CN112780233B - Device and method for simulating exploitation of free gas hydrate under bottom - Google Patents
Device and method for simulating exploitation of free gas hydrate under bottom Download PDFInfo
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- CN112780233B CN112780233B CN202110042597.6A CN202110042597A CN112780233B CN 112780233 B CN112780233 B CN 112780233B CN 202110042597 A CN202110042597 A CN 202110042597A CN 112780233 B CN112780233 B CN 112780233B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
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- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/34—Arrangements for separating materials produced by the well
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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Abstract
The invention relates to a device and a method for simulating the exploitation of free gas hydrate, which are characterized in that a gas-liquid seepage control system is arranged in a simulation reactor, and the simulation reactor is divided into a hydrate area and a free gas area; firstly, preparing a hydrate reservoir with overlying free gas by adopting a method of inverting a simulation reactor, and then turning the simulation reactor up and down to prepare a hydrate reservoir with underlying free gas; and then, developing a hydrate exploitation test, and automatically starting a gas-liquid seepage control system through the pressure difference between the hydrate layer and the free gas layer to realize the uniform distribution of gas-liquid seepage between the upper hydrate layer and the lower free gas layer in the exploitation process. The gas, water and hydrate saturation control precision in the hydrate layer and the free gas layer prepared by the invention is high, the operation is simple and convenient, the gas-liquid seepage characteristic between the hydrate layer and the free gas layer in the actual exploitation process can be accurately simulated, and the method can be applied to various different types of underlying free gas hydrate reservoir exploitation simulation tests.
Description
Technical Field
The invention relates to a natural gas hydrate exploitation simulation device and method, in particular to a device and method for underlying free gas hydrate exploitation simulation, and belongs to the technical field of new energy.
Background
Natural Gas Hydrate (Gas Hydrate for short) is a non-stoichiometric, ice-like, cage-like crystalline compound formed from low molecular weight hydrocarbon compounds in water and Natural Gas under low temperature and high pressure conditions. The natural gas hydrate mostly exists on the seabed, and has the advantages of large reserve, wide distribution, shallow burial, high energy density, no pollution and residue after combustion and the like. It is estimated that the organic carbon stored in the form of natural gas hydrate on earth accounts for 53% of the total organic carbon in the world, which is 2 times of the total carbon amount of three fossil fuels of coal, oil and natural gas. Therefore, natural gas hydrate is considered as an ideal clean alternative energy source in the 21 st century.
The natural gas hydrate exists in a loose sedimentary layer of a muddy seabed in a solid form, and phase transformation occurs in the exploitation process, so that the method has great exploitation difficulty compared with the exploitation of petroleum and natural gas. Research has shown that among many types of natural gas hydrate deposits, the natural gas hydrate deposit containing the underlying free gas is the hydrate type with the most commercial curriculum potential, and therefore, the deep research on the natural gas hydrate deposit has important significance and practical application value.
Compared with the field trial production of the natural gas hydrate, the indoor natural gas hydrate production physical simulation technology is the most effective means for developing the natural gas hydrate production research, and has the advantages of low cost, wide adaptability and the like. However, simulating a natural gas hydrate reservoir containing underlying free gas in a laboratory has great technical difficulties; the actual seabed natural gas hydrate reservoir containing the underlying free gas comprises sediments, hydrates and free water at the upper part of the reservoir, and the free gas layer at the lower part of the reservoir comprises sediments, free gas and water; in the process of simulating and preparing the hydrate reservoir in a laboratory, free gas at the lower part can permeate upwards, and free water at the upper part can permeate downwards, so that the existing natural gas hydrate exploitation simulating device is difficult to simulate and prepare a free gas hydrate reservoir at the bottom similar to an actual hydrate reservoir and carry out exploitation simulation research. The invention of China patent CN101240700B discloses a gas hydrate exploitation simulation experiment device containing a free gas layer, which mainly adopts a free gas kettle and a hydrate reaction kettle to respectively simulate an upper hydrate layer and a lower free gas reservoir, and connects the two separated reaction kettles by a gas pressure valve and a pipeline, but the connection of the gas pressure valve and the pipeline between the two reaction kettles is difficult to accurately simulate the gas-liquid seepage process between the upper hydrate reservoir and the lower free gas reservoir in the exploitation process.
Therefore, it is necessary to research and develop an accurate and reliable device and method for simulating the exploitation of the free gas hydrate of the underlying free gas, which is applied to the research of the exploitation simulation test of the marine free gas hydrate of the underlying free gas.
Disclosure of Invention
In view of the above problems, it is an object of the present invention to provide an accurate and reliable simulation apparatus and method for the recovery of free gas hydrates from the bottom gas.
In order to achieve the purpose, the invention adopts the following technical scheme that the device for simulating the exploitation of the free gas hydrate comprises: the simulation reactor is a pressure-resistant sealed cylindrical kettle body; the gas-liquid seepage control system is arranged in the simulation reactor and is configured to divide the internal cavity of the simulation reactor into a free gas area and a hydrate area, and porous media are filled in the free gas area and the hydrate area; a turnover device connected with the simulation reactor and configured to turn the simulation reactor 180 degrees; a gas-liquid distributor mounted at the bottom of the hydrate zone of the simulated reactor; the outlet end of the production well is positioned outside the simulation reactor, and the inlet end of the production well penetrates through the hydrate area of the simulation reactor and the gas-liquid seepage control system and then extends into the free gas area of the simulation reactor; the quantitative gas injection system is respectively connected with the gas-liquid distributor and the top of the free gas area of the simulation reactor through a valve and a pipeline; a quantitative liquid injection system connected to the top of the free gas zone and the hydrate zone of the simulated reactor through valves and pipelines, respectively; the outlet end of the gas-liquid separator is connected with the gas-liquid online metering system, and the inlet end of the gas-liquid separator is connected to the outlet end of the production well through a pressure stabilizing control system, a valve and a pipeline.
The device for simulating the exploitation of the underlying free gas natural gas hydrate preferably further comprises a first refrigeration system and a second refrigeration system, wherein a first reactor jacket and a second reactor jacket are respectively arranged outside the free gas area and the hydrate area of the simulation reactor along the circumferential direction, and the first refrigeration system and the second refrigeration system are respectively connected to the first reactor jacket and the second reactor jacket through valves and pipelines.
The device for simulating the exploitation of the underlying free gas natural gas hydrate preferably comprises: the porous plate is fixed on the inner wall of the simulation reactor close to one side of the hydrate area, and a plurality of seepage holes are uniformly distributed on the porous plate; the fixed retainer ring is fixed on the inner wall of the simulation reactor close to one side of the free gas area, and a gap is formed between the fixed retainer ring and the porous plate; the gas-liquid permeation plate is axially movably arranged in a gap between the porous plate and the fixed retainer ring; the pre-tightening springs are arranged between the gas-liquid permeation plate and the fixed check ring, and two ends of each pre-tightening spring are respectively connected with the gas-liquid permeation plate and the fixed check ring; the sealing plugs are fixedly connected to the upper part of the gas-liquid permeation plate and correspond to the seepage holes in the porous plate one by one, and the sealing plugs are configured to close or open the seepage holes in the porous plate; and the non-return mechanisms are arranged between the gas-liquid permeation plate and the fixed check ring, and two ends of the non-return mechanisms are respectively connected with the gas-liquid permeation plate and the fixed check ring.
The device for simulating the exploitation of the underlying free gas natural gas hydrate is preferably provided with temperature sensors at the upper part and the lower part of the free gas area and the hydrate area, and the temperature sensors are used for monitoring the temperatures of different parts in the simulation reactor on line; and meanwhile, pressure sensors are arranged in the free gas area and the hydrate area and used for monitoring the pressure in the simulation reactor on line.
Preferably, the fixed retainer ring is of an annular structure, a cross structure is integrally formed in the middle of the annular structure, five pre-tightening springs are distributed in the connecting part of the annular structure and the cross structure and in the middle of the cross structure, and two check mechanisms are symmetrically distributed on the cross structure positioned on two sides of the pre-tightening spring in the middle.
Preferably, the gas-liquid permeation plate is a porous sintered plate, a porous ceramic plate or a porous wire mesh plate and is used for ensuring that gas-liquid permeation flow between the hydrate area and the free gas area is uniformly distributed in the mining stage of the underlying free gas hydrate reservoir.
Preferably, the sealing plug is a conical rubber plug, the conical end of the sealing plug faces the porous plate, and the bottom surface of the sealing plug is fixed on the gas-liquid permeation plate.
The method for simulating the exploitation of the underlying free gas natural gas hydrate, which is realized by adopting the device, comprises the following steps:
firstly, preparing an overlying free gas hydrate reservoir:
1) installing a gas-liquid seepage control system and a gas-liquid distributor in the simulation reactor, and filling a porous medium in the simulation reactor;
2) sealing the simulation reactor, and starting a turnover device to adjust a free gas area of the simulation reactor to the top of the simulation reactor;
3) replacing air in the simulation reactor with natural gas, respectively injecting quantitative aqueous solution into a hydrate area and a free gas area of the simulation reactor by using a quantitative liquid injection system, and respectively injecting quantitative natural gas into the hydrate area and the free gas area of the simulation reactor by using a quantitative gas injection system to respectively enable the hydrate area and the free gas area of the simulation reactor to reach preset pressures;
4) controlling the temperature of the free gas zone to a predetermined temperature using a first refrigeration system and a first reactor jacket, and controlling the temperature of the hydrate zone to a predetermined temperature using a second refrigeration system and a second reactor jacket to form hydrates in the hydrate zone deposits, wherein free gas is present in the free gas zone, producing an overlying free gas hydrate reservoir having an upper free gas layer + a lower hydrate layer;
secondly, preparing a hydrate reservoir of the underlying free gas:
1) adjusting the pressure of a free gas area to be 1-3MPa higher than that of a hydrate area by adopting a quantitative gas injection system, and adjusting the temperature of a free gas layer by adopting a first refrigeration system and a first reactor jacket to ensure that the free gas area has preset free gas saturation;
2) turning over the simulation reactor containing the overlying free gas hydrate reservoir up and down by using a turning device to obtain an underlying free gas hydrate reservoir with a lower free gas layer and an upper hydrate layer;
thirdly, the free gas hydrate reservoir under the layer is mined:
1) starting a pressure stabilizing control system, setting the exploitation pressure, opening an exploitation well valve to begin hydrate exploitation, and exploiting a gas-liquid mixture in a free gas layer at the lower part of the simulation reactor through the exploitation well to simulate the reactor;
2) the pressure of the lower free gas layer is continuously reduced until the pressure difference between the upper hydrate layer and the lower free gas layer is increased to be larger than the opening pressure of the gas-liquid seepage control system, the gas-liquid seepage control system is opened, the upper hydrate layer is communicated with the lower free gas layer, gas-liquid mixture in the hydrate layer seeps to the lower free gas layer, the pressure of the upper hydrate layer is continuously reduced until the pressure is reduced to the hydrate decomposition pressure, and the hydrate in the upper hydrate layer is decomposed into gas and water;
3) after the gas-liquid mixture produced from the production well is separated by a gas-liquid separator, a gas-liquid online metering system (9) is adopted to meter the gas-production water-production rate and the accumulated gas-production water-production amount.
Preferably, the hydrate layer comprises porous medium + hydrate + aqueous solution + natural gas, or porous medium + hydrate + aqueous solution, or porous medium + hydrate + natural gas, or porous medium + hydrate;
the free gas layer comprises porous medium + hydrate + aqueous solution + natural gas, or porous medium + hydrate + natural gas, or porous medium + aqueous solution + natural gas, or porous medium + natural gas.
Preferably, the porous medium is various artificial porous media, seabed sediments or a mixture of the artificial porous media and the seabed sediments.
The method for simulating the exploitation of the underlying free gas hydrate is preferably used in the exploitation stage of the underlying free gas hydrate reservoir, and the exploitation method comprises depressurization exploitation, heat injection exploitation or combined exploitation of depressurization and heat injection;
the mining well comprises a vertical well, a horizontal well or a vertical well and a horizontal well;
the number of production wells may include a single well or multiple wells.
Due to the adoption of the technical scheme, the invention has the following advantages: the gas, water and hydrate saturation control precision in the hydrate layer and the free gas layer prepared by the invention is high, the operation is simple and convenient, the gas-liquid seepage characteristic between the hydrate layer and the free gas layer in the actual exploitation process can be accurately simulated, and the method can be applied to various different types of underlying free gas hydrate reservoir exploitation simulation tests.
Drawings
FIG. 1 is a schematic view of the apparatus of the present invention during the preparation of an underlying free gas hydrate reservoir;
FIG. 2 is a schematic view of the apparatus of the present invention during the production phase of an underlying free gas hydrate reservoir;
FIG. 3 is a schematic structural view of a gas-liquid seepage control system according to the present invention;
FIG. 4 is a schematic view of the structure of the multi-well plate of the present invention;
FIG. 5 is a schematic structural view of a fixed retainer ring, a pre-tightening spring and a non-return mechanism of the present invention;
fig. 6 is a schematic structural view of the gas-liquid permeation plate and the sealing plug of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the system or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used to define elements only for convenience in distinguishing between the elements, and unless otherwise stated have no special meaning and are not to be construed as indicating or implying any relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "disposed," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
The invention provides a device and a method for simulating the exploitation of a free gas natural gas hydrate, which are characterized in that a gas-liquid seepage control system is arranged in a simulation reactor so as to divide the simulation reactor into a hydrate area and a free gas area; firstly, preparing a hydrate reservoir with overlying free gas by adopting a method of inverting a simulation reactor, and then turning the simulation reactor up and down to prepare a hydrate reservoir with underlying free gas; and then, developing a hydrate exploitation test, and simulating a gas-liquid seepage process between an upper hydrate layer and a lower free gas layer in the exploitation process by using a gas-liquid seepage control system, so as to realize the simulation exploitation research of the free gas ocean natural gas hydrate under the gas-liquid seepage control system.
As shown in fig. 1 and fig. 2, the device for simulating the production of free gas hydrates under the base provided by the embodiment of the present invention includes: the simulation reactor 1 is a pressure-resistant sealed cylindrical kettle body; the gas-liquid seepage control system 2 is arranged in the simulation reactor 1, and the gas-liquid seepage control system 2 is configured to divide the internal cavity of the simulation reactor 1 into a free gas area and a hydrate area, and porous media are filled in the free gas area and the hydrate area; a turnover device 3 connected to the simulation reactor 1, wherein the turnover device 3 is configured to turn the simulation reactor 1 by 180 °; a gas-liquid distributor 4 installed at the bottom of the hydrate zone of the simulation reactor 1; the outlet end of the exploitation well 5 is positioned outside the simulation reactor 1, and the inlet end of the exploitation well 5 penetrates through the hydrate area of the simulation reactor 1 and the gas-liquid seepage control system 2 and then extends into the free gas area of the simulation reactor 1; the quantitative gas injection system 6 is respectively connected with the gas-liquid distributor 4 and the top of the free gas area of the simulation reactor 1 through a valve and a pipeline; a quantitative liquid injection system 7 connected to the top of the free gas zone and the hydrate zone of the simulated reactor 1 through valves and lines, respectively; the gas-liquid separator 8 and the online gas-liquid metering system 9, the outlet end of the gas-liquid separator 8 is connected with the online gas-liquid metering system 9, and the inlet end of the gas-liquid separator 8 is connected to the outlet end of the production well 5 through the pressure stabilizing control system 10, the valve and the pipeline.
Thus, in the stage of preparing the upper free gas hydrate reservoir, the free gas zone is disposed at the upper part of the simulated reactor 1, and the hydrate zone is disposed at the lower part of the simulated reactor 1 (as shown in FIG. 1); during the preparation and exploitation phases of the underlying free gas hydrate reservoir, the simulation reactor 1 is turned over by 180 ° by the turning device 3, the free gas zone is placed in the lower part of the simulation reactor 1 and the hydrate zone is placed in the upper part of the simulation reactor 1 (as shown in fig. 2).
In the above embodiment, preferably, the present invention further comprises a first refrigeration system 11 and a second refrigeration system 12, while a first reactor jacket 13 and a second reactor jacket 14 are respectively provided circumferentially outside the free gas zone and the hydrate zone of the simulation reactor 1, and the first refrigeration system 11 and the second refrigeration system 12 are respectively connected to the first reactor jacket 13 and the second reactor jacket 14 through valves and lines.
In the above embodiment, preferably, as shown in fig. 3 and 4, the gas-liquid seepage control system 2 includes: the porous plate 2-1 is fixed on the inner wall of the simulation reactor 1 close to one side of the hydrate area, and a plurality of seepage holes 2-2 are uniformly distributed on the porous plate 2-1; the fixed retainer ring 2-3 is fixed on the inner wall of the simulation reactor 1 close to one side of the free gas area, and a gap is formed between the fixed retainer ring 2-3 and the porous plate 2-1; the gas-liquid permeation plate 2-4 is axially movably arranged in a gap between the porous plate 2-1 and the fixed retainer ring 2-3; the gas-liquid permeation device comprises pre-tightening springs 2-5, wherein a plurality of pre-tightening springs 2-5 are arranged between a gas-liquid permeation plate 2-4 and a fixed check ring 2-3, and two ends of each pre-tightening spring 2-5 are respectively connected with the gas-liquid permeation plate 2-4 and the fixed check ring 2-3; the sealing plugs 2-6 are fixedly connected to the upper parts of the gas-liquid permeation plates 2-4 and correspond to the seepage holes 2-2 in the porous plate 2-1 one by one, and the sealing plugs 2-6 are configured to close or open the seepage holes 2-2 in the porous plate 2-1; and the non-return mechanisms 2-7 are arranged between the gas-liquid permeation plates 2-4 and the fixed check rings 2-3, and two ends of the non-return mechanisms 2-7 are respectively connected with the gas-liquid permeation plates 2-4 and the fixed check rings 2-3. Therefore, in the preparation stage of the submerged free gas hydrate reservoir, each sealing plug 2-6 is pressed into each seepage hole 2-2 of the porous plate 2-1 under the action of the pre-tightening spring 2-5 and the pressure difference between the free gas area and the hydrate area, so that gas-liquid seepage and exchange between the free gas area and the hydrate area are prevented; in the exploitation stage of the underlying free gas hydrate reservoir, when the pressure difference between the hydrate area and the free gas area is greater than the opening pressure of the gas-liquid seepage control system 2 (the opening pressure can be adjusted by a pre-tightening spring 2-5), the gas-liquid permeation plate 2-4 moves downwards under the action of the pressure difference between the hydrate area and the free gas area, each sealing plug 2-6 leaves each seepage hole 2-2 of the porous plate 2-1, the hydrate area and the free gas area are communicated, and the gas-liquid permeation plate 2-4 is fixed in position through a non-return mechanism 2-7 and a fixed check ring 2-3, so that the gas-liquid seepage control system 2 is always in an open state, and uniform gas-liquid seepage and exchange between the free gas area and the hydrate area in the exploitation process are ensured.
In the above embodiment, it is preferable that temperature sensors 15 are provided at the upper and lower portions of the free gas zone and the hydrate zone for on-line monitoring of the temperatures at different portions in the simulation reactor 1; meanwhile, pressure sensors 16 are provided inside both the free gas zone and the hydrate zone for on-line monitoring of the pressure inside the simulation reactor 1.
In the above embodiment, preferably, as shown in fig. 5, the fixed retainer 2-3 is a ring structure, a cross structure is integrally formed in the middle of the ring structure, five pre-tightening springs 2-5 are distributed at the connecting portion of the ring structure and the cross structure and in the middle of the cross structure, and two anti-return mechanisms 2-7 are symmetrically distributed on the cross structure at both sides of the middle pre-tightening spring 2-5.
In the above embodiment, preferably, as shown in fig. 6, the gas-liquid permeation plates 2 to 4 are porous sintered plates, porous ceramic plates, porous wire mesh plates, or the like, for ensuring the uniform distribution of gas-liquid permeation flow between the hydrate region and the free gas region in the extraction stage of the underlying free gas hydrate reservoir.
In the above embodiment, it is preferable that the sealing plug 2-6 is a conical rubber plug, the conical end of the sealing plug 2-6 faces the porous plate 2-1, and the bottom surface of the sealing plug 2-6 is fixed on the gas-liquid permeation plate 2-4.
Based on the device for simulating the exploitation of the free gas hydrate, the invention also provides a method for simulating the exploitation of the free gas hydrate, which comprises the following steps:
firstly, preparing an overlying free gas hydrate reservoir:
1) a gas-liquid seepage control system 2 and a gas-liquid distributor 4 are arranged in the simulation reactor 1, and porous media are filled in the simulation reactor 1;
2) sealing the simulation reactor 1, and starting the turnover device 3 to adjust the free gas area of the simulation reactor 1 to the top of the simulation reactor 1;
3) replacing air in the simulated reactor 1 with natural gas (such as methane), injecting quantitative aqueous solution into the hydrate area and the free gas area of the simulated reactor 1 by using a quantitative liquid injection system 7, and injecting quantitative natural gas into the hydrate area and the free gas area of the simulated reactor 1 by using a quantitative gas injection system 6 to respectively reach preset pressures (such as 15 MPa);
4) the temperature of the free gas zone is controlled to a predetermined temperature (e.g., 290K) using the first refrigeration system 11 and the first reactor jacket 13, and the temperature of the hydrate zone is controlled to a predetermined temperature (e.g., 285K) using the second refrigeration system 12 and the second reactor jacket 14 to form hydrates in the hydrate zone deposits (when the hydrate zone pressure is reduced to 8.5MPa) and free gas is present in the free gas zone to produce an overlying free gas hydrate reservoir having an upper free gas layer + a lower hydrate layer.
Secondly, preparing a hydrate reservoir of the underlying free gas:
1) adjusting the pressure in the free gas zone to 1-3MPa (e.g., 10.5MPa) above the pressure in the hydrate zone using the quantitative gas injection system 6 while adjusting the free gas blanket temperature (e.g., to 288K) using the first refrigeration system 11 and the first reactor jacket 13 to ensure that a predetermined free gas saturation in the free gas zone exists;
2) the simulation reactor 1 containing the overlying free gas hydrate reservoir is turned over up and down by using the turning device 3, and the underlying free gas hydrate reservoir having a lower free gas layer + an upper hydrate layer is prepared.
Thirdly, the free gas hydrate reservoir under the layer is mined:
1) starting the pressure stabilizing control system 10, setting the exploitation pressure, opening a valve of the exploitation well 5 to begin hydrate exploitation, and exploiting the gas-liquid mixture in the free gas layer at the lower part of the simulation reactor 1 out of the simulation reactor 1 through the exploitation well 5;
2) the pressure of the lower free gas layer is continuously reduced until the pressure difference between the upper hydrate layer and the lower free gas layer is increased to be larger than the opening pressure of the gas-liquid seepage control system 2, the gas-liquid seepage control system 2 is opened, the upper hydrate layer is communicated with the lower free gas layer, gas-liquid mixture in the hydrate layer seeps to the lower free gas layer, the pressure of the upper hydrate layer is continuously reduced until the pressure is reduced to the hydrate decomposition pressure, and the hydrate in the upper hydrate layer is decomposed into gas and water;
3) after the gas-liquid mixture produced from the production well 5 is separated by the gas-liquid separator 8, the gas-liquid online metering system 9 is adopted to meter the gas-production water-production rate and the accumulated gas-production water-production amount.
In the above embodiment, preferably, the hydrate layer comprises porous medium + hydrate + aqueous solution + natural gas, or porous medium + hydrate + aqueous solution, or porous medium + hydrate + natural gas, or porous medium + hydrate.
In the above embodiment, preferably, the free gas layer comprises porous medium + hydrate + aqueous solution + natural gas, or porous medium + hydrate + natural gas, or porous medium + aqueous solution + natural gas, or porous medium + natural gas.
In the above embodiment, preferably, the porous medium is various types of artificial porous media, seabed sediments or a mixture of the two.
In the above embodiment, preferably, in the stage of exploiting the underlying free gas hydrate reservoir, the exploitation method comprises depressurization exploitation, heat injection exploitation or combined exploitation of depressurization and heat injection; the exploitation well 5 is in a form of a vertical well, a horizontal well or a vertical well plus a horizontal well; the number of production wells 5 may include a single well or multiple wells.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (9)
1. An underlying free gas natural gas hydrate production simulation device, comprising:
the simulation reactor (1) is a pressure-resistant sealed cylindrical kettle body;
the gas-liquid seepage control system (2) is arranged in the simulation reactor (1), and the gas-liquid seepage control system (2) is configured to divide the internal cavity of the simulation reactor (1) into a free gas area and a hydrate area, and porous media are filled in the free gas area and the hydrate area;
a turning device (3) connected to the simulated reactor (1), the turning device (3) being configured to turn the simulated reactor (1) by 180 °;
a gas-liquid distributor (4) installed at the bottom of the hydrate zone of the simulation reactor (1);
the outlet end of the production well (5) is positioned outside the simulation reactor (1), and the inlet end of the production well (5) penetrates through the hydrate area of the simulation reactor (1) and the gas-liquid seepage control system (2) and then extends into the free gas area of the simulation reactor (1);
the quantitative gas injection system (6) is respectively connected with the gas-liquid distributor (4) and the top of the free gas area of the simulation reactor (1) through a valve and a pipeline;
a quantitative liquid injection system (7) connected to the top of the free gas zone and the hydrate zone of the simulated reactor (1) through valves and pipelines, respectively;
the gas-liquid separator (8) and the gas-liquid online metering system (9), wherein the outlet end of the gas-liquid separator (8) is connected with the gas-liquid online metering system (9), and the inlet end of the gas-liquid separator (8) is connected to the outlet end of the production well (5) through a pressure stabilizing control system (10), a valve and a pipeline;
the gas-liquid seepage control system (2) comprises:
the porous plate (2-1) is fixed on the inner wall of the simulation reactor (1) close to one side of the hydrate area, and a plurality of seepage holes (2-2) are uniformly distributed on the porous plate (2-1);
the fixed retainer ring (2-3) is fixed on the inner wall of the simulation reactor (1) close to one side of the free gas area, and a gap is formed between the fixed retainer ring (2-3) and the porous plate (2-1);
the gas-liquid permeation plate (2-4) is axially movably arranged in a gap between the porous plate (2-1) and the fixed retainer ring (2-3);
the pre-tightening springs (2-5), a plurality of the pre-tightening springs (2-5) are arranged between the gas-liquid permeation plate (2-4) and the fixed check ring (2-3), and two ends of each pre-tightening spring (2-5) are respectively connected with the gas-liquid permeation plate (2-4) and the fixed check ring (2-3);
the sealing plugs (2-6), a plurality of the sealing plugs (2-6) are fixedly connected to the upper part of the gas-liquid permeation plate (2-4) and correspond to the seepage holes (2-2) on the porous plate (2-1) one by one, and the sealing plugs (2-6) are configured to close or open the seepage holes (2-2) of the porous plate (2-1);
and the non-return mechanisms (2-7) are arranged between the gas-liquid permeation plates (2-4) and the fixed check rings (2-3), and two ends of the non-return mechanisms (2-7) are respectively connected with the gas-liquid permeation plates (2-4) and the fixed check rings (2-3).
2. The underlying free gas natural gas hydrate production simulation device according to claim 1, further comprising a first refrigeration system (11) and a second refrigeration system (12), while a first reactor jacket (13) and a second reactor jacket (14) are circumferentially provided outside the free gas zone and the hydrate zone of the simulation reactor (1), respectively, the first refrigeration system (11) and the second refrigeration system (12) being connected to the first reactor jacket (13) and the second reactor jacket (14), respectively, through valves and pipelines.
3. The underlying free gas natural gas hydrate production simulation device according to claim 1, wherein temperature sensors (15) are provided at both upper and lower portions of the free gas zone and hydrate zone for online monitoring of temperatures at different locations within the simulation reactor (1);
meanwhile, pressure sensors (16) are arranged in the free gas area and the hydrate area and used for monitoring the pressure in the simulation reactor (1) on line.
4. The underlying free gas natural gas hydrate exploitation simulation device according to claim 1, wherein the fixed retainer ring (2-3) is a ring-shaped structure, a cross-shaped structure is integrally formed in the middle of the ring-shaped structure, five pre-tightening springs (2-5) are distributed at the connection part of the ring-shaped structure and the cross-shaped structure and the middle part of the cross-shaped structure, and two check mechanisms (2-7) are symmetrically distributed on the cross-shaped structure at two sides of the pre-tightening springs (2-5) in the middle part.
5. The underlying free gas natural gas hydrate production simulation device according to claim 1, wherein the gas-liquid permeable plates (2-4) are porous sintered plates, porous ceramic plates or porous wire mesh plates for ensuring uniform gas-liquid seepage distribution between the hydrate zone and the free gas zone during the production phase of the underlying free gas hydrate reservoir.
6. The underlying free gas natural gas hydrate exploitation simulation device according to claim 1, wherein the sealing plug (2-6) is a conical rubber plug, the conical end of the sealing plug (2-6) faces the porous plate (2-1), and the bottom surface of the sealing plug (2-6) is fixed on the gas-liquid permeation plate (2-4).
7. An underlying free gas natural gas hydrate production simulation method implemented by the apparatus according to any one of claims 1 to 6, comprising the steps of:
firstly, preparing an overlying free gas hydrate reservoir:
1) a gas-liquid seepage control system (2) and a gas-liquid distributor (4) are arranged in the simulation reactor (1), and a porous medium is filled in the simulation reactor (1);
2) sealing the simulation reactor (1), and starting the turnover device (3) to adjust the free gas area of the simulation reactor (1) to the top of the simulation reactor (1);
3) replacing air in the simulation reactor (1) by natural gas, respectively injecting quantitative aqueous solution into a hydrate area and a free gas area of the simulation reactor (1) by adopting a quantitative liquid injection system (7), and respectively injecting quantitative natural gas into the hydrate area and the free gas area of the simulation reactor (1) by adopting a quantitative gas injection system (6) to enable the hydrate area and the free gas area of the simulation reactor (1) to respectively reach preset pressure;
4) controlling the temperature of the free gas zone to a predetermined temperature using a first refrigeration system (11) and a first reactor jacket (13), and controlling the temperature of the hydrate zone to a predetermined temperature using a second refrigeration system (12) and a second reactor jacket (14) to produce hydrates in the hydrate zone deposits, while free gas is present in the free gas zone, to produce an overlying free gas hydrate reservoir having an upper free gas layer + a lower hydrate layer;
secondly, preparing a hydrate reservoir of the underlying free gas:
1) adjusting the pressure of a free gas area to be 1-3MPa higher than that of a hydrate area by adopting a quantitative gas injection system (6), and adjusting the temperature of a free gas layer by adopting a first refrigeration system (11) and a first reactor jacket (13) to ensure that the free gas area has preset free gas saturation;
2) the simulation reactor (1) containing the overlying free gas hydrate reservoir is turned over up and down by adopting a turning device (3) to prepare the underlying free gas hydrate reservoir with a lower free gas layer and an upper hydrate layer;
thirdly, the free gas hydrate reservoir under the layer is mined:
1) starting a pressure stabilizing control system (10), setting the exploitation pressure, opening a valve of an exploitation well (5) to begin hydrate exploitation, and exploiting the gas-liquid mixture in a free gas layer at the lower part of the simulation reactor (1) through the exploitation well (5) to simulate the simulation reactor (1);
2) the pressure of the lower free gas layer is continuously reduced until the pressure difference between the upper hydrate layer and the lower free gas layer is increased to be larger than the opening pressure of the gas-liquid seepage control system (2), the gas-liquid seepage control system (2) is opened, the upper hydrate layer is communicated with the lower free gas layer, gas-liquid mixture in the hydrate layer seeps to the lower free gas layer, the pressure of the upper hydrate layer is continuously reduced until the pressure is reduced to the hydrate decomposition pressure, and the hydrate in the upper hydrate layer is decomposed into gas and water;
3) after the gas-liquid mixture produced from the production well (5) is separated by a gas-liquid separator (8), a gas-liquid online metering system (9) is adopted to meter the gas-production water production rate and the accumulated gas-production water production.
8. The underburden free gas natural gas hydrate production simulation method of claim 7, where hydrate layer comprises porous media + hydrate + aqueous solution + natural gas, or porous media + hydrate + aqueous solution, or porous media + hydrate + natural gas, or porous media + hydrate;
the free gas layer comprises a porous medium, a hydrate, an aqueous solution and natural gas, or the porous medium, the hydrate and the natural gas, or the porous medium, the aqueous solution and the natural gas, or the porous medium and the natural gas;
the porous medium is various artificial porous media, seabed sediment or a mixture of the artificial porous media and the seabed sediment.
9. The underlying free gas hydrate production simulation method of claim 7, wherein in the stage of production of the underlying free gas hydrate reservoir, the production method comprises depressurization production, heat injection production or combined depressurization and heat injection production;
the form of the production well (5) comprises a vertical well, a horizontal well or a vertical well and a horizontal well;
the number of production wells (5) comprises a single well or a plurality of wells.
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| CN111707800B (en) * | 2020-06-10 | 2021-11-05 | 大连理工大学 | Device and method for simulating remodeling and depressurization exploitation of natural gas hydrate reservoir of underlying gas |
| CN113719279B (en) * | 2021-09-08 | 2023-09-15 | 中国海洋石油集团有限公司 | Serially connected type free gas hydrate reservoir simulation device and method |
| CN115308799B (en) | 2022-09-05 | 2023-07-25 | 中国地质科学院地质力学研究所 | Method and system for identifying free gas structure of seismic imaging |
| CN117266798B (en) * | 2023-11-23 | 2024-01-16 | 中国石油大学(华东) | Physical simulation experiment device and method for combined exploitation of hydrate and shallow gas |
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