A method for differentiating and quantifying the mechanism of CO2 huff and puff in unconventional reservoirs to enhance oil recovery.

Abstract

This invention discloses a method for distinguishing and quantifying the enhanced oil recovery (EOR) mechanism of CO2 huff and puff in unconventional oil reservoirs, relating to the field of oil and gas extraction technology. The method is based on nuclear magnetic resonance (NMR) experiments to determine the T2 spectrum and one-dimensional frequency coding of saturated oil cores. By analyzing the T2 spectrum and one-dimensional frequency coding of saturated oil cores, the CO2 huff and puff recovery rate and the effective CO2 reach distance are calculated. Based on the experimental data, a component model is established and calibrated to fit the experimental recovery rate and effective CO2 reach distance, thereby distinguishing and quantifying the EOR mechanism at different stages of CO2 huff and puff. This method can accurately classify the enhanced oil recovery mechanism during CO2 huff and puff into oil expansion, oil molecule diffusion, elastic energy release, and dissolved gas drive, effectively identifying the main controlling mechanism of CO2 huff and puff enhancement, providing a basis for optimizing field operations.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, specifically to a method for distinguishing and quantifying the mechanism of CO2 huff and puff to enhance oil recovery in unconventional reservoirs. Background Technology

[0002] The economic development of unconventional oil and gas resources such as tight oil shale oil mainly relies on horizontal well drilling and hydraulic fracturing technology, with extremely low primary recovery rates. CO2 huff and puff, as a potential enhanced oil recovery (EOR) method, has shown promising application prospects in laboratory and pilot field tests.

[0003] CO2 huff and puff processes mainly consist of three stages: CO2 injection, well shut-in, and depressurization production. Multiple energy recovery mechanisms (EOR) work synergistically at each stage of the CO2 huff and puff process, jointly influencing the production enhancement effect. However, due to a lack of quantitative understanding of the contributions of each mechanism, it is difficult to determine the dominant mechanism under specific reservoir conditions, thus limiting the optimization of field process parameters and the prediction of effects. Currently, relying solely on experimental methods to distinguish and quantitatively evaluate different EOR mechanisms in the CO2 huff and puff process remains a significant challenge. Summary of the Invention

[0004] This invention aims to address the difficulty in distinguishing and quantitatively assessing various recovery mechanisms in CO2 huff and puff technology for unconventional reservoirs. To overcome the limitations of current experimental methods that cannot effectively quantify the contribution of each stage of energy recovery (EOR) mechanisms, thus hindering field process optimization, this invention proposes a method for distinguishing and quantifying CO2 huff and puff recovery mechanisms by combining experimental and numerical simulation approaches.

[0005] The present invention specifically adopts the following technical solution:

[0006] Methods for differentiating and quantifying the enhanced oil recovery mechanisms of CO2 huff and puff in unconventional reservoirs include the following steps:

[0007] (1) Calculation of effective CO2 range and recovery rate:

[0008] After saturating the experimental core with oil, it was placed in the experimental apparatus, and the core was scanned using a nuclear magnetic resonance spectrometer to determine the T2 spectrum and one-dimensional frequency code of the saturated oil core. CO2 was injected into the core from the right side of the experimental core at a constant pressure. The well was then shut in. After the well shut-in stage, the production stage began. The experimental core was scanned again using a nuclear magnetic resonance spectrometer to calculate the T2 spectrum and one-dimensional frequency code of the experimental core, and the effective CO2 action distance was calculated to evaluate the improvement of CO2 throughput performance by pulsed CO2 injection.

[0009] Among them, the effective range of CO2 is characterized as follows:

[0010] The effective distance of CO2 intake and output is detected by one-dimensional frequency coding based on different experimental core nuclear magnetic resonance spectrometers. The one-dimensional frequency coding partition of nuclear magnetic resonance includes three regions: the two ends are noise signal regions, the middle region is the effective signal region, and the region between the noise signal region and the effective signal region is the transition region.

[0011] The formula for calculating the oil saturation at a certain point in the experimental core after a single production run is:

[0012] (S1-S2) / (S3-S2)×100%;

[0013] In the formula, S1 is the signal amplitude at this point in the saturated oil experiment, S2 is the signal amplitude at this point in the dry core, and S3 is the signal amplitude at this point after one production run.

[0014] Calculation of recovery rate:

[0015] The formula for calculating the recovery rate is:

[0016] Q1 / (Q1+Q2)×100%;

[0017] In the formula, Q1 is the produced oil signal quantity, and Q2 is the remaining oil signal quantity;

[0018] (2) Establishment of component model

[0019] A two-dimensional monopore model was established using a GEM component simulator. The effective CO2 action distance and recovery rate of CO2 in the component model were statistically analyzed and compared with the experimental results in (1). The relative permeability curve and CO2 diffusion coefficient were adjusted to calibrate the component model until it corresponded to the experimental results.

[0020] (3) Differentiation and quantification of CO2 enhanced oil recovery mechanisms

[0021] To accurately quantify the contributions of the four enhanced oil recovery mechanisms, the oil components in the component model are divided into four categories: n-dodecane in the matrix oil phase, n-dodecane in the matrix gas phase, n-dodecane in the fracture oil phase, and n-dodecane in the fracture gas phase.

[0022] During the soaking stage, as CO2 diffuses into the oil phase, oil begins to appear in the fractures, causing the oil to expand. This volume expansion pushes the crude oil from the matrix into the fractures. The contribution of oil expansion is quantified by the following formula:

[0023] ;

[0024] In the formula, C os M fof M represents the molar number of n-dodecane in the oil phase within the fracture during the well-clogging stage. ifom M represents the initial molar number of n-dodecane in the oil phase of the matrix. ifgmR represents the initial molar number of n-dodecane in the gas phase within the matrix. Total Oil recovery rate;

[0025] The presence of n-dodecane in the gas phase within the fracture is due to the diffusion of oil components into the bulk CO2. The corresponding recovery rate driven by this diffusion process is called oil molecule diffusion, and its contribution is calculated as follows:

[0026] ;

[0027] In the formula, C od M's contribution to the overall oil recovery rate from oil molecule diffusion fgf This represents the number of moles of n-dodecane in the gas phase within the fracture during the well-clogging stage.

[0028] The CO2 huff and puff process is divided into two sub-stages based on reservoir pressure: the stage above the bubble point pressure and the stage below the bubble point pressure. In the first stage, when the reservoir pressure remains above the bubble point, the decrease in the number of n-dodecane moles in the matrix oil phase corresponds to the recovery rate driven by elastic energy release. This contribution is calculated as follows:

[0029] ;

[0030] In the formula, C eer M represents the contribution of elastic energy release to total oil recovery. fom M represents the number of moles of n-dodecane in the oil phase of the matrix during the production stage. fgm M represents the number of moles of n-dodecane in the gas phase within the matrix. pfom M represents the number of moles of n-dodecane in the oil phase of the matrix at the final time step of the well-clogging stage. pfgm P represents the number of moles of n-dodecane in the gas phase of the matrix at the final time step of the well-clogging stage, where P is the reservoir pressure. b This refers to the bubble point pressure.

[0031] In the second stage, when the reservoir pressure is below the bubble point, CO2 dissolved in the matrix oil phase begins to dissolve and condense into bubbles, driving oil into the fractures. The resulting decrease in the molar number of n-dodecane in the matrix oil phase corresponds to the oil recovery driven by dissolved gas, quantified by the following formula:

[0032] ;

[0033] In the formula, C dgd This contributes to the total recovery rate of dissolved gas drive.

[0034] Preferably, in the characterization of the effective range of CO2, the following two criteria were established to accurately define the effective range:

[0035] ① Determine the crack surface by taking the peak value located at the end of the inclined transition zone as the boundary point between the transition zone and the effective zone, and define it as the crack surface;

[0036] ②The effective distance of CO2 is quantified as the maximum intrusion depth of the CO2 front into the matrix from the fracture surface. The CO2 front is the first location in the right end of the core where the oil saturation exceeds 98%.

[0037] Preferably, the specific process for establishing the component model is as follows:

[0038] 1) A two-dimensional monopore model was established using a GEM component simulator to simulate a CO2 huff and puff experiment. The simulation model and the experimental core had the same physical dimensions, 8 cm long and 5 cm wide.

[0039] 2) Discretized into a 100×50×1 grid in a two-dimensional Cartesian coordinate system; under the initial conditions, porosity and permeability are uniformly distributed in the matrix zone and fracture zone, and the porosity and permeability parameters are consistent with those of the core.

[0040] 3) The core was thoroughly dried and saturated with n-dodecane during the experiment, so it was assumed that the initial oil saturation in the matrix was 100%; the initial CO2 saturation of the fracture zone was 100%; the injection wells and production wells were located within the fracture grid cells and completely overlapped.

[0041] 4) During the injection phase, open the injection well and close the production well; maintain the same injection pressure and well shut-in time as in the experiment; during the production phase, monitor the well entry, open the production well, and apply a bottomhole flow pressure of 100 kPa.

[0042] 5) Statistically compare the effective CO2 action distance and recovery rate of the CO2 hump and puff of the component model with the experimental results, and adjust the relative permeability curve and CO2 diffusion coefficient to calibrate the component model until it corresponds to the experimental results.

[0043] The present invention has the following beneficial effects:

[0044] Real-time monitoring of fluid transport within shale cores was conducted using nuclear magnetic resonance (NMR). Recovery rate and effective CO2 reach distance were calculated by analyzing the obtained dynamic T2 spectrum and one-dimensional frequency-coded signal. In numerical simulations, a core-scale compositional model was established and calibrated to fit the experimental recovery rate and effective CO2 reach distance, thereby distinguishing and quantifying the energy recovery and oxygenation (EOR) mechanisms at different stages of CO2 uptake.

[0045] This method can accurately classify the production enhancement mechanism in the CO2 huff and puff process into four types (oil expansion, oil molecule diffusion, elastic energy release, and dissolved gas drive), which can effectively determine the main control mechanism of CO2 huff and puff production enhancement and provide a basis for optimizing on-site operations. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the experimental setup;

[0047] Figure 2 A schematic diagram of one-dimensional frequency coding partitioning for nuclear magnetic resonance.

[0048] Figure 3 This is a dynamic T2 spectrum of the core.

[0049] Figure 4 This is a schematic diagram of a core-scale compositional model.

[0050] Figure 5 The final fitting plot of experimental and simulated recovery rate and effective distance;

[0051] Figure 6 The diagram illustrates the contribution of each mechanism when the injection pressure is 9 MPa and the well-clogging time is 8 h.

[0052] 1 – High-precision plunger pump; 2 – First six-way valve; 3 – High-pressure CO2 intermediate container; 4 – Three-way valve; 5 – Second six-way valve; 6 – Confining pressure fluid; 7 – Heat shrink tubing; 8 – Non-magnetic plug; 9 – Nuclear magnetic resonance spectrometer; 10 – First constant temperature water bath; 11 – Core holder; 12 – Valve; 13 – Back pressure valve; 14 – Hand pump; 15 – Waste liquid collection system; 16 – Second constant temperature water bath; 17 – First circulation pump; 18 – Second circulation pump; 19 – Core. Detailed Implementation

[0053] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and specific examples:

[0054] The experimental steps are as follows, and the experimental apparatus used is as follows: Figure 1 As shown.

[0055] Step 1) Use the first circulation pump 17, the second circulation pump 18, the first constant temperature water bath 10, and the second constant temperature water bath 16 to maintain the intermediate container 3 and the nuclear magnetic resonance spectrometer 9 at the set temperature.

[0056] Step 2) After saturating the experimental core 19 with oil, wrap the outside with heat-shrink tubing 7 and place it in the core holder 11. Place a non-magnetic plug 8 on the left side and scan the core with a nuclear magnetic resonance spectrometer 9 to determine the T2 spectrum and one-dimensional frequency coding of the saturated oil core. The one-dimensional frequency coding partitions are as follows: Figure 2 As shown;

[0057] Step 3) Control the confining pressure fluid 6 to apply confining pressure to the core holder to a certain pressure;

[0058] Step 4) Open valve 4 (three-way valve), valve 5 (second six-way valve), and valve 12, and allow CO2 to flow through for a period of time to expel residual air and moisture from the pipeline;

[0059] Step 5) Close valve 12, set high-precision plunger pump 1 to constant pressure mode to construct the initial pressure of high-pressure CO2 intermediate container 3. After reaching the initial pressure, CO2 is injected into the core from the right side of the core at a constant pressure.

[0060] Step 6) Keep the first six-way valve 2, the three-way valve 4, and the second six-way valve 5 open; the well-clogging stage begins.

[0061] Step 7) After the well-closing stage is completed, close the second six-way valve 5 and open valve 12 to start the production stage. The hand pump 14 and back pressure valve 13 control the production pressure at 100 kPa. The waste liquid obtained from the production is collected by the waste liquid collection system 15.

[0062] Step 8) Scan the core using a nuclear magnetic resonance spectrometer, calculate the T2 spectrum and one-dimensional frequency coding of the experimental core, calculate the CO2 effective distance and recovery rate, and evaluate the improvement of CO2 throughput performance by pulsed CO2 injection.

[0063] (1) Calculation of effective CO2 range and recovery rate:

[0064] Characterization of the effective range of CO2:

[0065] The effective distance of CO2 intake and output is detected by one-dimensional frequency encoding based on nuclear magnetic resonance imaging of different experimental cores.

[0066] A schematic diagram of one-dimensional frequency coding partitioning in nuclear magnetic resonance is shown below. Figure 2 As shown: It includes three regions, with noise signal regions at both ends, effective signal region in the middle, and transition region between noise signal region and effective signal region.

[0067] To accurately define the effective distance, the following two criteria were established:

[0068] ① Determine the crack surface. The peak value located at the end of the inclined transition zone is taken as the boundary between the transition zone and the effective zone, and it is defined as the crack surface.

[0069] ②The effective distance of CO2 is quantified as the maximum intrusion depth of the CO2 front into the matrix from the fracture surface. The CO2 front is the first location in the right end of the core where the oil saturation exceeds 98%.

[0070] The formula for calculating the oil saturation at a certain point in the experimental core after a single production run is:

[0071] (S1-S2) / (S3-S2)×100%;

[0072] In the formula, S1 is the signal amplitude at this point in the saturated oil experiment, S2 is the signal amplitude at this point in the dry core, and S3 is the signal amplitude at this point after one production run.

[0073] Calculation of recovery rate:

[0074] Core recovery rate calculation method based on nuclear magnetic resonance technology, such as Figure 3 As shown, the formula for calculating the recovery rate is:

[0075] Q1 / (Q1+Q2)×100%;

[0076] In the formula, Q1 is the produced oil signal quantity, and Q2 is the remaining oil signal quantity.

[0077] (2) Establishment of component model

[0078] 1) A two-dimensional monopore model was established using a component simulator to simulate CO2 huff and puff experiments, such as... Figure 4 As shown. The simulation model has the same physical dimensions as the experimental core, 8cm long and 5cm wide;

[0079] 2) Discretized into a 100×50×1 grid in a two-dimensional Cartesian coordinate system; under the initial conditions, porosity and permeability are uniformly distributed in the matrix zone and fracture zone, and the porosity and permeability parameters are consistent with those of the core.

[0080] 3) The core was thoroughly dried and saturated with n-dodecane during the experiment, so it was assumed that the initial oil saturation in the matrix was 100%; the initial CO2 saturation of the fracture zone was 100%; the injection wells and production wells were located within the fracture grid cells and completely overlapped.

[0081] 4) During the injection phase, open the injection well and close the production well; maintain the same injection pressure and well shut-in time as in the experiment; during the production phase, monitor the well entry, open the production well, and apply a bottomhole flow pressure of 100 kPa.

[0082] 5) The effective CO2 reach and recovery rate of the CO2 huff and puff model were statistically analyzed and compared with experimental results. The relative permeability curve and CO2 diffusion coefficient were adjusted to calibrate the component model until they corresponded to the experimental results. The fitting results are as follows: Figure 5 As shown.

[0083] (3) Differentiation and quantification of CO2 enhanced oil recovery (EOR) mechanisms

[0084] To accurately quantify the contributions of the four enhanced oil recovery mechanisms, the oil components in the component model are divided into four categories: n-dodecane in the matrix oil phase, n-dodecane in the matrix gas phase, n-dodecane in the fracture oil phase, and n-dodecane in the fracture gas phase.

[0085] During the soaking stage, as CO2 diffuses into the oil phase, oil begins to appear in the fractures, causing the oil to expand. This volume expansion pushes the crude oil from the matrix into the fractures. The contribution of oil expansion is quantified by the following formula:

[0086] ;

[0087] In the formula, C os M fof M represents the molar number of n-dodecane in the oil phase within the fracture during the well-clogging stage. ifom M represents the initial molar number of n-dodecane in the oil phase of the matrix. ifgm R represents the initial molar number of n-dodecane in the gas phase within the matrix. Total Oil recovery rate;

[0088] The presence of n-dodecane in the gas phase within the fracture is due to the diffusion of oil components into the bulk CO2. The corresponding recovery rate driven by this diffusion process is called oil molecule diffusion, and its contribution is calculated as follows:

[0089] ;

[0090] In the formula, C od M's contribution to the overall oil recovery rate from oil molecule diffusion fgf This represents the number of moles of n-dodecane in the gas phase within the fracture during the well-clogging stage.

[0091] The CO2 huff and puff process can be divided into two sub-stages based on reservoir pressure: the stage above the bubble point pressure and the stage below the bubble point pressure. In the first stage, when the reservoir pressure remains above the bubble point, the decrease in the number of n-dodecane moles in the matrix oil phase corresponds to the recovery rate driven by elastic energy release. The calculation method for this contribution is as follows:

[0092] ;

[0093] In the formula, C eer M represents the contribution of elastic energy release to total oil recovery. form M represents the number of moles of n-dodecane in the oil phase of the matrix during the production stage. fgm M represents the number of moles of n-dodecane in the gas phase within the matrix. pform M represents the number of moles of n-dodecane in the oil phase of the matrix at the final time step of the well-clogging stage. pfgm P represents the number of moles of n-dodecane in the gas phase of the matrix at the final time step of the well-clogging stage, where P is the reservoir pressure. b This refers to the bubble point pressure.

[0094] In the second stage, when the reservoir pressure is below the bubble point, CO2 dissolved in the matrix oil phase begins to dissolve and condense into bubbles, driving oil into the fractures. The resulting decrease in the molar number of n-dodecane in the matrix oil phase corresponds to the oil recovery driven by dissolved gas, quantified by the following formula:

[0095] ;

[0096] In the formula, C dgdThis contributes to the total recovery rate of dissolved gas drive.

[0097] Figure 6 The contributions of each mechanism are presented when the injection pressure is 9 MPa and the soaking time is 8 h. The results show that under these conditions, the total oil recovery is 5.3%. Among them, dissolved gas drive is the main driving mechanism, accounting for more than 50% of the recovery; followed by oil molecule diffusion, contributing about 27.5%, while elastic energy release contributes the least, only 4.1%.

[0098] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for differentiating and quantifying the mechanism of CO2 huff and puff enhanced oil recovery in unconventional reservoirs, characterized in that, Includes the following steps: (1) Calculation of effective CO2 range and recovery rate: After saturating the experimental core with oil, it was placed in the experimental apparatus, and the core was scanned using a nuclear magnetic resonance spectrometer to determine the T2 spectrum and one-dimensional frequency code of the saturated oil core. CO2 was injected into the core from the right side of the experimental core at a constant pressure. The well was then shut in. After the well shut-in stage, the production stage began. The experimental core was scanned again using a nuclear magnetic resonance spectrometer to calculate the T2 spectrum and one-dimensional frequency code of the experimental core, and the effective CO2 action distance was calculated to evaluate the improvement of CO2 throughput performance by pulsed CO2 injection. Among them, the effective range of CO2 is characterized as follows: The effective range of CO2 is detected by one-dimensional frequency coding based on nuclear magnetic resonance (NMR) instruments of different experimental cores. The one-dimensional frequency coding partition of NMR includes three regions: the two ends are noise signal regions, the middle region is the effective signal region, and the region between the noise signal region and the effective signal region is the transition region. The formula for calculating the oil saturation at a certain point in the experimental core after a single production run is: (S1-S2) / (S3-S2)×100%; In the formula, S1 is the signal amplitude at this point in the saturated oil experiment, S2 is the signal amplitude at this point in the dry core, and S3 is the signal amplitude at this point after one production run. Calculation of recovery rate: The formula for calculating the recovery rate is: Q1 / (Q1+Q2)×100%; In the formula, Q1 is the produced oil signal quantity, and Q2 is the remaining oil signal quantity; (2) Establishment of component model A two-dimensional monopore model was established using a GEM component simulator. The effective CO2 action distance and recovery rate of CO2 in the component model were statistically analyzed and compared with the experimental results in (1). The relative permeability curve and CO2 diffusion coefficient were adjusted to calibrate the component model until it corresponded to the experimental results. (3) Differentiation and quantification of CO2 enhanced oil recovery mechanisms To accurately quantify the contributions of the four enhanced oil recovery mechanisms, the oil components in the component model are divided into four categories: n-dodecane in the matrix oil phase, n-dodecane in the matrix gas phase, n-dodecane in the fracture oil phase, and n-dodecane in the fracture gas phase. During the soaking stage, as CO2 diffuses into the oil phase, oil begins to appear in the fractures, causing the oil to expand. This volume expansion pushes the crude oil from the matrix into the fractures. The contribution of oil expansion is quantified by the following formula: ； where C os is the contribution of oil swelling to the total recovery factor, M fof is the number of moles of n-dodecane in the oil phase in the fracture at the soak stage, M ifom is the initial number of moles of n-dodecane in the oil phase in the matrix, M ifgm is the initial number of moles of n-dodecane in the gas phase in the matrix, R Total is the oil recovery factor; The presence of n-dodecane in the gas phase within the fracture is due to the diffusion of oil components into the bulk CO2. The corresponding recovery rate driven by this diffusion process is called oil molecule diffusion, and its contribution is calculated as follows: ； In the formula, C od M's contribution to the overall oil recovery rate from oil molecule diffusion fgf This represents the number of moles of n-dodecane in the gas phase within the fracture during the well-clogging stage. The CO2 huff and puff process is divided into two sub-stages based on reservoir pressure: the stage above the bubble point pressure and the stage below the bubble point pressure. In the first stage, when the reservoir pressure remains above the bubble point, the decrease in the number of n-dodecane moles in the matrix oil phase corresponds to the recovery rate driven by elastic energy release. This contribution is calculated as follows: ； In the formula, C eer M represents the contribution of elastic energy release to total oil recovery. fom M represents the number of moles of n-dodecane in the oil phase of the matrix during the production stage. fgm M represents the number of moles of n-dodecane in the gas phase within the matrix. pfom M represents the number of moles of n-dodecane in the oil phase of the matrix at the final time step of the well-clogging stage. pfgm P represents the number of moles of n-dodecane in the gas phase of the matrix at the final time step of the well-clogging stage, where P is the reservoir pressure. b This refers to the bubble point pressure. In the second stage, when the reservoir pressure is below the bubble point, CO2 dissolved in the matrix oil phase begins to dissolve and condense into bubbles, driving oil into the fractures. The resulting decrease in the molar number of n-dodecane in the matrix oil phase corresponds to the oil recovery driven by dissolved gas, quantified by the following formula: ； In the formula, C dgd This contributes to the total recovery rate of dissolved gas drive.

2. The method for differentiating and quantifying the mechanism of CO2 huff and puff in unconventional reservoirs to enhance oil recovery as described in claim 1, characterized in that, In characterizing the effective range of CO2, the following two criteria were established to accurately define the effective range: ① Determine the crack surface by taking the peak value located at the end of the inclined transition zone as the boundary point between the transition zone and the effective zone, and define it as the crack surface; ②The effective distance of CO2 is quantified as the maximum intrusion depth of the CO2 front into the matrix from the fracture surface. The CO2 front is the first location in the right end of the core where the oil saturation exceeds 98%.

3. The method for differentiating and quantifying the mechanism of CO2 huff and puff for enhanced oil recovery in unconventional reservoirs as described in claim 1, characterized in that, The specific process of establishing the component model is as follows: 1) A two-dimensional monopore model was established using a component simulator to simulate a CO2 huff and puff experiment. The simulation model and the experimental core had the same physical dimensions, 8 cm long and 5 cm wide. 2) Discretized into a 100×50×1 grid in a two-dimensional Cartesian coordinate system; under the initial conditions, porosity and permeability are uniformly distributed in the matrix zone and fracture zone, and the porosity and permeability parameters are consistent with those of the core. 3) The core was thoroughly dried and saturated with n-dodecane during the experiment, so it was assumed that the initial oil saturation in the matrix was 100%; the initial CO2 saturation of the fracture zone was 100%; the injection wells and production wells were located within the fracture grid cells and completely overlapped. 4) During the injection phase, open the injection well and close the production well; the injection pressure and well shut-in time should remain consistent with the experiment. During the production phase, focus on well entry, opening production wells, and applying a bottomhole flow pressure of 100 kPa; 5) Statistically compare the effective CO2 action distance and recovery rate of the CO2 hump and puff of the component model with the experimental results, and adjust the relative permeability curve and CO2 diffusion coefficient to calibrate the component model until it corresponds to the experimental results.

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