CN111502603A

CN111502603A - Pore fluid collecting device, device and method for simulating exploitation of natural gas hydrate

Info

Publication number: CN111502603A
Application number: CN202010333645.2A
Authority: CN
Inventors: 高永海; 高冬至; 尹法领; 孙宝江; 陈野; 赵欣欣; 苏鑫垚; 祁亚强
Original assignee: China University of Petroleum East China
Current assignee: China University of Petroleum East China
Priority date: 2020-04-24
Filing date: 2020-04-24
Publication date: 2020-08-07

Abstract

The invention relates to natural gas hydrate exploitation, and particularly discloses a pore fluid acquisition device which comprises an acquisition pipe (11), a cock (14), an acquisition cavity (12) and a delivery pipe (13) which are sequentially connected and used for extending into a hydrate reservoir to acquire pore fluid, wherein the cock (14) is matched with the acquisition cavity (12) to control the connection and disconnection of the acquisition pipe (11) and the acquisition cavity (12), and valves are respectively arranged on the acquisition pipe (11) and the delivery pipe (13). In addition, the invention also relates to a device and a method for simulating the exploitation of the natural gas hydrate. The acquisition device provided by the invention can acquire the pore fluid of the hydrate reservoir and simultaneously maintain the pressure of the hydrate reservoir simulated by an experiment.

Description

Pore fluid collecting device, device and method for simulating exploitation of natural gas hydrate

Technical Field

The invention relates to natural gas hydrate exploitation, in particular to a pore fluid collecting device. In addition, the invention also relates to a device and a method for simulating the exploitation of the natural gas hydrate.

Background

Natural gas hydrate is a cage-shaped crystal substance generated by natural gas and water under specific temperature and pressure conditions, is like ice and snow, and is commonly called as 'combustible ice' because the cage-shaped crystal substance can be ignited. With the increasing shortage of energy, natural gas hydrate gradually draws the attention of domestic and foreign scientists, and relevant exploration, exploitation and experimental research is carried out. As a high-density energy source, the energy source has wide distribution, large reserve and shallow burial, and becomes an ideal alternative energy source in the 21 st century.

At present, the exploitation method of natural gas hydrate mainly comprises a depressurization method, a thermal excitation method, a chemical reagent method and comprehensive application of the three methods, and the basic idea is to artificially break the temperature and pressure balance condition of the natural gas hydrate, so that the natural gas hydrate is decomposed and then the natural gas is extracted to the ground, but the schemes can cause problems of landslide or settlement of the seabed and the like.

Therefore, people pay more and more attention to the technology for exploiting the natural gas hydrate by carbon dioxide replacement based on the replacement principle recently, natural gas in the natural gas hydrate is replaced by the carbon dioxide to obtain the carbon dioxide hydrate and the natural gas, so that exploitation of the natural gas hydrate can be realized, underground sealing of the carbon dioxide can be realized, and the greenhouse effect is reduced.

Because field experimental research on the natural gas hydrate is complex, the current experimental research on carbon dioxide displacement exploitation of the natural gas hydrate is mainly indoor experimental simulation, and a more appropriate exploitation process is determined through simulation experiments so as to guide field exploration and development. However, the existing experimental device is difficult to meet the research requirements of the existing carbon dioxide replacement exploitation of natural gas hydrate, only components of pore fluid at a reaction starting point and a reaction stopping point can be obtained, the pore fluid cannot be collected in the replacement process, the dynamic change and decomposition process of the natural gas hydrate in the replacement process cannot be reflected, and the guiding significance for field exploitation is small.

In view of the above, a new experimental device needs to be designed.

Disclosure of Invention

The technical problem to be solved by the first aspect of the present invention is to provide a pore fluid collecting device, which can collect the pore fluid of a hydrate reservoir while maintaining the pressure of the hydrate reservoir simulated by an experiment.

The technical problem to be solved by the second aspect of the present invention is to provide a device for simulating the production of natural gas hydrate, the device can perform simulated production of carbon dioxide replacement natural gas hydrate, and a pore fluid collecting device in the device can collect pore fluid of a hydrate reservoir at each position, and simultaneously maintain the pressure of the hydrate reservoir simulated by an experiment.

The third aspect of the invention aims to solve the technical problem of providing an experimental method for simulating the exploitation of the natural gas hydrate, wherein the experimental method can reflect the dynamic change and the decomposition process of the natural gas hydrate in the process of putting carbon dioxide into the exploitation of the natural gas hydrate.

In order to solve the technical problem, a first aspect of the present invention provides a pore fluid collecting device, which includes a collecting tube, a cock, a collecting cavity, and a delivery tube, which are connected in sequence and used for extending into a hydrate reservoir to collect pore fluid, wherein the cock is matched with the collecting tube to control the connection and disconnection between the collecting tube and the collecting cavity, and valves are respectively disposed on the collecting tube and the delivery tube.

Specifically, the cock is rotatably connected with the collection cavity, the cock and the collection cavity are provided with through holes, when the through hole of the collection cavity is opposite to the through hole of the cock, the collection tube is communicated with the collection cavity, and when the through hole of the collection cavity is staggered with the through hole of the cock, the collection tube is disconnected from the collection cavity.

The invention provides a device for simulating the exploitation of natural gas hydrate, which comprises a material supply unit, a temperature and pressure control unit, a reaction unit, a collection unit and a recovery metering unit, wherein the reaction unit comprises a reaction container, and the material supply unit is connected with the reaction container so as to be capable of providing materials required by a synthetic hydrate reservoir; the temperature and pressure control unit can control the reaction container to have temperature and pressure conditions required for forming a hydrate reservoir; the collection unit comprises the pore fluid collection device, the pressure sensor and the temperature sensor of claim 1 or 2, so as to collect the pore fluid in the reaction container and measure the pressure and the temperature in the reaction container; the recovery metering unit is capable of collecting and metering the composition and volume of the fluid discharged from the reaction vessel.

As a preferred structural style, reaction vessel is double-deck bushing structure, bushing structure includes inner tube and outer tube, the inside of inner tube forms into the reaction chamber, form into the annular chamber between inner tube and the outer tube, warm-pressing the control unit and include water tank, inlet tube and outlet pipe, be equipped with the booster pump on the inlet tube, be equipped with the back pressure valve on the outlet pipe, inlet tube and outlet pipe all one end with the annular chamber intercommunication, the other end with the water tank intercommunication.

Preferably, the sleeve structure is provided with a measuring interface, and the measuring interface is a through hole formed in the side walls of the inner pipe and the outer pipe.

More preferably, the sleeve structure is provided with a plurality of measuring ports along the circumferential direction.

Further preferably, a plurality of measurement interfaces circumferentially arranged on the sleeve structure serve as a group of measurement interfaces, and a plurality of groups of measurement interfaces are axially arranged on the sleeve structure at intervals.

As a specific structural form, the material supply unit comprises a first storage tank for storing natural gas, a second storage tank for storing carbon dioxide and a third storage tank for storing water, the first storage tank, the second storage tank and the third storage tank are respectively communicated with the reaction chamber through a first conveying pipe, a second conveying pipe and a third conveying pipe, and the first conveying pipe, the second conveying pipe and the third conveying pipe are respectively provided with a back pressure valve.

As a specific structural form, the recycling metering unit comprises a collecting container, the collecting container is communicated with the reaction cavity through a recycling pipe, and a back pressure valve is arranged on the recycling pipe.

The third aspect of the invention provides an experimental method for simulating exploitation of natural gas hydrates, which comprises the following steps:

s01, simulating a hydrate reservoir;

s02, injecting carbon dioxide into the hydrate reservoir stratum;

s03, extracting pore fluid at each position of the hydrate reservoir;

and S04, analyzing the components of the pore fluid.

The pore fluid collecting device in the basic technical scheme comprises a collecting pipe, a cock, a collecting cavity and a delivery pipe which are sequentially connected and used for extending into a hydrate reservoir to collect pore fluid, wherein the cock is suitable for being matched with the collecting pipe to control the connection and disconnection of the collecting pipe and the collecting cavity, and valves are respectively arranged on the collecting pipe and the delivery pipe. The collecting pipe can extend into the hydrate reservoir stratum to collect pore fluid, the collected pore fluid is transmitted to the collecting cavity through the cock, and the eduction pipe is connected with other measuring containers to analyze the components of the pore fluid. Because the acquisition cavity is smaller, carbon dioxide is continuously injected into the cavity where the hydrate reservoir is located, and the acquisition device can acquire pore fluid at any position in the hydrate reservoir under the condition that the air pressure of the hydrate reservoir is hardly changed. The decomposition degree of the natural gas hydrate and the position of a reaction development front edge are judged by analyzing the components of the pore fluid, and guidance is provided for researching the technology for exploiting the natural gas hydrate by replacing carbon dioxide.

Further advantages of the present invention, as well as the technical effects of preferred embodiments, are further described in the following detailed description.

Drawings

FIG. 1 is a schematic structural view of one embodiment of a pore fluid collection apparatus of the present invention;

FIG. 2 is a schematic structural view of one embodiment of the bushing configuration of the present invention;

FIG. 3 is a schematic block diagram of an embodiment of an apparatus for simulating production of natural gas hydrates in accordance with the present invention;

fig. 4 is a flow chart of an experimental method of simulating production of natural gas hydrates in accordance with the present invention.

Description of the reference numerals

11 collection tube 12 collection cavity

13 delivery pipe 14 cock

15 sealing device

21 pressure sensor 22 temperature sensor

31 reaction chamber 32 annular chamber

33 measurement interface

41 water tank 42 inlet pipe

43 outlet pipe

51 first storage tank 52 second storage tank

53 third tank 54 first transfer pipe

55 second delivery pipe 56 third delivery pipe

61 collecting container 62 recovery pipe

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In the description of the present invention, it should be noted that, unless explicitly stated or limited otherwise, the terms "connected" and "disposed" are to be interpreted broadly, e.g., as a fixed connection, a detachable connection, or an integral connection; the two elements may be connected directly or indirectly through intervening media, or may be connected through one another or in any combination thereof. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

It is to be understood that, as in fig. 1, the term "upper" refers to the end of the delivery tube 13 and "lower" refers to the end of the collection tube 11, based on the orientation or positional relationship shown in the drawings, merely to facilitate the description of the invention and to simplify the description, and does not indicate or imply that the device or component being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus is not to be construed as limiting the invention.

In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

Referring to fig. 1, the pore fluid collecting device according to the basic technical solution of the present invention has an overall sealed structure, and fluid does not escape when being transported in the collecting device, and includes a collecting tube 11, a cock 14, a collecting cavity 12 and a delivery tube 13 which are connected in sequence and used for extending into a hydrate reservoir to collect pore fluid, the cock 14 and the collecting cavity 12 are matched to control the connection and disconnection of the collecting tube 11 and the collecting cavity 12, and valves are respectively disposed on the collecting tube 11 and the delivery tube 13. In particular, the collection tube 11 may be threadably or snap-fit connected to the stopcock 14, the stopcock 14 may be snap-fit connected to the collection chamber 12, and the delivery tube 13 may be integrally formed with the collection chamber 12. When the collecting device is used, the cock 14 and the collecting cavity 12 do not need to be separated, the cock 14 and the collecting cavity 12 are matched to control the connection and disconnection of the collecting cavity 12 and the collecting pipe 11, the collecting pipe 11 and the cock 14 are preferably in threaded connection so as to be convenient to detach, and when pore fluid needs to be collected, the cock 14 and the collecting cavity 12 are connected with the collecting pipe 11.

It is noted that a hydrate reservoir is a sediment layer containing natural gas hydrates, and pore fluids, which may include water, methane and carbon dioxide during experiments to recover methane from natural gas hydrates by carbon dioxide displacement, exist with the particles that are the hydrate reservoir. The composition of the pore fluid is analyzed, the decomposition degree of the natural gas hydrate and the position of a reaction development front edge can be judged, the dynamic characteristics of the replacement process and the change of the natural gas hydrate in the replacement process are researched, the reaction rule is further researched, and guidance is provided for the actual development of the combustible ice.

The experimental device for exploiting the natural gas hydrate by carbon dioxide replacement in the prior art is generally provided with a simulation cavity for simulating a hydrate reservoir, and because the simulation cavity is a sealed structure and needs to strictly maintain the pressure in the simulation cavity, it is difficult to extract pore fluid in the simulation cavity in the carbon dioxide replacement process, and the dynamic characteristics of the replacement process and the decomposition state of the natural gas hydrate cannot be recorded in detail.

The acquisition device is simple in structure and convenient to operate, and can acquire pore fluid in the simulation cavity under the condition of maintaining the pressure environment of the simulation cavity. The specific method of use of the collection device of the present invention is described below in conjunction with a simulated chamber of a conventional laboratory device. The collection tube 11 is separated from the collection cavity 12 in advance, the cock 14 or the collection cavity 12 is adjusted so that the cock 14 can seal one end of the collection cavity 12, the valve of the delivery tube 13 is opened, the delivery tube 13 is communicated with other air pressure regulators, such as a vacuum pump and the like, so as to reduce the pressure in the collection cavity 12, and the valve on the delivery tube 13 is closed after the adjustment is finished, so that the pressure in the collection cavity 12 can be preset. Before the experiment begins, a valve on the collecting pipe 11 is closed, the collecting pipe 11 of the collecting device is firstly inserted into a simulation cavity, specifically, a small hole is formed in the side wall of the simulation cavity, the collecting pipe 11 penetrates through the small hole to enter the simulation cavity, a sealing ring is correspondingly arranged in the small hole, and the sealing ring tightly extrudes the side wall of the collecting pipe 11 to prevent gas in the simulation cavity from escaping, or an epoxy resin sealant can be coated between the small hole and the side wall of the collecting pipe 11; the hydrate reservoir is simulated and formed in the simulation cavity, and the collecting pipe 11 and the simulation cavity can be regarded as being in the same pressure system; after the simulation of the hydrate reservoir is completed, carbon dioxide is injected into the simulation cavity, the collection cavity 12 is connected with the collection pipe 11 through the cock 14, a valve of the collection pipe 11 is opened at a set time, the collection cavity 12 is communicated with the collection pipe 11, the collection pipe 11 can quickly absorb pore fluid due to the fact that the pressure in the collection cavity 12 is smaller than the pressure in the simulation cavity, the pore fluid is conveyed into the collection cavity 12, after the collection is completed, the valve on the collection pipe 11 is closed, one end of the collection cavity 12 is sealed through the cock 14, finally, the collection cavity 12 is separated from the collection pipe 11, the valve on the delivery pipe 13 is opened, the pore fluid in the collection cavity 12 is delivered to other containers, and the components of the pore fluid are analyzed.

Because the volume of the acquisition cavity 12 is small, the time for extracting pore fluid is extremely short, and carbon dioxide is continuously injected into the simulation cavity, the pressure in the simulation cavity is almost unchanged, so that the hydrate in the simulation cavity is not decomposed due to sudden change of the pressure of the simulation cavity, and the experiment failure caused by misjudgment is avoided; because the collection cavity 12 can be separated from the collection tube 11, in the experimental process, on one hand, the pore fluid of the hydrate reservoir stratum at the same position can be collected at different time by replacing the collection cavity 12, and on the other hand, an independent pressure system is formed in the collection cavity 12, the collection cavity 12 can be connected with the collection tube 11 after internal pressure treatment is well done, the pressure in the collection cavity 12 can be reduced in advance, and therefore the pore fluid can be quickly sucked into the collection cavity 12; after the collection is finished, collection chamber 12 can also be convenient with gather the pipe 11 separation, be convenient for draw out the fluid in the collection chamber 12 and carry out the analysis.

As a specific structure, referring to fig. 1, the cock 14 is rotatably connected to the collecting cavity 12, and more specifically, the lower end of the collecting cavity 12 is provided with a boss, the upper end of the cock 14 is provided with a clamping groove matched with the boss, and a sealing structure, such as a sealing ring, may be further provided between the collecting cavity 12 and the cock 14 to prevent the gas flow from escaping from the gap between the collecting cavity 12 and the cock 14. The cock 14 and the collection cavity 12 are provided with through holes, when the collection cavity 12 or the cock 14 is rotated to enable the through hole of the collection cavity 12 to be opposite to the through hole of the cock 14, the collection tube 11 and the collection cavity 12 are in a communicated state, and when the collection cavity 12 or the cock 14 is rotated to enable the through hole of the collection cavity 12 to be staggered with the through hole of the cock 14, the collection tube 11 and the collection cavity 12 are in a disconnected state. In this way, it is possible to conveniently and quickly maintain the connection or disconnection between the collection tube 11 and the collection chamber 12 at any time. Alternatively, other ways of engaging stopcock 14 with collection chamber 12 to control the connection and disconnection of collection tube 11 to collection chamber 12 may be used, such as providing a valve in stopcock 14, and controlling the connection and disconnection of collection tube 11 to collection chamber 12 by adjusting the valve in stopcock 14.

Preferably, the collection pipe 11 is an elongated needle-shaped structure suitable for being inserted into a hydrate reservoir, which facilitates the collection pipe 11 to be inserted into a simulation cavity to absorb pore fluid, and further preferably, the valve on the collection pipe 11 is a needle valve, which can withstand greater pressure, and the valve on the delivery pipe 13 is a pressure control valve, which can be adjusted to conveniently and quickly control the on-off of the delivery pipe 13.

The device for simulating the exploitation of the natural gas hydrate comprises a material supply unit, a temperature and pressure control unit, a reaction unit, a collection unit and a recovery metering unit, wherein the reaction unit comprises a reaction container, and the material supply unit is connected with the reaction container so as to be capable of providing materials required by the synthesis of the hydrate, such as water and natural gas; the main factors influencing the generation of the hydrate reservoir are temperature and pressure, relatively low temperature and high pressure are needed, and the temperature and pressure control unit can control the reaction container to have the temperature and pressure conditions needed for forming the hydrate reservoir; the acquisition unit comprises a pore fluid acquisition device in any one of the technical schemes, and further comprises a pressure sensor 21 and a temperature sensor 22, the pore fluid acquisition device is used for acquiring pore fluid in the reaction container, and the pressure sensor 21 and the temperature sensor 22 are used for measuring pressure and temperature in the reaction container; the recovery metering unit is capable of collecting and metering the components and volume of the fluid discharged from the reaction vessel. When the device is used specifically, the valve on the collection pipe 11 is in a closed state, the temperature and pressure control unit provides a proper temperature and pressure condition for the reaction vessel, the material supply unit firstly injects materials required for synthesizing natural gas hydrate, such as water, natural gas and the like, into the reaction vessel, after the hydrate reservoir synthesis is completed, carbon dioxide is injected into the reaction vessel through the material supply unit to react with the natural gas hydrate, the position of a reaction front edge can be obtained approximately through calculation, the pressure in the collection cavity 12 is adjusted, at the moment, the valve of the discharge pipe 13 is closed, the collection cavity 12 rotates to enable the through hole of the collection cavity 12 to be staggered with the through hole of the cock 14, thus, the collection cavity 12 forms a closed and independent pressure system, the cock 14 is connected with the collection pipe 11 in a threaded manner, the valve on the collection pipe 11 is opened, the collection cavity 12 is rotated until the through hole of the collection cavity 12 is opposite to the through hole, so that gather pipe 11 and gathering chamber 12 intercommunication, gather the pore fluid, after gathering, close the valve on gathering pipe 11, rotate and gather chamber 12 and block the fluid transmission between gathering chamber 12 and the pipe 11 of gathering for gather chamber 12 and form an independent pressure system once more, dismantle the separation with cock 14 and gather pipe 11 at last, be convenient for do further analysis to the composition in gathering chamber 12. Because carbon dioxide is continuously injected into the reaction vessel, the volume of the collection cavity 12 of the collection device is smaller, and the pressure in the reaction vessel is hardly changed, so that the hydrate in the reaction vessel is not largely decomposed due to pressure mutation. The device for simulating the exploitation of the natural gas hydrate can collect pore fluid in the reaction generation process, judge the position and the development speed of the reaction development front edge by analyzing the pore fluid in the collection cavity 12, monitor whether the reaction is normally carried out or not, and verify the position and the development speed of the reaction development front edge and a theoretical calculation result mutually.

As a specific structure form, referring to fig. 2, the reaction vessel is a double-layer casing structure, the casing structure includes an inner pipe and an outer pipe, the inner part of the inner pipe forms a reaction chamber 31, an annular chamber 32 is formed between the inner pipe and the outer pipe, a hydrate reservoir can be simulated in the reaction chamber 31, the annular chamber 32 can be filled with flowing water, on one hand, the temperature in the reaction chamber 31 can be controlled by a water bath method, and on the other hand, the water pressure in the annular chamber 32 can be increased to apply confining pressure to the reaction chamber 31. Specifically, the equal both ends opening of outer tube and inner tube, the supporting both ends that set up sealed lid and use shutoff sleeve pipe structure, the outer tube is the rigid pipe body, can adopt the rigid pipe of stainless steel, and the inner tube can be made for materials such as silica gel, rubber, and when the water pressure increase in the annular chamber 32, the inner tube can receive the extrusion, thereby the pressure in the hydrate reservoir stratum in the reaction chamber 31 is adjusted in the inner tube deformation. With bushing structure adapted, warm-pressing the control unit includes water tank 41, inlet tube 42 and outlet pipe 43, be equipped with the booster pump on the inlet tube 42, be equipped with the back pressure valve on the outlet pipe 43, can adjust the water pressure size in the annular chamber 32 through adjusting booster pump and back pressure valve, and then provide suitable pressure environment for the hydrate reservoir, inlet tube 41 and the equal one end of outlet pipe 42 communicate with annular chamber 32, the other end and water tank 41 intercommunication, after suitable temperature is adjusted to the water in the water tank 41, pressurize through the booster pump, flow into annular chamber 32, after the pressure in the annular chamber 32 surpassed the settlement numerical value, the back pressure valve is automatic to be opened, water flows into water tank 41 again through outlet pipe 42. The water in the annular cavity 32 can uniformly apply confining pressure to the hydrate reservoir and maintain the temperature of the hydrate reservoir, and can accurately and stably provide proper temperature and pressure conditions for generating the hydrate reservoir.

In order to enable the probe of the sensor and the collection tube 11 of the collection device to be inserted into the reaction chamber 31, referring to fig. 2, the sleeve structure is provided with a measurement interface 33, and the measurement interface 33 is a through hole formed in the side walls of the inner tube and the outer tube. Of course, in order to maintain the pressure in the reaction chamber 31, a sealing structure, such as a sealing ring, is provided on the measurement port 33, so that when the collection tube 11 of the sensor probe or the collection device passes through the measurement port 33 and enters the reaction chamber 31, the fluid can be prevented from escaping from the measurement port 33 and damaging the pressure environment of the reaction chamber 31.

Preferably, the sleeve structure is circumferentially provided with a plurality of measurement interfaces 33 through which the collection tube 11 and various sensor probes can pass into the reaction chamber 31. More specifically, referring to fig. 2, fig. 2 shows a cross section of the reaction chamber 31, three measurement interfaces 33 are uniformly arranged at intervals in the circumferential direction of the casing structure, and the probe of the temperature sensor 22, the probe of the pressure sensor 21 and the collection tube 11 of the collection device respectively penetrate through the three measurement interfaces 33, so that in the reaction process, detailed and accurate temperature and pressure of the hydrate reservoir at a certain position can be obtained, and the collected pore fluid at the position comprehensively and detailedly reflects the state of the hydrate reservoir at the position, thereby providing guidance for a method for extracting hydrate by carbon dioxide.

Further preferably, a plurality of measurement interfaces 33 arranged circumferentially on the sleeve structure are provided as a set of measurement interfaces 33, and a plurality of sets of measurement interfaces 33 are provided at axial intervals on the sleeve structure. Therefore, the states of the hydrate reservoirs at a plurality of positions can be reflected, the leading edge position of carbon dioxide replacement is verified, the dynamic characteristics of the replacement process and the morphological change of hydrates in the replacement process are further researched, and guidance is provided for researching the natural gas hydrate exploitation process.

As a concrete configuration, the material supply unit includes a first storage tank 51 for storing natural gas, a second storage tank 53 for storing carbon dioxide, and a third storage tank 54 for storing water, the first storage tank 51, the second storage tank 52, and the third storage tank 53 are respectively communicated with the reaction chamber 31 through a first transfer pipe 54, a second transfer pipe 55, and a third transfer pipe 56, and back pressure valves are provided on the first transfer pipe 54, the second transfer pipe 55, and the third transfer pipe 56. The first storage tank 51, the second storage tank 52, and the third storage tank 53 are all high-pressure vessels, and the pressure values of the back-pressure valves on the first transfer pipe 54, the second transfer pipe 55, and the third transfer pipe 56 are set, respectively, so that natural gas, carbon dioxide, and water are transferred into the reaction chamber 31 at the set pressures.

The recycling metering unit comprises a collecting container 61, the collecting container 61 is communicated with the reaction cavity 31 through a recycling pipe 62, and a back pressure valve is arranged on the recycling pipe 62. When the pressure in the reaction chamber 31 exceeds a set value, the back pressure valve on the recovery pipe 62 is automatically opened, and the fluid in the reaction chamber 31 is discharged into the collection container 61 through the recovery pipe 62. The collection container 61 is mainly used for collecting and metering the fluid components and volume discharged from the reaction chamber 31 after the reaction is finished, and is used for analyzing the decomposition degree of the hydrate and evaluating the effect of the production method.

Referring to fig. 3, the apparatus for simulating exploitation of natural gas hydrates according to the preferred embodiment of the present invention includes a reaction vessel, the reaction vessel is a double-layered casing structure, the casing structure includes an inner tube and an outer tube, a reaction chamber 31 is formed inside the inner tube, an annular chamber 32 is formed between the inner tube and the outer tube, a temperature and pressure control unit includes a water tank 41, a water inlet tube 42 and a water outlet tube 43, a booster pump is disposed on the water inlet tube 42, a back pressure valve is disposed on the water outlet tube 43, one end of each of the water inlet tube 41 and the water outlet tube 42 is communicated with the annular. The sleeve structure is provided with three measuring interfaces 33 along the circumferential direction, the three measuring interfaces 33 circumferentially arranged on the sleeve structure are used as a group of measuring interfaces 33, and the sleeve structure is provided with a plurality of groups of measuring interfaces 33 at intervals in the axial direction. Probes of collection tube 11, pressure sensor 21 and temperature sensor 22 of the pore fluid collection device can be advanced into reaction chamber 31 through measurement interface 33. One end of the reaction chamber 31 is respectively communicated with a first storage tank 51 for storing natural gas, a second storage tank 53 for storing carbon dioxide and a third storage tank 54 for storing water through a first delivery pipe 54, a second delivery pipe 55 and a third delivery pipe 56, wherein the first delivery pipe 54, the second delivery pipe 55 and the third delivery pipe 56 are respectively provided with a back pressure valve; the other end of the reaction chamber 31 is communicated with the collection container 61 through a recovery pipe 62, and a back pressure valve is arranged on the recovery pipe 62.

Referring to fig. 4, the present invention further provides an experimental method for simulating the production of natural gas hydrates, which is described below with reference to the apparatus for simulating the production of natural gas hydrates according to the preferred embodiment of the present invention.

S01, simulating a hydrate reservoir. Referring to fig. 3, gravel is filled and compacted in the reaction chamber 31, both ends of the sleeve structure are sealed, back pressure valves on the first delivery pipe 54 and the third delivery pipe 56 are adjusted to inject natural gas and water into the reaction chamber 31 at a set pressure, water in the water tank 41 is adjusted to a proper temperature, and water flows into the annular chamber 32 through the water inlet pipe 42 after being pressurized by the booster pump and then flows out from the water outlet pipe 43 to provide a proper temperature and pressure condition for the reaction chamber 32. After a period of time, hydrates are formed in the gravel pores, completing the simulation of the hydrate reservoir.

And S02, injecting carbon dioxide into the hydrate reservoir. The back pressure valves of the first delivery pipe 54 and the third delivery pipe 56 are closed, and the back pressure valve of the second delivery pipe 55 is opened, so that the carbon dioxide is continuously injected into the reaction chamber 31. Carbon dioxide begins to displace and produce natural gas hydrates.

And S03, extracting pore fluid at each position of the hydrate reservoir. According to theoretical calculation, the position of the reaction development front, such as the position of methane decomposition and the position of carbon dioxide displacement front, is judged, and the needle valve on the collection tube 11 at the position is opened to collect the pore fluid from the position into the collection cavity 12.

And S04, analyzing the components of the pore fluid. If water is collected in the collection cavity 12, the natural gas hydrate is in a decomposition stage; if no water is collected in the collection cavity 12, a valve of the delivery pipe 13 is opened, gas in the collection cavity 12 is transferred to another cavity, the pressure in the cavity is smaller than the simulated formation pressure in the reaction cavity 31, so that hydrate decomposition is induced by depressurization, whether replacement occurs or not is judged after analyzing the gas produced by hydrate decomposition, if the content of carbon dioxide in the gas is more than that of methane, the replacement reaction may start just, if the content of methane is more than that of carbon dioxide, the reaction in the region may just end, and if only carbon dioxide exists, the reaction is already ended.

The device for simulating the exploitation of the natural gas hydrate in the preferred embodiment of the invention can successfully extract the pore fluid of the hydrate reservoir at each position without changing the pressure in the reaction cavity 31, judge the position of the reaction development front, reflect the dynamic change and decomposition process of the natural gas hydrate in the replacement process, and reveal the reaction rule of the natural gas hydrate exploitation by carbon dioxide replacement.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, numerous simple modifications can be made to the technical solution of the invention, including combinations of the individual specific technical features in any suitable way. The invention is not described in detail in order to avoid unnecessary repetition. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.

Claims

1. The pore fluid collecting device is characterized by comprising a collecting pipe (11), a cock (14), a collecting cavity (12) and a delivery pipe (13) which are sequentially connected and used for extending into a hydrate reservoir to collect pore fluid, wherein the cock (14) is matched with the collecting cavity (12) to control the connection and disconnection of the collecting pipe (11) and the collecting cavity (12), and valves are respectively arranged on the collecting pipe (11) and the delivery pipe (13).

2. A void fluid collection device according to claim 1, wherein the cock (14) is rotatably connected to the collection chamber (12), the cock (14) and the collection chamber (12) being provided with through holes, the collection tube (11) being in communication with the collection chamber (12) when the through hole of the collection chamber (12) is opposite to the through hole of the cock (14), the collection tube (11) being in disconnection from the collection chamber (12) when the through hole of the collection chamber (12) is misaligned with the through hole of the cock (14).

3. A device for simulating exploitation of natural gas hydrate is characterized by comprising a material supply unit, a temperature and pressure control unit, a reaction unit, a collection unit and a recovery metering unit,

the reaction unit comprises a reaction vessel, and the material supply unit is connected with the reaction vessel so as to be capable of providing materials required by a synthetic hydrate reservoir;

the temperature and pressure control unit can control the reaction container to have temperature and pressure conditions required for forming a hydrate reservoir;

the collection unit comprises the pore fluid collection device of claim 1 or 2, a pressure sensor (21) and a temperature sensor (22) to enable collection of pore fluid and measurement of pressure and temperature within the reaction vessel;

the recovery metering unit is capable of collecting and metering the composition and volume of the fluid discharged from the reaction vessel.

4. The device for simulating exploitation of natural gas hydrate according to claim 3, wherein the reaction container is a double-layer sleeve structure, the sleeve structure comprises an inner pipe and an outer pipe, the inner part of the inner pipe is formed into the reaction cavity (31), an annular cavity (32) is formed between the inner pipe and the outer pipe, the temperature and pressure control unit comprises a water tank (41), a water inlet pipe (42) and a water outlet pipe (43), a booster pump is arranged on the water inlet pipe (42), a back pressure valve is arranged on the water outlet pipe (43), one end of each of the water inlet pipe (41) and the water outlet pipe (42) is communicated with the annular cavity (32), and the other end of each of the water inlet pipe (41) and.

5. The simulated natural gas hydrate production apparatus as claimed in claim 4, wherein the casing structure is provided with a measuring interface (33), and the measuring interface (33) is a through hole formed in the side wall of the inner pipe and the outer pipe.

6. The simulated production natural gas hydrate apparatus of claim 5 wherein the casing structure is provided with a plurality of measurement ports (33) in a circumferential direction.

7. The simulated natural gas hydrate production apparatus as claimed in claim 6, wherein the plurality of measurement ports (33) circumferentially arranged on the casing structure are provided as a set of measurement ports (33), and the casing structure is provided with a plurality of sets of measurement ports (33) at axial intervals.

8. The apparatus for simulating exploitation of natural gas hydrates according to claim 4, wherein the material supply unit comprises a first storage tank (51) for storing natural gas, a second storage tank (53) for storing carbon dioxide, and a third storage tank (54) for storing water, the first storage tank (51), the second storage tank (52), and the third storage tank (53) are respectively communicated with the reaction chamber (31) through a first delivery pipe (54), a second delivery pipe (55), and a third delivery pipe (56), and back pressure valves are respectively arranged on the first delivery pipe (54), the second delivery pipe (55), and the third delivery pipe (56).

9. The device for simulating the exploitation of natural gas hydrates according to claim 4, wherein the recovery metering unit comprises a collection container (61), the collection container (61) is communicated with the reaction chamber (32) through a recovery pipe (62), and a back pressure valve is arranged on the recovery pipe (62).

10. An experimental method for simulating exploitation of natural gas hydrates is characterized by comprising the following steps:

s01, simulating a hydrate reservoir;

s02, injecting carbon dioxide into the hydrate reservoir stratum;

s03, extracting pore fluid at each position of the hydrate reservoir;

and S04, analyzing the components of the pore fluid.