Characterization method for quantifying contribution degrees of different mechanisms to improvement of gas reservoir recovery efficiency

Abstract

The invention relates to the technical field of oil and gas field development, in particular to a characterization method for quantifying contribution degrees of different mechanisms to improvement of gas reservoir recovery efficiency, which comprises the following steps: constructing an equivalent long rock core through a permeability harmonic average value, and restoring real reservoir seepage characteristics; three groups of experiments of natural exhaustion, static pressurization re-exhaustion and continuous gas injection displacement are adopted to realize physical decoupling of pressurization energy supplementation and a physical displacement mechanism; in combination with a homologous rock powder adsorption experiment, competitive adsorption contribution is accurately determined; a quantitative calculation model is established based on experimental data, and independent increments and comprehensive contribution degrees of the three mechanisms are obtained respectively. The method can solve the problem that the independent contribution degree of each single mechanism to extraction cannot be objectively and accurately quantified in the technology for improving the natural gas recovery efficiency through carbon dioxide displacement in the prior art.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and in particular to a method for characterizing the contribution of different mechanisms to improving gas reservoir recovery. Background Technology

[0002] Currently, under the background of "dual carbon" goals and energy security strategy, carbon dioxide displacement enhances natural gas recovery (…). The technology combines the advantages of increasing natural gas production with... The dual benefits of geological preservation have become a core direction for the coordinated development of oil and gas development and carbon emission reduction. Existing research and field practice indicate that injecting [resources] into gas reservoirs... Or contains impurities Mixed gases can effectively enhance gas reservoir recovery and achieve carbon sequestration through multiple mechanisms such as pressurization and energy replenishment, physical displacement, and competitive adsorption.

[0003] In recent years, existing technologies have used long core displacement experiments and numerical simulations to study the effects of gas injection parameters on the displacement of gas. The impact of displacement gas reservoir recovery and burial rate was investigated, and key parameters such as injection timing, injection rate, bound water saturation, and development method on reservoir recovery and burial rate were systematically analyzed. The impact of the burial rate clarifies the pure and containing , Impurities such as impurities The study examined the changes in gas breakthrough characteristics, recovery rate, and storage rate during the displacement process, confirming the technical feasibility of non-pure carbon dioxide displacement for enhancing natural gas recovery and providing a theoretical reference for optimizing gas injection parameters. Through overall displacement experiments and numerical fitting, this type of research revealed the macroscopic development effects of carbon dioxide displacement for enhancing natural gas recovery under different operating conditions, promoting the understanding of the mechanism and field application of gas injection enhancement technology.

[0004] However, existing research and experimental methods on the mechanisms of carbon dioxide displacement for enhanced natural gas recovery (EGR) still have significant technical limitations: Current long core displacement and numerical simulation methods can only obtain overall performance indicators such as macroscopic recovery rate, breakthrough timing, and burial rate, but cannot physically decouple and quantitatively separate the three core enhancement mechanisms: pressurization and energy replenishment, physical displacement, and competitive adsorption. In conventional displacement processes, pressurization and energy replenishment are highly coupled and occur synchronously, making it difficult to separate their respective contributions at the physical level. Simultaneously, due to the hysteresis effect of seepage in rock pores, the true contribution of microscopic competitive adsorption cannot be accurately determined through conventional plunger sample experiments. Existing technologies rely excessively on numerical simulation "black box" algorithms, resulting in numerous subjective assumptions, large fitting errors, and incomplete mechanism coverage. This makes it impossible to objectively and accurately quantify the independent contribution of each individual mechanism to EGR, leading to a lack of rigorous quantitative support for reservoir injection scheme optimization, gas source medium selection, and CCUS benefit assessment. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a method for characterizing the contribution of different mechanisms to improving gas reservoir recovery, so as to solve the problem that the existing carbon dioxide displacement technology for improving natural gas recovery cannot objectively and accurately quantify the independent contribution of each single mechanism to the improvement and recovery.

[0006] The basic solution provided by this invention is a method for characterizing the contribution of different mechanisms to improving gas reservoir recovery, comprising: S1: Obtain a core sample from the plunger sample, and after drying the core sample, measure its permeability and length. S2: Based on the permeability and length of the core sample, the preset permeability harmonic average calculation method is called to calculate the harmonic average permeability of each core sample. Based on the harmonic average permeability, the core samples are sorted and placed into the rubber sleeve of the long core holder in sequence to obtain an equivalent long core. S3: Establish water saturation for the equivalent long core in the long core holder, saturate the equivalent long core with methane, and raise the temperature and pressure of the experimental environment of the equivalent long core to the reservoir temperature and pressure. S4: Perform pressure decay treatment on the equivalent long core after saturation treatment by stepwise depressurization until the preset waste pressure is reached. Record the volume data of produced methane to obtain the methane production without gas injection intervention. ; S5: Based on the exhaustion to the abandonment pressure, inject gas into the equivalent long core to the preset pressure, stabilize for a preset time until the internal fluid reaches static equilibrium, and then gradually reduce the pressure to the abandonment pressure again. Record the volume multiple of methane in the produced gas to obtain the methane production due to the stripping physical pushing effect. ; S6: Repeat steps S3-S4 with the equivalent long core from S5, injecting the same gas as in step S5 into the equivalent long core at a constant rate to conduct a gas injection and recovery experiment. When the flow rate in the equivalent long core is detected to be steadily increasing at a preset rate, the gas components are detected by chromatography. When the methane content in the gas components is lower than the preset methane content threshold, the gas injection and recovery experiment is stopped, yielding the methane production from pure gas displacement. ; S7: Based on methane production Methane production and methane production The methane increment contributed by the boosting and replenishing effect and the methane increment contributed by the displacement effect are calculated. The preset calculation method for the contribution of gas injection boosting and the preset calculation formula for the contribution of gas injection displacement are used to calculate the contribution of boosting and replenishing effect and the contribution of displacement effect respectively. S8: Obtain rock powder of the same origin as the equivalent long core for gas adsorption experiments, measure methane dissipation, and calculate the methane increment of the equivalent long core under competitive adsorption based on the methane dissipation. S9: Based on the methane increment under competitive adsorption, the methane increment contributed by pressurization and energy replenishment, and the methane increment contributed by displacement, calculate the comprehensive contribution of competitive adsorption, pressurization and energy replenishment, and displacement. S10: Integrate the contribution of pressurization and energy replenishment, displacement and competitive adsorption, pressurization and energy replenishment, and displacement and output the evaluation results of the contribution of oil recovery rate during the gas reservoir enhancement and production process.

[0007] Furthermore, S4 includes: S4-1: Obtain the equivalent long core after saturation treatment, install a flow meter at the outlet end of the long core holder of the equivalent long core, and connect the confining pressure pump to the long core holder. S4-2: Pressure attenuation treatment of equivalent long core is carried out by confining pressure pump at a pressure of 1 MPa. During the treatment, the pressure is further reduced after the flow meter shows 0, until it is exhausted to the abandonment pressure of 8 MPa. S4-3: The chromatograph calibration factor is calibrated using a standard gas. After calibration, the chromatograph is used to detect methane in the produced gas to obtain the methane yield without gas injection interference. The expression is: ; in, Let be the volume of gas produced by the i-th stage of depressurization; The volume fraction of methane in the i-th stage depressurization product gas; The dead volume of the experimental system. This represents the number of stages of exhaustion and degradation.

[0008] Furthermore, S5 includes: S5-1: The equivalent long core, which has been depleted to 8 MPa, is pressurized by injecting carbon dioxide gas into the confining pressure pump. After the gas is injected to 12 MPa, it is stabilized for 12 hours until the fluid inside the equivalent long core reaches static equilibrium. S5-2: The equivalent long core that has reached static equilibrium is then depressurized to 8 MPa in stages using a confining pressure pump at a pressure of 1 MPa per stage. During the depressurization process, the pressure is further reduced when the flow rate of the flow meter shows 0. S5-3: The chromatograph calibration factor is calibrated using standard gas. After calibration, the volume ratio of methane in the produced gas is detected by the chromatograph, and the methane yield is calculated. The expression is: ; in, Let J be the volume of gas produced by the j-th stage of depressurization. The volume fraction of methane in the product gas from the j-th stage of depressurization. The dead volume of the experimental system. This refers to the number of stages in the pressure reduction phase.

[0009] Furthermore, S6 includes: S6-1: The equivalent long core obtained in step S5 is subjected to saturation treatment in step S3 and pressure attenuation treatment in step S4 to obtain an equivalent long core with pressure attenuated to 8MPa. S6-2: Carbon dioxide gas is injected into the equivalent long core at a constant rate using a confining pressure pump. Simultaneously, a flow meter is activated to monitor the flow rate inside the equivalent long core. When the flow rate increases steadily according to the preset flow rate, the components of the produced gas are detected by a chromatograph. S6-3: Use standard gas to calibrate the chromatograph calibration factor. After calibration, the chromatograph detects methane in the produced gas. If the methane content is lower than the preset methane content threshold, stop the gas injection and calculate the methane yield. The expression is: ; in, Let be the volume of gas produced during the k-th measurement period. Let methane be the volume fraction in the produced gas during the k-th time period. The dead volume of the experimental system. This refers to the number of metering points during the gas injection and extraction stage.

[0010] Furthermore, S7 includes: S7-1: Methane extraction yield Methane production and methane production ; S7-2: The contribution of the pressurization boost effect is calculated using the preset calculation method. The expression is: ; ; ; in, The degree of contribution to pressurization and energy replenishment; This represents the total increase in methane content; The increase in methane volume contributed to the pressurization and energy replenishment effect; S7-3: Calculate the contribution of the displacement effect using the preset gas injection displacement contribution formula. The expression is: ; ; in, To the extent of contribution to displacement, The increase in methane contributed to the displacement process.

[0011] Furthermore, S8 includes: S8-1: Rock powder was prepared by scraping and crushing from the same source core sample of equivalent long core, and the amount of methane eluent was measured by gas adsorption experiment of the rock powder. S8-2: The methane increment independently contributed by the equivalent long core under competitive adsorption is obtained by equivalent conversion of the methane dissipation amount. .

[0012] Furthermore, S9 includes: S9-1: Obtaining the methane increment under competitive adsorption The increase in methane volume contributed by the boosting and replenishing effect The increase in methane contributed by displacement The global total methane increment is calculated, and the expression is: ; in, This represents the total global methane increment. S9-2: Based on global total methane increment The combined contributions of competitive adsorption, pressurization and energy replenishment, and displacement were calculated separately, and the expressions are as follows: ; ; ; in, The overall contribution of competitive adsorption. To assess the overall contribution of pressurization and energy replenishment, The overall contribution of displacement.

[0013] Furthermore, in S2, the expression for the preset calculation method of the harmonic average permeability is: ; in, This is the harmonic average of the permeability. This represents the total length of all core samples used in the calculation. Let i be the length dimension of the i-th core sample. Let i be the permeability value of the i-th core sample; This represents the number of core samples.

[0014] Furthermore, S3 includes: S3-1: Apply a preset confining pressure to the long core holder where the assembled equivalent long core is located by using a confining pressure pump, and remove the free water in the core voids of the equivalent long core by using an ultra-high speed centrifugation method to establish a water saturation that matches the real gas reservoir. S3-2: Methane gas with a purity of ≥99.99% is continuously injected into the long core holder by a displacement pump, and the inlet and outlet pressures and gas composition of the long core holder are monitored in real time until the equivalent long core reaches a state of complete methane saturation. S3-3: In the experimental environment of the equivalent long core, the temperature is increased to 100℃ and the pressure is increased to 27MPa, and the temperature and pressure are kept constant.

[0015] The technical solution of this invention: In the technical solution of this application, firstly, multiple plunger samples are sorted and assembled based on the harmonic average permeability to construct an equivalent long core consistent with the seepage law of a real gas reservoir, eliminating experimental deviations caused by the scale effect and heterogeneity of short cores, and ensuring that the experimental conditions are equivalently matched with the real seepage environment of the reservoir; then, the coupling mechanism is decoupled through three experimental steps, namely: Natural pressure depletion experiment: Without any gas injection intervention, the equivalent long core of saturated methane was gradually depressurized to the abandonment pressure to obtain the basic production. , as a benchmark for natural mining; Static pressurization and depletion experiment: After depletion to the exhaust pressure, gas is injected to pressurize to the set pressure and statically balanced, then depressurized to the exhaust pressure to obtain the production generated by the sum of pressurization replenishment and base recovery. Physically remove the displacement effect; Continuous gas injection displacement experiment: After resaturation, full-process gas injection displacement was carried out to obtain the yield from the combined effect of pressurization and physical displacement. This fully reflects the macro-level effects of displacement and extraction.

[0016] Subsequently, adsorption-desorption experiments were conducted using rock powder from the same source as the equivalent long core. The amount of methane desorbed was directly measured, and then the methane increment contributed by competitive adsorption was obtained by equivalent conversion of core pore volume and adsorption mass, thus avoiding measurement errors caused by core seepage stagnation and flow interference. Finally , , Based on this, the incremental pressure and energy replenishment and the incremental physical displacement are calculated step by step; then, combined with the incremental competitive adsorption, the total incremental global extraction is obtained; finally, the independent contribution and comprehensive contribution of the three major mechanisms are calculated using preset formulas to form a complete quantitative result.

[0017] The beneficial effects of this invention are as follows: 1. To solve the problem that pressurization and displacement occur simultaneously and cannot be separated in conventional displacement experiments, the contributions of the two mechanisms can be independently identified at the physical level through stepwise experiments of "static pressurization-re-exhaustion" and "continuous gas injection displacement", avoiding the distortion of results caused by coupling effects. 2. To address the problem that the contribution of competitive adsorption cannot be accurately measured due to the sluggish flow in rock pores, an equivalent conversion experiment using homologous rock powder adsorption is adopted to objectively reflect the real effect of microscopic adsorption on extraction, thereby improving the accuracy and reliability of mechanism quantification. 3. It solves the problems of existing methods having too many human assumptions, large fitting errors, and incomplete mechanism coverage. It is based entirely on indoor measured yield and adsorption data, without relying on simulation fitting, and the results are objective, reproducible, and highly reliable. 4. To address the lack of quantitative evidence on the mechanism of gas injection development in gas reservoirs, this paper directly provides the contribution ratio of pressurization and energy replenishment, physical displacement, and competitive adsorption, providing rigorous quantitative support for gas injection timing, injection rate, gas source medium selection, CCUS benefit assessment, and on-site scheme optimization. Attached Figure Description

[0018] Figure 1 This is a flowchart of an embodiment of the present invention; Figure 2 This is a schematic diagram of the long core displacement device in an embodiment of the present invention; Figure 3 Notes in the embodiments of the present invention / Schematic diagram for improving oil recovery rate; Figure 4 This is a note regarding the embodiments of the present invention. Contribution of different extraction mechanisms; Figure 5 This is a note regarding the embodiments of the present invention. Contribution of different extraction mechanisms. Detailed Implementation

[0019] The following detailed description illustrates the specific implementation method: The basic implementation examples are as follows: Figure 1 As shown: A method for quantifying the contribution of different mechanisms to enhanced gas recovery includes: S1: Obtain a core sample from the plunger sample, and after drying the core sample, measure its permeability and length. In this embodiment, eight sandstone core samples were selected. The core samples were first dried in an oven at 100°C for 24 hours to ensure no residual moisture remained inside. Subsequently, the mass, permeability, and geometric dimensions of the core samples were measured, including length and diameter. The rock physical properties of the core samples are detailed in Table 1. Table 1. Rock physical properties of core samples

[0020] Meanwhile, to better execute the experiments of the technical solution of this application, a long core displacement experimental device is adopted. The composition and connection relationship of each device are as follows: Figure 2 As shown, the device includes a displacement pump, a confining pressure pump, a back pressure pump, an intermediate container, a long core holder, a back pressure valve, a gas flow meter, a gas chromatograph, and a pressure acquisition system. The connections between the components are as follows: the outlet of the displacement pump is connected to the inlet of the intermediate container; the outlet of the intermediate container is connected to the inlet of the long core holder; the confining pressure pump is connected to the rubber sleeve of the long core holder for applying confining pressure; the outlet of the long core holder is connected to the inlet of the back pressure valve; the outlet of the back pressure valve is connected to the inlet of the gas chromatograph; the outlet of the gas chromatograph is connected to the inlet of the gas flow meter; the control end of the back pressure valve is connected to the back pressure pump; the pressure acquisition system includes an inlet pressure gauge and an outlet pressure gauge, which are respectively installed at the inlet and outlet of the long core holder for real-time monitoring of pressure changes during the displacement process.

[0021] Meanwhile, in the long core displacement experimental apparatus of this application, high-purity methane ( As a representative gas of natural gas, it is used , and All gases were supplied by standard gas cylinders with a purity of 99.99%; in the experimental environment of the experimental apparatus, the maximum temperature was 150℃, the maximum pressure was 60MPa, the accuracy of monitoring the outlet flow rate was 0.1ml / min, the accuracy of monitoring the outlet gas composition was 0.01%, the injection rate was 0.1-0.4 ml / min, and the inner diameter of the high temperature and high pressure long core holder was 25mm.

[0022] S2: Based on the permeability and length of the core samples, the preset harmonic permeability average calculation method is used to calculate the harmonic permeability average of each core sample. The core samples are then sorted based on the harmonic permeability average and sequentially placed into the rubber sleeve of the long core holder to obtain an equivalent long core. The expression for the preset harmonic permeability average calculation method is as follows: ; in, This is the harmonic average of the permeability. This represents the total length of all core samples used in the calculation. Let i be the length dimension of the i-th core sample. Let i be the permeability value of the i-th core sample; This represents the number of core samples.

[0023] S3: Establishing water saturation for the equivalent long core in the long core holder, saturating the equivalent long core with methane, and raising the experimental environment of the equivalent long core to reservoir temperature and pressure; wherein, S3 includes: S3-1: The assembled equivalent long core is placed in a long core holder, and a preset confining pressure is applied using a confining pressure pump. A semi-permeable membrane displacement method is then used to remove free water from the core pores of the equivalent long core, establishing a water saturation level matching that of a real gas reservoir. Specifically, the semi-permeable membrane displacement method involves: First, the core was saturated using a constant-pressure water injection method, and then water was injected into the core. Displacement is carried out, and the established water saturation is determined by measuring the drainage volume at the outlet end. The value of water saturation can be determined based on geological data.

[0024] S3-2: Methane gas with a purity of ≥99.99% is continuously injected into the long core holder by a displacement pump. The inlet and outlet pressures and gas composition of the long core holder are monitored in real time. When the inlet and outlet pressure difference is less than 0.05MPa and the outlet methane volume fraction remains stable, it is determined that the equivalent long core has reached the state of complete methane saturation. S3-3: In the experimental environment of the equivalent long core, the temperature is raised to 100℃ and the pressure is raised to 27MPa. The constant temperature and pressure are maintained for no less than 12 hours to make the temperature field, pressure field and fluid distribution inside the core reach a uniform equilibrium.

[0025] S4: Perform pressure decay treatment on the equivalent long core after saturation treatment by stepwise depressurization until the preset waste pressure is reached. Record the volume data of produced methane to obtain the methane production without gas injection intervention. S4 includes: S4-1: Obtain the equivalent long core after saturation treatment. Install a flow meter at the outlet end of the long core holder of the equivalent long core and connect a confining pressure pump to the long core holder. Specifically, connect a back pressure valve, a gas chromatograph and a high-precision gas flow meter in sequence at the outlet end of the long core holder. The outlet pressure is controlled by the back pressure pump and the back pressure valve. Install pressure sensors at the inlet and outlet ends of the long core holder to collect and record inlet pressure, outlet pressure and differential pressure data in real time to ensure that the pressure decay process is controllable, monitorable and reproducible.

[0026] S4-2: Pressure attenuation treatment of the equivalent long core is carried out using a confining pressure pump at pressures of 1 MPa per step. During the treatment, the pressure is further reduced after the flow meter shows a flow rate of 0, until the pressure is attenuated to the abandonment pressure of 8 MPa. Specifically, the attenuation treatment in this application is carried out by using a step-by-step pressure reduction method with a preset abandonment pressure of 8 MPa as the endpoint, to conduct a natural pressure attenuation experiment. 1. Using 1 MPa as a pressure reduction step, the back pressure at the outlet end is reduced by a back pressure pump, so that the equivalent long core pore pressure decreases step by step; 2. After each stage of pressure reduction is completed, maintain the current pressure and observe the real-time flow rate of the high-precision gas flow meter; 3. When the flow meter shows that the flow rate drops to 0 ml / min and remains stable for at least 30 minutes, it is determined that methane has been fully produced under this stage pressure, and then the next stage pressure reduction is carried out; 4. Repeat the above process of depressurization-stabilization-zero gas production until the equivalent long core pore pressure drops to the preset abandonment pressure of 8 MPa, thus completing the entire process of natural pressure decay without gas injection intervention.

[0027] S4-3: Throughout the pressure decay process, the chromatograph calibration factor is calibrated using standard gases, such as 70% carbon dioxide and 30% methane. This calibrates the chromatograph, and the produced gas is then passed through the chromatograph for methane detection to obtain the methane yield without gas injection intervention. The expression is: ; in, Let be the volume of gas produced by the i-th stage of depressurization; The volume fraction of methane in the i-th stage depressurization product gas; The dead volume of the experimental system. This represents the number of stages of exhaustion and degradation.

[0028] S5: Based on the exhaustion to the abandonment pressure, inject gas into the equivalent long core to the preset pressure, stabilize for a preset time until the internal fluid reaches static equilibrium, and then gradually reduce the pressure to the abandonment pressure again. Record the volume multiple of methane in the produced gas to obtain the methane production due to the stripping physical pushing effect. S5 includes: S5-1: The equivalent long core, depleted to 8 MPa, is pressurized by injecting carbon dioxide gas using a confining pressure pump. After injection to 12 MPa, it is stabilized for 12 hours until the fluid inside the equivalent long core reaches static equilibrium. Specifically, the equivalent long core, having completed step S4 and depleted to an abandoned pressure of 8 MPa, is kept at a confining pressure 5 MPa higher than the pore pressure to maintain core structural stability. Carbon dioxide gas with a purity ≥99.99% is slowly injected into the long core holder using a displacement pump to uniformly increase the pore pressure of the equivalent long core from 8 MPa to the preset pressure of 12 MPa. After pressurization, the core inlet and outlet valves are closed, placing the core in a completely static and sealed state. It is then kept at a constant temperature (100℃) for 12 hours to ensure that carbon dioxide and residual methane diffuse fully within the pores, and that the pressure and component fields are completely uniform, achieving thermodynamic static equilibrium and completely eliminating flow displacement.

[0029] In this embodiment, as Figure 3 As shown, after exhaustion to 8 MPa, injection or This application addresses the issue of effectively improving gas reservoir recovery rates. Or note A comparative analysis was conducted to determine which methods are more beneficial for improving gas reservoir recovery. Among them, under the experimental pressure of 8 MPa and temperature of 100℃, It is in a supercritical state. and Significant differences in physical properties exist between them, which is beneficial for forming a stable displacement front during the displacement process, thereby effectively suppressing viscous fingering and improving macroscopic sweep efficiency. Meanwhile, supercritical... Adsorbed on the surface of reservoir pores Competitive adsorption occurs, promoting the adsorption state Desorption and participation in the flow further improve the efficiency of microscopic displacement.

[0030] In comparison, Under the same conditions, it remains in the gas phase, and... Due to their similar physical properties, the two substances are prone to gas-phase mixing and miscibility during displacement, making it difficult to maintain a clear displacement interface; furthermore, because Its adsorption capacity on the reservoir medium surface is weaker than It is difficult to replace the adsorbed state. Therefore, in terms of enhancing natural gas recovery, injection... The effect is significantly better than injection .

[0031] S5-2: The equivalent long core that has reached static equilibrium is then depressurized to 8 MPa in stages using a confining pressure pump at 1 MPa increments. During the depressurization process, the pressure is further reduced when the flow meter shows a flow rate of 0. Specifically, the re-attenuation experiment is carried out with the abandoned pressure of 8 MPa as the endpoint, using the same equal-step depressurization method as in S4. 1. Using 1 MPa as a pressure reduction step, the outlet back pressure is adjusted by the back pressure pump to gradually reduce the core pore pressure; 2. Maintain stable pressure after each stage of pressure reduction, and monitor the outlet high-precision gas flow meter in real time; 3. When the flow rate drops to 0 ml / min and remains stable for at least 30 minutes, it is determined that methane has been fully produced under the current pressure, and then the next stage of pressure reduction is carried out; 4. Repeat the above process until the core pore pressure drops to 8 MPa, completing the entire re-attenuation process contributed solely by pressurization and energy replenishment.

[0032] S5-3: During the entire re-attenuation process, the calibration factor of the chromatograph needs to be calibrated again using standard gas. The produced gas is monitored by the chromatograph, and the volume multiple of methane in the produced gas is recorded. The methane yield is then calculated to obtain the production yield. The expression is: ; in, Let J be the volume of gas produced by the j-th stage of depressurization. The volume fraction of methane in the product gas from the j-th stage of depressurization. The dead volume of the experimental system. This refers to the number of stages in the pressure reduction phase.

[0033] S6: Repeat steps S3-S4, injecting the same gas as in step S5 into the equivalent long core at a constant rate to conduct a gas injection and recovery experiment. When the flow rate in the equivalent long core is detected to be steadily increasing at a preset rate, the gas components are detected by chromatograph. When the methane content in the gas components is lower than the preset methane content threshold, the gas injection and recovery experiment is stopped, and the methane production from pure gas displacement is obtained. S6 includes: S6-1: The equivalent long core obtained in step S5 is subjected to saturation treatment in step S3 and pressure attenuation treatment in step S4 to obtain an equivalent long core with pressure attenuated to 8 MPa. In this embodiment, after cleaning, drying and reassembling the equivalent long core after step S5, the water saturation and methane saturation treatment are established again according to the method in step S3, and the temperature is raised to 100°C and the pressure is raised to 27 MPa. The temperature and pressure are kept constant for no less than 12 hours, and then the pressure is gradually reduced to the abandonment pressure of 8 MPa according to step S4 to ensure that the initial state of this gas injection displacement experiment is consistent with S4 and S5. S6-2: Carbon dioxide gas is injected into the equivalent long core at a constant rate using a confining pressure pump. Simultaneously, a flow meter is activated to monitor the flow rate inside the equivalent long core. When the flow rate steadily increases according to the preset flow rate, the components of the produced gas are detected by a chromatograph. Specifically, the confining pressure is kept 5 MPa higher than the pore pressure. Carbon dioxide gas with a purity of ≥99.99% is injected into the inlet end of the equivalent long core at a constant injection rate (0.5 ml / min in this embodiment) using a displacement pump to carry out a continuous gas injection displacement and extraction experiment. Throughout the experiment, the inlet and outlet pressures and pressure difference were monitored by a pressure sensor, and the output gas flow rate was recorded in real time by a high-precision gas flow meter. When the flow meter showed a stable flow rate without drastic fluctuations, it was determined that the displacement had entered a stable flow state, and the gas chromatograph was simultaneously turned on to continuously detect the components of the output gas and the volume fraction of methane online.

[0034] In this embodiment, as Figure 4 and Figure 5As shown, pressurization and energy replenishment play a dominant role in the displacement process. This is because, under continuous gas injection conditions, this mechanism creates an effective macroscopic pressure gradient by establishing a high-pressure zone at the injection end, thereby driving the reservoir fluid to migrate as a whole towards the production end.

[0035] The experimental conditions were set at a pressure of 8 MPa and a temperature of 100 °C. Under these temperature and pressure conditions, In a supercritical state, it possesses both the low viscosity of a gas and the high density of a liquid, giving it excellent flowability and sweep efficiency during displacement, enabling it to effectively enter micropores and displace residual natural gas. In contrast, and Due to their similar physical properties, both substances are prone to gas-phase mixing and fingering at the displacement front, resulting in relatively low displacement efficiency. Therefore, under these experimental conditions, The displacement contribution was significantly higher than .

[0036] S6-3: This step also requires calibrating the chromatograph's correction factor. Then, the methane content threshold is preset to 5 mol%. When the chromatograph shows a methane volume fraction ≤ 5 mol% in the produced gas after three consecutive detections, it is determined that the mobile methane in the core has been sufficiently displaced. Gas injection and displacement are immediately stopped. The volume of produced gas and the methane volume fraction are recorded at fixed time intervals, and the total methane production during the entire displacement process is accumulated. The methane yield is then calculated. The expression is: ; in, Let be the volume of gas produced during the k-th measurement period. Let methane be the volume fraction in the produced gas during the k-th time period. The dead volume of the experimental system. This refers to the number of metering points during the gas injection and extraction stage.

[0037] S7: Based on methane production Methane production and methane production The calculation of methane increments contributed by the boosting and displacement effects is performed, and the contribution rates of the boosting and displacement effects are calculated using preset calculation methods and formulas. Specifically, S7 includes: S7-1: Methane extraction yield Methane production and methane production ; S7-2: The contribution of the pressurization boost effect is calculated using the preset calculation method. The expression is: ; ; ; in, The degree of contribution to pressurization and energy replenishment; This represents the total increase in methane content; The increase in methane volume contributed to the pressurization and energy replenishment effect; S7-3: Calculate the contribution of the displacement effect using the preset gas injection displacement contribution formula. The expression is: ; ; in, To the extent of contribution to displacement, The increase in methane contributed to the displacement process.

[0038] In particular, step S7 employs a quantitative calculation model that decouples mechanisms, addressing the problem in existing technologies that can only measure overall recovery rate and cannot separate pressurization and physical displacement. First, the calculation model converts absolute increments into relative contribution percentages, allowing for comparison, evaluation, and optimization of mechanistic contributions under different gas reservoirs and experimental conditions, thus solving the technical pain point of being unable to quantitatively compare the strength of mechanisms. Second, all variables are derived from indoor experimental calibration data, without assumptions, fitting, or empirical parameters, making it an experiment-driven quantitative method. Finally, the pressurization and displacement increments calculated in this step can be directly linked to the competitive adsorption in step S8 and the global total contribution in step S9, forming a fully decoupled, fully quantified, and fully closed calculation system encompassing the three major mechanisms of pressurization / energy replenishment, physical displacement, and competitive adsorption.

[0039] S8: Obtain rock powder from the same source as the equivalent long core for gas adsorption experiments, measure methane dissipation, and calculate the methane increment of the equivalent long core under competitive adsorption based on the methane dissipation; wherein, S8 includes: S8-1: Rock powder was prepared by scraping and crushing core samples from the same source as the equivalent long core, and gas adsorption experiments were conducted using the rock powder to measure the amount of methane released. Specifically, crack-free and uncontaminated core blocks were cut from the same source core samples constituting the equivalent long core, crushed, ground, and sieved to prepare rock powder with a particle size of 100-120 mesh. The rock powder was dried in a 100℃ oven for 24 hours, cooled to room temperature, and then placed in a desiccator for later use to ensure that the powder was free of free water and impurities, thus eliminating the effect of moisture on adsorption. Interference in the analysis results; The dried rock powder was loaded into the sample container of a high-temperature, high-pressure adsorption instrument, and methane adsorption was carried out at the same experimental temperature (100℃) as the equivalent long rock core. Analysis of the experiment: 1. Introduce high-purity methane (purity ≥ 99.99%) into the sample container, pressurize to 12 MPa and keep it at a constant temperature for 8 hours to allow the rock powder to reach full methane adsorption saturation; 2. Slowly reduce the pressure to the exhaust pressure of 8 MPa, and maintain the pressure until no gas is released. Use a high-precision gas metering device to measure and record the total volume of methane released. This volume represents the volume of homologous rocks under the same temperature and pressure conditions. The amount of methane eluent from the displacement; 3. The experiment was repeated 3 times, and the average value was taken as the final methane dissolution rate to reduce random error in the experiment.

[0040] S8-2: The methane increment independently contributed by the equivalent long core under competitive adsorption is obtained by equivalent conversion of the methane dissipation amount. Specifically, based on the total methane analysis volume of the equivalent long core... The rock powder sample mass m and the total adsorbed powder mass M in the sample container are equivalently converted into the methane increment contributed independently by competitive adsorption at the equivalent long core scale. The expression is: ; ; in, The methane content is expressed per unit mass of core.

[0041] In step S8 of this application, the displacement process is further... The contribution of competitive adsorption was quantitatively analyzed. Based on static adsorption experimental data, under an equilibrium pressure of 8 MPa, the contribution of sandstone powder to... The adsorption capacity is approximately 0.75. The adsorption capacity of intact core samples is approximately one-tenth that of powder samples. This difference is mainly attributed to the fact that powder samples expose more adsorption sites, while core samples contain cement and pore structures that restrict the adsorption space. Based on this, it can be inferred that the adsorption capacity of long core samples after saturation... The adsorption capacity is approximately 23 Assuming injection It can achieve adsorption state through competitive adsorption. If complete desorption occurs, the competitive adsorption mechanism contributes approximately 8% to the recovery improvement. This result indicates that in sandstone... While competitive adsorption makes a certain contribution during the process, its role is still secondary compared to macroscopic displacement mechanisms such as pressurization and energy replenishment.

[0042] S9: Based on the methane increments due to competitive adsorption, pressurization and energy replenishment, and displacement, calculate the combined contribution of competitive adsorption, pressurization and energy replenishment, and displacement; where S9 includes: S9-1: Obtaining the methane increment under competitive adsorption The increase in methane volume contributed by the boosting and replenishing effect The increase in methane contributed by displacement The global total methane increment is calculated, and the expression is: ; in, This represents the total global methane increment. S9-2: Based on global total methane increment The combined contributions of competitive adsorption, pressurization and energy replenishment, and displacement were calculated separately, and the expressions are as follows: ; ; ; in, The overall contribution of competitive adsorption. To assess the overall contribution of pressurization and energy replenishment, The overall contribution of displacement.

[0043] S10: Integrate the contribution of pressurization and energy replenishment, displacement and competitive adsorption, pressurization and energy replenishment, and displacement and output the evaluation results of the contribution of oil recovery rate during the gas reservoir enhancement and production process.

[0044] Therefore, through the overall technical solution of this application, this method can address different displacement mechanisms (such as pressurization and energy replenishment, competitive adsorption, and supercritical adsorption). (such as replacement) in The study separated and quantitatively characterized the roles in the process, thus overcoming the limitation of traditional macroscopic displacement experiments in resolving multi-mechanism synergistic effects. The relevant research findings can provide insights for optimizing field [displacement / displacement]. The injection scheme provides theoretical basis and technical support, which helps to formulate differentiated injection strategies for different reservoir conditions and provides an important reference for the coordinated promotion of gas reservoir development and carbon emission reduction under the "dual carbon" target.

[0045] The above are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for quantifying the contribution of different mechanisms to enhanced gas reservoir recovery, characterized in that: include: S1: Obtain a core sample from the plunger sample, and after drying the core sample, measure its permeability and length. S2: Based on the permeability and length of the core sample, the preset permeability harmonic average calculation method is called to calculate the harmonic average permeability of each core sample. Based on the harmonic average permeability, the core samples are sorted and placed into the rubber sleeve of the long core holder in sequence to obtain an equivalent long core. S3: Establish water saturation for the equivalent long core in the long core holder, saturate the equivalent long core with methane, and raise the temperature and pressure of the experimental environment of the equivalent long core to the reservoir temperature and pressure. S4: Perform pressure decay treatment on the equivalent long core after saturation treatment by stepwise depressurization until the preset waste pressure is reached. Record the volume data of produced methane to obtain the methane production without gas injection intervention. ; S5: Based on the exhaustion to the abandonment pressure, inject gas into the equivalent long core to the preset pressure, stabilize for a preset time until the internal fluid reaches static equilibrium, and then gradually reduce the pressure to the abandonment pressure again. Record the volume multiple of methane in the produced gas to obtain the methane production due to the stripping physical pushing effect. ; S6: Repeat steps S3-S4 with the equivalent long core from S5, injecting the same gas as in step S5 into the equivalent long core at a constant rate to conduct a gas injection and recovery experiment. When the flow rate in the equivalent long core is detected to be steadily increasing at a preset rate, the gas components are detected by chromatography. When the methane content in the gas components is lower than the preset methane content threshold, the gas injection and recovery experiment is stopped, yielding the methane production from pure gas displacement. ; S7: Based on methane production Methane production and methane production The methane increment contributed by the boosting and replenishing effect and the methane increment contributed by the displacement effect are calculated. The preset calculation method for the contribution of gas injection boosting and the preset calculation formula for the contribution of gas injection displacement are used to calculate the contribution of boosting and replenishing effect and the contribution of displacement effect respectively. S8: Obtain rock powder of the same origin as the equivalent long core for gas adsorption experiments, measure methane dissipation, and calculate the methane increment of the equivalent long core under competitive adsorption based on the methane dissipation. S9: Based on the methane increment under competitive adsorption, the methane increment contributed by pressurization and energy replenishment, and the methane increment contributed by displacement, calculate the comprehensive contribution of competitive adsorption, pressurization and energy replenishment, and displacement. S10: Integrate the contribution of pressurization and energy replenishment, displacement and competitive adsorption, pressurization and energy replenishment, and displacement and output the evaluation results of the contribution of oil recovery rate during the gas reservoir enhancement and production process.

2. The method for characterizing the contribution of different mechanisms to enhanced gas recovery as described in claim 1, characterized in that: S4 includes: S4-1: Obtain the equivalent long core after saturation treatment, install a flow meter at the outlet end of the long core holder of the equivalent long core, and connect the confining pressure pump to the long core holder. S4-2: Pressure attenuation treatment of equivalent long core is carried out by confining pressure pump at a pressure of 1 MPa. During the treatment, the pressure is further reduced after the flow meter shows 0, until it is exhausted to the abandonment pressure of 8 MPa. S4-3: The chromatograph calibration factor is calibrated using a standard gas. After calibration, the chromatograph is used to detect methane in the produced gas to obtain the methane yield without gas injection interference. The expression is: ； in, Let be the volume of gas produced by the i-th stage of depressurization; The volume fraction of methane in the i-th stage depressurization product gas; The dead volume of the experimental system. This represents the number of stages of exhaustion and degradation.

3. The method for characterizing the contribution of different mechanisms to enhanced gas recovery as described in claim 2, characterized in that: S5 includes: S5-1: The equivalent long core, which has been depleted to 8 MPa, is pressurized by injecting carbon dioxide gas into the confining pressure pump. After the gas is injected to 12 MPa, it is stabilized for 12 hours until the fluid inside the equivalent long core reaches static equilibrium. S5-2: The equivalent long core that has reached static equilibrium is then depressurized to 8 MPa in stages using a confining pressure pump at a pressure of 1 MPa per stage. During the depressurization process, the pressure is further reduced when the flow rate of the flow meter shows 0. S5-3: The chromatograph calibration factor is calibrated using standard gas. After calibration, the volume ratio of methane in the produced gas is detected by the chromatograph, and the methane yield is calculated. The expression is: ； in, Let J be the volume of gas produced by the j-th stage of depressurization. The volume fraction of methane in the product gas from the j-th stage of depressurization. The dead volume of the experimental system. This refers to the number of stages in the pressure reduction phase.

4. The method for characterizing the contribution of different mechanisms to enhanced gas recovery as described in claim 3, characterized in that: S6 includes: S6-1: The equivalent long core obtained in step S5 is subjected to saturation treatment in step S3 and pressure attenuation treatment in step S4 to obtain an equivalent long core with pressure attenuated to 8MPa. S6-2: Carbon dioxide gas is injected into the equivalent long core at a constant rate using a confining pressure pump. Simultaneously, a flow meter is activated to monitor the flow rate inside the equivalent long core. When the flow rate increases steadily according to the preset flow rate, the components of the produced gas are detected by a chromatograph. S6-3: Use standard gas to calibrate the chromatograph calibration factor. After calibration, the chromatograph detects methane in the produced gas. If the methane content is lower than the preset methane content threshold, stop the gas injection and calculate the methane yield. The expression is: ； in, Let K be the volume of gas produced during the k-th metering period. The volume fraction of methane in the produced gas during the k-th time period. The dead volume of the experimental system. This refers to the number of metering points during the gas injection and extraction stage.

5. The method for characterizing the contribution of different mechanisms to enhanced gas recovery as described in claim 1, characterized in that: S7 includes: S7-1: Methane extraction yield Methane production and methane production ; S7-2: The contribution of the pressurization boost effect is calculated using the preset calculation method. The expression is: ； ； ； in, The degree of contribution to pressurization and energy replenishment; This represents the total increase in methane content; The increase in methane volume contributed to the pressurization and energy replenishment effect; S7-3: Calculate the contribution of the displacement effect using the preset gas injection displacement contribution formula. The expression is: ； ； in, To the extent of contribution to displacement, The increase in methane contributed to the displacement process.

6. The method for characterizing the contribution of different mechanisms to enhanced gas recovery as described in claim 5, characterized in that: S8 includes: S8-1: Rock powder was prepared by scraping and crushing from the same source core sample of equivalent long core, and the amount of methane eluent was measured by gas adsorption experiment of the rock powder. S8-2: The methane increment independently contributed by the equivalent long core under competitive adsorption is obtained by equivalent conversion of the methane dissipation amount. .

7. The method for characterizing the contribution of different mechanisms to enhanced gas recovery as described in claim 6, characterized in that: S9 includes: S9-1: Obtaining the methane increment under competitive adsorption The increase in methane volume contributed by the boosting and replenishing effect The increase in methane contributed by displacement The global total methane increment is calculated, and the expression is: ； in, This represents the total global methane increment. S9-2: Based on global total methane increment The combined contributions of competitive adsorption, pressurization and energy replenishment, and displacement were calculated separately, and the expressions are as follows: ； ； ； in, The overall contribution of competitive adsorption. To assess the overall contribution of pressurization and energy replenishment, The overall contribution of displacement.

8. The method for characterizing the contribution of different mechanisms to enhanced gas recovery as described in claim 1, characterized in that: In step S2, the expression for the preset calculation method of the harmonic average permeability is: ； in, This is the harmonic average of the permeability. This represents the total length of all core samples used in the calculation. Let i be the length dimension of the i-th core sample. Let i be the permeability value of the i-th core sample; This represents the number of core samples.

9. The method for characterizing the contribution of different mechanisms to enhanced gas recovery as described in claim 1, characterized in that: S3 includes: S3-1: Apply a preset confining pressure to the long core holder where the assembled equivalent long core is located by using a confining pressure pump, and remove the free water in the core voids of the equivalent long core by using an ultra-high speed centrifugation method to establish a water saturation that matches the real gas reservoir. S3-2: Methane gas with a purity of ≥99.99% is continuously injected into the long core holder by a displacement pump, and the inlet and outlet pressures and gas composition of the long core holder are monitored in real time until the equivalent long core reaches a state of complete methane saturation. S3-3: In the experimental environment of the equivalent long core, the temperature is increased to 100℃ and the pressure is increased to 27MPa, and the temperature and pressure are kept constant.

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