 20%, the PMS sends a command to the platform production control system to shut down production.

[0024] Importantly, it should be noted that the construction and arrangement of the present application shown in multiple different exemplary embodiments are merely illustrative. Although only a few embodiments are described in detail in this disclosure, those who refer to this disclosure should easily understand that many modifications are possible without substantially departing from the novel teachings and advantages of the subject matter described in this application (e.g., changes in the dimensions, scales, structures, shapes and proportions of various components, and parameter values (such as temperature, pressure, etc.), installation arrangements, use of materials, colors, orientations, etc.). For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of the element may be inverted or otherwise changed, and the nature, number or position of discrete elements may be altered or changed. Therefore, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be changed or reordered according to alternative embodiments. In the claims, any "means-plus-function" clause is intended to cover the structure that performs the recited function herein, and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present invention. Therefore, the present invention is not limited to a specific embodiment, but extends to various modifications that still fall within the scope of the appended claims.

[0025] In addition, to provide a concise description of the exemplary embodiments, not all features of the actual embodiments may be described (i.e., those features that are not relevant to the currently considered best mode of implementing the present invention or those features that are not relevant to the implementation of the present invention).

[0026] It should be understood that, in the development of any actual implementation, such as in any engineering or design project, a large number of specific implementation decisions can be made. Such development efforts may be complex and time-consuming, but for those of ordinary skill in the art who benefit from this disclosure, without undue experimentation, such development efforts will be routine work of design, manufacture, and production.

[0027] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for supplying power to an offshore wellhead platform using high-pressure natural gas, characterized in that: It includes high-pressure natural gas extracted from offshore platforms, which is pressure-regulated by oil nozzles and measured by flow meters before being connected to the production manifold. Part of the natural gas is taken out from the production manifold to the ETG twin-rotor expansion generator, and the other part of the natural gas is reduced in pressure by the PV valve and connected to the inlet of the external transmission cooler for external transmission. The ETG twin-rotor expansion generator uses the pressure reduction and expansion of natural gas to generate electricity. The natural gas after power generation by the ETG twin-rotor expansion generator enters the inlet of the external transmission cooler for external transmission. The inlet of the ETG twin-rotor expansion generator is equipped with a flow meter and a flow control valve for flow regulation.

2. The method for powering an offshore wellhead platform using high-pressure natural gas according to claim 1, characterized in that: The dual-rotor pressure difference energy generator is combined with a battery energy storage system for power supply. When intermittent equipment and loads are started, the battery energy storage system responds and supplements power. The pressure difference energy generation is combined with the electrochemical energy storage system to power the wellhead platform. A power management system (PMS) is used to automatically control the pressure difference energy generator and energy storage.

3. The method for supplying power to an offshore wellhead platform using high-pressure natural gas according to claim 2, characterized in that: The specific coordinated control process of the pressure difference generator and the battery energy storage system is as follows: A. During the platform grid startup phase, the two energy storage systems ESS1 and ESS2 should have a charge greater than 90%. One of them is selected through the PMS to be put into operation, and the other is in hot standby state. After the PMS instructs ESS1 to establish grid load operation, the differential pressure generator is soft-started and connected to the grid. The PMS instructs ESS1 to gradually reduce the output power to low-load operation and maintain grid-connected operation with the differential pressure generator. ESS1 maintains stable control of the grid voltage and frequency. B. Energy storage system switching: When ESS1 runs for a period of time and the charge is less than 20%, PMS receives status information and sends a startup command to ESS2. ESS2 switches from hot standby to synchronous operation with ESS1. After stable synchronous operation is achieved, PMS system instructs ESS2 to take over grid control, ESS1 exits control, and control switching is completed. ESS1 and ESS2 continue to operate synchronously. After that, PMS system sends a command to the differential pressure generator control cabinet to increase the differential pressure power generation. PMS instructs ESS1 to enter charging mode, and the charging power is the same as the power increased by the differential pressure generator. When the charge of ESS1 reaches 95%, PMS instructs ESS1 to switch to hot standby state and stop charging and discharging. C. When the pressure difference generator fails and stops, the running energy storage system quickly replenishes electricity to maintain the operation of the power grid. When the energy storage charge reaches 20%, the PMS sends a command to the platform production control system to shut down production.

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