Hydrate sample porosity and saturation measuring device considering stress influence and measuring and calculating method

Abstract

The invention relates to a hydrate sample porosity and saturation measuring device considering stress influence and a measuring and calculating method. A high-pressure reaction kettle of the device is internally provided with a confining pressure cavity filled with confining pressure liquid; the sample is arranged in the confining pressure cavity, and the outer wall of the sample is wrapped in the flexible sleeve; pores are formed in the sample; the confining pressure system comprises a confining pressure pump; the confining pressure pump is connected with the confining pressure cavity through a pipeline; the back pressure system comprises a back pressure valve; the back pressure valve is connected with the confining pressure cavity through a pipeline; the measuring system is connected with the back pressure valve through a pipeline; the pore pressure system comprises a gas pore pressure inlet valve, a gas pore pressure pipeline pressure gauge, a pressure reducing valve and a high-pressure gas cylinder which are connected in sequence; the gas pore pressure inlet valve is connected with the bottom of the sample through a pipeline; the measuring device can measure the in-situ porosity and saturation of the sediment in the hydrate sample, and the accuracy of establishing the relationship between the hydrate saturation and the physical property is improved by calculating the porosity and saturation of the hydrate sample.

Description

Technical Field

[0001] The invention belongs to the technical field of measuring porosity and saturation of experimentally prepared hydrate sediment samples, and specifically relates to a hydrate sample porosity and saturation measuring device and a measuring calculation method taking stress influence into consideration. Background Art

[0002] In nature, natural gas hydrates exist in the pores of soil sediments in the deep seabed and permafrost areas. Due to their abundant reserves, they are considered one of the most important alternative energy sources in the 21st century and have attracted widespread attention from scholars around the world. Early studies on the physical properties of natural gas hydrates mainly used field coring and geophysical measurements. These studies have long cycles and high costs, making it difficult to conduct a systematic and complete exploration of the physical properties of natural gas hydrates. Later, researchers prepared natural gas hydrate sediment samples in the laboratory and conducted a systematic study of the physical properties of natural gas hydrates.

[0003] In the study of the physical properties of gas hydrate sediment samples, it is necessary to determine the porosity and saturation of the sediments. In conventional methods, the porosity of the sediments is usually measured by mercury injection under normal pressure conditions. Since gas hydrate sediments need to exist stably under certain pressure conditions (confining pressure / pore pressure), changes in pressure will change the porosity of the sediments. Therefore, conventional methods will produce large errors in the porosity measurement of gas hydrate sediments. The accuracy of saturation measurement is directly related to the porosity measurement and will also be greatly affected.

[0004] Accurately measuring porosity and saturation is crucial to establishing an accurate relationship between hydrate saturation and physical properties. In the laboratory, gas hydrate sediment samples need to be generated in situ and physical properties measured. Since changes in pressure will change the porosity of sediments, it is urgent to establish a measurement device and measurement calculation method for the porosity and saturation of hydrate samples in situ that takes into account the influence of stress to improve the accuracy of subsequent analysis. Summary of the invention

[0005] In view of at least one of the problems in the above-mentioned prior art, the object of the present invention is to provide a hydrate sample porosity and saturation measurement device and a measurement calculation method taking into account the influence of stress. The measurement device can measure the in-situ porosity and saturation of sediments in the hydrate sample, and improve the accuracy of establishing the relationship between hydrate saturation and physical properties by calculating the porosity and saturation of the hydrate sample.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A device for measuring porosity and saturation of hydrate samples taking stress influence into consideration, comprising:

[0008] A high-pressure reactor, the interior of which is a confining pressure chamber filled with confining pressure liquid;

[0009] A sample is arranged in the confining pressure chamber, the top of the sample is connected to the top surface of the high-pressure reactor, the bottom of the sample is connected to the bottom surface of the high-pressure reactor, the outer wall of the sample is wrapped in a flexible sleeve, and the flexible sleeve is used to isolate the sample from the confining pressure liquid; the sample has pores;

[0010] A confining pressure system, comprising a confining pressure pump, wherein the confining pressure pump is connected to the confining pressure chamber through a pipeline;

[0011] A back pressure system, comprising a back pressure valve, wherein the back pressure valve is connected to the confining pressure chamber through a pipeline;

[0012] A measuring system connected to the back pressure valve through a pipeline;

[0013] The pore pressure system comprises a gas pore pressure inlet valve, a gas pore pressure pipeline pressure gauge, a pressure reducing valve and a high-pressure gas cylinder which are connected in sequence. The gas pore pressure inlet valve is connected to the bottom of the sample through a pipeline.

[0014] Preferably, a confining pressure valve is provided between the confining pressure pump and the confining pressure chamber.

[0015] Preferably, a pore pressure release pipeline is connected to the top of the sample, and a pore pressure release valve is provided on the pore pressure release pipeline.

[0016] Preferably, the measuring system comprises a measuring cylinder, and the measuring cylinder is connected to the back pressure valve.

[0017] A method for measuring and calculating the porosity and saturation of a hydrate sample considering stress influence is based on the hydrate sample porosity and saturation measuring device considering stress influence as described in any one of the above, and comprises the following steps:

[0018] S01. Obtain the sample volume V and the initial pore volume V1, and calculate the initial sample porosity

[0019] S02, maintaining the pressure of the high-pressure reactor and starting to produce hydrate;

[0020] S03. After hydrate formation, record the pore volume V1 after hydrate formation and calculate the porosity of the sample after hydrate formation.

[0021] S04. Calculate the hydrate saturation. The saturation calculation formula is as follows:

[0022]

[0023] Where: S h is the hydrate saturation, is the initial sample porosity, is the porosity of the sample after hydrate formation.

[0024] Preferably, the step of obtaining the sample volume V and the initial pore volume V1 includes:

[0025] Add a sample into the autoclave, adjust the confining pressure of the confining pressure chamber and the pore pressure of the sample to a preset pressure, at which the pore pressure is P;

[0026] Close all pipeline valves and adjust the pressure reducing valve to increase the pressure in the pipeline between the gas orifice pressure inlet valve and the pressure reducing valve to P+ΔP;

[0027] Open the gas pore pressure inlet valve to connect the gas to the void, and open the back pressure valve to reduce the confining pressure liquid pressure to the initial confining pressure, and record the discharged liquid volume, which is the change in pore volume ΔV;

[0028] After the pore pressure is stable, record the reading of the gas pore pressure line pressure gauge, which is the pore pressure P1 at this time, and calculate the pore compression factor C and the pore volume V1 of the sample;

[0029] According to Boyle's law, the pore volume of the sample is calculated as follows:

[0030]

[0031] Among them, V1 is the initial pore volume, V2 is the volume of the pipeline between the gas pore pressure inlet valve and the sample, and V3 is the volume of the pipeline between the gas pore pressure inlet valve and the pressure reducing valve.

[0032] Preferably, the initial sample porosity is calculated The calculation formula of sample porosity is:

[0033]

[0034] in, is the initial sample porosity, V1 is the initial pore volume, V is the sample volume, d is the flexible sleeve diameter, and l is the flexible sleeve length.

[0035] Preferably, there is a quantitative relationship between the change in pore volume ΔV and the change in pore pressure ΔP, and the relationship formula is:

[0036]

[0037] Where C is the pore compression factor, V1 is the initial pore volume, and σ is the confining pressure;

[0038] The pore compression factor C is calculated by the above formula.

[0039] Preferably, the pore pressure is changed, and the pore volume of the sample under different pore pressures is obtained through the relationship formula between the change in pore volume ΔV and the change in pore pressure ΔP.

[0040] Preferably, after the hydrate formation step, the following steps are performed:

[0041] Close all pipeline valves and adjust the pressure reducing valve to increase the pressure in the pipeline between the gas orifice pressure inlet valve and the pressure reducing valve to P+ΔP;

[0042] Open the gas pore pressure inlet valve to connect the gas pore pressure injection system with the pores, and open the back pressure valve to reduce the confining pressure liquid pressure to the initial confining pressure, and record the discharged liquid volume, which is the change in pore volume ΔV;

[0043] After the pore pressure is stable, record the reading of the gas pore pressure line pressure gauge, which is the pore pressure P1 at this time. Calculate the pore volume V1 after hydrate formation by using the pore compression factor C and the pore volume calculation formula of the sample;

[0044] The porosity of the sample after hydrate formation is calculated using the sample porosity calculation formula.

[0045] The present invention adopts the above technical solution, which has the following advantages:

[0046] 1. The hydrate sample porosity and saturation measurement device and measurement calculation method considering stress influence provided by the present invention can realize the measurement of sample porosity and saturation during the in-situ preparation of the hydrate sample, and improve the accuracy of establishing the relationship between hydrate saturation and physical properties by calculating the porosity and saturation of the hydrate sample.

[0047] 2. The hydrate sample porosity and saturation measurement device and measurement calculation method considering stress influence provided by the present invention take into account the influence of stress change on pore volume.

[0048] 3. The present invention provides a hydrate sample porosity and saturation measurement device and measurement calculation method that considers stress influence, and proposes a method for calculating the pore volume of the sample under different pore pressures based on a set of measurement results. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the principle of a device for measuring the porosity and saturation of a hydrate sample taking into account the influence of stress provided in the first embodiment of the present invention.

[0050] Figure 2 This is a flow chart of a method for measuring and calculating the porosity and saturation of a hydrate sample taking into account the influence of stress, provided in the second embodiment of the present invention.

[0051] Markings in the accompanying drawings:

[0052] 100 is the sample, 1 is the high-pressure reactor, 2 is the confining pressure chamber, 3 is the confining pressure valve, 4 is the confining pressure pump, 5 is the back pressure valve, 6 is the measuring cylinder, 7 is the gas pore pressure inlet valve, 8 is the gas pore pressure pipeline pressure gauge, 9 is the pressure reducing valve, 10 is the high-pressure gas cylinder, and 11 is the pore pressure release valve. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0054] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "front", "rear", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or component referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention. The direction of the arrow in the figure represents the direction of liquid flow.

[0055] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "assembly", "setting", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] The present invention provides a hydrate sample porosity and saturation measurement device and a measurement and calculation method taking stress influence into consideration. The measurement device can measure the in-situ porosity and saturation of sediments in the hydrate sample, and improve the accuracy of establishing the relationship between hydrate saturation and physical properties by calculating the porosity and saturation of the hydrate sample.

[0057] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0058] Example 1

[0059] Please refer to Figure 1 and Figure 2As shown, the present embodiment provides a hydrate sample porosity and saturation measurement device considering stress influence, comprising a high-pressure reactor 1, a sample 100, a confining pressure system, a back pressure system and a measurement system;

[0060] The high-pressure reactor 1 is a flexible high-pressure reactor, the outer side of the high-pressure reactor 1 is a supporting shell, and the interior of the high-pressure reactor 1 is a confining pressure chamber 2 filled with a confining pressure liquid; the confining pressure liquid is used to provide confining pressure for the sample 100, and the confining pressure liquid can be water, ethylene glycol or low-temperature hydraulic oil.

[0061] The sample 100 is arranged in the confining pressure chamber 2, the top of the sample 100 is connected to the top surface of the high-pressure reactor 1, the bottom of the sample 100 is connected to the bottom surface of the high-pressure reactor 1, and the outer wall of the sample 100 is wrapped in a flexible sleeve, which is used to isolate the sample 100 from the confining pressure liquid; there are pores in the sample; and the pore pressure and the confining pressure are independently controlled by the flexible sleeve.

[0062] The confining pressure system includes a confining pressure pump 4, which is a high-pressure infusion pump. The confining pressure pump 4 is connected to the confining pressure chamber 2 through a pipeline. In the experiment, the confining pressure system provides a pressure source for the confining pressure chamber 2. A confining pressure valve 3 is arranged between the confining pressure pump 4 and the confining pressure chamber 2.

[0063] The back pressure system includes a back pressure valve 5, which is connected to the confining pressure chamber 2 through a pipeline. In the experiment, the set pressure of the back pressure valve 5 is set to be the same as the confining pressure. When the confining pressure liquid pressure is higher than the preset confining pressure, the confining pressure liquid is discharged from the back pressure valve 5 to reduce the confining pressure.

[0064] The measuring system includes a measuring cylinder 6, which is connected to the back pressure valve 5 through a pipeline; the measuring cylinder 6 is used to measure the volume of the confining pressure liquid flowing out of the back pressure valve 5, which is the change in the discharged liquid volume, that is, the pore volume.

[0065] The pore pressure system includes a gas pore pressure inlet valve 7, a gas pore pressure line pressure gauge 8, a pressure reducing valve 9 and a high-pressure gas cylinder 10 which are connected in sequence. The gas pore pressure inlet valve 7 is connected to the bottom of the sample 100 through a pipeline. The high-pressure gas cylinder 10 is used as a gas pressure source; the pressure reducing valve 9 is used to control the outflow gas pressure; the gas pore pressure inlet valve 8 is used to disconnect the high-pressure gas cylinder 10 from the high-pressure reactor 1, so that the two form a relatively independent space.

[0066] In this embodiment, a pore pressure release pipeline is connected to the top of the sample 100, and a pore pressure release valve 11 is provided on the pore pressure release pipeline. After the experiment is over, the pressure is released through the pore pressure release pipeline to release the gas in the sample 100, and then the device can be disassembled, the sample 100 can be taken out, and the next experiment can be carried out.

[0067] In this embodiment, all pipelines are seamless steel pipes, and the volume of the pipelines remains unchanged when the pipeline pressure changes.

[0068] Example 2

[0069] Please refer to Figure 2 As shown, this embodiment provides a method for measuring and calculating the porosity and saturation of a hydrate sample considering the influence of stress, which is based on the device for measuring the porosity and saturation of a hydrate sample considering the influence of stress in Example 1, and includes the following steps:

[0070] S01. Obtain the sample volume V and the initial pore volume V1, and calculate the initial sample porosity

[0071] S02, maintaining the pressure of the high-pressure reactor 1 and starting to produce hydrate;

[0072] S03. After hydrate formation, record the pore volume V1 after hydrate formation and calculate the porosity of the sample after hydrate formation.

[0073] S04. Calculate hydrate saturation.

[0074] The saturation calculation formula (1) is as follows:

[0075]

[0076] Where: S h is the hydrate saturation, is the initial sample porosity, is the porosity of the sample after hydrate formation.

[0077] Specifically, during the in-situ hydrate generation process, the porosity and saturation of the hydrate sample considering the stress effect in the experiment are measured and calculated as follows:

[0078] Step 1: Add the sample 100 into the autoclave, and adjust the confining pressure of the confining pressure cavity and the pore pressure of the void to the preset pressure through the confining pressure system and the gas pore pressure injection system respectively. At this time, the pore pressure is P;

[0079] Step 2, close each pipeline valve in the device, adjust the pressure reducing valve 9, so that the pressure in the pipeline between the gas pore pressure inlet valve and the pressure reducing valve increases to P+ΔP, where ΔP is the pore pressure change;

[0080] Step 3: Open the gas pore pressure inlet valve 7 to connect the gas pore pressure injection system with the pores, and open the back pressure valve 5 to reduce the confining pressure liquid pressure to the initial confining pressure. The liquid flows into the measuring cylinder through the confining pressure valve 3. The discharged liquid volume is recorded by the measuring cylinder. The discharged liquid volume is the change in the pore volume ΔV.

[0081] Step 4: After the pore pressure is stable, record the reading of the gas pore pressure line pressure gauge 8, which is the pore pressure P1 at this time, and calculate the pore compression factor C and the pore volume V1 of the sample;

[0082] Step 5: Maintain the pressure of the high-pressure reactor 1 to start hydrate generation. After the hydrate is generated, perform the following steps:

[0083] Close all pipeline valves in the device and adjust the pressure reducing valve 9 to increase the pressure in the pipeline between the gas hole pressure inlet valve and the pressure reducing valve to P+ΔP;

[0084] Open the gas pore pressure inlet valve 7 to connect the gas pore pressure injection system with the pores, and open the back pressure valve 5 to reduce the confining pressure liquid pressure to the initial confining pressure, and record the discharged liquid volume, which is the change in pore volume ΔV;

[0085] After the pore pressure stabilizes, record the reading of the gas pore pressure line pressure gauge. At this time, the pore pressure P1 is calculated through the pore compression factor C and the pore volume calculation formula of the sample to calculate the pore volume V1 after hydrate formation.

[0086] Step 6: Use the sample porosity calculation formula to calculate the sample porosity after hydrate formation. And finally calculate the hydrate saturation.

[0087] In this embodiment, the pore compression factor C and the sample pore volume V1 are calculated;

[0088] According to Boyle's law, formula (2),

[0089] P(V1+V2)+(P+ΔP)V3=P1(V1+V2+V3+ΔV) (2);

[0090] The pore volume calculation is carried out according to Boyle's law, and the pore volume calculation formula (3) of the sample is:

[0091]

[0092] Among them, V1 is the initial pore volume, V2 is the volume of the pipeline between the gas pore pressure inlet valve and the sample, and V3 is the volume of the pipeline between the gas pore pressure inlet valve and the pressure reducing valve.

[0093] V2 is the volume of the pipeline between the gas pore pressure inlet valve and the sample, and the calculation expression (4) is:

[0094]

[0095] Among them, d2 is the diameter of this part of the pipeline, and l2 is the length of this part of the pipeline.

[0096] V3 is the volume of the pipeline between the gas hole pressure inlet valve and the pressure reducing valve 7, and the calculation expression (5) is:

[0097]

[0098] Among them, d3 is the diameter of this part of the pipeline, and l3 is the length of this part of the pipeline.

[0099] After obtaining the initial pore volume, calculate the initial sample porosity The calculation formula (6) for the sample porosity is:

[0100]

[0101] in, is the initial porosity of the sample, V1 is the initial pore volume, V is the sample volume, d is the diameter of the flexible sleeve, and l is the length of the flexible sleeve.

[0102] There is a quantitative relationship between the change in pore volume ΔV and the change in pore pressure ΔP, and the relationship formula (7) is:

[0103]

[0104] Where C is the pore compression factor, V1 is the initial pore volume, and σ is the confining pressure;

[0105] The pore compression factor C can be obtained by calculation using the above formula.

[0106] In this embodiment, after the pore compression factor is obtained, the pore pressure is changed, and the pore volume of the sample under different pore pressures is obtained through the relationship between the change in pore volume ΔV and the change in pore pressure ΔP, without repeated measurement. The change in pore pressure represents the effect of stress change on the sample.

[0107] In this embodiment, after the hydrate of sample 100 is generated, the pore volume V1 after the hydrate is generated is calculated by the pore compression factor C and the pore volume calculation formula (3) of the sample; the porosity of the sample after the hydrate is generated is calculated by the calculation formula (6) of the sample. Substituting these two parameters into the saturation calculation formula (1), the hydrate saturation S is calculated. h .

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for measuring porosity and saturation of hydrate samples taking into account the influence of stress, characterized in that: include: A high-pressure reactor, the interior of which is a confining pressure chamber filled with confining pressure liquid; A sample is arranged in the confining pressure chamber, the top of the sample is connected to the top surface of the high-pressure reactor, the bottom of the sample is connected to the bottom surface of the high-pressure reactor, the outer wall of the sample is wrapped in a flexible sleeve, and the flexible sleeve is used to isolate the sample from the confining pressure liquid; the sample has pores; A confining pressure system, comprising a confining pressure pump, wherein the confining pressure pump is connected to the confining pressure chamber through a pipeline; A back pressure system, comprising a back pressure valve, wherein the back pressure valve is connected to the confining pressure chamber through a pipeline; A measuring system connected to the back pressure valve through a pipeline; The pore pressure system comprises a gas pore pressure inlet valve, a gas pore pressure pipeline pressure gauge, a pressure reducing valve and a high-pressure gas cylinder which are connected in sequence. The gas pore pressure inlet valve is connected to the bottom of the sample through a pipeline.

2. The device for measuring porosity and saturation of hydrate samples considering stress influence according to claim 1, characterized in that: A confining pressure valve is arranged between the confining pressure pump and the confining pressure chamber.

3. The device for measuring porosity and saturation of hydrate samples considering stress influence according to claim 1, characterized in that: The top of the sample is connected with a pore pressure release pipeline, and a pore pressure release valve is arranged on the pore pressure release pipeline.

4. The device for measuring porosity and saturation of hydrate samples considering stress influence according to claim 1, characterized in that: The measuring system comprises a measuring cylinder connected to the back pressure valve.

5. A method for measuring and calculating the porosity and saturation of hydrate samples taking into account the influence of stress, characterized in that: The hydrate sample porosity and saturation measurement device considering stress influence according to any one of claims 1 to 4 is completed, comprising the following steps: S01. Obtain the sample volume V and the initial pore volume V1, and calculate the initial sample porosity S02, maintaining the pressure of the high-pressure reactor and starting to produce hydrate; S03. After hydrate formation, record the pore volume V1 after hydrate formation and calculate the porosity of the sample after hydrate formation. S04. Calculate the hydrate saturation. The saturation calculation formula is as follows: Where: S h is the hydrate saturation, is the initial sample porosity, is the porosity of the sample after hydrate formation.

6. The method for measuring and calculating the porosity and saturation of hydrate samples considering stress influence according to claim 5, characterized in that: The step of obtaining the sample volume V and the initial pore volume V1 includes: Add a sample into the autoclave, adjust the confining pressure of the confining pressure chamber and the pore pressure of the sample to a preset pressure, at which the pore pressure is P; Close all pipeline valves and adjust the pressure reducing valve to increase the pressure in the pipeline between the gas orifice pressure inlet valve and the pressure reducing valve to P+ΔP; Open the gas pore pressure inlet valve to connect the gas to the void, and open the back pressure valve to reduce the confining pressure liquid pressure to the initial confining pressure, and record the discharged liquid volume, which is the change in pore volume ΔV; After the pore pressure is stable, record the reading of the gas pore pressure line pressure gauge, which is the pore pressure P1 at this time, and calculate the pore compression factor C and the pore volume V1 of the sample; According to Boyle's law, the pore volume of the sample is calculated as follows: Among them, V1 is the initial pore volume, V2 is the volume of the pipeline between the gas pore pressure inlet valve and the sample, and V3 is the volume of the pipeline between the gas pore pressure inlet valve and the pressure reducing valve.

7. The method for measuring and calculating the porosity and saturation of hydrate samples considering stress influence according to claim 6, characterized in that: Calculate the initial sample porosity The calculation formula of sample porosity is: in, is the initial sample porosity, V1 is the initial pore volume, V is the sample volume, d is the flexible sleeve diameter, and l is the flexible sleeve length.

8. The method for measuring and calculating the porosity and saturation of hydrate samples considering stress influence according to claim 7, characterized in that: There is a quantitative relationship between the change in pore volume ΔV and the change in pore pressure ΔP, and the relationship formula is: Where C is the pore compression factor, V1 is the initial pore volume, and σ is the confining pressure; The pore compression factor C is calculated by the above formula.

9. The method for measuring and calculating the porosity and saturation of hydrate samples considering stress influence according to claim 8, characterized in that: By changing the pore pressure, the pore volume of the sample under different pore pressures can be obtained through the relationship between the change in pore volume ΔV and the change in pore pressure ΔP.

10. The method for measuring and calculating the porosity and saturation of hydrate samples considering stress influence according to claim 8, characterized in that: After the post-hydrate formation step, the following steps are performed: Close all pipeline valves and adjust the pressure reducing valve to increase the pressure in the pipeline between the gas orifice pressure inlet valve and the pressure reducing valve to P+ΔP; Open the gas pore pressure inlet valve to connect the gas pore pressure injection system with the pores, and open the back pressure valve to reduce the confining pressure liquid pressure to the initial confining pressure, and record the discharged liquid volume, which is the change in pore volume ΔV; After the pore pressure is stable, record the reading of the gas pore pressure line pressure gauge, which is the pore pressure P1 at this time. Calculate the pore volume V1 after hydrate formation by using the pore compression factor C and the pore volume calculation formula of the sample; The porosity of the sample after hydrate formation is calculated using the sample porosity calculation formula.

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