A method for evaluating carbon dioxide flooding and storage effect coupled with nuclear magnetic resonance-production analysis

Abstract

The present application belongs to the technical field of carbon capture, utilization and storage, and particularly relates to a method for evaluating CO2 flooding and storage effect by coupling nuclear magnetic resonance and production analysis. The method comprises the following steps: preparation; single CO2 or CO2 composite medium displacement; quantitative evaluation of oil displacement effect; quantitative evaluation of storage effect; comprehensive evaluation of CO2 flooding and storage effect. Nuclear magnetic resonance (NMR) and production analysis are coupled to evaluate the CO2 flooding and storage effect, and the quantitative coupling of micro mechanism and macro output is realized.

Description

Technical Field

[0001] This invention belongs to the technical field of carbon capture, utilization and storage, and specifically relates to a method for evaluating the effect of carbon dioxide flooding and storage coupled with nuclear magnetic resonance-product analysis. Background Technology

[0002] CO2 enhanced oil recovery and storage (CO2-EOR) involves injecting captured CO2 into oil reservoirs. This not only displaces crude oil and improves oil recovery but also stores CO2 in the underground reservoir for extended periods, achieving a synergistic effect of CO2 resource utilization and emission reduction. However, the displacement mechanism of CO2 under formation conditions is complex, involving multiphase and multi-component coupled processes such as the miscibility / immiscibility of CO2 with crude oil, the dissolution of CO2 in formation water, and the reaction of CO2 with minerals. Accurate evaluation of its oil recovery and storage effects is a key scientific foundation for promoting the large-scale application of CCUS (carbon capture, utilization, and storage).

[0003] CO2 flooding is an important technology for enhancing oil recovery. It comprehensively utilizes the synergistic effects of multiple mechanisms, including viscosity reduction, expansion, miscibility to reduce interfacial tension, light hydrocarbon extraction, dissolved gas drive, and formation dissolution, to improve recovery while simultaneously providing the dual benefits of oil displacement and geological preservation. However, in actual oilfield development, pure CO2 is costly and its source is limited. Therefore, CO2 is often mixed with other gases or used as a displacement medium, such as industrial waste gas or associated gas. Commonly used mixtures in the field include CO2 with hydrocarbon gases such as CH4, CO2 with flue gas, CO2 with nitrogen, and CO2 with sulfur-containing gases such as H2S.

[0004] However, CO2 and its composite gas flooding also have some problems. In highly heterogeneous reservoirs (such as those with well-developed fractures and large permeability differences), gas can easily surge along high-permeability channels or fractures, resulting in a small swept volume. Furthermore, the viscosity of CO2 is much lower than that of crude oil (usually 1-2 orders of magnitude lower), which is very unfavorable in terms of mobility ratio, making fingering and gas channeling highly likely. To suppress gas channeling and expand the swept volume, existing technologies have proposed Water Alternating Gas (WAG) injection. By alternately injecting CO2 and water, the mobility ratio of CO2 is improved, the swept volume is expanded, and the oil displacement efficiency is increased. This has become one of the important technical solutions for CO2 flooding to enhance oil recovery.

[0005] While some studies have applied nuclear magnetic resonance (NMR) technology alone to CO2 flooding experiments to observe fluid saturation and T2 spectrum changes in core pores, NMR technology has not been applied to methods for evaluating CO2 flooding and storage effectiveness. Furthermore, existing methods for evaluating CO2 flooding and storage effectiveness suffer from the following prominent problems: First, the microscopic mechanisms and macroscopic outputs are independent and separate. Nuclear magnetic resonance (NMR) technology is mostly used as an auxiliary observation tool, only qualitatively showing the changes in pore fluid distribution before and after displacement. Output data (such as oil production, gas production, pressure, gas-oil ratio, etc.) are analyzed separately to evaluate the oil displacement effect. A quantitative coupling model has not been established between the two, which means that the displacement / storage mechanism at the microscopic pore scale cannot be mutually verified and explained with the macroscopic output laws, resulting in weak evaluation results.

[0006] Second, the testing is mainly static / phased, which cannot achieve in-situ dynamic monitoring of the displacement process. Most existing nuclear magnetic resonance displacement experimental devices require interruption of the displacement process, suspension of flow, or even removal of the core to complete the nuclear magnetic resonance scan. This is a "post-completion" and "segmented" evaluation, which cannot continuously track the real-time evolution of the pore fluid state during the displacement process. It is difficult to capture the dynamic process of transient seepage phenomena such as gas channeling, fingering, and miscible front breakthrough, and it is easy to miss key mechanism information.

[0007] Third, the quantitative characterization of CO2 storage mechanisms is insufficient, and the uncertainty in CO2 storage calculation is significant. Most existing methods focus on recovery / displacement efficiency evaluation, with relatively weak evaluation of CO2 storage effectiveness. Traditional storage estimation methods such as the single material balance method have large errors and cannot quantitatively distinguish the contribution ratios of different CO2 storage mechanisms such as structural storage, bound storage, dissolution storage, and mineralization storage. Therefore, they cannot meet the actual needs of CCUS projects for storage safety assessment and accurate storage calculation.

[0008] Fourth, the evaluation results suffer from high uncertainty and limited reliability. Single macroscopic production data (such as an increase in the gas-oil ratio) cannot provide real-time observation of fluid distribution and crude oil utilization within the core. It relies solely on indirect inversion from production-end data, resulting in limited information and difficulty in revealing the fluid displacement mechanism within the microscopic pores during the displacement process. Single nuclear magnetic resonance (NMR) technology is only used to qualitatively or semi-quantitatively demonstrate changes in pore fluid distribution before and after displacement. It fails to establish a quantitative coupling model with real-time macroscopic production data (such as oil production, gas production, and pressure response), leading to a "disconnect" between microscopic pore-scale information and macroscopic production effects. This prevents the quantitative explanation and mutual verification of macroscopic production patterns by microscopic mechanisms.

[0009] Fifth, the analysis of produced fluids is incomplete. Most existing experimental devices only perform simple metering of the produced liquid and lack the ability to perform multi-component online accurate analysis of produced gas, produced water and produced oil. They cannot accurately calculate the distribution ratio of CO2 in the gas, water and oil phases, and it is difficult to accurately assess the CO2 sequestration ratio and sequestration efficiency.

[0010] Sixth, the comprehensive evaluation method for the combined effect of CO2 composite media displacement and CO2 sequestration is still imperfect. At present, CO2 composite media displacement experiments lack a systematic method that can simultaneously and quantitatively calculate carbon sequestration efficiency and CO2 oil displacement efficiency and realize gas-liquid-solid three-phase carbon balance analysis, making it difficult to comprehensively evaluate the carbon sequestration and oil displacement effects of CO2-EOR projects. Summary of the Invention

[0011] The purpose of this invention is to provide a method for evaluating the effectiveness of carbon dioxide flooding and storage by coupling nuclear magnetic resonance (NMR) with production analysis. This invention couples NMR with production measurement analysis to evaluate the effectiveness of CO2 flooding and storage, achieving quantitative coupling between microscopic mechanisms and macroscopic production.

[0012] The technical solution of this invention is as follows: A method for evaluating the effectiveness of carbon dioxide flooding and sequestration coupled with nuclear magnetic resonance (NMR) and production analysis, comprising the following steps: (1) Preparation: S1. Select representative plunger cores from the target block, wash and dry them; determine the core porosity; test the core porosity using a porosity measuring instrument.

[0013] S2. First, the core was vacuum-saturated with oil and the initial T2 spectrum was tested by nuclear magnetic resonance to clarify the pore structure and pore distribution of the core under the initial conditions.

[0014] Then, after washing and drying, the initial T2 and HSE spectrum scans were performed again by nuclear magnetic resonance to obtain the reference nuclear magnetic signal intensity values ​​of the core.

[0015] S3. First, the core is vacuum-saturated with formation water. The confining pressure and temperature are applied to the core to simulate formation conditions. Crude oil is injected into the core at a constant rate or pressure until it is in a bound water state. The water production rate at the outlet is <2%.

[0016] Then, T2 and HSE spectrum scans were performed again by nuclear magnetic resonance to obtain NMR data of saturated oil under bound water conditions; these data served as comparative parameters for subsequent evaluation of displacement effects.

[0017] (2) Displacement by a single CO2 or CO2 composite medium: S1. Inject a single CO2 into the core at constant pressure or constant rate to perform single CO2 displacement; or inject a CO2 composite medium alternately / simultaneously into the core at constant pressure or constant rate to perform CO2 composite medium displacement.

[0018] It should be noted that when CO2 is combined with other gases to form a composite medium, the other gases must not contain CO2. This is to avoid situations where the same type of gas, such as flue gas, contains an unknown volume fraction of CO2, making it impossible to accurately measure the total amount of CO2 injected, and thus impossible to determine the proportion of CO2 to be sealed.

[0019] In addition, to avoid interference with the NMR results, hydrocarbon gases such as CH4 and gases containing H atoms such as H2S are avoided when using other gases for recombination.

[0020] When using alternating gas-water displacement, the formation water needs to be prepared using heavy water (D2O); if H2O is used, a certain mass fraction of MnCl2 needs to be added to shield the H in the H2O. + The influence of signal interference on nuclear magnetic resonance.

[0021] S2. During the displacement process, the core is scanned in real time using nuclear magnetic resonance T2 spectrum and HSE spectrum at preset time intervals. The time interval can be set according to requirements, such as at intervals of a certain number of pore volumes (PV) or at fixed time intervals. The displacement flow does not need to be interrupted during real-time scanning, nor does the core need to be removed.

[0022] S3. During the real-time nuclear magnetic resonance scanning process, the produced fluid data at the core outlet end is simultaneously collected through the production metering and analysis system, including cumulative oil production, cumulative gas production, cumulative water production, instantaneous oil production, instantaneous gas production, instantaneous water production, gas-oil ratio (GOR), and other results.

[0023] The output measurement and analysis system includes a pressure gauge at the extraction end, a gas flow meter, a gas chromatograph, an output water flow meter, an ion chromatograph, an output oil flow meter, and a Fourier transform infrared spectrometer.

[0024] The pressure gauge at the extraction end is used to detect the real-time pressure at the extraction end. The gas flow meter is used to determine the gas production rate.

[0025] Gas chromatographs are used to detect and analyze the full composition of produced gases, including CO2, N2, CH4, C2H6 and hydrocarbons with more than C3 atoms. They can obtain the volume fraction and precise content of CO2 and various gases in real time, providing a data basis for calculating CO2 sequestration.

[0026] The water production flow meter is used to measure the cumulative water production. The oil production flow meter is used to measure the cumulative oil production.

[0027] Ion chromatography (IC) is used to quantitatively analyze the concentration of various ions in the produced water, providing data for calculating the amount of CO2 dissolved in the aqueous phase and the degree of gas-water-rock reaction.

[0028] Fourier transform infrared spectroscopy (FTIR) is used to analyze the functional group composition of produced oil and the amount of CO2 dissolved in crude oil.

[0029] The corresponding time points and cumulative injection volume pore volume multiples (PV) are recorded. The T2 spectrum and HSE spectrum data at each time point are calibrated and aligned with the production dynamic data at the same time point to form a time-series coupled dataset of micropore response and macro production response.

[0030] S4. After the displacement is completed, record and organize all the data. Then, wash and dry the core used in the experiment. Measure the porosity of the core after displacement.

[0031] Then, the core after displacement was vacuum-saturated with crude oil and subjected to nuclear magnetic resonance T2 spectrum testing to obtain the pore structure and pore distribution of the core after displacement.

[0032] (3) Quantitative evaluation of oil displacement effect: S1. According to formula (1), calculate the microscopic oil displacement efficiency at different times during the displacement process based on the change of signal intensity area in the T2 spectrum at different times. (1); In the formula, —Microscopic oil displacement efficiency calculated by NMR at a certain moment, %; all relaxation time periods in the T2 spectrum obtained at that moment; —The sum of the signal intensities during all relaxation time periods of the saturated oil NMR T2 (after subtracting the area correction of the matrix NMR signal intensity) is dimensionless; —The sum of the signal intensities during all relaxation time periods of the NMR at a given moment (after subtracting the area correction of the matrix NMR signal intensity), dimensionless.

[0033] S2. Calculate the microscopic oil displacement efficiency after the entire displacement process is completed according to formula (2). ; (2) In the formula, —Microscopic oil displacement efficiency calculated by NMR after the entire displacement process is completed, %; All relaxation time periods in the T2 spectrum obtained after the entire displacement process is completed. —The sum of the signal intensities during all relaxation time periods of the saturated oil NMR T2 (after subtracting the area correction of the matrix NMR signal intensity) is dimensionless; —The sum of the signal intensities during all relaxation time periods of the NMR T2 obtained after the entire displacement is completed (after subtracting the area correction of the matrix NMR signal intensity), dimensionless.

[0034] Generally, pores with relaxation times of 0.001ms-1ms are defined as micropores; pores with relaxation times of 1ms-10ms are defined as small pores; pores with relaxation times of 10ms-100ms are defined as medium pores; and pores with relaxation times of more than 100ms are defined as large pores.

[0035] S3. According to formula (3), calculate the HSE oil displacement efficiency at different times during the displacement process based on the change of signal intensity area in the T2 spectrum at different times. (3); In the formula, —The oil displacement efficiency calculated by NMR HSE at a certain moment, %; corresponding to all locations in the entire core. —The sum of all signal intensity values ​​at all locations in the entire core corresponding to the saturated oil NMR (after correction by subtracting the matrix NMR signal intensity value), dimensionless; —The sum of all signal intensity values ​​at all locations in the entire core at a given moment (after subtracting the matrix NMR signal intensity value for correction), dimensionless.

[0036] S4. Calculate the total HSE oil displacement efficiency after the entire displacement process is completed according to formula (4): (4); In the formula, —HSE total oil displacement efficiency calculated by NMR, %; corresponding to all locations in the core; —The sum of all signal intensity values ​​at the core location corresponding to the saturated oil NMR (HSE) (after correction by subtracting the matrix NMR signal intensity value), dimensionless; —The sum of all signal intensity values ​​at the corresponding core location on the nuclear magnetic resonance (HSE) after the entire displacement process is completed (after subtracting the matrix NMR signal intensity value for correction), dimensionless.

[0037] Macroscopic oil displacement efficiency =Microscopic oil displacement efficiency =HSE Total Oil Displacement Efficiency .

[0038] Macroscopic oil displacement efficiency refers to the recovery rate obtained from the macroscopic recovery rate of the production metering analysis system, after coupling correction with nuclear magnetic resonance (NMR) results. Furthermore, the microscopic oil displacement efficiency results obtained from NMR T2 and HSE spectra are consistent.

[0039] S5. Based on the original oil content of the collected core and the cumulative oil production collected by the production metering and analysis system, calculate the macro-recovery rate according to formula (5). (5); In the formula, —Macro-recovery rate, %; This macro-recovery rate is obtained from the produced fluid data collected at the core extraction end by the production metering and analysis system; —Cumulative oil production, measured in mL, collected by the production measurement and analysis system; —Initial oil content in the core, mL.

[0040] S6. First, calculate the NMR-product coupling correction coefficient according to formula (6). k ; (6); —NMR-product coupling correction coefficient, dimensionless; —Macroscopic oil displacement efficiency, %; of which... =Microscopic oil displacement efficiency ; —Macro-level recovery rate,%.

[0041] Then, the output fluid data collected by the output metering and analysis system are multiplied by... k The value was used to perform NMR-output coupling correction.

[0042] The microscopic oil displacement efficiency obtained from nuclear magnetic resonance (NMR) testing is used to correct the macroscopic recovery rate obtained from the production metering analysis system, establishing a quantitative correlation between the two. This is used to cross-verify and identify potential ineffective displacement stages such as gas channeling and fingering. For example, a sudden increase in the macroscopic gas-oil ratio might occur while the microscopic T2 spectrum shows untapped oil remaining in low- to medium-porosity areas. Furthermore, the correction coefficient obtained from the NMR testing results is used to correct the experimental results from the production metering analysis system, ensuring data accuracy.

[0043] (4) Quantitative evaluation of the sealing effect: S1. Calculate the amount of CO2 stored in the core according to formula (7); (7); In the formula, —CO2 sequestration volume, mL; —The total amount of CO2 injected from the inlet, in mL; —The amount of CO2 produced at the core outlet obtained by the NMR-production coupling correction production measurement analysis system in step (3), in mL; —The amount of CO2 dissolved in the produced water obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of CO2 dissolved in the produced oil obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL.

[0044] The amount of CO2 produced at the core outlet was determined by a combination of an outlet gas flow meter and a gas chromatograph.

[0045] The amount of CO2 dissolved in the produced water was analyzed by ion chromatography using HCO3. - and CO3 2- The concentration was calculated.

[0046] The amount of CO2 dissolved in the produced oil was obtained by measuring the CO2 solubility fraction using a Fourier transform infrared spectrometer.

[0047] S2. Calculate the CO2 sequestration efficiency in the core according to formula (8). ; (8); —CO2 sequestration efficiency, % —CO2 sequestration volume, mL; —The total amount of CO2 injected from the inlet, in mL.

[0048] S3. Classify CO2 sequestration types into dissolution sequestration, bound sequestration, and mineralization sequestration, and calculate the proportion of different CO2 sequestration types: First, calculate the CO2 dissolution and sequestration ratio according to formulas (9)-(16): (9); In the formula, η water —Contribution of aqueous phase carbon in dissolution sequestration, %; characterizing the proportion of CO2 sequestrated in dissolved water during dissolution sequestration. —The amount of CO2 dissolved in the produced water obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of water produced at the core outlet obtained by the NMR-production coupling correction production metering analysis system in step (3) S6, in mL.

[0049] (10); In the formula, ηoil —Oil phase carbon contribution rate in dissolution sequestration, %; characterizing the proportion of CO2 sequestrated in the form dissolved in oil during dissolution sequestration. —The amount of CO2 dissolved in the produced oil obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of oil produced at the core outlet obtained by the NMR-production coupling correction production metering analysis system in step (3) S6, in mL.

[0050] (11); In the formula, —Residual oil content in the core, mL; —Initial oil content of the core, mL; —The amount of oil produced at the core outlet obtained by the NMR-production coupling correction production metering analysis system in step (3) S6, in mL.

[0051] (12); In the formula, —Residual water volume in the core, mL; —The volume of water injected into the core at the inlet, in mL; —Core pore volume before displacement, mL; S wi —Bound water saturation, dimensionless; —The amount of water produced at the core outlet obtained by the NMR-production coupling correction production metering analysis system in step (3) S6, in mL.

[0052] (13); In the formula, —Volume of CO2 dissolved in water in the core sample, mL; η water —Contribution of aqueous phase carbon in dissolution-sequestration, % —Residual water volume in the core, mL.

[0053] (14); In the formula, —Volume of CO2 dissolved in oil in the core, mL; ηoil —Oil phase carbon contribution rate during dissolution-sequestration, % —Residual oil content in the core, mL.

[0054] (15); In the formula, —CO2 dissolution and storage efficiency, % —Volume of CO2 dissolved in water in the core sample, mL; —Volume of CO2 dissolved in oil in the core, mL; —The volume of CO2 injected at the inlet, in mL.

[0055] (16); In the formula, —CO2 dissolution and sequestration ratio, % —Volume of CO2 dissolved in water in the core sample, mL; —Volume of CO2 dissolved in oil in the core, mL; —CO2 sequestration volume, mL.

[0056] Then, calculate the CO2 binding and sequestration ratio according to formulas (17)-(21): (17); In the formula, —Contribution of gaseous carbon in bound storage %, representing the proportion of CO2 trapped in the core in the gas phase during confinement; —The amount of CO2 mixed in other gases as a composite medium, collected by the NMR-product coupling correction product metering analysis system in step (3) S6, in mL; —The gas output at the core outlet obtained by the NMR-output coupling correction output metering analysis system in step (3) S6, in mL.

[0057] (18); In the formula, —Residual gas volume in the core, mL; —The core pore volume after displacement, in mL; —Residual oil content in the core, mL; —Residual water volume in the core, mL.

[0058] (19); In the formula, —Amount of CO2 present as free gas in the core, mL; —Residual gas volume in the core, mL; —Contribution of gaseous carbon in bound storage ,% represents the proportion of CO2 trapped in the core in the gas phase during confinement.

[0059] (20); In the formula, —CO2 binding and sequestration efficiency, % —Amount of CO2 present as free gas in the core, mL; —The volume of CO2 injected at the inlet, in mL.

[0060] (twenty one); In the formula, —CO2 confinement and sequestration percentage, % —Amount of CO2 present as free gas in the core, mL; —CO2 sequestration volume, mL.

[0061] Finally, the CO2 mineralization sequestration ratio is calculated according to formulas (22)-(25): (twenty two); In the formula, —The total amount of CO2 collected by the NMR-product coupling correction output measurement analysis system in step (3), in mL; —The amount of CO2 dissolved in the produced oil obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of CO2 dissolved in the produced water obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of CO2 mixed in other gases as a composite medium, collected by the NMR-output coupling correction output measurement and analysis system in step (3) S6, in mL.

[0062] (twenty three); In the formula, —Amount of CO2 sequestered in the core via mineralization, in mL; —The volume of CO2 injected at the inlet, in mL; —The total amount of CO2 collected by the NMR-product coupling correction output measurement analysis system in step (3), in mL; —Volume of CO2 dissolved in water in the core sample, mL; —Volume of CO2 dissolved in oil in the core, mL; —Amount of CO2 present as free gas in the core, mL.

[0063] (twenty four); In the formula, —CO2 mineralization and sequestration efficiency, % —Amount of CO2 sequestered in the core via mineralization, in mL; —The volume of CO2 injected at the inlet, in mL.

[0064] (25); In the formula, —CO2 mineralization and sequestration ratio, % —Amount of CO2 sequestered in the core via mineralization, in mL; —CO2 sequestration volume, mL.

[0065] in, .

[0066] By combining core porosity tests before and after the experiment with nuclear magnetic resonance T2 relaxation spectroscopy to determine the changes in pore structure and pore distribution, the changes in pore volume were clarified. The proportions of different CO2 sequestration types were quantitatively determined by combining nuclear magnetic resonance results with the results of its corrected production measurement analysis system.

[0067] It should be noted that the CO2 quantity (volume) obtained from the output measurement analysis system described in the evaluation method and the CO2 quantity (volume) injected have been converted into the CO2 quantity (volume) under experimental (formation) conditions (experimental temperature and experimental pressure) through the real gas equation of state.

[0068] (5) Comprehensive evaluation of CO2 oil displacement and storage effects: S1. Calculate the sealing stability index according to formulas (26) and (27) respectively. Co-storage index of carbon and oil : (26); In the formula, —Storage Stability Index, %; its full name is Storage Stability Index; —Stability weighting coefficients for different storage types, dimensionless; where... =0.5, =0.25, =0.75; mineralized storage is the most stable and has the highest weight; bound storage has the lowest weight because the risk of free gas phase is relatively the greatest. —CO2 dissolution and sequestration ratio, % —CO2 confinement and sequestration percentage, % —CO2 mineralization and sequestration ratio,%.

[0069] (27); In the formula, —Carbon-oil Geosynergy Index, %; its full name is Carbon-oil Geosynergy Index; —The weighting coefficient for CO2 displacement and storage, dimensionless; where When the primary objective is storage (such as a pure geological storage project), then α = 0.7 and β = 0.3; when the primary objective is oil displacement (such as a CCUS-EOR commercial project), then α = 0.3 and β = 0.7; when the objective is balanced (such as a CCUS-EOR collaborative project), then α = 0.5 and β = 0.5. WHAT —CO2 storage efficiency; OE —CO2 oil displacement efficiency; among which... OE = .

[0070] S2. Combining the quantitative evaluation of the oil displacement effect in step (3) and the quantitative evaluation of the sealing effect in step (4), they are divided into different levels and a single-index graded evaluation is carried out. CO2 storage efficiency CE classification is as follows: When CE ≥ 75%, the grade is I, which is excellent; indicating strong sealing capability. When 50% ≤ CE < 75%, the grade is II, which is good; indicating that the storage capability is relatively good. When 25%≤CE<50%, the level is III, medium; indicating that the storage capacity is average. When CE < 25%, the grade is IV, which is poor; indicating weak sealing capability.

[0071] Oil displacement efficiency (OE) classification is as follows: When OE ≥ 75%, the grade is A, which is excellent; indicating good oil displacement effect. When 50%≤OE<75%, the grade is B, which is good; indicating that the oil displacement effect is relatively good. When 25%≤OE<50%, the grade is C, which is medium; indicating that the oil removal effect is average. When OE < 25%, the grade is D, which is poor; indicating poor oil removal effect.

[0072] S3. Introducing a storage stability index AND To evaluate the internal stability of the sealing efficiency; when AND At ≥75%, the storage stability is excellent, mainly through mineralization / dissolution storage, and it is stable in the long term; When 50%≤ AND When the content is less than 75%, the storage stability is good; When 25%≤ AND When the percentage is less than 50%, the proportion of bound storage in storage stability is relatively high, which needs to be monitored and monitored in the long term. when AND When the content is less than 25%, the storage stability is poor, and the main method is binding storage, which has a relatively high risk of leakage.

[0073] S4. Cross-reference the storage efficiency level (I-IV) with the oil displacement efficiency level (AD) to construct a dual-index comprehensive evaluation matrix.

[0074] When the CE level is I and the OE level is A, the overall level is excellent, indicating high performance in both storage and oil displacement, and the target block can be prioritized for development / promotion. When the CE level is I and the OE level is B, the overall level is excellent, indicating high performance in both storage and oil displacement, and the target block can be prioritized for development / promotion. When the CE level is I and the OE level is C, the overall rating is excellent, indicating high storage efficiency and high oil displacement effect, and the target block can be given special attention. When the CE rating is I and the OE rating is D, the overall rating is good, indicating that it is above average, still has development value, and can be used as a reserve plan. When the CE level is II and the OE level is A, the overall level is excellent, indicating high performance in both oil storage and oil displacement, and the target block can be prioritized for development / promotion. When the CE rating is Level II and the OE rating is Level B, the overall rating is excellent, indicating high storage efficiency and high oil displacement effect, and the target block should be given special attention. When the CE rating is Level II and the OE rating is Level C, the overall rating is good, indicating that it is above average, still has development value, and can be used as a reserve plan. When the CE rating is Level II and the OE rating is Level D, the overall rating is medium, indicating that a trade-off needs to be made and the evaluation should be conducted after cost / process optimization. When the CE level is III and the OE level is A, the overall rating is excellent, indicating high storage efficiency and high oil displacement effect, and the target block should be given special attention. When the CE level is III and the OE level is B, the overall level is good, indicating that it is above average, still has development value, and can be used as a reserve plan. When the CE level is III and the OE level is C, the overall level is medium, indicating that a trade-off needs to be made and the evaluation should be carried out after cost / process optimization. When the CE level is III and the OE level is D, the overall level is poor, indicating that both indicators are not ideal and it is not recommended to prioritize implementation. Geological conditions or processes need to be reassessed. When the CE level is IV and the OE level is A, the overall rating is good, indicating that it is above average, still has development value, and can be used as a reserve plan. When the CE level is IV and the OE level is B, the overall level is medium, which means that a trade-off needs to be made and evaluated after cost / process optimization. When the CE level is IV and the OE level is C, the overall level is poor, indicating that both indicators are not ideal. It is not recommended to prioritize implementation and the geological conditions or process need to be reassessed. When the CE grade is IV and the OE grade is D, the overall grade is poor, indicating that both indicators are not ideal. It is not recommended to prioritize implementation and the geological conditions or process need to be reassessed.

[0075] S5, Introduction of carbon-oil co-storage index BUT A comprehensive evaluation of CO2 oil displacement and storage effects was conducted using a dual-indicator comprehensive evaluation and a weighted comprehensive evaluation. when BUT When the percentage is ≥80%, the grade is Excellent. When 60%≤ BUT When the percentage is less than 80%, the grade is excellent. When 40%≤ BUT When the percentage is less than 60%, the grade is good. When 20%≤ BUT When the percentage is less than 40%, the grade is medium. when BUT When it is less than 20%, the grade is poor.

[0076] The simulation device for evaluating the effect of carbon dioxide flooding and storage coupled with nuclear magnetic resonance-production analysis includes a CO2 intermediate container, other intermediate containers as composite media, a nuclear magnetic resonance spectrometer, and a core holder placed in the nuclear magnetic resonance spectrometer; the core holder is connected to a confining pressure displacement pump via a pipeline.

[0077] The inlet of the CO2 intermediate container is connected to a displacement injection pump via a pipeline; the outlet of the CO2 intermediate container is connected to a fluid switching valve on a pipeline located on one side of the inlet end of the core holder via a pipeline and a gas flow meter I; a CO2 drying pipe is installed on the pipeline between the outlet of the CO2 intermediate container and the gas flow meter I.

[0078] The inlet of the intermediate container for other media is connected to a displacement injection pump via a pipeline; the outlet of the intermediate container for other media is connected to the fluid switching valve via a pipeline and a gas-liquid dual-purpose flow meter.

[0079] A pressure gauge is installed on the pipeline between the fluid switching valve and the inlet end of the core holder.

[0080] The CO2 drying tube is filled with silica gel or molecular sieve desiccant to remove moisture carried in the gas source, ensuring that the gas entering gas flow meter I is completely dry.

[0081] Other media intermediate containers can be filled with formation water, nitrogen, etc.

[0082] The fluid switching valve enables the alternating injection of CO2 and other media, simulating the CO2 composite media displacement process. The CO2 injection and other media injections can be combined and connected to the fluid switching valve and inlet pressure gauge.

[0083] The outlet end of the core holder is connected to a back pressure valve via a pipeline and a pressure gauge; the back pressure valve is connected to a back pressure displacement pump via a pipeline.

[0084] The other valve port of the back pressure valve is connected to a gas-liquid separation device via a pipeline; the gas phase outlet of the gas-liquid separation device is connected to a gas flow meter II via a pipeline and a gas drying pipe, and the gas flow meter II is connected to a gas chromatograph.

[0085] The gas drying tube is used to remove water vapor carried in the produced gas, preventing water vapor from interfering with the measurement accuracy of the gas flow meter II and the analysis results of the gas chromatograph, thus ensuring the measurement accuracy of the gas flow meter II and the accuracy of the gas chromatograph analysis.

[0086] The pressure gauge at the outlet of the core holder is used to detect the real-time pressure at the outlet, while the backpressure valve and backpressure displacement pump are used to provide the pore pressure (i.e., formation pressure) required for the experiment.

[0087] Gas chromatographs (GCs) are used to analyze the full composition of produced gases, including CO2, N2, CH4, C2H6 and hydrocarbons with more than C3 atoms. They can obtain the volume fraction and precise content of CO2 and various gases in real time, providing a data basis for calculating CO2 sequestration.

[0088] The liquid phase outlet of the gas-liquid separation device is connected to an oil-water separator via a pipeline. The water phase outlet of the oil-water separator is connected to an ion chromatograph via a pipeline and a liquid flow meter. The oil phase outlet of the oil-water separator is connected to a Fourier transform infrared spectrometer via a pipeline and a liquid flow meter. Both the ion chromatograph and the Fourier transform infrared spectrometer are connected to a liquid collection device.

[0089] The displacement injection pump, confining pressure displacement pump, gas flow meter I, gas flow meter II, gas-liquid dual-purpose flow meter, liquid flow meter, pressure gauge, back pressure valve, back pressure displacement pump, nuclear magnetic resonance spectrometer, gas chromatograph, ion chromatograph, and Fourier transform infrared spectrometer are all connected to the data acquisition device. This data acquisition device is connected to a data terminal control system to realize the synchronous acquisition, real-time display and storage of multi-channel data, as well as integrated control.

[0090] The beneficial effects of this invention are as follows: The nuclear magnetic resonance-production analysis coupled carbon dioxide flooding and storage effect evaluation method described in this invention realizes the coupling between nuclear magnetic resonance results and production measurement analysis system results. It overcomes the limitations of a single nuclear magnetic resonance method in directly reflecting macroscopic production dynamics and a single production measurement method in revealing microscopic pore-scale displacement mechanisms. It achieves integrated and high-precision joint evaluation of multiple objectives such as CO2 flooding efficiency evaluation, CO2 storage efficiency evaluation, and comprehensive evaluation of flooding and storage. It provides theoretical basis and technical support for scheme optimization and effect evaluation of CO2 flooding and geological storage integration (CCUS-EOR) projects.

[0091] The evaluation of CO2 oil displacement effect was achieved by comparing the real-time nuclear magnetic resonance T2 and HSE spectra before and after the CO2 composite medium displacement experiment to obtain the real-time microscopic oil displacement efficiency (the oil displacement efficiency results obtained from the two spectra are the same, i.e., the microscopic oil displacement efficiency is the same). =HSE Total Oil Displacement Efficiency The oil displacement efficiency under different pore sizes and at different core locations, combined with the real-time oil production, gas production, and water production measured by the production metering and analysis system, can yield real-time cumulative oil recovery, gas-oil ratio, and water cut. The real-time cumulative oil recovery obtained from the production metering and analysis system is corrected by the real-time microscopic oil displacement efficiency obtained from nuclear magnetic resonance to ensure the reliability of subsequent CO2 sequestration evaluation.

[0092] The CO2 sequestration effect evaluation uses real-time injection volume and output measurement analysis system data corrected by nuclear magnetic resonance (NMR) to calculate the real-time total CO2 sequestration amount and CO2 sequestration rate through the principle of mass balance. This invention classifies CO2 sequestration in the experiment into three types: bound sequestration (CO2 exists in the gas phase in the core, occupying a certain core pore volume), dissolution sequestration (CO2 dissolves in the oil and water phases in the core, existing in a dissolved state and not occupying a separate pore volume), and mineralization sequestration (CO2 reacts with formation water and some minerals in the core, and exists in the form of certain mineral ions). Combined with NMR technology, in-situ real-time dynamic monitoring is achieved, and the proportion of different types of CO2 sequestration is quantitatively distinguished, improving the accuracy of sequestration evaluation. The coupling of microscopic NMR data and macroscopic output data reduces the ambiguity and uncertainty of the evaluation results.

[0093] By using nuclear magnetic resonance (NMR) devices to monitor the fluid distribution and crude oil utilization inside the core in real time, and combining precise injection metering (including drying treatment) at the inlet end and real-time gas-liquid full-component metering analysis of the output metering and analysis system at the outlet end, we can achieve precise quantitative characterization of carbon sequestration efficiency, CO2 oil displacement efficiency and multi-component output fluid during CO2 composite media displacement, thus forming a complete and reliable evaluation method for CO2 oil displacement and sequestration effects.

[0094] This invention achieves precise quantitative analysis of CO2 sequestration rate calculation, dynamic oil displacement analysis, real-time oil displacement efficiency calculation, crude oil recovery degree analysis, different pore utilization analysis, and multi-component analysis of produced fluids during CO2 composite media displacement. It realizes the leap from "macroscopic general evaluation" to "clear microscopic mechanism and accurate macroscopic law" in the evaluation of CO2 oil displacement and sequestration effect. It can dynamically, quantitatively, and finely evaluate the CO2 oil displacement efficiency and the contribution rate of various sequestration mechanisms such as confined sequestration, dissolution sequestration, and mineralization sequestration, providing a more reliable evaluation method for the effect of CO2 oil displacement and sequestration integration (CO2-EOR).

[0095] Furthermore, the simulation device corresponding to the evaluation method has a high degree of integration, realizing the coupling of the nuclear magnetic resonance-product measurement and analysis system. It achieves real-time synchronous coupling of the entire process of "displacement-monitoring-measurement", avoiding the problems of data acquisition time misalignment and inconsistent operating conditions caused by the independent operation of the nuclear magnetic resonance detection device and the product measurement device in traditional evaluation methods. It significantly improves the efficiency of experimental operation and reduces experimental errors caused by human intervention, and has stronger engineering applicability. Attached Figure Description

[0096] Figure 1This is a schematic diagram of a simulation device for evaluating the effectiveness of the carbon dioxide flooding and storage method coupled with nuclear magnetic resonance-product analysis.

[0097] Among them, 1 is the displacement injection pump, 2 is the CO2 intermediate container, 3 is the intermediate container for other media, 4 is the CO2 drying tube, 5 is the gas flow meter I, 6 is the gas-liquid dual-purpose flow meter, 7 is the fluid switching valve, 8 is the pressure gauge, 9 is the core used in the experiment, 10 is the nuclear magnetic resonance spectrometer, 11 is the core holder, 12 is the confining pressure displacement pump, 13 is the back pressure displacement pump, 14 is the back pressure valve, 15 is the gas drying tube, 16 is the gas flow meter II, 17 is the gas chromatograph, 18 is the gas-liquid separation device, 19 is the oil-water separator, 20 is the liquid flow meter, 21 is the ion chromatograph, 22 is the Fourier transform infrared spectrometer, 23 is the liquid collection device, 24 is the data acquisition device, and 25 is the data terminal control system.

[0098] Figure 2 The image shows the nuclear magnetic resonance T2 spectrum after alternating displacement of CO2 and water under certain reservoir conditions.

[0099] Figure 3 The image shows the nuclear magnetic resonance HSE spectrum after alternating displacement by CO2 and water under certain reservoir conditions.

[0100] Figure 4 This is a bar chart comparing the microscopic oil displacement efficiency and macroscopic recovery rate under certain reservoir conditions using alternating CO2 and water displacement.

[0101] Figure 5 The results show the comparison of the nuclear magnetic resonance T2 spectra characterizing the pore structure before and after the experiment.

[0102] Figure 6 This is a graph showing the relationship between oil recovery rate and PV number under certain reservoir conditions, where CO2 and water are used in alternating displacement. Detailed Implementation

[0103] The technical solution of the present invention will be described in detail below.

[0104] Example 1 The simulation device for evaluating the effect of carbon dioxide flooding and storage coupled with nuclear magnetic resonance-production analysis includes a CO2 intermediate container 2, an intermediate container 3 containing other media as a composite medium, a nuclear magnetic resonance spectrometer 10, and a core holder 11 placed in the nuclear magnetic resonance spectrometer 10; the core holder 11 holds the core 9 used in the experiment. The core holder 11 is connected to a confining pressure displacement pump 12 via a pipeline.

[0105] The inlet of the CO2 intermediate container 2 is connected to a displacement injection pump 1 via a pipeline; the outlet of the CO2 intermediate container 2 is connected to a fluid switching valve 7 located on one side of the inlet end of the core holder 11 via a pipeline and a gas flow meter I5; a CO2 drying pipe 4 is installed on the pipeline between the outlet of the CO2 intermediate container 2 and the gas flow meter I5.

[0106] The intermediate CO2 container 2 contains CO2 with a purity of 99.9%, and the CO2 drying tube 4 is filled with 200-mesh silica gel, with a dosage of 200g. The gas flow meter I5 has a range of 0~500mL / min and an accuracy of ±0.5%FS.

[0107] The inlet of the intermediate container 3 for other media is connected to a displacement injection pump 1 via a pipeline; the outlet of the intermediate container 3 for other media is connected to the fluid switching valve 7 via a pipeline and a gas-liquid dual-purpose flow meter 6.

[0108] A pressure gauge 8 is installed on the pipeline between the fluid switching valve 7 and the inlet end of the core holder 11; The outlet end of the core holder 11 is connected to the back pressure valve 14 via a pipeline and a pressure gauge 8; the back pressure valve 14 is connected to the back pressure displacement pump 13 via a pipeline.

[0109] The online NMR monitoring system adopts the MacroMR12-150H-HTHP large-aperture magnetic resonance analysis and visualization system. The core holder is made of non-magnetic material with an outer diameter of 60mm. The high-performance probe optimized and matched with the holder has a gain greater than 20dB, a bandwidth greater than 30kHz, a maximum withstand pressure of 40MPa, a maximum withstand temperature of 80℃, and a magnetic field strength of 0.05T.

[0110] The other valve port of the back pressure valve 14 is connected to the gas-liquid separator 18 via a pipeline; the gas phase outlet of the gas-liquid separator 18 is connected to a gas flow meter II 16 via a pipeline and a gas drying pipe 15, and the gas flow meter II 16 is connected to a gas chromatograph 17.

[0111] The gas drying tube was filled with molecular sieve desiccant, 150g in quantity. The gas chromatograph used was an Agilent 7890B with a TCD / FID dual detector.

[0112] The liquid phase outlet of the gas-liquid separation device 18 is connected to an oil-water separator 19 via a pipeline. The aqueous phase outlet of the oil-water separator 19 is connected to an ion chromatograph 21 via a pipeline and a liquid flow meter 20. The ion chromatograph is a Dionex ICS-5000. + .

[0113] The oil phase outlet of the oil-water separator 19 is connected to the Fourier transform infrared spectrometer 22 via a pipeline and a liquid flow meter 20. The Fourier transform infrared spectrometer is a Bruker TENSOR 27 with a wavenumber range of 400–4000 cm⁻¹. -1 .

[0114] Both the ion chromatograph 21 and the Fourier transform infrared spectrometer 22 are connected to a liquid collection device 23.

[0115] The displacement injection pump 1, confining pressure displacement pump 12, gas flow meter I 5, gas flow meter II 16, gas-liquid dual-purpose flow meter 6, liquid flow meter 20, pressure gauge 8, back pressure valve 14, back pressure displacement pump 13, nuclear magnetic resonance spectrometer 10, gas chromatograph 17, ion chromatograph 21, and Fourier transform infrared spectrometer 22 are all connected to data acquisition device 24, which is connected to data terminal control system 25.

[0116] Example 2 Using a low-permeability sandstone reservoir (porosity φ=10.6%, permeability K=1.73mD) as the experimental object, the carbon dioxide flooding and storage effect was evaluated by using the apparatus described in Example 1 and the method of the present invention.

[0117] The confining pressure was 25 MPa, the experimental temperature was 80℃, and the back pressure was 15 MPa.

[0118] The specific steps of the nuclear magnetic resonance-product analysis coupled carbon dioxide flooding and storage effect evaluation method are as follows: (1) Preparation: S1. Select an experimental core with a diameter of 25 mm and a length of 63 mm, and wash and dry the core according to the standard GB / T 29172-2012 "Core Analysis Methods".

[0119] Pore ​​volume was obtained using a helium porosimeter. V pore =3.278mL, confirming porosity φ =10.6%.

[0120] S2. First, the core was vacuum-saturated with oil and the initial T2 spectrum was tested by nuclear magnetic resonance to clarify the pore structure and pore distribution of the core under the initial conditions.

[0121] Then, after washing and drying, the initial T2 relaxation spectrum was scanned to obtain the matrix T2 spectrum. The system was evacuated to a pressure <50 Pa for 12 h; the formation water was then pressurized and saturated for 48 h.

[0122] S3. Inject simulated formation crude oil (density 0.782 g / mL, viscosity 3.2 mPa·s, 80℃) at a constant rate of 0.05 mL / min until oil is continuously produced at the outlet and the water content is less than 2%.

[0123] NMR scans of T2 and HSE spectra in saturated oil were performed to calculate the bound water saturation. S wi =21.8%, initial oil saturation S oi =78.2%, initial crude oil volume V oil,initial =2.563mL.

[0124] Among them, the initial oil saturation S oi Calculated using the following formula: ; In the formula, —Initial oil saturation, dimensionless; —Initial oil content of the core, mL; —Core pore volume, mL; —Bound water saturation, dimensionless.

[0125] (2) CO2-water combined displacement experiment: S1. Inject at a constant rate of 0.05 mL / min, injecting 0.2 PV of CO2 and 0.2 PV of simulated formation water in each round, for a total of 5 rounds of alternating injection, with a total injection volume of 2 PV.

[0126] S2, T2 and HSE tests can be performed in real time during the displacement process.

[0127] S3. Measure the volume of the gas phase, aqueous phase, and oil phase produced, and analyze the corresponding fluid components using gas chromatography, ion chromatography, and Fourier transform infrared spectroscopy, respectively.

[0128] Record the corresponding time points and cumulative injection volume pore volume multiples (PV). Align the T2 spectrum and HSE spectrum data at each time point with the production dynamic data at the same time point according to a unified time standard to form a time-series coupled dataset of micropore response and macroscopic production response. A selection of the time-series coupled dataset is shown in Table 1 below.

[0129] Table 1 Temporal Coupling Dataset (Excerpt) .

[0130] S4. After the displacement is completed, record and organize all the data. Then, wash and dry the core used in the experiment. Measure the porosity of the core after displacement.

[0131] Porosity after displacement was measured φ' =10.3%, corresponding to the pore volume after displacement. V’ pore =3.185mL, indicating a slight decrease in pore space due to mineralization precipitation during the displacement process.

[0132] (3) Quantitative evaluation of oil displacement effect: Based on the changes in the intensity and area of ​​the T2 spectrum signal before and after the experiment, the microscopic oil displacement efficiency characterized by nuclear magnetic resonance is calculated according to formula (2). OE NMR =65.26%.

[0133] Calculate the macro-harvest rate according to formula (5) OE 产出 =63.60%, and the NMR-product coupling correction coefficient is obtained according to formula (6). k =1.026.

[0134] Then, the output fluid data collected by the output metering and analysis system are multiplied by... k The value was used to perform NMR-product coupling correction.

[0135] The macroscopic oil displacement efficiency was then derived from the coupled and corrected data. OE out =65.26%; Satisfied OE out =Microscopic oil displacement efficiency OE NMR .

[0136] Corresponding oil production V oil =1.673 mL, residual oil content in the core V inoil =0.890mL.

[0137] The cumulative measurement of the corrected output measurement and analysis system was effectively verified, based on the oil displacement efficiency. OE According to the grading standard, if 50% ≤ 65.26% < 75%, it is rated as Grade B (Good), indicating good oil displacement effect.

[0138] (4) Quantitative evaluation of the sealing effect: S1. Based on the real-time metering data of produced gas, produced water, and produced oil from the production metering and analysis system, and after nuclear magnetic coupling correction coefficients... k After correction, the calculation yields: CO2 output from the core outlet =1.1245mL.

[0139] CO2 dissolved in the produced water =0.5643mL.

[0140] CO2 dissolved in produced oil =0.1740mL.

[0141] In addition, the total amount of CO2 injected from the inlet end =3.278mL.

[0142] Calculated according to formula (7): =1.4152mL.

[0143] S2, The final CO2 sequestration efficiency is calculated. WHAT =43.17%.

[0144] According to CO2 storage efficiency WHAT According to the grading standard, 25% ≤ 43.17% < 50% is rated as Level III (Medium), indicating average sealing capacity.

[0145] S3. Classify CO2 sequestration types into dissolution sequestration, bound sequestration, and mineralization sequestration, and calculate the proportion of different CO2 sequestration types: The carbon contribution rates of the aqueous and oil phases obtained from the output metering analysis system are as follows: η water =20.59% and η oil =10.40%.

[0146] Quantitative classification of dissolution and sealing, =0.2578mL, =0.0926mL.

[0147] Dissolved and sealed CO2 amount and The total amount was 0.3504 mL; the amount of CO2 sealed was... =1.4152mL.

[0148] Thus, the proportion of CO2 dissolved and sealed to the total sealed amount can be calculated, i.e., the CO2 dissolved and sealed proportion λ. 溶解封存 =24.76%.

[0149] Combined with the change in core pore volume before and after displacement, ΔPV = 0.093 mL, V pore =3.278mL, obtained =3.185; Residual water volume in the core V inwater=1.2523 mL, residual oil content in the core V inoil =0.890mL.

[0150] The amount of CO2 trapped and sequestered refers to the amount of CO2 existing as free gas in the core. = =3.185 - 0.890 - 1.2523 = 1.0427 mL; CO2 sequestration volume =1.4152mL.

[0151] Thus, the CO2 binding and sequestration ratio λ is calculated. 束缚封存 =73.68%, corresponding to CO2 existing in the form of free gas in the core, which constitutes the main body of confined storage.

[0152] Total CO2 injected from the inlet =3.278mL, the total amount of CO2 collected by the production measurement and analysis system. =1.8628 mL, the volume of CO2 dissolved in water in the core sample. =0.2578 mL, the volume of CO2 dissolved in the oil in the core. =0.0926 mL, the amount of CO2 present as free gas in the core. =1.0427mL.

[0153] The amount of CO2 sequestered in the core via mineralization was thus calculated. =0.0221mL; CO2 sequestration volume =1.4152mL.

[0154] CO2 mineralization and sequestration ratio λ 矿化封存 =1.56%.

[0155] Because the injection scale in this embodiment was strictly controlled according to the core pore volume multiple (PV) and the cumulative injection volume was relatively small, the mineralization retention ratio was higher compared to the large-dose injection condition, which is consistent with the characteristic that mineralization reaction is more sensitive to changes in pore volume in small-scale core experiments. The total retention ratio of the three types was 100%, and the specific results are shown in Table 2.

[0156] Table 2 Sealing Results

[0157] (5) Comprehensive evaluation of CO2 oil displacement and storage effects: Calculate the storage stability index: AND =0.75×1.56%+0.5×24.76%+0.25×73.68%=31.97%.

[0158] according to ANDAccording to the grading standard, 25% ≤ 31.97% < 50%, the storage stability is rated as medium. This indicates that under the conditions of this experiment, CO2 storage was mainly based on bound storage. Although the proportion of mineralized storage increased slightly, its overall contribution was still limited. The structural stability of long-term storage still needs to be further monitored and confirmed through experiments with longer periods or larger scales.

[0159] The CO2 sequestration efficiency of this embodiment WHAT =43.17% (Level III, Medium) and CO2 oil displacement efficiency OE =65.26% (Grade B, Good) A dual-index cross-evaluation was conducted, and the overall grade was found to be "Good". This means that under the WAG displacement conditions in this experiment, the oil displacement and storage effects of this low-permeability sandstone reservoir were both at a good level, indicating that it still has development value and can be used as a reserve block.

[0160] Calculate the carbon-oil co-storage index (using α=β=0.5 for a balanced CCUS-EOR co-storage project): BUT =α×CE+β×OE=0.5×43.17%+0.5×65.26%=54.215%.

[0161] according to BUT According to the grading standard, 40% ≤ 54.215% < 60% is rated as "Good".

[0162] The above results demonstrate that the nuclear magnetic resonance-production analysis coupled evaluation method described in this invention can simultaneously and quantitatively evaluate the CO2 oil displacement effect and the sequestration effect (including sequestration type and structure) in the same core experiment. Furthermore, the macro-recovery rate, corrected by the nuclear magnetic resonance micro-oil displacement efficiency coupling correction coefficient, is the macro-oil displacement efficiency. OE out The result was 65.26%, which is reliable. The evaluation method and simulation device described in this invention can accurately evaluate the CO2 oil displacement and storage effect of CO2-composite media displacement, and has good application research value.

Claims

1. A method for evaluating the effectiveness of carbon dioxide flooding and sequestration coupled with nuclear magnetic resonance-product analysis, characterized in that, Includes the following steps: (1) Preparation: S1. Select representative plunger cores from the target block, wash and dry them; determine the core porosity; S2. First, the core was vacuum-saturated with oil and the initial T2 spectrum was tested by nuclear magnetic resonance. Then, after washing and drying, the initial T2 and HSE spectrum scans were performed again by nuclear magnetic resonance to obtain the reference nuclear magnetic signal intensity values ​​of the core. S3. First, the core is vacuum-saturated with formation water. Confining pressure and temperature are applied to the core to simulate formation conditions. Crude oil is injected into the core at a constant rate or pressure until it is in a bound water state. The water production rate at the outlet is <2%. Then, T2 and HSE spectrum scans were performed again by nuclear magnetic resonance to obtain NMR data of saturated oil under bound water conditions; (2) Displacement by a single CO2 or CO2 composite medium: S1. Inject single CO2 into the core using a constant pressure or constant rate injection method to perform single CO2 displacement; or inject a CO2 composite medium into the core using a constant pressure or constant rate injection method to perform CO2 composite medium displacement. S2. During the displacement process, the core is scanned in real time using nuclear magnetic resonance T2 spectrum and HSE spectrum at preset time intervals. S3. During the real-time nuclear magnetic resonance scanning process, the output fluid data at the core outlet is collected simultaneously through the output measurement and analysis system. The corresponding time points and cumulative injection volume pore volume multiples are recorded. The T2 spectrum and HSE spectrum data at each time point are calibrated and aligned with the production dynamic data at the same time point to form a time-series coupled dataset of micropore response and macro production response. S4. After the displacement is completed, all data are recorded and organized. Then, the core used in the experiment is washed with oil and dried. The porosity of the core after displacement is measured. Then, the core after displacement was vacuum-saturated with crude oil and subjected to nuclear magnetic resonance T2 spectrum testing. (3) Quantitative evaluation of oil displacement effect: S1. According to formula (1), calculate the microscopic oil displacement efficiency at different times during the displacement process based on the change of signal intensity area in the T2 spectrum at different times. （1）； In the formula, —Microscopic oil displacement efficiency at a given moment, calculated using NMR spectroscopy, % —The sum of signal intensities during all relaxation time periods of saturated oil NMR T2, dimensionless; —The sum of signal intensities during all relaxation time intervals of the nuclear magnetic resonance imaging at a given moment T2, dimensionless; S2. Calculate the microscopic oil displacement efficiency after the entire displacement process is completed according to formula (2). ; （2） In the formula, —Microscopic oil displacement efficiency calculated by NMR after the entire displacement process is completed, % —The sum of signal intensities during all relaxation time periods of saturated oil NMR T2, dimensionless; —The sum of the signal intensities during all relaxation time periods of the nuclear magnetic resonance T2 obtained after the entire displacement is completed, dimensionless; S3. According to formula (3), calculate the HSE oil displacement efficiency at different times during the displacement process based on the change of signal intensity area in the T2 spectrum at different times. （3）； In the formula, —The oil displacement efficiency calculated by NMR HSE at a certain moment, % —The sum of all signal intensity values ​​at all locations in the entire core by HSE (High-Saturation Oil NMR) is dimensionless. —The sum of all signal intensity values ​​at all locations in the entire core corresponding to a certain moment in nuclear magnetic resonance HSE, dimensionless; S4. Calculate the total HSE oil displacement efficiency after the entire displacement process is completed according to formula (4): （4）； In the formula, —HSE total oil displacement efficiency calculated by NMR, % —The sum of all signal intensity values ​​at the corresponding core location in saturated oil nuclear magnetic resonance (HSE), dimensionless; —The sum of all signal intensity values ​​at the corresponding core location on the nuclear magnetic resonance HSE after the entire displacement is completed, dimensionless; S5. Based on the original oil content of the collected core and the cumulative oil production collected by the production metering and analysis system, calculate the macro-recovery rate according to formula (5). （5）； In the formula, —Macro-oil recovery rate, % —Cumulative oil production, measured in mL, collected by the production measurement and analysis system; —Initial oil content of the core, mL; S6. First, calculate the NMR-product coupling correction coefficient according to formula (6). k ; （6）； —NMR-product coupling correction coefficient, dimensionless; —Macroscopic oil displacement efficiency, %; of which... =Microscopic oil displacement efficiency ; —Macro-oil recovery rate, % Then, the output fluid data collected by the output metering and analysis system are multiplied by... k Values ​​were used for NMR-product coupling correction. (4) Quantitative evaluation of the sealing effect: S1. Calculate the amount of CO2 stored in the core according to formula (7); （7）； In the formula, —CO2 sequestration volume, mL; —The total amount of CO2 injected from the inlet, in mL; —The amount of CO2 produced at the core outlet obtained by the NMR-production coupling correction production measurement analysis system in step (3), in mL; —The amount of CO2 dissolved in the produced water obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of CO2 dissolved in the produced oil obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; S2. Calculate the CO2 sequestration efficiency in the core according to formula (8). ; （8）； —CO2 sequestration efficiency, % —CO2 sequestration volume, mL; —The total amount of CO2 injected from the inlet, in mL; S3. Classify CO2 sequestration types into dissolution sequestration, bound sequestration, and mineralization sequestration, and calculate the proportion of different CO2 sequestration types: First, calculate the CO2 dissolution and sequestration ratio according to formulas (9)-(16): （9）； In the formula, η water —Contribution of aqueous phase carbon in dissolution-sequestration, % —The amount of CO2 dissolved in the produced water obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of water produced at the core outlet obtained by the NMR-production coupling correction production metering analysis system in step (3) S6, in mL; （10）； In the formula, η oil —Oil phase carbon contribution rate during dissolution-sequestration, % —The amount of CO2 dissolved in the produced oil obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of oil produced at the core outlet obtained by the NMR-production coupling correction production metering analysis system in step (3) S6, in mL; （11）； In the formula, —Residual oil content in the core, mL; —Initial oil content of the core, mL; —The amount of oil produced at the core outlet obtained by the NMR-production coupling correction production metering analysis system in step (3) S6, in mL; （12）； In the formula, —Residual water volume in the core, mL; —The volume of water injected into the core at the inlet, in mL; —Core pore volume before displacement, mL; S wi —Bound water saturation, dimensionless; —The amount of water produced at the core outlet obtained by the NMR-production coupling correction production metering analysis system in step (3) S6, in mL; （13）； In the formula, —Volume of CO2 dissolved in water in the core sample, mL; η water —Contribution of aqueous phase carbon in dissolution-sequestration, % —Residual water volume in the core, mL; （14）； In the formula, —Volume of CO2 dissolved in oil in the core, mL; η oil —Oil phase carbon contribution rate during dissolution-sequestration, % —Residual oil content in the core, mL; （15）； In the formula, —CO2 dissolution and storage efficiency, % —Volume of CO2 dissolved in water in the core sample, mL; —Volume of CO2 dissolved in oil in the core, mL; —The volume of CO2 injected at the inlet, in mL; （16）； In the formula, —CO2 dissolution and sequestration ratio, % —Volume of CO2 dissolved in water in the core sample, mL; —Volume of CO2 dissolved in oil in the core, mL; —CO2 sequestration volume, mL; Then, calculate the CO2 binding and sequestration ratio according to formulas (17)-(21): （17）； In the formula, —Contribution of gaseous carbon in bound storage ,% —The amount of CO2 mixed in other gases as a composite medium, collected by the NMR-product coupling correction product metering analysis system in step (3) S6, in mL; —The amount of gas produced at the core outlet obtained by the NMR-produced gas metering analysis system in step (3) S6, in mL; （18）； In the formula, —Residual gas volume in the core, mL; —The core pore volume after displacement, in mL; —Residual oil content in the core, mL; —Residual water volume in the core, mL; （19）； In the formula, —Amount of CO2 present as free gas in the core, mL; —Residual gas volume in the core, mL; —Contribution of gaseous carbon in bound storage ,% （20）； In the formula, —CO2 binding and sequestration efficiency, % —Amount of CO2 present as free gas in the core, mL; —The volume of CO2 injected at the inlet, in mL; （21）； In the formula, —CO2 confinement and sequestration percentage, % —Amount of CO2 present as free gas in the core, mL; —CO2 sequestration volume, mL; Finally, the CO2 mineralization sequestration ratio is calculated according to formulas (22)-(25): （22）； In the formula, —The total amount of CO2 collected by the NMR-product coupling correction output measurement analysis system in step (3), in mL; —The amount of CO2 dissolved in the produced oil obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of CO2 dissolved in the produced water obtained by the NMR-produced output measurement and analysis system in step (3) S6, in mL; —The amount of CO2 mixed in other gases as a composite medium, collected by the NMR-product coupling correction product metering analysis system in step (3) S6, in mL; （23）； In the formula, —Amount of CO2 sequestered in the core via mineralization, in mL; —The volume of CO2 injected at the inlet, in mL; —The total amount of CO2 collected by the NMR-product coupling correction output measurement analysis system in step (3), in mL; —Volume of CO2 dissolved in water in the core sample, mL; —Volume of CO2 dissolved in oil in the core, mL; —Amount of CO2 present as free gas in the core, mL; （24）； In the formula, —CO2 mineralization and sequestration efficiency, % —Amount of CO2 sequestered in the core via mineralization, in mL; —The volume of CO2 injected at the inlet, in mL; （25）； In the formula, —CO2 mineralization and sequestration ratio, % —Amount of CO2 sequestered in the core via mineralization, in mL; —CO2 sequestration volume, mL; (5) Comprehensive evaluation of CO2 oil displacement and storage effects: S1. Calculate the sealing stability index according to formulas (26) and (27) respectively. Co-storage index with carbon and oil : （26）； In the formula, —Storage stability index, % —Stability weighting coefficients for different storage types, dimensionless; where... =0.5, =0.25, =0.75; —CO2 dissolution and sequestration ratio, % —CO2 confinement and sequestration percentage, % —CO2 mineralization and sequestration ratio, % （27）； In the formula, —Carbon-oil co-storage index, % —The weighting coefficient for CO2 displacement and storage, dimensionless; where ; CE —CO2 storage efficiency; OE —CO2 oil displacement efficiency; among which... OE = ; S2. Combining the quantitative evaluation of the oil displacement effect in step (3) and the quantitative evaluation of the sealing effect in step (4), they are divided into different levels and a single-index graded evaluation is carried out. CO2 storage efficiency (CE) classification is as follows: When CE ≥ 75%, the grade is Level I; When 50% ≤ CE < 75%, the grade is Level II; When 25%≤CE<50%, the grade is Level III; When CE < 25%, the rating is Level IV; Oil displacement efficiency (OE) classification is as follows: When OE ≥ 75%, the grade is A; When 50%≤OE<75%, the grade is B; When 25%≤OE<50%, the grade is C; If OE < 25%, the grade is D; S3. Introducing a storage stability index SI To evaluate the internal stability of the sealing efficiency; when SI At ≥75%, the storage stability is excellent; When 50%≤ SI When the content is less than 75%, the storage stability is good; When 25%≤ SI When the content is less than 50%, the storage stability is moderate. when SI When the content is less than 25%, the storage stability is poor. S4. Combine the storage efficiency level with the oil displacement efficiency level to construct a comprehensive evaluation based on two indicators; When the CE rating is Level I and the OE rating is Level A, the overall rating is Excellent. When the CE rating is Level I and the OE rating is Level B, the overall rating is Excellent. When the CE rating is Level I and the OE rating is Level C, the overall rating is Excellent. When the CE rating is I and the OE rating is D, the overall rating is Good. When the CE rating is Level II and the OE rating is Level A, the overall rating is Excellent. When the CE rating is Level II and the OE rating is Level B, the overall rating is Excellent. When the CE rating is Level II and the OE rating is Level C, the overall rating is Good. When the CE rating is Level II and the OE rating is Level D, the overall rating is Medium. When the CE rating is Level III and the OE rating is Level A, the overall rating is Excellent. When the CE rating is III and the OE rating is B, the overall rating is Good. When the CE rating is Level III and the OE rating is Level C, the overall rating is Medium. When the CE rating is III and the OE rating is D, the overall rating is poor. When the CE rating is IV and the OE rating is A, the overall rating is Good. When the CE rating is IV and the OE rating is B, the overall rating is medium. When the CE rating is IV and the OE rating is C, the overall rating is poor. When the CE rating is IV and the OE rating is D, the overall rating is poor. S5, Introduction of carbon-oil co-storage index CI A comprehensive evaluation of CO2 oil displacement and storage effects was conducted by performing a dual-indicator comprehensive evaluation and a weighted comprehensive evaluation. when CI When the percentage is ≥80%, the grade is Excellent. When 60%≤ CI When the percentage is less than 80%, the grade is excellent. When 40%≤ CI When the percentage is less than 60%, the grade is good. When 20%≤ CI When the percentage is less than 40%, the grade is medium. when CI When it is less than 20%, the grade is poor.

2. The method for evaluating the effectiveness of carbon dioxide flooding and sequestration coupled with nuclear magnetic resonance-product analysis according to claim 1, characterized in that, In step (2), the S3 production metering and analysis system, which is driven by a single CO2 or CO2 composite medium, collects the production fluid data at the core outlet, including cumulative oil production, cumulative gas production, cumulative water production, instantaneous oil production, instantaneous gas production, instantaneous water production, and gas-oil ratio.

3. The method for evaluating the effectiveness of carbon dioxide flooding and sequestration coupled with nuclear magnetic resonance-product analysis according to claim 1, characterized in that, The production metering and analysis system described in step (2) of S3, which involves displacement by a single CO2 or CO2 composite medium, includes a production end pressure gauge, a gas flow meter, a gas chromatograph, a production water flow meter, an ion chromatograph, a production oil flow meter, and a Fourier transform infrared spectrometer.

Images