Laboratory simulation experiment method for whole process dynamic imbibition law of fracturing fluid in tight gas reservoir

Abstract

The application relates to a laboratory simulation experiment method of a whole-process dynamic imbibition law of a compact gas reservoir fracturing fluid, which comprises the following steps: preparing a fracturing fluid gel breaking filtrate according to a target block field fracturing fluid system configuration, preparing a natural core of a target reservoir, measuring and recording the initial mass and initial permeability of the core; debugging a nuclear magnetic resonance machine, determining the receiver phase and the radio frequency pulse frequency; simulating an imbibition experiment, obtaining the migration law of the fracturing fluid in the core with different imbibition time changes, the dynamic change law of the water saturation of the core and the time of the migration of the fracturing fluid to each core end face through the nuclear magnetic resonance machine; measuring and recording the core mass after the imbibition is completed; simulating fracturing fluid gel breaking well closure; simulating a displacement experiment, continuously measuring the data at different time and the water saturation values of different sections of the core; measuring and recording the core mass after the displacement is completed, and calculating the core flowback rate. The application integrally realizes the whole process of simulating the action of the fracturing fluid and the reservoir, and conforms to the actual field conditions.

Description

Technical Field

[0001] This invention relates to a technology for characterizing the damage of fracturing fluid to reservoirs during the entire process of unconventional oil and gas fracturing fluid infiltration, shut-in, and flowback displacement. Specifically, it is an integrated indoor simulation experimental method for fracturing fluid infiltration-shut-in-flowback displacement based on nuclear magnetic resonance technology, that is, an indoor simulation experimental method for the dynamic infiltration law of fracturing fluid in tight gas reservoirs throughout the entire process. Background Technology

[0002] Currently, tight gas is mainly extracted using horizontal well multi-stage fracturing technology. This technology artificially creates fractures in the reservoir, increasing its permeability, connectivity, and conductivity, thus accelerating extraction. However, as fracturing operations proceed, fracturing fluid seeps into the reservoir under capillary force. This fluid entry obstructs the gas flow channels, damaging the reservoir, reducing permeability, decreasing fracture conductivity, and ultimately lowering gas recovery rates.

[0003] Currently, nuclear magnetic resonance (NMR) technology is widely and maturely applied in the petroleum industry, often combined with laboratory percolation or displacement experiments to investigate the migration of fracturing fluid in reservoirs at the microscopic level. However, related experimental schemes often only involve one of the fracturing fluid percolation or displacement processes, lacking simulation experiments of the complete interaction between the reservoir and fracturing fluid during fracturing operations. The experimental results can often only be qualitatively described and cannot be quantitatively specified, and they often do not involve exploring the dynamic changes in reservoir water saturation. Summary of the Invention

[0004] The purpose of this invention is to provide an indoor simulation experiment method for the dynamic permeation law of fracturing fluid in tight gas reservoirs throughout the entire process. This indoor simulation experiment method for the dynamic permeation law of fracturing fluid in tight gas reservoirs is used to solve the problem that existing simulation experiment methods cannot simulate the entire process of interaction between fracturing fluid and reservoir.

[0005] The technical solution adopted by this invention to solve its technical problem is as follows: the indoor simulation experimental method for the dynamic permeation law of fracturing fluid in tight gas reservoirs throughout the entire process includes the following steps: Step 1: Prepare fracturing fluid filtrate according to the on-site fracturing fluid system of the target block, prepare natural core samples of the target reservoir, and measure and record the initial mass of the core samples. m 0 and initial penetration rate K 0; Step 2: Debug the MRI machine and determine the receiver phase and radio frequency pulse frequency; Step 3: Simulate the seepage test. The core is loaded into the core holder and the confining pressure is applied. The output pressure of the constant pressure and constant speed pump is determined according to the pump stop pressure difference during the on-site fracturing operation in the target block. The migration law of the fracturing fluid in the core with different seepage times, the dynamic change law of the core water saturation, and the time of fracturing fluid migration to each core end face are obtained by nuclear magnetic resonance. Step 4: Measure and record the core mass after the permeation experiment. m 1; Step 5: Simulate fracturing fluid breakup and shut in the well; Step 6: Simulated displacement experiment. After shutting in the well, the core is loaded into the core holder in reverse and nitrogen is used for reverse displacement. The gas flow rate under different displacement pressure differentials is measured and recorded. The one-dimensional frequency encoding, T2 spectrum and nuclear magnetic resonance imaging of the core at different times are continuously measured by nuclear magnetic resonance machine. The water saturation values ​​of the core adsorption end face and different sections of the core under different displacement pressure differentials are scanned, and the data are recorded and saved. Step 7: Measure and record the core mass after the displacement experiment. m 2. The core flowback rate was calculated, and the migration law of fracturing fluid in the core with different flowback pressures during the displacement process, the core initiation pressure gradient, flowback time, and the dynamic change law of core water saturation were obtained.

[0006] Step 3 of the above scheme is as follows: The core is loaded into the core holder and confined pressure is applied. Based on the geological conditions and production conditions of the target reservoir, combined with the on-site fracturing construction parameters, the reservoir conditions and on-site fracturing construction environment are completely simulated. The output pressure of the constant pressure and constant speed pump is determined based on the pump stop pressure difference during on-site fracturing construction in the target block. The one-dimensional frequency encoding and nuclear magnetic resonance imaging of the core at different times during the seepage process are continuously measured by nuclear magnetic resonance machine. The water saturation values ​​of the core seepage end face and different sections of the core are scanned at different times under the initial state of the core and as the fracturing fluid enters the core. The data are recorded and saved to obtain the migration law of the fracturing fluid in the core with different seepage times, the dynamic change law of the core water saturation, and the time of fracturing fluid migration to each core end face. During one-dimensional frequency encoding and nuclear magnetic resonance imaging (NMR) processing, the detected NMR signals are entirely derived from the fracturing liquid phase of the intrusive reservoir, enabling a non-destructive and precise characterization of the fluid distribution inside the core. By designing a gradient along the sample axis, NMR analysis of selected layers at different spatial locations of the core can be achieved, obtaining the variation characteristics of physical property parameters at different locations of the core. During the signal acquisition process of the READ acquisition channel, the signal is , represented as: (1) In the formula, It is the collected signal. These are the coordinates for the selected layer direction; It is a complex number; It is the K-space wave vector of nuclear magnetic resonance; This is the additional wave vector caused by the gradient; Selecting the layer direction The coordinates are a function of the acquisition time (n*tau) of the READ acquisition channel; the wave vector is defined between 180° RF pulses. It disappeared; the nuclear magnetic resonance signal reached the maximum signal of the spin echo.

[0007] Step six of the above scheme specifically involves: loading the core into the core holder in reverse; under fully simulated reservoir conditions and on-site fracturing conditions, using nitrogen for reverse displacement; starting from 0 MPa, slowly increasing the cylinder output pressure sequentially as follows: 0.2 MPa, 0.5 MPa, 0.7 MPa, 1 MPa, 1.5 MPa, and 2 MPa, with each pressure value held for 5 minutes. If the test data shows no change, continue increasing the pressure displacement until the gas completely displaces the mobile liquid phase in the core. The gas flow rate was measured and recorded under different displacement pressure differentials. During the displacement process, the one-dimensional frequency encoding, T2 spectrum, and NMR imaging of the core were continuously measured at different times using a nuclear magnetic resonance (NMR) machine. The water saturation values ​​of the core adsorption end face and different sections of the core under different displacement pressure differentials were scanned, and the data were recorded and saved. The test data included the peak area of ​​the NMR T2 spectrum, the one-dimensional frequency encoding curve, the water saturation value of the core, the fracturing fluid signal in the NMR imaging, and the gas flow rate measured by the soap film flow meter.

[0008] The above scheme describes the method for preparing fracturing fluid gel-breaking filtrate as follows: Based on the fracturing fluid system in the target block, prepare the fracturing fluid gel-breaking filtrate. According to the fracturing fluid system composition table, add the additives one by one to the water while simultaneously stirring with an electric stirrer. After the additives are added, continue stirring for 1 hour until the additives are fully dissolved. Then, place the solution in a digital display constant temperature water bath, set the temperature to the target reservoir temperature, and heat in the water bath for 2 hours to obtain the same fracturing fluid gel-breaking filtrate as used in the on-site fracturing operation.

[0009] The above-mentioned percolation experimental apparatus includes a nuclear magnetic resonance (NMR) machine, a core holder, a constant temperature chamber, a data collection device, and a computer. The core is placed in the core holder, and the temperature of the core is monitored by a temperature sensor. The core holder is installed in the NMR machine, and a confining pressure pump applies confining pressure to the core. A constant pressure and constant speed pump and an intermediate container are connected to the inlet end of the core holder, and a back pressure valve and a back pressure pump are connected to the outlet end of the core holder. Pressure sensors are installed at both the inlet and outlet ends of the core holder. The NMR machine and the back pressure valve are both located in the constant temperature chamber.

[0010] The difference between the displacement and percolation experimental devices in the above schemes is that nitrogen cylinders are used to replace the constant pressure and constant speed pump and intermediate container, and a soap film flow meter is installed on the back pressure valve. After the percolation experiment is completed, the well is shut in, and the constant pressure and constant speed pump and intermediate container are replaced with nitrogen cylinders. The back pressure valve is connected to the soap film flow meter to continue the displacement experiment. This realizes an integrated simulation of indoor fracturing fluid percolation-well shut-in-flowback displacement, simulating the complete process of fracturing fluid from entering the reservoir to flowing back to the surface under microscopic conditions. Beneficial effects

[0011] (1) The integrated solution of the present invention simulates the entire process of fracturing fluid interacting with the reservoir, which is more in line with the actual situation of fracturing construction on site.

[0012] (2) This invention utilizes a low-field nuclear magnetic resonance instrument combined with field parameters to quantitatively and visually characterize the migration of fracturing fluid in the reservoir and the dynamic changes in reservoir water saturation, providing specific parameters for determining the percolation damage of fracturing fluid and the post-fracturing flowback pressure differential.

[0013] (3) Based on low-field nuclear magnetic resonance correlation technology, this invention simulates the field fracturing construction conditions, explores the complete process of fracturing fluid from entering the reservoir to being discharged to the surface under microscopic conditions, and designs an indoor fracturing fluid infiltration-shut-out-displacement integrated experimental method; visualizes the migration of fracturing fluid in the reservoir and the dynamic changes of reservoir water saturation, and provides a quantitative basis for fracturing fluid infiltration damage, well shut-in time determination and post-fracturing flowback pressure difference determination.

[0014] (4) This invention uses microscopic nuclear magnetic resonance and its imaging technology to study the migration law of fracturing fluid in the core with different absorption time, the dynamic change law of core water saturation, and the time of fracturing fluid migration to each core end face.

[0015] (5) This invention uses microscopic nuclear magnetic resonance and its imaging technology to study the migration law of fracturing fluid in the core under different flowback pressures during the reverse displacement process after infiltration, the starting pressure gradient of each core, flowback time, flowback rate and dynamic change law of core water saturation. Attached Figure Description

[0016] Figure 1 This is a flowchart of the percolation experiment in this invention; Figure 2 This is a flowchart of the displacement experiment in this invention; Figure 3 It is an NMR pulse sequence diagram; Figure 4 This is a schematic diagram of the one-dimensional imaging calculation results.

[0017] In the diagram: 1 Nuclear magnetic resonance machine 2 Rock core 3 Rock core holder 4 Constant pressure and constant speed pump 5 Confining pressure pump 6 Intermediate container 7 Pressure sensor 8 Soap film flow meter 9 Back pressure valve 10 Back pressure pump 11 Constant temperature chamber 12 Data collection device 13 Computer 14 Nitrogen cylinder Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings: The indoor simulation experiment method for the dynamic absorption law of fracturing fluid in tight gas reservoirs throughout the entire process includes the following steps: (1) Prepare fracturing fluid filtrate according to the fracturing fluid system in the target block, prepare natural cores of the target reservoir, and measure and record the initial mass of the cores. m 0 and initial penetration rate K 0; The preparation process of the fracturing fluid filtrate is as follows: According to the composition table of the fracturing fluid system, add the additives one by one to the water as required, and stir with an electric stirrer at the same time. After the additives are added, continue to stir with the stirrer for 1 hour. After the chemicals are fully dissolved, stop stirring and put it into a digital display constant temperature water bath. Set the temperature to the target reservoir temperature and heat in the water bath for 2 hours to obtain the fracturing fluid filtrate that is the same as the fracturing fluid used in the on-site fracturing operation.

[0019] (2) Debug the nuclear magnetic resonance machine and determine the receiver phase, radio frequency pulse frequency and other parameters.

[0020] (3) Testing before the formal experiment to ensure the smooth progress of subsequent experiments.

[0021] (4) Begin the percolation test. Based on the geological and production conditions of the target reservoir, combined with the on-site fracturing parameters, specific experimental conditions are obtained to completely simulate the reservoir conditions and the on-site fracturing environment. For example... Figure 1 As shown, during the infiltration experiment, the left end of the core holder is connected to a constant pressure and speed pump and an intermediate container to pump fracturing fluid into the core at a constant temperature and pressure; the right end of the core holder is connected to a back pressure valve to control the outlet pressure; after the experiment begins, the inlet pressure is closed to simulate the pump stoppage situation on site; the data collection device is connected to a computer to record and save the nuclear magnetic resonance imaging images, one-dimensional frequency codes, and core water saturation data at different times obtained in the experiment.

[0022] The core was loaded into the core holder and annular pressure was applied. The output pressure of the constant pressure and constant speed pump was determined based on the pump stop pressure difference during the fracturing operation in the target block. The one-dimensional frequency encoding and nuclear magnetic resonance imaging of the core at different times during the experiment were continuously measured using nuclear magnetic resonance equipment. The water saturation values ​​of the core in the initial state and at different times (initially set at 2 min, 5 min, 10 min, 15 min, 20 min, 30 min, 40 min, 50 min, 60 min, 80 min... the specific scanning time can be adjusted according to the specific experimental conditions) at the core in the initial state and as the fracturing fluid entered the core were scanned. The data were recorded and saved. Nuclear magnetic resonance (NMR) technology, based on the resonance response characteristics of hydrogen protons (¹H), can achieve non-destructive and precise characterization of fluid distribution inside the core. Since the hydrogen signals from the high-purity nitrogen used in gas drive and the fluorinated oil used as the confining pressure medium in the holder are negligible, the NMR signals detected in the experiment originate entirely from the fracturing fluid phase invading the reservoir.

[0023] The principle of one-dimensional nuclear magnetic resonance (NMR) imaging pulse sequence is to design a gradient along the sample axis to achieve NMR analysis of selected layers at different spatial locations of the core, thereby obtaining the variation characteristics of physical parameters at different locations of the core. The pulse sequence diagram is shown below. Figure 3 As shown: During the signal acquisition process of the READ acquisition channel, the signal is , represented as: (1) In the formula, It is the collected signal. These are the coordinates for the selected layer direction; It is a complex number; It is the K-space wave vector of nuclear magnetic resonance; This is the additional wave vector caused by the gradient; It is the macroscopic magnetization signal obtained from the spin excitation of the H nucleus of the test sample, used as the layer selection direction. The coordinates are a function of the READ acquisition channel's acquisition time (n*tau) for each acquisition. The wave vector is defined between 180° RF pulses. It disappeared; the nuclear magnetic resonance signal reached the maximum signal of the spin echo.

[0024] obtained As a function of the layer selection direction (z) coordinate, the corresponding multiple layers, such as Figure 4 As shown, the scanning parameters are fixed, and the following is simplified to... This represents the axial fluid content. The larger the nuclear magnetic resonance signal at a certain location, the higher the hydrogen-containing fluid content at that location.

[0025] (5) After the permeation experiment, measure and record the core mass at this time.m 1.

[0026] (6) After the simulated fracturing fluid breakage and shut-in (steaming) time in the well, refer to Figure 2 The displacement experiment was initiated by loading the core into the core holder in reverse and using nitrogen for reverse displacement. The cylinder output pressure was slowly increased from 0 MPa (initially set at 0.2 MPa, 0.5 MPa, 0.7 MPa, 1 MPa, 1.5 MPa, 2 MPa... each pressure value was maintained for 5 minutes). If the main test data (NMR T2 peak area, one-dimensional frequency coding curve, core water saturation value, fracturing fluid signal in NMR imaging, and gas velocity measured by the soap film flowmeter) showed no change, the pressure was increased and the experiment continued until the gas... The experiment continues until all movable liquid phase in the core is expelled (the pressure value can be adjusted according to the specific experimental conditions). The gas flow rate under different displacement pressure differentials is measured and recorded. During the experiment, the one-dimensional frequency code, T2 spectrum and nuclear magnetic resonance imaging of the core at different times are continuously measured using nuclear magnetic resonance equipment. The core is scanned after the infiltration experiment ends (before the displacement experiment begins), and as nitrogen enters the core, the fracturing fluid displaced in the core is discharged back into the core. The water saturation values ​​of the core infiltration end face and different sections of the core under different displacement pressure differentials are recorded and saved.

[0027] like Figure 2 As shown, during the displacement experiment, the left end of the core holder 3 is connected to a nitrogen cylinder to provide nitrogen for the displacement experiment at a stable pressure flow rate; the right end of the core holder is connected to a soap film flow meter 8 (or other flow meter) to measure the gas flow rate under different displacement pressure differences in a timely manner; the data collection device is connected to a computer to record and save the nuclear magnetic resonance imaging images, one-dimensional frequency codes, and core water saturation data under different displacement pressure differences obtained in the experiment.

[0028] (7) After the displacement experiment, measure and record the core mass at this time. m 2. The calculated core runoff rate is... F .

[0029] Principle of this invention: Low-field nuclear magnetic resonance one-dimensional spectral projection usually refers to the T2 distribution spectrum (one-dimensional T2 spectrum) obtained by Fourier transforming the CPMG echo train. The essence of one-dimensional spectral projection is as follows: echo attenuation signal → inversion solution of transverse relaxation time T2 distribution, the spectral line is the T2 distribution function F(T2).

[0030] The one-dimensional spectral CPMG raw measurement signal is an attenuation sequence composed of echo amplitudes acquired from the CPMG sequence, and its expression is: ; in: S(t i): The i-th echo time t i The measured signal amplitude; F(T2): T2 distribution function (one-dimensional NMR spectral line), whose physical meaning is the signal intensity corresponding to different T2 components, that is, the spectral line of the one-dimensional spectrum; , For CPMG echo interval; Measurement noise; integration interval: T2,min~T2,max, relaxation time search range.

[0031] This is a first-type Fredholm integral equation, belonging to an ill-conditioned inverse problem, which requires regularization to obtain the spectral line T2; the solution process is as follows: ① Discretize the continuous T2 into M log-equal interval nodes: ; ② Signal Discreteness: N echo points ; ③ Hydrogen nucleus matrix (Relaxed core): ,in ; ④ Discrete model: ; ; Discrete T2 point The vector distribution outputs a one-dimensional NMR spectrum. ， x-axis T 2,j ， ordinate 。

[0032] Some key parameters are explained as follows: ① The low-field NMR one-dimensional spectrum is not obtained by direct Fourier transform, unlike the high-field NMR spectrum. It is the T2 distribution output by regularization inversion of the integral equation, commonly known in engineering as "spectral projection"; ② In rock and core experiments: short T2 corresponds to bound fluid, long T2 corresponds to movable fluid, and F(T2) is the one-dimensional spectrum of fluid distribution.

[0033] See Figure 1 The percolation experimental apparatus includes a nuclear magnetic resonance (NMR) machine 1, a core holder 3, a constant temperature chamber 11, a data collection device 12, and a computer 13. The core 2 is placed in the core holder 3, and the temperature of the core is monitored by a temperature sensor. The core holder 3 is installed in the NMR machine 1, and a confining pressure is applied to the core 2 by a confining pressure pump 5. A constant pressure and constant speed pump 4 and an intermediate container 6 are connected to the inlet end of the core holder. The outlet end of the core holder is connected to a back pressure valve 9 and a back pressure pump 10. Pressure sensors 7 are installed at both the inlet and outlet ends of the core holder. The NMR machine 1 and the back pressure valve 9 are both placed in the constant temperature chamber 11.

[0034] See Figure 2 The displacement test device differs from the percolation test device in that the constant pressure and constant speed pump 4 and intermediate container 6 are replaced with nitrogen cylinder 14, and soap film flow meter 8 is installed on the back pressure valve 9. After the percolation test is completed, the well is shut in, and the constant pressure and constant speed pump 4 and intermediate container 6 are replaced with nitrogen cylinder 14. The back pressure valve 9 is connected to soap film flow meter 8 to continue the displacement test, realizing the integrated simulation of indoor fracturing fluid percolation-well shut-in-flowback displacement, simulating the complete process of fracturing fluid from entering the reservoir to flowing back to the surface under microscopic conditions.

[0035] This invention combines nuclear magnetic resonance technology with an integrated experimental scheme for fracturing fluid infiltration-shut-down-flowback displacement, which simulates the entire process of fracturing fluid interaction with the reservoir during fracturing operations, as well as the dynamic changes in core water saturation during the experiment. Any improvements, additions, or modifications made by those skilled in the art without departing from the concept of this invention are within the scope of protection of this invention.

Claims

1. An indoor simulation experimental method for the dynamic permeation law of fracturing fluid in tight gas reservoirs throughout the entire process, characterized in that... Includes the following steps: Step 1: Prepare fracturing fluid filtrate according to the fracturing fluid system in the target block, prepare natural cores of the target reservoir, and measure and record the initial mass and initial permeability of the cores; Step 2: Debug the MRI machine and determine the receiver phase and radio frequency pulse frequency; Step 3: Simulate the seepage test. The core is loaded into the core holder and confined pressure is applied. The output pressure of the constant pressure and constant speed pump is determined according to the pump stop pressure difference during the on-site fracturing operation in the target block. The migration law of fracturing fluid in the core with different seepage times, the dynamic change law of core water saturation, and the time of fracturing fluid migration to each core end face are obtained by nuclear magnetic resonance. Step 4: Measure and record the core mass after the percolation experiment; Step 5: Simulate fracturing fluid breakup and shut in the well; Step 6: Simulated displacement experiment. After shutting in the well, the core is loaded into the core holder in reverse and nitrogen is used for reverse displacement. The gas flow rate under different displacement pressure differentials is measured and recorded. The one-dimensional frequency encoding, T2 spectrum and nuclear magnetic resonance imaging of the core at different times are continuously measured by nuclear magnetic resonance machine. The water saturation values ​​of the core adsorption end face and different sections of the core under different displacement pressure differentials are scanned, and the data are recorded and saved. Step 7: Measure and record the core mass after the displacement experiment, calculate the core flowback rate, and obtain the migration law of fracturing fluid in the core with different flowback pressures during the displacement process, the core initiation pressure gradient, flowback time, and the dynamic change law of core water saturation.

2. The indoor simulation experimental method for the dynamic permeation law of fracturing fluid in tight gas reservoirs throughout the entire process according to claim 1, characterized in that: Step three specifically involves: loading the core into the core holder and applying confining pressure; based on the target reservoir geological conditions and production conditions, combined with on-site fracturing construction parameters, fully simulating the reservoir conditions and on-site fracturing construction environment; determining the output pressure of the constant pressure and constant speed pump based on the pump stop pressure difference during on-site fracturing construction in the target block; continuously measuring the one-dimensional frequency encoding and nuclear magnetic resonance imaging of the core at different times during the seepage process using a nuclear magnetic resonance machine; scanning the water saturation values ​​of the core seepage end face and different sections of the core at different times under the initial state of the core and as the fracturing fluid enters the core; recording and saving the data; and obtaining the migration law of the fracturing fluid in the core with different seepage times, the dynamic change law of the core water saturation, and the time of fracturing fluid migration to each core end face. During one-dimensional frequency encoding and nuclear magnetic resonance imaging (NMR) processing, the detected NMR signals are entirely derived from the fracturing liquid phase of the intrusive reservoir, enabling a non-destructive and precise characterization of the fluid distribution inside the core. By designing a gradient along the sample axis, NMR analysis of selected layers at different spatial locations of the core can be achieved, obtaining the variation characteristics of physical property parameters at different locations of the core. During the signal acquisition process of the READ acquisition channel, the signal is , represented as: （1） In the formula, It is the collected signal. These are the coordinates for the selected layer direction; It is a complex number; It is the K-space wave vector of nuclear magnetic resonance; This is the additional wave vector caused by the gradient; Selecting the layer direction The coordinates are a function of the acquisition time (n*tau) of the READ acquisition channel; the wave vector is defined between 180° RF pulses. It disappeared; the nuclear magnetic resonance signal reached the maximum signal of the spin echo.

3. The indoor simulation experimental method for the dynamic permeation law of fracturing fluid in tight gas reservoirs throughout the entire process, as described in claim 2, is characterized in that: Step six specifically involves: loading the core into the core holder in reverse; under fully simulated reservoir conditions and on-site fracturing conditions, using nitrogen for reverse displacement; starting from 0 MPa, slowly increasing the cylinder output pressure sequentially as follows: 0.2 MPa, 0.5 MPa, 0.7 MPa, 1 MPa, 1.5 MPa, and 2 MPa, with each pressure value lasting 5 minutes. If the test data shows no change, continue increasing the pressure displacement until the gas completely displaces the mobile liquid phase in the core. Measure and record the gas flow rate under different displacement pressure differentials. During the displacement process, continuously measure the one-dimensional frequency encoding, T2 spectrum, and NMR imaging of the core at different times using a nuclear magnetic resonance (NMR) machine. Scan the water saturation values ​​of the core's adsorption end face and different cross sections under different displacement pressure differentials, and record and save the data. The test data includes the peak area of ​​the NMR T2 spectrum, the one-dimensional frequency encoding curve, the core water saturation value, the fracturing fluid signal in the NMR imaging, and the gas flow rate measured by the soap film flow meter.

4. The indoor simulation experimental method for the dynamic permeation law of fracturing fluid in tight gas reservoirs throughout the entire process according to claim 3, characterized in that: The method for preparing fracturing fluid gel breaking filtrate is as follows: Prepare fracturing fluid gel breaking filtrate according to the fracturing fluid system in the target block. According to the fracturing fluid system composition table, add the additives one by one to the water and stir simultaneously with an electric stirrer. After the additives are added, continue stirring with the stirrer for 1 hour. After the additives are fully dissolved, put it into a digital display constant temperature water bath, set the temperature to the target reservoir temperature, and heat in the water bath for 2 hours to obtain fracturing fluid gel breaking filtrate that is the same as the fracturing fluid used in the on-site fracturing operation.

5. The indoor simulation experimental method for the dynamic permeation law of fracturing fluid in tight gas reservoirs throughout the entire process, as described in claim 4, is characterized in that: The percolation experimental apparatus includes a nuclear magnetic resonance (NMR) machine, a core holder, a constant temperature chamber, a data collection device, and a computer. The core is placed in the core holder, and the temperature of the core is monitored by a temperature sensor. The core holder is installed in the NMR machine, and a confining pressure pump applies confining pressure to the core. A constant pressure and constant speed pump and an intermediate container are connected to the inlet end of the core holder, and a back pressure valve and a back pressure pump are connected to the outlet end of the core holder. Pressure sensors are installed at both the inlet and outlet ends of the core holder. The NMR machine and the back pressure valve are both located in the constant temperature chamber.

6. The indoor simulation experimental method for the dynamic permeation law of fracturing fluid in tight gas reservoirs throughout the entire process, as described in claim 5, is characterized in that: The displacement experimental device differs from the percolation experimental device in that a nitrogen cylinder replaces the constant pressure and constant speed pump and the intermediate container, and a soap film flow meter is installed on the back pressure valve. After the percolation experiment is completed, the well is shut in, and the constant pressure and constant speed pump and the intermediate container are replaced with a nitrogen cylinder. The back pressure valve is connected to the soap film flow meter to continue the displacement experiment. This realizes an integrated simulation of indoor fracturing fluid percolation-well shut-in-flowback displacement, simulating the complete process of fracturing fluid from entering the reservoir to flowing back to the surface under microscopic conditions.

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