Experimental device and method for component desorption-phase change-pore deformation coupling characteristics of condensate gas in shale multi-scale pore space

Abstract

The invention belongs to the technical field of unconventional natural gas exploration and development, and particularly relates to an experimental device for component desorption-phase change-pore deformation coupling characteristics of condensate gas in a shale multi-scale pore space, which comprises a constant temperature device, a fluid injection system, a nuclear magnetic resonance analysis system and a fluid recovery system, the fluid injection system comprises a high-pressure gas source, a first stop valve, a first plunger pump and a first gas flow meter, the nuclear magnetic resonance analysis system comprises a second stop valve, a low-field nuclear magnetic resonance spectrometer, a sample kettle, a third stop valve and a computer, and the fluid back pressure system comprises a second gas flow meter, a back pressure valve and a second plunger pump; according to the invention, real-time monitoring of fluid phase state change characteristics and pore evolution rules in a multi-scale pore space in the depletion exploitation process of the shale condensate gas reservoir can be realized at the same time, the condensate gas desorption amount in the depletion exploitation process is quantified, and condensate gas desorption-phase change-pore deformation coupling characteristics are explored.

Description

Technical Field

[0001] The present invention belongs to the technical field of unconventional natural gas exploration and development, and specifically relates to an experimental device and method for the desorption-phase change-pore deformation coupling characteristics of condensate gas components in multi-scale pore space of shale. Background Art

[0002] The Jurassic continental shale condensate gas resources in the Sichuan Basin are rich and are expected to become an important formation to start China's "continental shale gas revolution". Depletion production is one of the most commonly used means of developing condensate gas reservoirs. As the pressure decreases during depletion production, gaseous hydrocarbons will condense a portion of liquid hydrocarbons, resulting in "retrograde condensation". After the retrograde condensation phase transition of the condensate gas reservoir, the gas well production capacity is greatly reduced, and the phenomenon of oil and gas co-production is generally presented. Clarifying the oil and gas production law of the condensate gas component is the key to achieving the rational and efficient development of condensate gas reservoirs. However, the heterogeneous pore structure and surface chemical properties of continental shale reservoirs, the diverse fluid occurrence states and phase states, the complex interface effects, and the strong medium deformation characteristics lead to the complex oil and gas production law of shale condensate gas reservoirs, which brings huge challenges to the development of shale condensate gas reservoirs. At the same time, it is difficult to use the development experience of conventional condensate gas reservoirs in the development of shale condensate gas reservoirs, and relevant theoretical understandings need to be explored and innovated.

[0003] At present, there is still a lack of effective experimental means to study the coupling characteristics of condensate gas desorption-phase change-pore deformation in the multi-scale deformation medium space of shale. The constant volume depletion experiment is the most commonly used method to simulate the phase change of condensate gas in the depletion development process of conventional condensate gas reservoirs. This experiment is usually carried out under high temperature and high pressure conditions to simulate the production process of condensate gas under the original formation pressure. In the experiment, the condensate gas sample is depleted at a constant volume in a PVT container. The pressure is gradually reduced to a specific value. After each pressure reduction, the fluid is kept for a period of time to reach a new equilibrium state, and the changes in the phase state of the fluid under different pressures are observed and recorded. This experiment can predict key parameters such as phase change pressure, gas-oil ratio and recovery rate in the depletion development process of condensate gas reservoirs. The influence of porous media can be simulated by adding materials such as glass beads in the PVT container. However, the constant volume depletion experiment cannot quantify the changes in the adsorbed gas content in the porous medium, and cannot determine the deformation behavior of the porous medium. The shale gas isothermal adsorption / desorption experiment is an important experiment in shale gas exploration and development, which can study the adsorption\desorption characteristics of shale to gas and the phase behavior of shale gas. This experiment mainly evaluates the adsorption capacity and desorption characteristics of shale by gradually increasing or decreasing the gas pressure in the shale sample under constant temperature conditions, measuring and recording the adsorption and desorption of gas by shale under different pressures. The fluid phase change pressure can also be determined by the sudden change of the content. However, this experiment can only obtain the total gas content change and phase change pressure in all pore spaces in the sample, but cannot distinguish the difference between desorption and phase change in pores of different scales, and this method cannot consider the deformation behavior of the sample during adsorption / desorption. For complete rock samples, such as coal rock columns, some scholars attach stress plates to the outer surface of the coal rock columns, and during the adsorption / desorption experiment, the deformation behavior of the coal sample can be studied through the stress plates. However, this method can only obtain the volume strain behavior of the complete sample, and cannot obtain the deformation characteristics of pores of different scales in the sample during the adsorption / desorption process, and this method is not suitable for amorphous shale granular samples. Nuclear magnetic resonance (NMR) experiments are an important technical means widely used in the field of unconventional oil and gas development in recent years. By measuring the NMR relaxation signal of saturated 1H fluid in porous media, relevant information such as pore structure, pore size distribution, fluid occurrence characteristics and permeability can be indirectly obtained. Conventional low-field NMR instruments can only test rock samples without temperature and pressure loading, which is far from the high temperature and high pressure environment in which actual rock samples are located in deep reservoirs. In addition, they can only test rock samples before and after the experiment, and cannot monitor the fluid state and phase change characteristics during the depletion production pressure drop in real time. Some scholars have integrated low-field NMR instruments with high-temperature and high-pressure displacement devices to form low-field NMR online testing technology, which can realize real-time monitoring of 1H fluid adsorption / desorption in rock samples under high temperature and high pressure, and can distinguish the fluid state in different types of pores in the sample.However, currently, the low-field NMR instrument is placed at both ends of the core holder. Since the rubber sleeve in the core holder is in contact with the core seal, it mainly tests the fluid content in the micropores, mesopores, macropores and other pore spaces in the sample, and cannot reflect the influence of the bulk phase space such as natural fractures and artificial fractures, and cannot accurately reflect the multi-scale pore space in the shale reservoir. At the same time, the core holder usually contains a complete cylindrical shale core sample, and the fluid adsorption and desorption rate is slow, which makes the experimental test cycle long and the cost high. In addition, the pore size distribution curve of the sample can be obtained by low-field NMR testing, but it is usually used to characterize the pore structure characteristics of shale samples before adsorption and desorption, and does not consider the influence of pore deformation during decompression and desorption. At present, the experimental method for real-time detection of the pore deformation coupling behavior in multi-scale pore space during fluid desorption and phase change needs to be determined. Summary of the invention

[0004] The purpose of the present invention is to provide an experimental research method for the desorption-phase change-pore deformation coupling characteristics of condensate gas components in multi-scale pore space of shale, which can simultaneously realize the real-time monitoring of the phase change characteristics of fluids and the pore evolution law in the multi-scale pore space during the exhaustion exploitation of shale condensate gas reservoirs, quantify the desorption amount of condensate gas during exhaustion exploitation, and explore the desorption-phase change-pore deformation coupling characteristics of condensate gas. The present invention is helpful to support the evaluation of the exhaustion exploitation potential of shale condensate gas, explore the reasonable and efficient development mode of shale condensate gas, and promote the scale and efficiency of shale condensate gas resources.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0006] An experimental device and method for the desorption-phase change-pore deformation coupling characteristics of condensate gas components in multi-scale pore space of shale, comprising a constant temperature device, a fluid injection system, a nuclear magnetic resonance analysis system and a fluid recovery system, wherein the fluid injection system comprises a high-pressure gas source, a first stop valve, a first plunger pump and a first gas flow meter, the nuclear magnetic resonance analysis system is in the constant temperature device, the nuclear magnetic resonance analysis system comprises a second stop valve, a low-field nuclear magnetic resonance instrument, a sample kettle, a third stop valve and a computer, and the fluid back pressure system comprises a second gas flow meter, a back pressure valve and a second plunger pump;

[0007] The high-pressure gas source contains shale condensate mixed gas, and the high-pressure gas source is connected to the first plunger pump through the first stop valve. A first evacuation / vacuuming pipeline, a first gas flow meter, a first pressure gauge and a thermometer are sequentially arranged between the first plunger pump and the sample kettle. The second stop valve is connected between the first plunger pump and the sample kettle. The first gas flow meter is used to measure the total amount of gas injected into the sample kettle. The first pressure gauge is used to measure the pressure of the sample kettle after the condensate gas is injected. The thermometer is used to measure the temperature of the nuclear magnetic resonance analysis system in the constant temperature device.

[0008] The sample kettle is installed in the low-field nuclear magnetic resonance instrument, and the outlet end of the sample kettle is connected to the back pressure valve through the third stop valve and the second gas flow meter, and the outlet end of the sample kettle is also connected to the second pressure gauge and the second emptying / vacuuming pipeline in sequence, the back pressure valve is connected to the second plunger pump, the second pressure gauge is used to measure the pressure of the sample kettle after the condensate gas is desorbed, the second gas flow meter is used to measure the total amount of gas desorbed, and the low-field nuclear magnetic resonance instrument is connected to the computer through a data connection.

[0009] The first plunger pump is an ISCO high-precision pump, and the cylinder of the sample kettle is made of a non-magnetic, hydrogen-free, high-temperature and high-pressure resistant polyetheretherketone material.

[0010] The low-field nuclear magnetic resonance instrument adopts a high-temperature and high-pressure low-field nuclear magnetic resonance instrument.

[0011] The present invention also provides an experimental device and method for testing the desorption-phase change-pore deformation coupling characteristics of condensate gas components in multi-scale pore space of shale, and the experimental method comprises the following steps:

[0012] Step S100: pre-processing before the experiment, preparing the shale samples required for the experiment, configuring the shale condensate mixed gas components, checking that all pipeline connections of the experimental device are leak-free and that the experimental device is in normal working condition;

[0013] Step S200: determining a base signal;

[0014] Step S300: calibrating the hydrocarbon component amount-fluid nuclear magnetic resonance signal amount;

[0015] Step S400: injection and recovery of fluid.

[0016] The step S100 also includes a shale sample preparation step:

[0017] Step S110: Collect 20 shale samples from the target area;

[0018] Step S120: using a crusher to crush the block shale sample, then using a ball mill to grind the shale fragments, and then using a 200-mesh sieve to screen the ground particle sample to collect shale powder less than 75 μm;

[0019] Step S130: extract the prepared shale sample, dry it under vacuum and store it.

[0020] The step S100 also includes a shale condensate mixed gas configuration step:

[0021] Step S140: preparing bottled pure methane gas and bottled pure normal pentane gas with a purity of at least 99%, and preparing a configuration system, the configuration system including instruments such as a gas flow meter, a mixer, and a collection device for gas configuration;

[0022] Step S150: Use nitrogen to evacuate and vacuum the system to eliminate the influence of air and other impurities in the configuration system, open the methane gas cylinder and connect it to the gas flow meter, control the methane flow rate to 0.8 units, add pentane liquid to the evaporation device, turn on the heating device, control the temperature to stably evaporate pentane into gas, connect the evaporation device to the gas flow meter, and control the normal pentane flow rate to 0.2 units;

[0023] Step S160: Connect the gas flow meter outlets of methane and n-pentane to the gas mixer, adjust the flow rates of the two gases to ensure that the molar ratio of methane to pentane reaches 0.8:0.2, turn on the mixer, fully mix the two gases and connect them to the gas collection device for collection, perform component analysis on the collected mixed gas using a gas chromatograph to verify whether the molar ratio of methane to pentane meets the requirements, and obtain a methane + n-pentane mixed gas with a molar ratio of 0.8:0.2.

[0024] The step S200 includes the following steps:

[0025] Step S210: When the sample kettle is empty, the temperature of the entire nuclear magnetic resonance analysis system is restored to the actual reservoir temperature condition by using a constant temperature device;

[0026] Step S220: Open all valves of the experimental device, use the first evacuation / vacuuming pipeline and the second evacuation / vacuuming pipeline to evacuate the experimental device, and the evacuation time is not less than 12 hours to eliminate the air in the system. After the empty sample kettle is evacuated, use a low-field nuclear magnetic resonance instrument to measure its nuclear magnetic signal as the base signal of the empty sample kettle;

[0027] Step S230: Fill the sample kettle with shale samples, the filling amount of the shale samples in the sample kettle does not exceed two-thirds of the capacity of the sample kettle, and use a constant temperature device to restore the temperature of the entire nuclear magnetic resonance analysis system to the actual reservoir temperature condition;

[0028] Step S240: Open all valves of the experimental device, use the first emptying / vacuuming pipeline and the second emptying / vacuuming pipeline to evacuate the experimental device for no less than 12 hours to eliminate the air in the system. After the sample kettle filled with shale samples is evacuated, use a low-field nuclear magnetic resonance instrument to measure its nuclear magnetic signal as the base signal of the sample kettle filled with shale samples.

[0029] The step S300 specifically includes performing the following operations on the empty sample kettle and the sample kettle filled with shale samples respectively:

[0030] Step S310: Open the first stop valve and the second stop valve, and inject the shale condensate mixed gas in the high-pressure gas source into the sample kettle through the first plunger pump. During this process, the pressure of the sample kettle is monitored by the first pressure gauge, and the total amount of gas injected is measured by the first gas flow meter;

[0031] Step S320: After the fluid in the sample kettle is fully saturated, close the first stop valve and the second stop valve, open the third stop valve, and use the back pressure valve and the second plunger pump to gradually reduce the outlet pressure of the sample kettle to achieve desorption of the condensate gas in the sample kettle. During the desorption process, use the second gas flowmeter to measure the total amount of desorbed gas to achieve calibration of the amount of hydrocarbon components in pores of different scales and the amount of fluid nuclear magnetic resonance signals.

[0032] The step S400 includes the following steps:

[0033] Step S410: taking out the shale sample from the sample kettle, and repeating step S100 to inspect the experimental device;

[0034] Step S420: repeat the operation steps of step S200, refill the shale sample, restore the sample kettle temperature and perform vacuum treatment to complete the pre-experimental pretreatment;

[0035] Step S430: Open the first stop valve and the second stop valve, and use the first plunger pump to inject the condensate gas component from the high-pressure gas source into the sample kettle. During the injection process, use the first pressure gauge to monitor the pressure of the sample kettle in real time until the pressure of the sample kettle restores the pressure condition of the target reservoir, and then close the first stop valve and the second stop valve;

[0036] Step S440: leaving the experimental device at rest for 6 hours to allow the injected fluid to fully contact the shale sample and fully restore the original occurrence state of the hydrocarbon fluid molecules under the actual target reservoir conditions;

[0037] Step S450: After the fluid in the sample kettle is fully saturated, the third stop valve is opened, and the outlet pressure of the sample kettle is gradually reduced by using the back pressure valve and the second plunger pump to achieve desorption of the condensate gas in the sample kettle under different pressure conditions;

[0038] Step S460: During the desorption process, the transverse NMR relaxation time T2 spectra in the sample kettle at different pressures are recorded in real time, and the signal peak amplitude integral of the T2 spectrum curve is used, combined with the hydrocarbon component amount-fluid NMR signal amount relationship calibrated in step S300, to determine the condensate gas component content at different pressures in different types of spaces in the sample kettle.

[0039] Compared with the prior art, the present invention has the following advantages:

[0040] 1. Conventional low-field nuclear magnetic resonance instruments can only test rock samples without temperature and pressure loading, which is far from the high temperature and high pressure environment in which the actual rock samples are located in deep reservoirs. In addition, they can only test rock samples before and after the experiment, and cannot monitor the phase change characteristics of the fluid and the pore evolution law of the rock samples in the process of depletion production, compression and absorption in real time. The improved high temperature and high pressure low-field nuclear magnetic resonance analysis system to be used in the present invention can simulate the adsorption, phase change and desorption process of hydrocarbon components by combining fluid injection and fluid recovery modules, and can monitor the phase change characteristics of the fluid and the pore evolution law of the rock samples in real time during the above dynamic process.

[0041] 2. The pore structure of shale reservoirs is complex, with the characteristics of coexistence of multiple types of pore structures. Pore spaces of different scales will have different effects on the desorption characteristics and phase behavior of condensate gas components. At the same time, the deformation characteristics of pore spaces of different scales are also different. Past physical experiments did not consider the impact of multiple types of pore spaces. This project intends to use a high-temperature, high-pressure, low-field nuclear magnetic resonance instrument to add a sample kettle. By adding shale samples to the sample kettle, a multi-scale pore space is constructed, thereby considering the impact of pore spaces of different scales, and real-time monitoring of the phase change characteristics of fluids in pore spaces of different scales and the pore evolution laws of rock samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention is further illustrated by means of the non-limiting examples given in the accompanying drawings.

[0043] Figure 1 It is a schematic diagram of the overall structure of the experimental device of the present invention;

[0044] Figure 2 To study the coupling characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale;

[0045] Figure 3 It is the calibration process of hydrocarbon component quantity-NMR signal quantity in multi-scale pore space of shale;

[0046] Figure 4 It is the analysis process of pore deformation law in multi-scale pore space of shale;

[0047] Figure 5This is a schematic diagram of the phase change of condensate gas components and the change of pore deformation NMR T2 spectrum of shale samples during the "re-evaporation" process of shale condensate gas;

[0048] The main component symbols are described as follows:

[0049] High-pressure gas source 1, first stop valve 2, first plunger pump 3, first evacuation / vacuuming pipeline 4, first gas flowmeter 5, first pressure gauge 6, thermometer 7, second stop valve 8, low-field nuclear magnetic resonance apparatus 9, sample kettle 10, third stop valve 11, constant temperature device 12, computer 13, second pressure gauge 14, second gas flowmeter 15, second evacuation / vacuuming pipeline 16, back pressure valve 17, second plunger pump 18. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0051] Embodiment 1:

[0052] like Figure 1 The experimental device and method for the desorption-phase change-pore deformation coupling characteristics of condensate gas components in multi-scale pore space of shale shown in the figure include a constant temperature device 12, a fluid injection system, a nuclear magnetic resonance analysis system and a fluid recovery system, the fluid injection system includes a high-pressure gas source 1, a first stop valve 2, a first plunger pump 3 and a first gas flow meter 5, the nuclear magnetic resonance analysis system is in the constant temperature device 12, the nuclear magnetic resonance analysis system includes a second stop valve 8, a low-field nuclear magnetic resonance instrument 9, a sample kettle 10, a third stop valve 11 and a computer 13, and the fluid back pressure system includes a second gas flow meter 15, a back pressure valve 17 and a second plunger pump 18;

[0053] The high-pressure gas source 1 contains shale condensate mixed gas, and the high-pressure gas source 1 is connected to the first plunger pump 3 through the first stop valve 2. The first emptying / vacuuming pipeline 4, the first gas flow meter 5, the first pressure gauge 6 and the thermometer 7 are sequentially arranged between the first plunger pump 3 and the sample kettle 10. The second stop valve 8 is connected between the first plunger pump 3 and the sample kettle 10. The first gas flow meter 5 is used to measure the total amount of gas injected into the sample kettle 10. The first pressure gauge 6 is used to measure the pressure of the sample kettle 10 after the condensate gas is injected. The thermometer 7 is used to measure the temperature of the nuclear magnetic resonance analysis system in the constant temperature device 12;

[0054] The sample kettle 10 is installed in the low-field nuclear magnetic resonance instrument 9, and the outlet end of the sample kettle 10 is connected to the back pressure valve 17 through the third stop valve 11 and the second gas flow meter 15, and the outlet end of the sample kettle 10 is also connected to the second pressure gauge 14 and the second emptying / vacuuming pipeline 16 in sequence, the back pressure valve 17 is connected to the second plunger pump 18, the second pressure gauge 14 is used to measure the pressure of the sample kettle 10 after the condensate gas is desorbed, the second gas flow meter 15 is used to measure the total amount of gas desorbed, and the low-field nuclear magnetic resonance instrument 9 is connected to the computer 13 through a data connection.

[0055] As a further preference of this embodiment, the first plunger pump 3 is an ISCO high-precision pump, and the cylinder of the sample kettle 10 is made of a non-magnetic, hydrogen-free, high-temperature and high-pressure resistant polyetheretherketone material.

[0056] As a further preference of this embodiment, the low-field nuclear magnetic resonance instrument 9 adopts a high-temperature and high-pressure low-field nuclear magnetic resonance instrument, which can invert the fluid content, distribution and fluid-containing pore structure information by testing the relaxation process of 1H-containing fluid in porous media under a high-temperature and high-pressure environment in a deep reservoir under an external magnetic field, and has the characteristics of non-destructive, fast and accurate.

[0057] Embodiment 2:

[0058] Based on the experimental device provided in Example 1, an experimental method is proposed, comprising the following steps:

[0059] Step S100: pre-treatment before the experiment, prepare the shale samples required for the experiment, configure the shale condensate mixed gas components, check that all pipeline connections of the experimental device are leak-free and the experimental device is in normal working condition; this step also includes the shale sample preparation step and the shale condensate mixed gas configuration step, which are as follows:

[0060] Step S110: Collect 20 shale samples from the target area. The TOC of the shale samples is greater than 2%, and each sample is greater than 300g;

[0061] Step S120: using a crusher to crush the block shale sample, then using a ball mill to grind the shale fragments, and then using a 200-mesh sieve to screen the ground particle sample to collect shale powder less than 75 μm;

[0062] Step S130: extract the prepared shale sample, dry it under vacuum and store it.

[0063] Step S140: preparing bottled pure methane gas and bottled pure normal pentane gas with a purity of at least 99%, and preparing a configuration system, the configuration system including instruments such as a gas flow meter, a mixer, and a collection device for gas configuration;

[0064] Step S150: Use nitrogen to evacuate and vacuum the system to eliminate the influence of air and other impurities in the configuration system, open the methane gas cylinder and connect it to the gas flow meter, control the methane flow rate to 0.8 units, add pentane liquid to the evaporation device, turn on the heating device, control the temperature to stably evaporate pentane into gas, connect the evaporation device to the gas flow meter, and control the normal pentane flow rate to 0.2 units;

[0065] Step S160: Connect the gas flow meter outlets of methane and n-pentane to the gas mixer, adjust the flow rates of the two gases to ensure that the molar ratio of methane to pentane reaches 0.8:0.2, turn on the mixer, fully mix the two gases and connect them to the gas collection device for collection, perform component analysis on the collected mixed gas using a gas chromatograph to verify whether the molar ratio of methane to pentane meets the requirements, and obtain a methane + n-pentane mixed gas with a molar ratio of 0.8:0.2.

[0066] Step S200: Determine the base signal; in this step, the following operation steps are specifically included:

[0067] Step S210: When the sample kettle 10 is empty, the temperature of the entire nuclear magnetic resonance analysis system is restored to the actual reservoir temperature condition of 347K by using the constant temperature device 12;

[0068] Step S220: Open all valves of the experimental device, use the first evacuation / vacuuming pipeline 4 and the second evacuation / vacuuming pipeline 16 to evacuate the experimental device, and the evacuation time is not less than 12 hours to eliminate the air in the system to avoid its influence on the NMR relaxation results of the hydrocarbon components. After the empty sample kettle 10 is evacuated, use the low-field NMR instrument 9 to measure its NMR signal as the base signal of the empty sample kettle 10;

[0069] Step S230: Fill the sample kettle 10 with shale samples, the amount of shale samples filled in the sample kettle 10 not exceeding two-thirds of the capacity of the sample kettle 10, and use the constant temperature device 12 to restore the temperature of the entire nuclear magnetic resonance analysis system to the actual reservoir temperature condition;

[0070] Step S240: Open all valves of the experimental device, and use the first emptying / vacuuming pipeline 4 and the second emptying / vacuuming pipeline 16 to evacuate the experimental device. The vacuuming time is not less than 12 hours to eliminate the air in the system to avoid its influence on the nuclear magnetic resonance relaxation results of the hydrocarbon components. After the sample kettle 10 filled with shale samples is evacuated, use the low-field nuclear magnetic resonance instrument 9 to measure its nuclear magnetic signal as the base signal of the sample kettle 10 filled with shale samples.

[0071] Step S300: Calibrate the hydrocarbon component amount-fluid NMR signal amount; in this step, the following operations are performed on the empty sample kettle 10 and the sample kettle 10 filled with shale samples respectively:

[0072] Step S310: Open the first stop valve 2 and the second stop valve 8, and inject the shale condensate mixed gas in the high-pressure gas source 1 into the sample kettle 10 through the first plunger pump 3. During this process, the pressure of the sample kettle 10 is monitored by the first pressure gauge 6, and the total amount of gas injected is measured by the first gas flow meter 5;

[0073] Step S320: After the fluid in the sample kettle 10 is fully saturated, close the first stop valve 2 and the second stop valve 8, open the third stop valve 11, and use the back pressure valve 17 and the second plunger pump 18 to gradually reduce the outlet pressure of the sample kettle 10 to achieve desorption of the condensate gas in the sample kettle 10. During the desorption process, use the second gas flowmeter 15 to measure the total amount of desorbed gas to achieve calibration of the amount of hydrocarbon components in pores of different scales and the amount of fluid nuclear magnetic resonance signals;

[0074] Different scales specifically refer to the micropores, mesopores and macropores of shale samples, and the dissolved state, adsorbed state and free state of pore fluids correspond to them respectively. In the experiment, the pore space in which the pore fluid is located can be judged by its occurrence state. The empty sample kettle and the sample kettle filled with shale samples here are just operations used for pre-treatment before the experiment to quantitatively calibrate pore fluids in different occurrence states.

[0075] Step S400: injection and recovery of fluid; in this step, the following operation steps are specifically included:

[0076] Step S410: taking out the shale sample from the sample kettle 10, and repeating step S100 to inspect the experimental device;

[0077] Step S420: repeat the operation steps of step S200, refill the shale sample, restore the temperature of the sample kettle 10, and perform vacuum treatment to complete the pre-experimental pretreatment;

[0078] Step S430: Open the first stop valve 2 and the second stop valve 8, and use the first plunger pump 3 to inject the condensate gas component from the high-pressure gas source 1 into the sample kettle 10. During the injection process, use the first pressure gauge 6 to monitor the pressure of the sample kettle 10 in real time until the pressure of the sample kettle 10 is restored to the pressure condition of the target reservoir 48MPa, and then close the first stop valve 2 and the second stop valve 8;

[0079] Step S440: leaving the experimental device at rest for 6 hours to allow the injected fluid to fully contact the shale sample and fully restore the original occurrence state of the hydrocarbon fluid molecules under the actual target reservoir conditions;

[0080] Step S450: After the fluid in the sample kettle 10 is fully saturated, the third stop valve 11 is opened, and the outlet pressure of the sample kettle 10 is gradually reduced by the back pressure valve 17 and the second plunger pump 18, so as to realize the desorption of the condensate gas in the sample kettle 10 under different pressure conditions;

[0081] Step S460: During the desorption process, the NMR transverse relaxation time T2 spectra in the sample kettle 10 at different pressures are recorded in real time, and the signal peak amplitude integral of the T2 spectrum curve is used, combined with the hydrocarbon component amount-fluid NMR signal amount relationship calibrated in step S300, to determine the condensate gas component content at different pressures in different types of spaces in the sample kettle 10.

[0082] Embodiment 3:

[0083] By using the experimental device for the desorption-phase change-pore deformation coupling characteristics of condensate gas components in the multi-scale pore space of shale, combined with the experimental method for the desorption-phase change-pore deformation coupling characteristics of condensate gas components in the multi-scale pore space of shale, the analysis of the desorption-phase change-pore deformation coupling characteristics of condensate gas components in the multi-scale pore space of shale during depletion depressurization mining can be systematically realized, specifically including the following three aspects:

[0084] A1: Calibration of hydrocarbon component quantity-fluid NMR signal quantity. Considering the different relaxation contributions of dissolved, adsorbed and free states of hydrocarbon components, shale samples and empty sample kettles are proposed to calibrate the corresponding relationship between dissolved, adsorbed and free states of hydrocarbon components and NMR signal quantity. First, the fluid NMR signal is obtained by deducting the base signal from the NMR signal tested during the desorption process. For free hydrocarbons, an empty sample kettle is proposed for calibration. In theory, there is only one signal peak in the fluid NMR signal, corresponding to the free hydrocarbons. The corresponding relationship can be expressed as:

[0085] Formula (1): xA1 = Q1;

[0086] In the formula, x is the coefficient corresponding to free hydrocarbons, A1 is the nuclear magnetic signal corresponding to free hydrocarbons, and Q1 is the occurrence of free hydrocarbons.

[0087] During the calibration process, a gas flow meter is used to measure the total amount of gas entering the empty sample kettle and the total amount of gas discharged from the empty sample kettle. The two are subtracted to obtain the free hydrocarbon content Q1 in the empty sample kettle. The pressure at the outlet of the empty sample kettle is changed by a fluid recovery system. Each time the pressure is changed, the change in the total amount of gas in the empty sample kettle is measured to obtain the free hydrocarbon content Q1 in the empty sample kettle under different pressures. Combined with the change in the fluid nuclear magnetic signal Q1 during the test, the corresponding data between the free hydrocarbon content Q1 and the fluid nuclear magnetic signal A1 under different fluid pressures can be obtained. Finally, based on the corresponding data between the free hydrocarbon content Q1 and the fluid nuclear magnetic signal A1, the least squares method is used to fit the coefficient x, thereby realizing the calibration of the corresponding relationship between the free hydrocarbon content and its nuclear magnetic signal. In the formal test, the free hydrocarbon content can be directly determined by combining the above-mentioned calibrated corresponding relationship with the free hydrocarbon nuclear magnetic signal.

[0088] For dissolved and adsorbed hydrocarbons, shale samples are proposed for calibration. For shale samples, the nuclear magnetic resonance signal theoretically has three signal peaks, corresponding to dissolved, adsorbed and free hydrocarbons respectively. During the calibration process, a gas flow meter is used to measure the total amount of gas entering the shale sample kettle and the total amount of gas discharged from the shale sample kettle. The total amount of hydrocarbons in the shale sample kettle Q0 is obtained by subtracting the two. The corresponding relationship between the calibrated free hydrocarbon amount Q1 and the fluid nuclear magnetic resonance signal amount A1 is used, combined with the nuclear magnetic resonance signal amount A1 corresponding to the free hydrocarbons in the nuclear magnetic resonance T2 spectrum, the amount of free hydrocarbons in the shale sample Q1 is determined, and the amount of free hydrocarbons Q1 is subtracted from the measured total hydrocarbon amount Q0 to obtain the amount of adsorbed and dissolved hydrocarbons Q0-Q1. The fluid recovery system changes the pressure at the outlet of the sample kettle. Each time the pressure is changed, the change in the total gas volume in the shale sample kettle is measured. The free hydrocarbon content Q1 in the shale sample is determined by combining the corresponding relationship between the free hydrocarbon content Q1 calibrated in the empty sample kettle and the fluid nuclear magnetic signal A1 and the nuclear magnetic signal A1 corresponding to the free hydrocarbon in the nuclear magnetic resonance T2 spectrum. The free hydrocarbon content Q1 is deducted from the total hydrocarbon content Q0 measured under different pressures to obtain the corresponding data between the adsorbed and dissolved hydrocarbon content Q0-Q1 and the adsorbed and dissolved fluid nuclear magnetic signal under different fluid pressures. It is assumed that the corresponding relationship between the adsorbed and dissolved hydrocarbon content Q0-Q1 and the adsorbed and dissolved fluid nuclear magnetic signal is a simple linear relationship, which can be expressed as:

[0089] Formula (2): yA2 = Q2;

[0090] Formula (3): zA3=Q3;

[0091] Where y and z are the coefficients corresponding to adsorbed hydrocarbons and free hydrocarbons, A2 and A3 are the fluid NMR signal quantities corresponding to adsorbed hydrocarbons and free hydrocarbons, respectively, and Q2 and Q3 are the total hydrocarbon reserves and the free hydrocarbon reserves, respectively.

[0092] The total hydrocarbon reserves, free hydrocarbon reserves, adsorbed hydrocarbon reserves and dissolved hydrocarbon reserves satisfy the following relationship:

[0093] Formula (4): Q0 = Q1 + Q2 + Q3;

[0094] Combining equations (2), (3) and (4), the coefficients y and z corresponding to the adsorbed hydrocarbons and free hydrocarbons can be obtained by fitting the least square method based on the corresponding data between the adsorbed and dissolved hydrocarbon reserves Q2 and Q3 and their fluid nuclear magnetic resonance signal quantities A2 and A3, respectively, so as to calibrate the corresponding relationship between the adsorbed and dissolved hydrocarbon reserves and their fluid nuclear magnetic resonance signal quantities. In formal tests, the reserves of adsorbed and dissolved hydrocarbons can be directly determined through the above-mentioned calibrated corresponding relationship combined with the adsorbed and dissolved hydrocarbon nuclear magnetic resonance signal quantities.

[0095] In order to obtain more stable and reliable data fitting results, and taking into account the specific experimental conditions, the number of corresponding data groups required for the above two experiments should be between 10 and 20 groups. Combined with the above-mentioned calibrated relationship between the amount of dissolved, adsorbed and free hydrocarbon components and the amount of fluid NMR signals, the microscopic distribution state of hydrocarbon components in multi-scale space can be quantified.

[0096] A2: Analysis of phase change rules. It is planned to combine the NMR T2 spectrum curve tested during the desorption and phase change of the fluid components and the changes in the pressure in the sample kettle to monitor the phase change rules of the fluids in different types of storage spaces in the shale samples in real time. The phase change of the fluid components is determined by the sudden change of the NMR signal on the NMR T2 spectrum curve. When the phase of the fluid components changes, the NMR signal will change significantly. Combined with the reading of the pressure gauge during the desorption process, the phase change pressure of the fluid components at the reservoir temperature can be determined. Combined with the T2 spectrum curve of the NMR of the shale sample, the fluid in the sample kettle is finely divided into dissolved state, adsorbed state and free state. According to the changes in the NMR T2 spectrum nuclear magnetic signal corresponding to each type of fluid storage space, the phase change rules of the fluid components in the different scale storage spaces of the shale samples are determined.

[0097] A3: Analysis of pore deformation law: It is planned to monitor the pore deformation law of shale in real time based on the nuclear magnetic resonance T2 spectrum curve tested during the desorption and phase change of fluid components. The transverse relaxation time T2 of the fluid in the shale sample is mainly contributed by the surface relaxation term. The relaxation time of the pore fluid can be expressed as:

[0098] Formula (5): Where T2 is the transverse relaxation time, ρ2 is the transverse surface relaxation rate, S is the pore surface area, and V is the pore volume.

[0099] If it is assumed that the pores inside the shale sample have a simple shape, the above formula can be converted to:

[0100] Formula (6): In the formula, F s is the geometric shape factor and r is the pore radius.

[0101] Furthermore, the pore radius r can be expressed as:

[0102] Formula (7): r = ρ2F s T2;

[0103] For the same pore space of the same shale sample, the geometric shape factor F in the above formula is s and the transverse surface relaxation rate ρ2 are both constants, so the pore radius r is proportional to the transverse relaxation time T2. The longer the transverse relaxation time T2, the larger the corresponding pore radius r. Considering the multi-scale pore space of shale, the geometric shape factor F corresponding to the storage space of dissolved, adsorbed and free hydrocarbons is s The lateral surface relaxation rate ρ2 and the transverse surface relaxation rate ρ2 need to be measured separately. It should be noted that due to the continuous discharge of the fluid in the shale sample in the sample kettle during the desorption process, this study cannot obtain the pore volume and porosity changes of the shale sample based on the amplitude of the T2 spectrum nuclear magnetic resonance signal.

[0104] Based on the above theoretical foundation, this test explores the changes in the pore size distribution of shale samples during the desorption process, as well as the changes in the pore size range and average pore size of different types of pores. The key to obtaining the pore radius r of the shale sample through conversion of formula (7) is to determine the geometric shape factor F of the shale sample. s and the transverse surface relaxation rate ρ2.

[0105] It is planned to identify the main pore morphology of shale samples by scanning electron microscopy, and then determine the geometric shape factor F s For slit pores, cylindrical pores, and spherical pores, the corresponding geometric shape factors are 1, 2, and 3, respectively. Considering the multi-scale pore space of shale, the pore shapes of different scales have an effect on the geometric shape factor F. s The contribution of different scales of pore space is different, and the geometric shape factor F s There is a difference.

[0106] It is planned to identify the pore morphology distribution of shale samples under multi-scale pore space by scanning electron microscopy. During the scanning process, in order to ensure the accuracy and rationality of the measurement results, at least three shale samples are scanned, and each shale sample is scanned at least once in the x, y and z directions. For the obtained scanning electron microscope images, the relevant image analysis software is used to calculate the basic parameters such as the perimeter, area, major axis, minor axis, etc. of the pores, and the geometric shape factor F of pore spaces of different scales. s Different from the above-mentioned basic parameters, the pore space of shale samples is precisely divided into different scales: the pore space corresponding to dissolved hydrocarbons has a pore size of less than 1 nm; the pore space corresponding to adsorbed hydrocarbons has a pore size of 1-50 nm; the pore space corresponding to free hydrocarbons has a pore size greater than 50 nm. Based on the precisely divided multi-scale pore sizes, the geometric shape factors F corresponding to the storage spaces of dissolved, adsorbed and free hydrocarbons are calculated respectively. s .

[0107] For a specific scale of pore diameter, the pore shape coefficient is further determined using relevant software based on the basic parameters determined above. The pore shape coefficient can characterize the roundness or roughness of the pore. The lower the pore shape coefficient, the more irregular the pore edge. The specific shape of the pore is judged by its size: when the pore shape coefficient is 1, it represents a spherical pore; when the pore shape coefficient is between 1 and 2, it represents a cylindrical pore; when the pore shape coefficient is between 2 and 3, it represents a slit pore. After determining the pore shape distribution in the scanning electron microscope image, the pore areas of spherical pores, cylindrical pores and slit pores are calculated using relevant image analysis software. For a specific scale of pore space, its surface ratio is a constant. Therefore, the ratio of the pore areas of spherical pores, cylindrical pores and slit pores is the ratio of their corresponding pore volumes, so that the weight of the entire pore space occupied by the spherical pores, cylindrical pores and slit pores in the scanning electron microscope image can be obtained. For all the scanning electron microscope images of shale samples obtained, the weighted average of the weights of the entire pore space occupied by all spherical pores, cylindrical pores and slit pores is taken to obtain the final weight of the entire pore space occupied by the spherical pores, cylindrical pores and slit pores. Finally, according to the final weight of the entire pore space occupied by the spherical pores, cylindrical pores and slit pores, the weighted average of the geometric shape factors of the spherical pores, cylindrical pores and slit pores is taken, and finally the geometric shape factor F of the pore space of different scales of the shale sample can be obtained. s The geometric shape factor F of pores at different scales in shale s It can be expressed as:

[0108] Formula (9): F s =x1f1+x2f2+x3f3;

[0109] Among them, f1, f2 and f3 represent the geometric shape factors corresponding to spherical pores, cylindrical pores and slit pores, respectively, and are 1, 2 and 3 respectively. x1, x2 and x3 represent the weights of the entire pore space occupied by spherical pores, cylindrical pores and slit pores, respectively.

[0110] It is proposed to indirectly obtain the transverse surface relaxation rate ρ2 by combining the nitrogen adsorption curve. First, the nitrogen adsorption test results are used to obtain the pore surface area S through the BET model, and the pore volume V through the BJH model, and then the S / V is obtained. Considering the multi-scale pore space of shale, there are differences between the pore surface area S and pore volume V of different scale spaces. Assuming that the pore surface area S and pore volume V of different scale pore spaces have the same change range, the pore spaces of different scales have the same S / V, and then the logarithmic average value T of the T2 spectrum is calculated. 2LMConsidering the multi-scale pore space of shale, the occurrence state and occurrence amount of hydrocarbon components in pore spaces of different scales are different, resulting in differences in the logarithmic average values ​​of T2 spectra in pore spaces of different scales. Therefore, the logarithmic average values ​​of T2 spectra in pore spaces of different scales need to be measured separately. For the pore spaces corresponding to the dissolved state, adsorbed state and free state, the three signal peaks from left to right in the nuclear magnetic resonance T2 spectrum are respectively corresponding to the three signal peaks in the nuclear magnetic resonance T2 spectrum. The logarithmic average values ​​of T2 spectra are calculated respectively, so as to obtain the logarithmic average values ​​of T2 spectra in pore spaces of different scales. 2LM . Corresponding to T 2LM The calculation formula is:

[0111] Formula (8): Where, T 2i is T2 of the i-th point; A i is the amplitude of the i-th point, A T is the total amplitude of the T2 spectrum.

[0112] Then, the logarithmic mean value T of the T2 spectrum is calculated according to formula (8): 2LM Considering the multi-scale pore space of shale, the occurrence state and occurrence amount of hydrocarbon components in pore spaces of different scales are different, resulting in differences in the logarithmic average values ​​of T2 spectra in pore spaces of different scales. Therefore, the logarithmic average values ​​of T2 spectra in pore spaces of different scales need to be measured separately. For the pore spaces corresponding to the dissolved state, adsorbed state and free state, the three signal peaks from left to right in the nuclear magnetic resonance T2 spectrum are respectively corresponding to the three signal peaks in the nuclear magnetic resonance T2 spectrum. The logarithmic average values ​​of T2 spectra are calculated respectively, so as to obtain the logarithmic average values ​​of T2 spectra in pore spaces of different scales. 2LM .

[0113] At the same time, due to the continuous discharge of fluid from the shale sample in the sample kettle during the desorption process, the NMR T2 spectrum changes continuously with pressure. Therefore, the logarithmic average value of the T2 spectrum T 2LM As a function of desorption pressure, the logarithmic mean value of T2 spectrum at different desorption pressures during the test analysis process is T 2LM It is planned to change different desorption pressures through the fluid recovery system during the above desorption test, and record the nuclear magnetic resonance T2 spectrum under the corresponding pressure to determine the logarithmic average value T of the T2 spectrum under different desorption pressures. 2LM .

[0114] According to the logarithmic average T2 spectrum at different desorption pressures 2LM , thereby calibrating the desorption pressure and the logarithmic average value of the T2 spectrum T 2LM The corresponding relationship:

[0115] Formula (10): Where, P is the desorption pressure, is the logarithmic mean value of T2 spectrum2LM The corresponding relationship between it and the desorption pressure P.

[0116] According to the obtained specific surface area value S / V and the logarithmic average value T of T2 spectrum 2LM , combined with formula (5), the lateral surface relaxation rate ρ2 of shale samples under different desorption pressures is obtained:

[0117] Formula (11): Where Z is the specific surface area, and its value is S / V.

[0118] For the pore spaces corresponding to the dissolved, adsorbed and free states, the occurrence states and occurrence amounts of hydrocarbon components in pore spaces of different scales are different, resulting in differences in the logarithmic average values ​​of the T2 spectra of pore spaces of different scales. For the three signal peaks in the nuclear magnetic resonance T2 spectrum, the logarithmic average values ​​of the T2 spectrum are calculated respectively using the above analysis process, thereby obtaining the logarithmic average values ​​of the T2 spectrum at different desorption pressures of pore spaces of different scales. 2LM .

[0119] Finally, the geometric shape factor F of the multi-scale pore space of the shale sample is obtained. s By substituting the transverse surface relaxation rate ρ2 under different desorption pressures of pore spaces of different scales into formula (7), the pore radius r of the shale sample under the multi-scale pore space of shale can be obtained. Combined with the T2 curve of nuclear magnetic resonance, the pore size distribution curve of the shale sample can be obtained.

[0120] In addition, the fluid in the sample kettle is finely divided into different occurrence states by combining the T2 spectrum curve of the shale sample nuclear magnetic resonance. According to the relationship between the dissolved, adsorbed and free hydrocarbon components and the fluid nuclear magnetic resonance signal quantity calibrated in A1, the microscopic distribution state of the hydrocarbon components in the multi-scale space is quantified. According to the change of the T2 spectrum range corresponding to each type of fluid occurrence state, the change of the pore size range of the corresponding occurrence space is converted. According to the change of the T2 mean value of the T2 spectrum range of each type of occurrence space, the average radius deformation degree of the corresponding occurrence space is quantitatively described.

[0121] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An experimental device for the desorption-phase change-pore deformation coupling characteristics of condensate gas components in multi-scale pore space of shale, comprising a constant temperature device, a fluid injection system, a nuclear magnetic resonance analysis system and a fluid recovery system, characterized in that: The fluid injection system includes a high-pressure gas source, a first stop valve, a first plunger pump and a first gas flow meter, the nuclear magnetic resonance analysis system is in the constant temperature device, the nuclear magnetic resonance analysis system includes a second stop valve, a low-field nuclear magnetic resonance instrument, a sample kettle, a third stop valve and a computer, and the fluid back pressure system includes a second gas flow meter, a back pressure valve and a second plunger pump; The high-pressure gas source contains shale condensate mixed gas, and the high-pressure gas source is connected to the first plunger pump through the first stop valve. A first evacuation / vacuuming pipeline, a first gas flow meter, a first pressure gauge and a thermometer are sequentially arranged between the first plunger pump and the sample kettle. The second stop valve is connected between the first plunger pump and the sample kettle. The first gas flow meter is used to measure the total amount of gas injected into the sample kettle. The first pressure gauge is used to measure the pressure of the sample kettle after the condensate gas is injected. The thermometer is used to measure the temperature of the nuclear magnetic resonance analysis system in the constant temperature device. The sample kettle is installed in the low-field nuclear magnetic resonance instrument, and the outlet end of the sample kettle is connected to the back pressure valve through the third stop valve and the second gas flow meter, and the outlet end of the sample kettle is also connected to the second pressure gauge and the second emptying / vacuuming pipeline in sequence, the back pressure valve is connected to the second plunger pump, the second pressure gauge is used to measure the pressure of the sample kettle after the condensate gas is desorbed, the second gas flow meter is used to measure the total amount of gas desorbed, and the low-field nuclear magnetic resonance instrument is connected to the computer through a data connection.

2. The experimental device for the coupled characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale according to claim 1, characterized in that: The first plunger pump is an ISCO high-precision pump, and the cylinder of the sample kettle is made of a non-magnetic, hydrogen-free, high-temperature and high-pressure resistant polyetheretherketone material.

3. The experimental device for the coupled characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale according to claim 2, characterized in that: The low-field nuclear magnetic resonance instrument adopts a high-temperature and high-pressure low-field nuclear magnetic resonance instrument.

4. An experimental method using the experimental device for the coupled characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale according to any one of claims 1 to 3, characterized in that: The experimental method comprises the following steps: Step S100: pre-processing before the experiment, preparing the shale samples required for the experiment, configuring the shale condensate mixed gas components, checking that all pipeline connections of the experimental device are leak-free and that the experimental device is in normal working condition; Step S200: Determine the base signal; Step S300: calibrating the hydrocarbon component amount-fluid nuclear magnetic resonance signal amount; Step S400: injection and recovery of fluid.

5. The experimental device and method for the coupled characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale according to claim 4, characterized in that: The step S100 also includes a shale sample preparation step: Step S110: Collect 20 shale samples from the target area; Step S120: using a crusher to crush the block shale sample, then using a ball mill to grind the shale fragments, and then using a 200-mesh sieve to screen the ground particle sample to collect shale powder less than 75 μm; Step S130: extract the prepared shale sample, dry it under vacuum and store it.

6. The experimental device and method for the coupled characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale according to claim 5, characterized in that: The step S100 also includes a shale condensate mixed gas configuration step: Step S140: preparing bottled pure methane gas and bottled pure normal pentane gas with a purity of at least 99%, and preparing a configuration system, the configuration system including instruments such as a gas flow meter, a mixer, and a collection device for gas configuration; Step S150: Use nitrogen to evacuate and vacuum the system to eliminate the influence of air and other impurities in the configuration system, open the methane gas cylinder and connect it to the gas flow meter, control the methane flow rate to 0.8 units, add pentane liquid to the evaporation device, turn on the heating device, control the temperature to stably evaporate pentane into gas, connect the evaporation device to the gas flow meter, and control the normal pentane flow rate to 0.2 units; Step S160: Connect the gas flow meter outlets of methane and n-pentane to the gas mixer, adjust the flow rates of the two gases to ensure that the molar ratio of methane to pentane reaches 0.8:0.2, turn on the mixer, fully mix the two gases and connect them to the gas collection device for collection, perform component analysis on the collected mixed gas using a gas chromatograph to verify whether the molar ratio of methane to pentane meets the requirements, and obtain a methane + n-pentane mixed gas with a molar ratio of 0.8:0.

2.

7. The experimental device and method for the coupled characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale according to claim 6, characterized in that: The step S200 includes the following steps: Step S210: When the sample kettle is empty, the temperature of the entire nuclear magnetic resonance analysis system is restored to the actual reservoir temperature condition by using a constant temperature device; Step S220: Open all valves of the experimental device, use the first evacuation / vacuuming pipeline and the second evacuation / vacuuming pipeline to evacuate the experimental device, and the evacuation time is not less than 12 hours to eliminate the air in the system. After the empty sample kettle is evacuated, use a low-field nuclear magnetic resonance instrument to measure its nuclear magnetic signal as the base signal of the empty sample kettle; Step S230: Fill the sample kettle with shale samples, the filling amount of the shale samples in the sample kettle does not exceed two-thirds of the capacity of the sample kettle, and use a constant temperature device to restore the temperature of the entire nuclear magnetic resonance analysis system to the actual reservoir temperature condition; Step S240: Open all valves of the experimental device, use the first emptying / vacuuming pipeline and the second emptying / vacuuming pipeline to evacuate the experimental device for no less than 12 hours to eliminate the air in the system. After the sample kettle filled with shale samples is evacuated, use a low-field nuclear magnetic resonance instrument to measure its nuclear magnetic signal as the base signal of the sample kettle filled with shale samples.

8. The experimental device and method for the coupled characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale according to claim 7, characterized in that: The step S300 specifically includes performing the following operations on the empty sample kettle and the sample kettle filled with shale samples respectively: Step S310: Open the first stop valve and the second stop valve, and inject the shale condensate mixed gas in the high-pressure gas source into the sample kettle through the first plunger pump. During this process, the pressure of the sample kettle is monitored by the first pressure gauge, and the total amount of gas injected is measured by the first gas flow meter; Step S320: After the fluid in the sample kettle is fully saturated, close the first stop valve and the second stop valve, open the third stop valve, and use the back pressure valve and the second plunger pump to gradually reduce the outlet pressure of the sample kettle to achieve desorption of the condensate gas in the sample kettle. During the desorption process, use the second gas flowmeter to measure the total amount of desorbed gas to achieve calibration of the amount of hydrocarbon components in pores of different scales and the amount of fluid nuclear magnetic resonance signals.

9. The experimental device and method for the coupled characteristics of desorption-phase change-pore deformation of condensate gas components in multi-scale pore space of shale according to claim 8, characterized in that: The step S400 includes the following steps: Step S410: taking out the shale sample from the sample kettle, and repeating step S100 to inspect the experimental device; Step S420: repeat the operation steps of step S200, refill the shale sample, restore the sample kettle temperature and perform vacuum treatment to complete the pre-experimental pretreatment; Step S430: Open the first stop valve and the second stop valve, and use the first plunger pump to inject the condensate gas component from the high-pressure gas source into the sample kettle. During the injection process, use the first pressure gauge to monitor the pressure of the sample kettle in real time until the pressure of the sample kettle restores the pressure condition of the target reservoir, and then close the first stop valve and the second stop valve; Step S440: leaving the experimental device at rest for 6 hours to allow the injected fluid to fully contact the shale sample and fully restore the original occurrence state of the hydrocarbon fluid molecules under the actual target reservoir conditions; Step S450: After the fluid in the sample kettle is fully saturated, the third stop valve is opened, and the outlet pressure of the sample kettle is gradually reduced by using the back pressure valve and the second plunger pump to achieve desorption of the condensate gas in the sample kettle under different pressure conditions; Step S460: During the desorption process, the transverse NMR relaxation time T2 spectra in the sample kettle at different pressures are recorded in real time, and the signal peak amplitude integral of the T2 spectrum curve is used, combined with the hydrocarbon component amount-fluid NMR signal amount relationship calibrated in step S300, to determine the condensate gas component content at different pressures in different types of spaces in the sample kettle.

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