Integrated simulation device and method for combined production and storage of natural gas hydrate system

Abstract

The present invention belongs to the field of energy utilization technology, and relates to an integrated simulation device and method for combined production and storage of a natural gas hydrate system. The integrated simulation device for combined production and storage of a natural gas hydrate system includes a natural gas hydrate system unit, a carbon dioxide injection unit connected to the natural gas hydrate system unit, a data acquisition and control unit, and a combined production unit; the carbon dioxide injection unit and the combined production unit are respectively connected to the data acquisition and control unit; the natural gas hydrate system unit is divided into a natural gas hydrate unit and a shallow gas unit. The present invention can comprehensively simulate the entire process of methane production and carbon dioxide storage in a system where natural gas hydrates and shallow gas coexist, clarify the evolutionary dynamics and joint mechanism of combined production and storage of a natural gas hydrate system, and optimize and improve the combined production and storage plan of a natural gas hydrate system with production performance, carbon burial stock and formation stability as multiple objectives, so as to provide a basis for integrated design work such as commercial development of hydrates and subsequent storage.

Description

Technical Field

[0001] The present invention relates to the technical field of energy utilization, and in particular to a natural gas hydrate system co-production-storage integrated simulation device and method. Background Art

[0002] Natural gas hydrate is an ice-like crystalline substance formed by gas and water molecules under specific temperature and pressure conditions. 3 The natural gas hydrate can be decomposed into about 0.8 m 3 of water and 164 m 3 Gas. Natural gas hydrate is regarded as one of the most promising new green energy sources due to its large resources, low pollution and high energy density. In addition, carbon dioxide hydrate has extremely high efficiency and stability. The storage of carbon dioxide to form carbon dioxide hydrate has become a promising method to reduce greenhouse gas emissions.

[0003] From the first hydrate trial production in the permafrost zone of Mackenzie Delta, Canada in 2002 to the hydrate trial production in Shenhu Sea Area of ​​South China Sea in 2020, a total of 11 trial productions have been carried out worldwide, but the trial production capacity is far below the commercial production capacity threshold. Through hydrate exploration in global seas, it is found that the natural gas hydrate layer and the underlying shallow gas layer form an intricate coexistence system in time and space. Therefore, the joint exploitation of the natural gas hydrate system where the natural gas hydrate layer and the underlying shallow gas layer coexist is the most promising goal for early commercial exploitation. When the natural gas hydrate system is completed, the abandoned natural gas hydrate system is an ideal place for carbon dioxide storage. This is not only because the phase equilibrium temperature and pressure conditions of carbon dioxide hydrate are lower than those of natural gas hydrates, which has a thermodynamic basis for carbon dioxide storage. There are also many advantages such as using the initial natural gas hydrate mining equipment to reduce costs, the memory effect of decomposed water to promote the formation of carbon dioxide hydrates, and carbon dioxide hydrates to improve the stability of the formation after mining. However, unlike the storage of carbon dioxide in abandoned natural gas hydrate reservoirs, there are significant differences in the reservoir properties and storage mechanisms of hydrate layers and shallow gas layers in natural gas hydrate systems, and there is still no relevant research on the mechanism of mutual influence between the joint storage of the two. In addition, current research can only focus on the joint exploitation of natural gas hydrate systems or the storage of carbon dioxide in abandoned natural gas hydrate reservoirs, and there is still a lack of comprehensive consideration and integrated research on the two.

[0004] Therefore, it is currently necessary to develop a physical simulation experimental device and method that can be used to simulate the integrated production and storage of natural gas hydrate systems, with the ability to carry out experimental research on combined production and subsequent storage of natural gas hydrate systems, to clarify the evolutionary dynamics and joint mechanisms of natural gas hydrate system production and storage, and to optimize and improve the production-storage plan with production performance, carbon storage and formation stability as multiple objectives, so as to provide a certain basis for the integrated design work such as commercial development of hydrates and subsequent storage. Summary of the invention

[0005] The present invention aims to solve the technical gap of multi-gas co-production in hydrate systems in the prior art. The purpose of the present invention is to provide a natural gas hydrate system co-production-storage integrated simulation device and method, so as to provide technical support for guiding the efficient development of actual hydrate systems and subsequent carbon dioxide storage.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A natural gas hydrate system co-production-storage integrated simulation device includes a natural gas hydrate system unit, and also includes a carbon dioxide injection unit, a data acquisition control unit, and a co-production unit connected to the natural gas hydrate system unit; the carbon dioxide injection unit and the co-production unit are respectively connected to the data acquisition control unit; the natural gas hydrate system unit is divided into a natural gas hydrate unit and a shallow gas unit.

[0008] The carbon dioxide injection unit includes a carbon dioxide gas cylinder, a mass flow controller and a temperature control device connected in sequence through pipelines; the temperature control device is connected to the natural gas hydrate unit and the shallow gas unit through pipelines. Furthermore, the temperature control device can be connected to the natural gas hydrate unit through several parallel pipelines, and the temperature control device can be connected to the natural gas hydrate unit through several parallel pipelines, so that carbon dioxide can be injected at different strata.

[0009] The data acquisition unit includes a data acquisition device and a pressure monitoring device, a temperature monitoring device, a gas chromatograph, a gas flow meter and a computer connected to the data acquisition device; the shallow gas unit and the natural gas hydrate unit are respectively connected to the pressure monitoring device; the shallow gas unit and the natural gas hydrate unit are respectively connected to the temperature monitoring device; the gas chromatograph is connected to the gas flow meter through an automatic control valve.

[0010] The combined production unit includes a back pressure valve, a solid-liquid separation device and a separation device connected by pipelines; the back pressure valve is respectively connected to the back pressure pump, the natural gas hydrate unit and the shallow gas unit through pipelines; the gas-liquid separation device is sequentially connected to the gas chromatograph and the gas flow meter through pipelines; the gas-liquid separation device is also connected to an electronic balance. Furthermore, the back pressure valve can be connected to the natural gas hydrate unit through several parallel pipelines, and can also be connected to the natural gas hydrate unit through several parallel pipelines to realize the production of different layers.

[0011] The natural gas hydrate system described in the present invention refers to a system in which natural gas hydrate and shallow gas coexist.

[0012] The natural gas hydrate system co-production-storage integrated simulation method of the present invention adopts the natural gas hydrate system co-production-storage integrated simulation device, and specifically comprises the following steps:

[0013] (1) Setting the production pressure, producing the gas hydrate unit and the shallow gas unit at the same time, and monitoring the temperature and pressure of the gas hydrate unit and the shallow gas unit;

[0014] (2) When the pressure of the shallow gas unit drops by 0.2 MPa / h, carbon dioxide is injected into the shallow gas unit, and the gas chromatograph monitors the composition of the produced gas and the pressure and temperature of the shallow gas unit;

[0015] (3) When the temperature of the hydrate unit drops by 0.5 °C / h, carbon dioxide is injected into the natural gas hydrate unit, and the gas chromatograph monitors the composition of the produced gas and the pressure and temperature of the natural gas hydrate unit;

[0016] In this process, the temperature control device can be adjusted according to the phase equilibrium conditions of carbon dioxide hydrate formation and the pressure data in the natural gas hydrate unit, and the carbon dioxide injection temperature can be set to study the effects of different carbon dioxide injection temperatures on the integrated production and storage of natural gas hydrate systems.

[0017] (4) When set condition I is reached, production is stopped and the water and gas production are recorded; when set condition II is reached, carbon dioxide injection is stopped.

[0018] The setting condition I described in step (4) is: in step (2) or (3), the gas chromatograph monitors that the carbon dioxide gas content in the produced gas composition accounts for more than 30%.

[0019] The setting condition II in step (4) is: the pressure of the shallow gas unit in step (2) and / or the pressure of the natural gas hydrate unit in step (3) reaches the initial formation pressure, and the carbon dioxide storage of the corresponding unit is stopped.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The device and method for simulating the integrated production and storage of natural gas hydrate systems provided by the present invention can comprehensively consider the entire process of methane production and carbon dioxide storage in the system where natural gas hydrates and shallow gas coexist, obtain various data such as reservoir pressure and temperature fluctuation characteristics, the changing laws of gas and water production, carbon dioxide storage characteristics, and formation subsidence laws, and systematically study the integrated plan of joint production and storage for the triple goals of production performance, carbon burial volume, and formation stability.

[0022] (2) During the simulation process, by selecting different injection layers, the pressure and temperature of injected CO2, etc., the influencing factors of the storage process can be studied, the effects of different injection conditions on storage can be evaluated, and the optimization of CO2 storage conditions and maximization of efficiency can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 It is a structural schematic diagram of the natural gas hydrate system combined production and storage integrated simulation device according to the present invention;

[0025] Figure 2 This is a distribution diagram of the pressure monitoring device and the temperature monitoring device in the natural gas hydrate system combined production and storage integrated simulation device described in the invention;

[0026] Among them: 1-1 natural gas hydrate unit, 1-2 shallow gas unit; 2-1 carbon dioxide cylinder, 2-2 mass flow controller, 2-3 temperature control device, 2-4 pressure reducing valve; 3-1 data acquisition device, 3-2 pressure monitoring device, 3-3 temperature monitoring device, 3-4 gas chromatograph, 3-5 gas flow meter, 3-6 computer, 3-8 automatic control valve; 4-1 gas-liquid separation device, 4-2 solid-liquid separation device, 4-3 electronic balance, 4-4 back pressure valve, 4-5 back pressure pump; 5-1 valve I, 5-2 valve II, 5-3 valve III, 5-4 valve IV, 5-5 valve V. DETAILED DESCRIPTION

[0027] For the convenience of description, if the words "upper" and "lower" appear in the present invention, they only indicate that they are consistent with the upper and lower directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0028] Example 1

[0029] A natural gas hydrate system co-production-storage integrated simulation device includes a natural gas hydrate system unit, and also includes a carbon dioxide injection unit, a data acquisition control unit, and a co-production unit connected to the natural gas hydrate system unit; the carbon dioxide injection unit and the co-production unit are respectively connected to the data acquisition control unit; the natural gas hydrate system unit is divided into a natural gas hydrate unit and a shallow gas unit.

[0030] The carbon dioxide injection unit comprises a carbon dioxide cylinder, a mass flow controller and a temperature control device which are connected in sequence through pipelines; the temperature control device is connected to the natural gas hydrate unit through two parallel pipelines, and the temperature control device is connected to the natural gas hydrate unit through two parallel pipelines to realize the injection of carbon dioxide into different strata.

[0031] The data acquisition unit includes a data acquisition device and a pressure monitoring device, a temperature monitoring device, a gas chromatograph, a gas flow meter and a computer connected to the data acquisition device; the shallow gas unit and the natural gas hydrate unit are respectively connected to the pressure monitoring device; the shallow gas unit and the natural gas hydrate unit are respectively connected to the temperature monitoring device; the gas chromatograph is connected to the gas flow meter through an automatic control valve.

[0032] The combined production unit includes a back pressure valve, a solid-liquid separation device and a separation device connected by pipelines; the back pressure valve is connected to the back pressure pump, the natural gas hydrate unit and the shallow gas unit through pipelines; the gas-liquid separation device is connected to the gas chromatograph and the gas flow meter in sequence through pipelines; the gas-liquid separation device is also connected to an electronic balance. The back pressure valve is connected to the natural gas hydrate unit through three parallel pipelines and to the natural gas hydrate unit through two parallel pipelines to realize the production of different layers.

[0033] Example 2

[0034] The integrated simulation method for combined production and storage of natural gas hydrate system adopts the integrated simulation device for combined production and storage of natural gas hydrate system described in Example 1, and specifically comprises the following steps:

[0035] (1) Setting the production pressure, producing the gas hydrate unit and the shallow gas unit at the same time, and monitoring the temperature and pressure of the gas hydrate unit and the shallow gas unit;

[0036] Specifically: according to the experimental requirements, the production pressure is set by the back pressure valve and the back pressure pump, one or more valves III of the natural gas hydrate unit are opened, and one or more valves IV of the shallow gas unit are opened; the produced gas, pore solution and sand-like particles are first separated into sand-like particles by a solid-liquid separation device, and then the pore solution is separated by a gas-liquid separation device and weighed and measured by an electronic balance; the automatic control valve is opened to determine the change in the methane content in the gas by a gas chromatograph; finally, the cumulative gas production and gas production rate are measured by a gas flow meter, and the data collector constantly collects the pressure and temperature data of the pressure monitoring devices and temperature monitoring devices in the natural gas hydrate unit and the shallow gas unit during the combined production process.

[0037] (2) When the pressure of the shallow gas unit drops by 0.2 MPa / h, carbon dioxide is injected into the shallow gas unit, and the gas chromatograph monitors the composition of the produced gas and the pressure and temperature of the shallow gas unit;

[0038] Since the shallow gas unit contains shallow gas layers, the flow rate of the fluid in the hydrate layer in the upper natural gas hydrate unit is faster during the depressurization production process, and the pressure drops more rapidly. It is necessary to focus on monitoring the pressure data of the shallow gas unit through the data logger. When the pressure drop of the shallow gas unit is 0.2 MPa / h, open one or more of the carbon dioxide cylinder, the pressure reducing valve, the gas mass flow controller, the temperature control device, the valve V and the valve II in sequence to seal the carbon dioxide in the shallow gas unit. At the same time, the automatic control valve is opened to determine the changes in the content of methane and carbon dioxide in the gas through a gas chromatograph.

[0039] (3) When the temperature of the natural gas hydrate unit drops by 0.5 °C / h, carbon dioxide is injected into the natural gas hydrate unit, and the gas chromatograph monitors the composition of the produced gas and the pressure and temperature of the natural gas hydrate unit;

[0040] Since the decomposition of natural gas hydrate absorbs heat during decompression, it is necessary to focus on monitoring the temperature data of the natural gas hydrate unit through a data logger. When the temperature drops by 0.5 °C / h, one or more of the carbon dioxide cylinder, the pressure reducing valve, the gas mass flow controller, the temperature control device, the valve V, and the valve I are opened in sequence to store carbon dioxide in the natural gas hydrate unit. In this process, the temperature control device can be adjusted according to the phase equilibrium conditions of carbon dioxide hydrate formation and the pressure data in the natural gas hydrate unit, and the carbon dioxide injection temperature can be set to study the effects of different carbon dioxide injection temperatures on the integrated production and storage of natural gas hydrate systems.

[0041] The injected carbon dioxide is measured by a gas mass flow controller to accumulate the injected carbon dioxide volume; the data logger constantly collects the pressure and temperature data in the natural gas hydrate unit and the shallow gas unit during the sealing process, and the automatic control valve is opened to determine the changes in the content of methane and carbon dioxide in the gas through a gas chromatograph.

[0042] (4) When set condition I is reached, production is stopped and the water and gas production are recorded; when set condition II is reached, carbon dioxide injection is stopped.

[0043] Taking into account the separation cost of methane and carbon dioxide gases, when the carbon dioxide gas content in the mixed gas measured by the gas chromatograph exceeds 30% in any one of steps (2) or (3), valve III, valve IV, back pressure pump, back pressure valve, solid-liquid separation device, gas-liquid separation device, electronic balance, automatic control valve, gas chromatograph and gas flow meter are closed, and the combined production of natural gas hydrate unit and shallow gas unit is stopped and the water production and gas production are recorded; at this time, carbon dioxide is still injected.

[0044] When the pressure of the shallow gas unit in step (2) and / or the pressure of the natural gas hydrate unit in step (3) reaches the initial formation pressure, the valves of the corresponding units are closed and the carbon dioxide injection of the response units is stopped. When the pressure of the last unit reaches the initial formation pressure, the carbon dioxide cylinder, the pressure reducing valve, the gas mass flow controller, the temperature control device and the valves of the corresponding units are closed to complete the carbon dioxide storage research of the natural gas hydrate system.

[0045] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A natural gas hydrate system co-production and storage integrated simulation method, characterized in that: The integrated simulation device for combined production and storage of natural gas hydrate system is adopted, which specifically includes the following steps: (1) Setting the production pressure, producing the gas hydrate unit and the shallow gas unit at the same time, and monitoring the temperature and pressure of the gas hydrate unit and the shallow gas unit; (2) When the pressure of the shallow gas unit drops by 0.2 MPa / h, carbon dioxide is injected into the shallow gas unit, and the gas chromatograph monitors the composition of the produced gas and the pressure and temperature of the shallow gas unit; (3) When the temperature of the hydrate unit drops by 0.5 °C / h, carbon dioxide is injected into the natural gas hydrate unit, and the gas chromatograph monitors the composition of the produced gas and the pressure and temperature of the natural gas hydrate unit; (4) When the set condition I is reached, production is stopped and the water and gas production are recorded; when the set condition II is reached, carbon dioxide injection is stopped; A natural gas hydrate system commingled production and storage integrated simulation device comprises a natural gas hydrate system unit, and also comprises a carbon dioxide injection unit connected to the natural gas hydrate system unit, a data acquisition control unit, and a commingled production unit; the carbon dioxide injection unit and the commingled production unit are respectively connected to the data acquisition control unit; the natural gas hydrate system unit is divided into a natural gas hydrate unit and a shallow gas unit; The carbon dioxide injection unit comprises a carbon dioxide gas cylinder, a mass flow controller and a temperature control device which are sequentially connected through pipelines; the temperature control device is respectively connected to the natural gas hydrate unit and the shallow gas unit through pipelines; The data acquisition unit includes a data acquisition device and a pressure monitoring device, a temperature monitoring device, a gas chromatograph, a gas flow meter and a computer connected to the data acquisition device; the shallow gas unit and the natural gas hydrate unit are respectively connected to the pressure monitoring device; the shallow gas unit and the natural gas hydrate unit are respectively connected to the temperature monitoring device; the gas chromatograph is connected to the gas flow meter through an automatic control valve; The combined production unit includes a back pressure valve, a solid-liquid separation device and a separation device connected by pipelines; the back pressure valve is respectively connected to the back pressure pump, the natural gas hydrate unit and the shallow gas unit through pipelines; the gas-liquid separation device is sequentially connected to the gas chromatograph and the gas flow meter through pipelines; the gas-liquid separation device is also connected to an electronic balance; The setting condition I described in step (4) is: in step (2) or (3), the carbon dioxide gas content in the produced gas components monitored by the gas chromatograph accounts for more than 30%; The setting condition II in step (4) is that the pressure of the shallow gas unit in step (2) and / or the pressure of the natural gas hydrate unit in step (3) reaches the initial formation pressure.

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