阅读说明：本技术 一种测定储层温压环境下岩石毛细管压力的方法及装置 (Method and device for measuring capillary pressure of rock under reservoir temperature and pressure environment ) 是由 徐亮 李琦 陈佺 谭永胜 于 2021-01-22 设计创作，主要内容包括：本发明公开了一种测定储层温压环境下岩石毛细管压力的方法及装置,步骤是：1)岩心进行洗油洗盐、烘干处理；2)岩心放置在夹持器中,用氟油对岩心施加围压并加热；3)岩心开展自吸实验,用核磁共振监测岩心基质部分的自吸行为；4)自吸实验结束后,岩心充分饱水,得到岩心的孔隙度；5)岩心饱水后,通过恒流法结合达西定律得到岩心的渗透率；6)计算得储层温压环境下岩心的毛管压力曲线。还涉及装置,岩心放置在胶套中,胶套固定在岩心夹持器内,岩心夹持器放置在的探头线圈内；氮气瓶依次与驱替泵、压力传感器、针阀,活塞容器、针阀相连。本发明得到岩心在储层温压条件下的岩心基质部分的毛细管压力曲线,更适合油藏开发现场使用。(The invention discloses a method and a device for measuring the capillary pressure of rock under the temperature and pressure environment of a reservoir, which comprises the following steps: 1) washing oil, salt and drying the rock core; 2) placing the core in a holder, and applying confining pressure and heating to the core by using fluorine oil; 3) carrying out a self-absorption experiment on the rock core, and monitoring the self-absorption behavior of a matrix part of the rock core by using nuclear magnetic resonance; 4) after the self-absorption experiment is finished, the rock core is fully saturated with water, and the porosity of the rock core is obtained; 5) after the core is saturated with water, obtaining the permeability of the core by combining a constant flow method with the Darcy law; 6) and calculating to obtain a capillary pressure curve of the rock core under the reservoir temperature and pressure environment. The core is placed in a rubber sleeve, the rubber sleeve is fixed in a core holder, and the core holder is placed in a probe coil; the nitrogen cylinder is connected with the displacement pump, the pressure sensor, the needle valve, the piston container and the needle valve in sequence. The capillary pressure curve of the core matrix part of the core under the reservoir temperature pressure condition is obtained, and the capillary pressure curve is more suitable for being used in an oil reservoir development field.)

1. A method for measuring the capillary pressure of rock under the condition of reservoir temperature and pressure comprises the following steps:

1) carrying out oil washing, salt washing and drying treatment on the rock core with the height of L;

2) placing the core in a holder, and applying confining pressure and heating to the core by fluorine oil without hydrogen atoms according to the actual temperature and pressure environment of a reservoir corresponding to the core;

3) with a known viscosity of μ_bThe water is applied to the rock core, the smaller pore pressure is less than 1kPa, the rock core can spontaneously absorb water from the end face under the action of the capillary pressure, and the nuclear magnetic resonance is used for measuring the T of the rock core in the self-absorption experiment process₂Spectrum according to T₂The spectrum orientation distinguishes self-absorption behavior of a rock core matrix and self-absorption of internal micro cracks and cracks of the rock core;

4) after the self-absorption action of the rock core is finished, applying a larger pore pressure larger than 1-2MPa to the rock core by using water to ensure that the rock core is completely saturated with water, and using nuclear magnetic resonance to measure T of the rock core under the saturated water₂Spectrum to obtain the porosity of the core matrixT of core in self-priming process₂T of spectrum and rock core in saturation state₂Spectrum comparison is carried out to obtain the water saturation S of the rock core matrix at different self-absorption experimental moments t_b；

5) After the core is saturated with water, applying a constant flow velocity to the core, measuring the pressure difference at two ends of the core, and obtaining the permeability k of the core through Darcy's law;

6) the capillary force curve of the core under the reservoir temperature and pressure environment is obtained through the following formula, and the relational expression of the volume of the water suction volume and the capillary pressure in the self-priming experiment process of the core is represented by the following formula (1):

wherein: v_bIs the internal water absorption volume of the core, P_ecIs the capillary pressure of the core and,is the porosity of the core, k is the liquid phase permeability, A is the area of the end face at the bottom of the core, S_bWater saturation, μ, of the core over time in a self-priming experiment_bThe liquid viscosity, t is the self-priming time.

Equation (1) is further derived to equation (2):

wherein: v_sThe volume of the core is L, and the length of the core is L;

v in formula (2)_b/V_sThe self-priming efficiency is formula (3):

the capillary pressure is obtained from the variation of equation (3) to equation (4)

Wherein: p_ecCapillary pressure of the core, S_bWater saturation, μ, of the core over time in a self-priming experiment_bIs the viscosity of the water and is,and k is the porosity of the core, k is the liquid phase permeability, t is the self-priming time, and L is the core length.

2. The device for measuring the capillary pressure of the rock in the reservoir temperature and pressure environment comprises a nuclear magnetic resonance equipment unit and a pressure loading unit, wherein the nuclear magnetic resonance equipment unit comprises a permanent magnet (2), a nuclear magnetic console (3) and a probe coil (4) which are connected through a USB data line; the pressure loading unit comprises a rock core (1), a rubber sleeve (5), a rock core holder (6), a nitrogen cylinder (7), a displacement pump (8), a first pressure gauge (9), a first needle valve (10), a first piston container (11), a second needle valve (12), a vacuum pump (14), a third needle valve (15), a second pressure gauge (16), a fourth needle valve (17), a fifth needle valve (18), a sixth needle valve (19) and a second piston container (20), and is connected through a pipeline, and the pressure loading unit is characterized in that: the core (1) is placed in a rubber sleeve (5), the rubber sleeve (5) is fixed in a core holder (6), the core holder (6) is placed in a probe coil (4), and the probe coil (4) and the core holder (6) are pushed to the center of a cavity formed by the permanent magnet (2); nitrogen cylinder (7), in proper order with displacement pump (8), first pressure sensor (9), first needle valve (10), first piston container (11), second needle valve (12) link to each other with rock core holder (6), first piston container (11) periphery is wrapped there is first electric heating jacket (13), vacuum pump (14) in proper order with third needle valve (15), second manometer (16), fourth needle valve (17), rock core holder (6), rock core (1) links to each other with fifth needle valve (18).

3. The device for measuring the capillary pressure of the rock under the condition of reservoir temperature and pressure as claimed in claim 2, wherein: the first needle valve (10) is sequentially connected with a sixth needle valve (19), a second piston container (20), a fourth needle valve (17), a rock core holder (6) and a rock core (1), and a second electric heating device (21) is wrapped on the periphery of the second piston container (20).

4. The device for measuring the capillary pressure of the rock under the condition of reservoir temperature and pressure as claimed in claim 2, wherein: the nuclear magnetic control console 3 is connected with the probe coil 4.

Technical Field

The invention belongs to the technical field of nuclear magnetic resonance, and particularly relates to a method for measuring the pressure of a rock capillary in a reservoir temperature and pressure environment, and a device for measuring the pressure of the rock capillary in the reservoir temperature and pressure environment.

Background

In recent years, the gas reserves of the compact sandstone in China reach 1/3 of the total reserves of natural gas, and become the main source of natural gas storage and production in China. The compact sandstone gas reservoir in China often has the characteristics of low porosity, low permeability, fissuring property and the like. The capillary pressure curve is used as an important physical property parameter for evaluating a tight sandstone gas reservoir and plays an important role in the fields of reservoir exploration, reservoir evaluation, reservoir development, seepage mechanism research and the like.

The current common core capillary pressure test methods comprise a semi-permeable plate method, a mercury pressing method and a centrifuge method. Among these methods, the semi-permeable plate method is too long in testing time, and the equilibrium time of one pressure point is usually several days or even tens of days for dense rocks. The mercury intrusion method can greatly improve the testing speed, but a mercury-rock-vacuum system is greatly different from the real reservoir environment, and a rock core tested by the mercury intrusion method is polluted by mercury, so that other tests cannot be carried out. Meanwhile, mercury is extremely toxic and harmful to human body. The centrifugal method puts high requirements on equipment, and particularly, common centrifugal equipment hardly meets the requirement of pressure difference for compact sandstone. The semi-permeable plate method and the mercury pressing method apply pressure environments with different gradients to the core, and the centrifugal method only builds a small pressure difference in the core. The three methods are all used for carrying out capillary pressure test on the rock core at room temperature, and the temperature condition of the compact sandstone rock core in the reservoir cannot be truly reflected.

The three capillary pressure testing methods can not effectively obtain the capillary pressure curve of the rock part without the artificial-cause fracture. The three testing methods are time-consuming and labor-consuming, and very high equipment cost or time cost is required to obtain the capillary pressure curve of the core. The rock core tested by the mercury pressing method and the centrifugal method is difficult to recycle, and other parameters such as porosity, permeability and the like are difficult to obtain through a rock core sample.

In summary, how to effectively obtain the capillary force curve of the rock matrix under the reservoir temperature and pressure condition and obtain more complete parameters by using less cores is a research problem to be solved urgently at present.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for measuring the capillary pressure of rock under the reservoir temperature and pressure environment, the method is easy to implement and simple and convenient to operate, the method does not need to measure the liquid discharge amount of a sample, and the method quantifies the fluid saturation in the sample in a self-priming experiment through a magnetic resonance technology.

The invention also aims to provide a device for measuring the capillary pressure of the rock under the reservoir temperature and pressure environment, which has a simple structure and is convenient to use.

In order to achieve the purpose, the invention adopts the following technical measures:

a method for measuring the capillary pressure of rock under the condition of reservoir temperature and pressure comprises the following steps:

1) and (5) carrying out oil washing, salt washing and drying treatment on the rock core with the height of L. Different temperatures are adopted for different types of cores, and the specific temperature refers to the standard in SY/T/5346-;

2) placing the core in a holder, and applying confining pressure and heating to the core by fluorine oil without hydrogen atoms according to the actual temperature and pressure environmental characteristics of a reservoir corresponding to the core;

3) with a known viscosity of μ_bWater, applying a small pore pressure (to the core:)<1kPa) and the core will spontaneously absorb water from the end face under the capillary pressure. Nuclear magnetic resonance for measuring T of rock core in self-absorption experimental process₂Spectrum according to T₂And the spectrum orientation distinguishes the self-priming behavior of the matrix of the rock core and the self-priming behavior of the micro-cracks and fractures inside the rock core.

4) After the self-absorption action of the core is finished, applying a larger pore pressure (to the core) by using water>1-2 MPa) to make the core completely saturated with water. Nuclear magnetic resonance for determining T of rock core in completely water-saturated state₂Spectrum to obtain the porosity of the matrix part of the coreDegree of rotationAt the same time will be from the T of the core in the process of self-absorption₂T of spectrum and rock core in saturation state₂Spectrum comparison is carried out to obtain the water saturation S of the matrix part of the rock core at different self-absorption experimental moments t_b。

5) And (3) after the core is completely saturated with water, applying a constant flow rate (0.01-1ml/min) to the core, measuring the pressure difference at two ends of the core, and obtaining the permeability k of the core through Darcy's law.

6) And (3) accurately obtaining a capillary force curve of the rock core under the reservoir temperature and pressure environment through the following formula 4. The core principle of the method for measuring the capillary pressure of the rock under the reservoir temperature and pressure environment is to perform data processing analysis on the spontaneous water absorption behavior of the core matrix part under the reservoir temperature and pressure. During the self-priming experiment of the core, the relationship between the volume of water intake and capillary pressure is given by the following equation 1:

wherein: v_bIs the internal water absorption volume of the core, P_ecIs the capillary pressure of the core and,is the porosity of the core, k is the liquid phase permeability, A is the area of the end face at the bottom of the core, S_bWater saturation, μ, of the core over time in a self-priming experiment_bThe liquid viscosity, t is the self-priming time.

Equation 1 can be further derived to equation 2:

wherein: v_sAnd L is the volume of the core, and the length of the core.

V in equation 2_b/V_sFor self-priming efficiency, further, equation 2 can be simplified to equation 3:

further, the capillary pressure can be obtained from the variation of equation 3, see equation 4

Wherein: p_ecCapillary pressure of the core, S_bWater saturation, μ, of the core over time in a self-priming experiment_bIs the viscosity of the water and is,and k is the porosity of the core, k is the liquid phase permeability, t is the self-priming time, and L is the core length.

In the testing steps, the step 3 and the step 4 are key steps, and the accurate determination of the water saturation of the matrix part of the rock core changing along with the time is the key task of the invention.

By the technical measures, the problem that the capillary pressure of the rock tested by the prior art is mostly not in the temperature and pressure environment of the reservoir is solved, the capillary pressure of the tested rock core is in the real state of the real reservoir, and the production practice is better met; meanwhile, the difficult problem of distinguishing the matrix and the fracture is solved, and the capillary pressure curve of the matrix part of the rock core can be measured. And multiple key physical property parameters such as porosity, permeability, capillary pressure curve and the like of the rock core are obtained through one-time experiment by utilizing multiple parameters of a nuclear magnetic resonance experiment machine. For experimental data, see FIGS. 2-4 in the examples, which are the experimental data obtained by the present method.

A device for measuring the capillary pressure of rock under the temperature and pressure environment of a reservoir comprises a nuclear magnetic resonance equipment unit and a pressure loading unit. The nuclear magnetic resonance equipment unit comprises a permanent magnet, a nuclear magnetic console and a probe coil which are connected through a USB data line. The pressure loading unit comprises a rock core, a rubber sleeve, a rock core holder, a nitrogen cylinder, a displacement pump, a first pressure gauge, a first needle valve, a first piston container, a second needle valve, a vacuum pump, a third needle valve, a second pressure gauge, a fourth needle valve, a fifth needle valve, a sixth needle valve and a second piston container, and is connected through pipelines, so that the whole system can carry out self-priming experiments of the capillary force method for measuring the rock core, and the pressure loading unit is characterized in that: the core is placed in the rubber sleeve, the rubber sleeve is fixed in the core holder, and the core holder is placed in the probe coil. The probe coil and the rock core holder are pushed to the center of the cavity formed by the permanent magnet; the nitrogen cylinder is sequentially connected with the displacement pump, the first pressure sensor, the first needle valve, the first piston container and the second needle valve, the second needle valve is connected with the rock core holder, the first electric heating sleeve is wrapped on the periphery of the first piston container, and the fluorine oil in the container is heated to a set temperature. And the displacement pump pushes the compressed nitrogen into the first piston container, and the hot fluorine oil stored in the first piston container is pushed into a confining pressure cavity between the core holder and the rubber sleeve through the second needle valve. For confining pressure to the core. And a second electric heating sleeve is wrapped on the periphery of the second piston container and used for heating water in the second piston container.

The permanent magnet is used for manufacturing a main magnetic field environment;

the probe coil is used for transmitting a CPMG pulse sequence to the rock core and receiving a relaxation signal fed back by water in the rock core;

the nuclear magnetic control console is used for adjusting the uniformity of a main magnetic field, controlling the probe coil to transmit a pulse sequence and receive a signal and processing a nuclear magnetic signal;

the rubber sleeve is used for placing a rock core, the rock core holder is used for fixing the rock core rubber sleeve, and a confining pressure cavity is formed between the rock core holder and the rubber sleeve;

the displacement pump is used for pushing the first piston container and the second piston container;

the vacuum pump is used for vacuumizing the rock core before a self-priming experiment;

the first piston container is used for applying confining pressure and stable temperature to the rock core in a self-suction experiment so as to simulate the real state of the rock core in a stratum;

the second piston container is used for applying pore pressure to the rock core in an experiment;

nitrogen cylinder, displacement pump, first manometer, first needle valve, first piston container, fourth needle valve, core holder connect gradually through the pipeline, through to core holder with it is right to form the high temperature fluorine oil that the intracavity was injected into and does not contain hydrogen atom between the gum cover core pressurization is heated.

And the vacuum pump, the third needle valve, the second pressure gauge, the fourth needle valve, the rock core holder and the rock core are sequentially connected and are used for vacuumizing the rock core at the initial stage of the self-priming experiment.

Nitrogen cylinder, displacement pump, first manometer, first needle valve, sixth needle valve, second piston container, fourth needle valve, rock core holder, rock core loop through the pipeline and link to each other for from inhaling the experiment right a less pore pressure is applyed to the rock core.

And the fifth needle valve is in a closed state in the self-priming experiment stage and is used for simulating the self-priming process under the real reservoir condition.

All parts of the pressure loading unit are connected through a displacement pipeline, so that the whole system can carry out the self-absorption experiment of the method for measuring the capillary force of the rock core.

The permanent magnet, the probe coil and the nuclear magnetic console are connected through a USB data line, and different self-absorption behavior characteristics of a rock core matrix and a fracture part are obtained by transmitting electromagnetic pulses to a rock core sample in a self-absorption experiment, monitoring echo signals and processing.

In the components, the core holder, the rubber sleeve, the first piston container and the second piston container are key components. And hot fluorine oil in the first piston container is injected into a confining pressure cavity formed between the core holder and the rubber sleeve and is used for creating a reservoir environment of the core in a real stratum. And water in the second piston container is injected into the rock core and is used for carrying out self-absorption experiments and permeability measurement experiments.

Compared with the prior art, the invention has the following advantages and effects:

1. the capillary pressure curve of the rock core is measured in a nondestructive mode, the disturbance to the rock core is small, and the pore structure of the rock core is not damaged.

2. And the capillary pressure curve of the rock core under the temperature and pressure of the in-situ state of the reservoir is measured, so that the method has more guiding significance for production.

3. Through T₂The spectral range is directionally selected to the rock matrix portion, eliminating the influence of microcracks and fractures on capillary pressure curve determination due to artificial causes in the drilling coring process.

4. The method is matched with a nuclear magnetic resonance technology, so that multiple parameters of one machine can be realized, and multiple parameters such as porosity, permeability, capillary pressure curve and the like of the rock core under the condition of reservoir temperature and pressure can be obtained through one experiment.

Drawings

FIG. 1 is a schematic diagram of an apparatus for measuring rock capillary pressure in a reservoir temperature and pressure environment;

FIG. 2 is T in the self-priming experiment process of the compact core in the example₂A diagram of the evolution result of the spectrum;

FIG. 3 is the saturated state T of the dense core in the example₂A spectrum result schematic diagram;

FIG. 4 is a schematic diagram of a calculation result of a capillary oil-water pressure curve of the dense core in the example.

Wherein:

1-core, 2-permanent magnet, 3-nuclear magnetic console, 4-probe coil, 5-rubber sleeve, 6-core holder (peek material), 7-nitrogen cylinder, 8-displacement pump (common), 9-first pressure gauge (common), 10-first needle valve (common), 11-first piston container (316L material), 12-second needle valve (common), 13-first electric heating sleeve (common), 14-vacuum pump (common), 15-third needle valve (common), 16-second pressure gauge (common), 17-fourth needle valve (common), 18-fifth needle valve (common), 19-sixth needle valve (common), 20-second piston container (316L material), 21-second electric heating sleeve (common).

Detailed Description

In order to facilitate the understanding and implementation of the present invention by those of ordinary skill in the art, the following will describe the present invention in further detail by taking a tight sandstone gas reservoir sample in the four-Sichuan basin of China as an example, and it should be understood that the implementation example described herein is only for illustrating and explaining the present invention and is not intended to limit the present invention.

Example 1:

a method for measuring the capillary pressure of rock under the condition of reservoir temperature and pressure comprises the following steps:

(1) selecting a relatively representative rock sample with the diameter of 25mm and the length of 50mm from a drilling and coring sample of a certain compact sandstone gas reservoir in the Sichuan basin, washing oil and salt of the rock core 1, and drying at 60 ℃.

(2) The confining pressure of the core is 5MPa, and the temperature is set to be 60 ℃.

(3) And vacuumizing the core 1 for more than eight hours and less than sixteen hours.

(4) The core 1 is in a main magnetic field environment created by the permanent magnet 2 to carry out a self-absorption experiment process.

(5) And the nuclear magnetic control console 3 controls the probe coil 4 to transmit a CPMG pulse sequence to the rock core 1 at regular intervals. After the pulse sequence is transmitted, the probe coil 4 receives a relaxation signal fed back by the core 1. The nuclear magnetic console 3 inverts the relaxation signal into T₂Spectra. Up to T₂The spectrum does not change with time, and the self-priming experiment is ended. The results of the self-priming experiments with nmr monitoring are shown in fig. 2. From previous studies, it can be known that water with a relaxation time of about 1000ms is generally fracture water in the core. In this case the capillary curve of the rock 1 matrix is calculated, so that water with a relaxation time of 1000ms is ignored in the calculation process, and only pore water with a relaxation time of less than 10ms is calculated.

(6) After the self-absorption experiment is finished, fully saturating the rock core with water to obtain T of the rock core 1 in a water-saturated state₂Spectra. The results of the experiment are shown in FIG. 3. T of the core 1 in a water-saturated state₂Part of the water with a relaxation time of the spectrum of 1000ms does not participate in the calculation as well.

T of rock matrix part of core 1 at different moments in self-priming process₂Under spectrumEnvelope area and T of rock matrix portion of said core 1 in saturation₂The quotient of the division of the envelope area under the spectrum is S in formula 4_b. The results of the change in the fluid saturation inside the core over time are shown in the following table:

self-priming test time (hours)	Liquid saturation (%)
		1	33.26
2	42.61
		3	47.71
4	52.79
		5	55.44
6	59.88
		7	64.20
8	68.00
		9	70.58
10	73.32
		11	73.78
13	77.33
		14	79.93
15	80.99
		16	82.15
17	84.41
		19	88.74
21	89.43
		23	90.34
25	91.00
		27	92.78
29	94.55
		31	95.15
33	95.88
		35	96.36
37	96.21

Note that the unit of self-priming experiment time needs to be changed to seconds when calculating the core capillary pressure according to equation 4.

(7) T by comparison with a standard sample of known water volume content₂Spectral contrast, porosity of the core 1, i.e. in equation 4This can be obtained by the following formula:

wherein: v_b,sIs the liquid volume inside the core 1 in the saturated state, A_sIs T of less than 100ms in FIG. 3₂Spectral area, A_ssT being a known standard₂Area of spectral envelope, V_stanIs the volume of the known standard sample,is the porosity of a known standard.

In this case, the core porosity was 8.9%.

(8) And (3) calculating the permeability of the core 1 according to Darcy's law by referring to a method for measuring the permeability of the core in SY/T/5346-.

In this case, the permeability of the core was 0.04 mD.

(9) The capillary pressure curve of the core 1 described in this example under the conditions of a confining pressure of 5MPa and a temperature of 60 ℃ can be obtained according to formula 4, and the result is shown in fig. 4.

The device and the method can measure the pressure curve of the rock capillary under the condition of reservoir stress temperature and pressure. Through T₂And (4) screening the spectrum, and directionally selecting the rock matrix part as a test part.

Example 2:

a device for measuring the capillary pressure of rock under the temperature and pressure environment of a reservoir comprises a nuclear magnetic resonance equipment unit and a pressure loading unit. The nuclear magnetic resonance equipment unit comprises a permanent magnet 2, a nuclear magnetic console 3 and a probe coil 4 which are connected through a USB data line; the pressure loading unit comprises a rock core 1, a rubber sleeve 5, a rock core holder 6, a nitrogen cylinder 7, a displacement pump 8, a first pressure gauge 9, a first needle valve 10, a first piston container 11, a second needle valve 12, a first electric heating sleeve 13, a vacuum pump 14, a third needle valve 15, a second pressure gauge 16, a fourth needle valve 17, a fifth needle valve 18, a sixth needle valve 19, a second piston container 20, a second electric heating sleeve 21 and a pipeline, and is characterized in that: the core 1 is placed in the rubber sleeve 5, the rubber sleeve 5 is fixed in the core holder 6, and the core holder 6 is placed in the probe coil 4. The probe coil 4 and the rock core holder 6 are pushed to the center of the cavity formed by the permanent magnet 2; the nitrogen cylinder 7 is sequentially connected with a displacement pump 8, a first pressure sensor 9, a first needle valve 10, a first piston container 11 and a second needle valve 12, the second needle valve 12 is connected with the rock core holder 6, a first electric heating sleeve 13 is wrapped on the periphery of the first piston container 11, and fluorine oil in the container is heated to 60 ℃. And the vacuum pump 14 is sequentially connected with a third needle valve 15, a second pressure gauge 16, a fourth needle valve 17, the core holder 6 and the core 1, and the core 1 is connected with a fifth needle valve 18 and used for vacuumizing the core and the pipeline. The displacement pump 8 pushes compressed nitrogen into the first piston container 11, hot fluorine oil stored in the first piston container 11 is pushed into a confining pressure cavity between the core holder 6 and the rubber sleeve 5 through the second needle valve 12, confining pressure is applied to the core to be 5MPa, and the core is heated to 60 ℃ by the hot fluorine oil.

The first needle valve 10 is sequentially connected with a sixth needle valve 19, a second piston container 20, a fourth needle valve 17, a rock core holder 6 and a rock core 1. The second piston container 20 is surrounded by a second electric heater 21 for heating the water in the container to a specified temperature. The displacement pump 8 pushes compressed nitrogen gas into the second piston container 20, and water stored in the second piston container 20 is pushed to the position of the core 1 through the fourth needle valve 17, and a pore pressure of 1kPa is applied. The fifth needle valve 18 is in a closed state. The core then undergoes spontaneous water absorption and the self-priming experiment begins.

The nuclear magnetic control console 3 is connected with the probe coil 4, and the nuclear magnetic control console 3 controls the probe coil 4 to transmit a CPMG pulse sequence to the rock core 1 at regular intervals. After the pulse sequence is transmitted, the probe coil 4 receives a relaxation signal fed back by the rock core 1 in the self-priming process and inverts the relaxation signal into T of the rock core₂Spectra. Up to T of the core₂The spectrum did not change and the self-priming experiment was completed.

The displacement pump 8 pushes compressed nitrogen into a second piston container 20, water stored in the second piston container 20 is pushed to the position of the core 1 through a fourth needle valve 17, a pore pressure of 1MPa is applied, and the duration is 8 hours, so that the core 1 is completely saturated with water.

The fifth needle valve 18 is opened. The displacement pump 8 pushes compressed nitrogen into the second piston container 20, water stored in the second piston container 20 is pushed to the position of the rock core 1 through the fourth needle valve 17, the flow rate is set to be 0.01mL/min, and after fluid flowing through the fifth needle valve 18 uniformly flows out, the reading of the first pressure gauge 9 is recorded. And (3) obtaining the permeability of the core 1 according to Darcy's law by referring to a method for measuring the permeability of the core in SY/T/5346-.

The present invention is not limited to the above-described embodiments, and various modifications and equivalent changes can be made by those skilled in the art without departing from the spirit and scope of the present invention. Still belong to the protection scope of the technical scheme of the invention.