Cross-scale characterization method and system for spatiotemporal characteristics of front migration in carbon dioxide displacement process

Abstract

The application discloses a method and system for cross-scale characterization of space-time characteristics of a front during a carbon dioxide displacement process, and the method comprises the following steps: obtaining a one-dimensional scale carbon dioxide component front position by obtaining a fluid cross-section T2 signal along a path before and after carbon dioxide displacement; obtaining an oil-water distribution feature under original two-dimensional scale conditions and an oil-water distribution feature under different gas injection conditions to obtain a two-dimensional scale carbon dioxide component front distribution position; performing numerical simulation based on the one-dimensional scale carbon dioxide component front position and the two-dimensional scale carbon dioxide component front distribution position to obtain set parameters of one-dimensional and two-dimensional numerical simulation; and correcting parameters of three-dimensional reservoir scale numerical simulation based on the set parameters of one-dimensional and two-dimensional numerical simulation to obtain a three-dimensional reservoir model, judging a miscible pressure front, a component front and a phase front feature during the carbon dioxide displacement process, and completing the cross-scale characterization of the space-time characteristics of the front during the carbon dioxide displacement process.

Description

Technical Field

[0001] This invention relates to the field of CO2-driven crude oil development technology, specifically to a cross-scale characterization method and system for the spatiotemporal characteristics of the leading edge migration during carbon dioxide displacement. Background Technology

[0002] Traditionally, the minimum miscibility pressure (MMP) is considered the decisive factor in the success of CO2-enhanced crude oil development. In oilfield development, it is typically compared with reservoir pressure to determine whether miscibility enhancement is feasible. However, for thick reservoirs with large top-to-bottom spans, high-dipping reservoirs, and complex small-faulted reservoirs with poor connectivity, significant pressure profile distribution characteristics exist in the horizontal plane, forming a non-equilibrium pressure system with both overpressure and underpressure. Vertically, the crude oil composition exhibits a gravity differentiation characteristic of "lighter at the top and heavier at the bottom," and temperature and pressure vary with reservoir depth gradients, causing the miscibility pressure threshold to jump with depth. Therefore, relying solely on the MMP test data of an oil sample at a specific location ignores the spatiotemporal variations of the formation pressure field during gas injection development and its impact on the miscibility distribution range.

[0003] Currently, most methods for characterizing leading-edge transport in gas-driven processes are based on numerical simulation and primarily focus on "single leading-edge transport paths".

[0004] (1) Patent title: Multiphase zone discrimination method based on the spatiotemporal variation characteristics of CO2 flooded reservoir fluids

[0005] This application provides a multiphase zone discrimination method based on the spatiotemporal variation characteristics of CO2-driven oil reservoir fluids. The method includes: acquiring the phase state data of formation fluids and the oil saturation of the reservoir at the observation location; inputting the phase state data into a numerical simulation component model to output fluid characteristic parameters of the formation fluids; inputting the oil saturation and fluid characteristic parameters into a reservoir geological model, and setting the production pressure of the production well module to a preset pressure; sequentially changing the CO2 injection rate of the injection well module to output first CO2 oil displacement parameters corresponding to each CO2 injection rate through the reservoir geological model; and determining the different phase zone distribution characteristics between the injection well and the production well based on the first CO2 oil displacement parameters. This technical solution can intuitively and accurately describe the CO2 oil displacement process, accurately predict the gas breakthrough time of production wells, the range of miscible zones, and the remaining oil exploitation potential, saving oil displacement costs and protecting resources.

[0006] (2) Patent title: A quantitative characterization method for CO2-driven miscibility based on three leading edges

[0007] This invention discloses a quantitative characterization method for CO2 flooding miscibility based on three fronts. The method includes the following steps: determining the CO2 component front and CO2 phase front of the target oilfield; establishing a three-dimensional spatial mechanism model of the target oilfield using CMG numerical simulation software and performing numerical simulation calculations; in the three-dimensional spatial mechanism model of the target oilfield, the miscibility range is the overlapping area between the CO2 component front and the CO2 phase front, and between the miscibility pressure front and the injection well; setting the numerical simulation time step, from start to end, recorded as i steps; and determining the total miscibility area at each time step based on the numerical simulation results, thus obtaining the miscibility degree of the target oilfield. This invention clarifies the CO2 component front and phase front through a one-dimensional core numerical model, determines the criteria for judging the miscibility range, and obtains a quantitative characterization method for CO2 flooding miscibility based on three fronts according to the numerical simulation results.

[0008] (3) Patent title: A quantitative characterization method for dynamic changes in the degree of miscibility of carbon dioxide flooding in long core samples

[0009] This invention discloses a method for quantitatively characterizing the dynamic changes in miscibility of carbon dioxide flooding in long core samples, relating to the field of enhanced oil recovery (EOR) technology. The method includes: Step 1, testing the minimum miscibility pressure of crude oil and carbon dioxide in the target reservoir using the capillary tube method; Step 2, conducting carbon dioxide flooding experiments using a long core model device to establish curves showing the changes in injection volume and gas front position at pressure measurement points before carbon dioxide is produced from the outlet; Step 3, establishing a curve showing the dynamic change in miscibility with injection volume by combining pressure at different pressure measurement points and gas front position, thus achieving a quantitative characterization of the dynamic changes in miscibility. This invention addresses the limitation of existing technologies for quantitatively characterizing the dynamic changes in miscibility, which only qualitatively classify miscibility as miscible and immiscible, failing to reflect the spatiotemporal changes in actual formation pressure. It improves the accuracy of characterization and makes the results more consistent with actual formation miscibility.

[0010] (4) Patent title: A method and system for optimizing carbon dioxide injection development based on the characteristics of incompletely miscible phases

[0011] This invention discloses a method and system for optimizing carbon dioxide injection development based on incomplete miscibility characteristics. The method includes the following steps: constructing a three-dimensional reservoir model based on laboratory experiments and reservoir numerical data; the three-dimensional reservoir model includes a fluid model and a reservoir model; obtaining the incomplete miscibility characteristics of carbon dioxide injection development based on the three-dimensional reservoir model; and completing the full life-cycle optimization development of carbon dioxide injection based on the incomplete miscibility characteristics. This invention improves upon existing injection-production optimization methods that do not consider the errors in recovery rate assessment, gas breakthrough time prediction, and hydrocarbon migration patterns caused by incomplete miscibility displacement characteristics. Combining mathematical and numerical simulation methods, based on the incomplete miscibility characteristics such as the composition front, phase front, and pressure front patterns in the carbon dioxide development process of low-permeability reservoirs, it comprehensively optimizes the injection method, well pattern and well spacing, and water-gas alternation regime during reservoir development.

[0012] Most existing methods for predicting the front during CO2 displacement rely on numerical simulations, leading to significant discrepancies between the prediction methods for different types of fronts during gas displacement and actual reservoir development. Furthermore, a systematic characterization and precise representation of the relationships between different types of typical fronts has not yet been developed. No cross-scale prediction method for different fronts during CO2 displacement in reservoirs has been established. Summary of the Invention

[0013] To address the above technical problems, this invention proposes a cross-scale characterization method and system for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement. The method specifically includes:

[0014] Step S1: Obtain the fluid NMR T2 signal of the core before carbon dioxide displacement under the original conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment; obtain the fluid NMR T2 signal of the core after carbon dioxide displacement under different gas injection conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment; obtain the one-dimensional carbon dioxide component front position based on the NMR T2 signal under the original conditions and the NMR T2 signal under different gas injection conditions.

[0015] Step S2: After creating bound formation water and saturated crude oil in the two-dimensional flat-plate scale physical model, record the oil-water distribution characteristics under the original conditions, carry out two-dimensional planar scale gas drive physical simulation experiments under different gas injection rates, obtain the oil-water distribution characteristics under different gas injection rates, and obtain the frontal distribution position of carbon dioxide components at the two-dimensional scale based on the oil-water distribution characteristics under the original conditions and the oil-water distribution characteristics under different gas injection rates.

[0016] Step S3: Perform numerical simulation based on the frontal position of carbon dioxide components at the one-dimensional scale and the frontal distribution position of carbon dioxide components at the two-dimensional scale to obtain the setting parameters for the one-dimensional numerical simulation and the setting parameters for the two-dimensional numerical simulation.

[0017] Step S4: Based on the set parameters of the one-dimensional numerical simulation and the set parameters of the two-dimensional numerical simulation, the parameters of the three-dimensional reservoir-scale numerical simulation are corrected to obtain a three-dimensional reservoir model. Based on the three-dimensional reservoir numerical simulation results, the characteristics of the miscible pressure front, component front, and phase front in the gas drive displacement process are judged, and the cross-scale characterization of the spatiotemporal characteristics of the front migration in the carbon dioxide displacement process is completed.

[0018] Preferably, in step S1, obtaining the one-dimensional carbon dioxide component front position specifically involves:

[0019] After adding bound formation water and saturated crude oil to the core of an online nuclear magnetic resonance core gas drive physical simulation experiment with improved cross-section scanning, the friction NMR T2 signal of the fluid in the core under the original conditions from the injection end to the production end was obtained.

[0020] Gas drive experiments were conducted under different gas injection rates to obtain the T2 NMR signal of the fluid in the core from the injection end to the production end under different gas injection rates.

[0021] The magnitudes of the T2 NMR signals along the path under different gas injection conditions are compared with those under the original conditions. When the difference between the T2 NMR signals along the path under different gas injection conditions and those under the original conditions is greater than 1%, the position of the carbon dioxide component front on a one-dimensional scale is obtained.

[0022] Preferably, in step S3, the process of obtaining the setting parameters for the one-dimensional numerical simulation specifically involves:

[0023] Collect basic parameters from core samples used in nuclear magnetic resonance experiments;

[0024] Using reservoir numerical simulation software, a model with the same dimensions as the basic parameters was established;

[0025] The initial parameters of the core were set for the model, and the carbon dioxide saturation distribution from the injection end to the production end under different gas injection rates was analyzed using numerical simulation software to obtain the numerical simulation results.

[0026] The results of numerical simulation and improved cross-sectional scanning online nuclear magnetic resonance core gas drive physical simulation experiments were compared to the CO2 component front location, oil recovery rate at the production end, and gas-oil ratio.

[0027] The fitting process of the numerical simulation software is adjusted based on the comparison results. The fitting process includes component fitting, minimum miscibility pressure and relative permeability curve fitting, until the error between all parameters of the numerical simulation results and the results of the online nuclear magnetic resonance core gas drive physical simulation experiment is less than 1%, thus obtaining the set parameters for the one-dimensional numerical simulation.

[0028] Preferably, in step S3, the process of obtaining the setting parameters for the two-dimensional numerical simulation specifically involves:

[0029] Based on reservoir numerical simulation software, a model with the same size as the two-dimensional flat plate in the two-dimensional planar scale gas drive physical simulation experiment was established, and the same porosity, permeability, oil saturation, initial temperature, and initial pressure parameters were set.

[0030] Import the results of the fitting process into the initial parameter settings of the two-dimensional planar numerical simulation;

[0031] Two-dimensional planar scale gas drive numerical simulations were carried out under different gas injection rates. Based on the carbon dioxide saturation distribution values ​​in the two-dimensional planar scale numerical simulation results, the position where CO2 is initially zero was identified as the CO2 component front, and the oil recovery rate and gas-oil ratio parameters at the production end in the numerical simulation results were derived.

[0032] The oil recovery rate and gas-oil ratio parameters at the production end in the numerical simulation results are compared with the CO2 component front position, oil recovery rate and gas-oil ratio parameters at the production end in the two-dimensional planar scale gas drive physical simulation experiment. Based on the parameter comparison error, the setting parameters for the two-dimensional numerical simulation are obtained.

[0033] Preferably, the process of obtaining the set parameters for the two-dimensional numerical simulation based on the parameter comparison error is as follows:

[0034] If the error of all parameters is less than 1%, then the fitting process of the numerical simulation method is considered to be accurate.

[0035] If any parameter error is greater than or equal to 1%, the fitting process of "component fitting, minimum miscibility pressure and relative permeability curve" will be readjusted until the output results simultaneously satisfy the results of one-dimensional numerical simulation and two-dimensional numerical simulation.

[0036] Preferably, the process of obtaining the three-dimensional reservoir model is as follows:

[0037] An initial three-dimensional reservoir model was established, and reservoir depth, reservoir temperature, reservoir pressure, reservoir porosity, reservoir permeability, reservoir oil saturation, reservoir temperature gradient, reservoir pressure coefficient, and saturation pressure parameters were set.

[0038] The results of the adjusted "component fitting, minimum miscibility pressure and relative permeability curves" are imported into the initial three-dimensional reservoir model to obtain the three-dimensional reservoir model.

[0039] This invention also provides a cross-scale characterization system for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement, used to implement the aforementioned method, comprising:

[0040] The one-dimensional leading edge position acquisition module is used to acquire the fluid NMR T2 signal of the core before carbon dioxide displacement under the original conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment, and to acquire the fluid NMR T2 signal of the core after carbon dioxide displacement under different gas injection conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment. Based on the NMR T2 signal under the original conditions and the NMR T2 signal under different gas injection conditions, the one-dimensional carbon dioxide component leading edge position is obtained.

[0041] The two-dimensional front position acquisition module is used to record the oil-water distribution characteristics under the original conditions after creating bound formation water and saturated crude oil in the two-dimensional flat plate scale physical model, carry out two-dimensional planar scale gas drive physical simulation experiments under different gas injection conditions, obtain the oil-water distribution characteristics under different gas injection conditions, and obtain the two-dimensional scale carbon dioxide component front distribution position based on the oil-water distribution characteristics under the original conditions and the oil-water distribution characteristics under different gas injection conditions.

[0042] The numerical simulation module is used to perform numerical simulations based on the frontal position of carbon dioxide components at the one-dimensional scale and the frontal distribution position of carbon dioxide components at the two-dimensional scale, so as to obtain the setting parameters for the one-dimensional numerical simulation and the setting parameters for the two-dimensional numerical simulation.

[0043] The cross-scale characterization module is used to correct the parameters of the three-dimensional reservoir-scale numerical simulation based on the set parameters of the one-dimensional numerical simulation and the set parameters of the two-dimensional numerical simulation, so as to obtain a three-dimensional reservoir model. Based on the three-dimensional reservoir numerical simulation results, the module judges the characteristics of the miscible pressure front, component front, and phase front in the gas drive displacement process, and completes the cross-scale characterization of the spatiotemporal characteristics of the front migration in the carbon dioxide displacement process.

[0044] Preferably, in the one-dimensional leading edge position acquisition module, the specific method for obtaining the leading edge position of carbon dioxide components at the one-dimensional scale is as follows:

[0045] After adding bound formation water and saturated crude oil to the core of an online nuclear magnetic resonance core gas drive physical simulation experiment with improved cross-section scanning, the friction NMR T2 signal of the fluid in the core under the original conditions from the injection end to the production end was obtained.

[0046] Gas drive experiments were conducted under different gas injection rates to obtain the T2 NMR signal of the fluid in the core from the injection end to the production end under different gas injection rates.

[0047] The T2 NMR signal along the path under different gas injection conditions is compared with the T2 NMR signal along the path under the original conditions. When the difference between the T2 NMR signal along the path and the T2 NMR signal under the original conditions is greater than 1%, the position of the carbon dioxide component front on a one-dimensional scale is obtained.

[0048] Preferably, in the numerical simulation module, the process of obtaining the setting parameters for the one-dimensional numerical simulation is as follows:

[0049] Collect basic parameters from core samples used in nuclear magnetic resonance experiments;

[0050] Using reservoir numerical simulation software, a model with the same dimensions as the basic parameters was established;

[0051] The initial parameters of the core were set for the model, and the carbon dioxide saturation distribution from the injection end to the production end under different gas injection rates was analyzed using numerical simulation software to obtain the numerical simulation results.

[0052] The results of numerical simulation and improved cross-sectional scanning online nuclear magnetic resonance core gas drive physical simulation experiments were compared to the CO2 component front location, oil recovery rate at the production end, and gas-oil ratio.

[0053] The fitting process of the numerical simulation software is adjusted based on the comparison results. The fitting process includes component fitting, minimum miscibility pressure and relative permeability curve fitting, until the error between all parameters of the numerical simulation results and the results of the online nuclear magnetic resonance core gas drive physical simulation experiment is less than 1%, thus obtaining the set parameters for the one-dimensional numerical simulation.

[0054] Preferably, in the numerical simulation module, the process of obtaining the set parameters for the two-dimensional numerical simulation is as follows:

[0055] Based on reservoir numerical simulation software, a model with the same size as the two-dimensional flat plate in the two-dimensional planar scale gas drive physical simulation experiment was established, and the same porosity, permeability, oil saturation, initial temperature, and initial pressure parameters were set.

[0056] The results of the fitting process are imported into the initial parameter settings for the two-dimensional planar numerical simulation.

[0057] Two-dimensional planar scale gas drive numerical simulations were carried out under different gas injection rates. Based on the carbon dioxide saturation distribution values ​​in the two-dimensional planar scale numerical simulation results, the position where CO2 is initially zero was identified as the CO2 component front, and the oil recovery rate and gas-oil ratio parameters at the production end in the numerical simulation results were derived.

[0058] The oil recovery rate and gas-oil ratio parameters at the production end in the numerical simulation results are compared with the CO2 component front position, oil recovery rate and gas-oil ratio parameters at the production end in the two-dimensional planar scale gas drive physical simulation experiment. Based on the parameter comparison error, the setting parameters for the two-dimensional numerical simulation are obtained.

[0059] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0060] This invention combines improved cross-sectional scanning online nuclear magnetic resonance core gas drive physical simulation experiments, two-dimensional planar etching model gas drive experiments, and three-dimensional multi-component numerical simulation technology. By analyzing the changes in nuclear magnetic resonance T2 signals along the path from the injection end to the production end during the online nuclear magnetic resonance core gas drive physical simulation experiments, and the CO2 migration front distribution in the two-dimensional planar etching model CO2 displacement experiments, the results of the numerical simulation technology are corrected. For the first time, a method has been established to accurately characterize different types of CO2 displacement processes at the one-dimensional core scale, two-dimensional planar scale, and three-dimensional reservoir scale. This method provides an important basis for the economic efficiency and rationality of reservoir CO2 injection development scheme design. Attached Figure Description

[0061] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0062] Figure 1 This is an improved online nuclear magnetic resonance core CO2 displacement physical simulation experimental system based on cross-sectional scanning, according to an embodiment of the present invention.

[0063] Figure 2 This embodiment of the invention uses online nuclear magnetic resonance (NMR) core T2 signals before and after CO2 displacement based on cross-sectional scanning, wherein... Figure 2 (a) is the T2 signal of NMR under the original conditions. Figure 2 (b) is the T2 signal of NMR after CO2 displacement with an injection volume of 0.2 PV;

[0064] Figure 3 This embodiment of the invention provides online nuclear magnetic resonance (NMR) imaging of core samples before and after CO2 displacement based on cross-sectional scanning, wherein... Figure 3 (a) is a two-dimensional planar scale model. Figure 3 (b) is the model after initial saturation with oil and water. Figure 3 (c) is an oil-water distribution diagram with 10% carbon dioxide injection; Figure 3 (d) shows the oil-water distribution at a 30% carbon dioxide injection rate;

[0065] Figure 4 This is a one-dimensional core numerical model of the same size as the embodiments of the present invention;

[0066] Figure 5 This is a schematic diagram of the leading edge distribution under different CO2 injection volumes in a two-dimensional planar scale according to an embodiment of the present invention;

[0067] Figure 6This is a schematic diagram of the frontal distribution of an oil reservoir when 0.2 PV CO2 is injected at a three-dimensional scale according to an embodiment of the present invention.

[0068] Figure 7 A flowchart illustrating the steps of a cross-scale characterization method for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement, as provided in an embodiment of the present invention.

[0069] Explanation of reference numerals in the attached figures: 1. Improved online nuclear magnetic resonance gas-driven physical simulation experimental equipment with cross-sectional scanning; 2. End caps of the core holder; 3. Online nuclear magnetic resonance core holder with cross-sectional scanning; 4. Data acquisition device; 5. Intermediate container filled with crude oil; 6. Intermediate container filled with formation water; 7. Intermediate container filled with gas; 8. Switch; 9. Injection pump; 10. Core; 11. Pressure and temperature acquisition system; 12. Sealing device on both sides of the long core; 13. Gas-liquid separation device; 14. Gas flow meter. Detailed Implementation

[0070] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0071] Example 1:

[0072] In this embodiment, the three fronts are defined as follows: the position between the injection and production wells where the formation pressure equals the minimum miscibility pressure between CO2 and crude oil is called the miscibility pressure front; the position closest to the injection well where the molar fraction of CO2 between the injection and production wells is 0 during the gas drive process is defined as the component front; and the position closest to the production well where the interfacial tension between CO2 and crude oil between the injection and production wells is 0 during the gas drive process is defined as the phase front.

[0073] Cross-scale characterization methods for the spatiotemporal features of carbon dioxide front transport during carbon dioxide displacement, such as Figure 7 As shown, the method includes:

[0074] Step S1: Obtain the fluid NMR T2 signal of the core before carbon dioxide displacement under the original conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment; obtain the fluid NMR T2 signal of the core after carbon dioxide displacement under different gas injection conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment; and obtain the one-dimensional carbon dioxide component front position based on the NMR T2 signal under the original conditions and the NMR T2 signal under different gas injection conditions.

[0075] In this embodiment, as Figure 1 As shown,

[0076] (1) Place the cleaned core 10 on the online nuclear magnetic resonance core holder 3 with cross-sectional scanning, and fix it by the plugs 2 at both ends of the core holder and the sealing devices 12 on both sides of the long core. Heat the online nuclear magnetic resonance core holder 3 with cross-sectional scanning to the formation temperature through the pressure and temperature acquisition system 11, evacuate the core 10, and increase the system pressure to above the saturation pressure; (2) Slowly inject formation water into the core 10 in the intermediate container 6 containing formation water at a rate of 0.05 mL / min; (3) Slowly inject crude oil into the core 10 in the intermediate container 5 containing crude oil at a rate of 0.05 mL / min, and slowly inject gas into the core 10 in the intermediate container 7 containing gas at a rate of 0.05 mL / min; (4) Measure the gas-oil ratio of the fluid at the production end of the core 10 through the gas-liquid separation device 13 and the gas flow meter 14. When the fluid gas-oil ratio is constant at the target reservoir gas-oil ratio, it is considered that the core saturated fluid is complete; (5) Based on the improved cross-sectional scanning online nuclear magnetic resonance gas drive physical simulation experimental equipment 1, switch 8 is turned on, and injection pump 9 injects formation water, crude oil and gas into intermediate container 7 containing formation water, intermediate container containing crude oil and intermediate container 7 containing gas through the switch. Through the cross-sectional scanning mode, the nuclear magnetic T2 signal of the fluid along the path from the injection end to the production end in the core is obtained using data acquisition device 4, and then the T2 signal of the fluid along the path from the injection end to the production end in the core 10 under the original conditions is obtained, such as Figure 2 As shown, Figure 2 (a) is the T2 signal of nuclear magnetic resonance under the original conditions; (6) open the inlet end of the online nuclear magnetic resonance core holder 3 with cross-sectional scanning, set the CO2 injection pressure to the oil and gas system pressure under miscible, near-miscible and immiscible conditions respectively, and inject CO2 with different pore volumes (PV) into the core at a constant rate of 0.10 ml / min from the intermediate container 7 containing gas; (7) based on the improved online nuclear magnetic resonance gas drive physical simulation experimental equipment 1 with cross-sectional scanning, obtain the T2 signal of the fluid in the core along the path from the injection end to the production end through the cross-sectional scanning mode, and then obtain the T2 signal along the path from the injection end to the production end of the core 10 under different CO2 injection conditions, such as Figure 2 As shown, Figure 2 (b) The NMR T2 signal after CO2 displacement with an injection volume of 0.2 PV; (8) The one-dimensional position of the CO2 component front is obtained based on the NMR T2 signal under the original conditions and the NMR T2 signal under different injection volumes. When the difference in T2 signal is greater than 1%, this position is recorded as the CO2 component front position. In addition, parameters such as oil recovery rate and gas-oil ratio at the production end are recorded.

[0077] Step S2: After creating bound formation water and saturated crude oil in the two-dimensional flat-plate scale physical model, record the oil-water distribution characteristics under the original conditions, conduct two-dimensional planar scale gas drive physical simulation experiments under different gas injection rates, obtain the oil-water distribution characteristics under different gas injection rates, and obtain the frontal distribution position of carbon dioxide components at the two-dimensional scale based on the oil-water distribution characteristics under the original conditions and the oil-water distribution characteristics under different gas injection rates.

[0078] (1) Vacuum the two-dimensional planar scale model, dye the formation water prepared based on heavy water blue, and fully saturate the formation water until there are no air bubbles in the model. The saturation of water ends. (2) Displace the formation water with crude oil until the production end of the two-dimensional planar scale model no longer produces water, and then displace 5PV. (3) Turn on the electron microscope, adjust the appropriate magnification, brightness, grayscale and contrast to make the picture clear, and record the image under the bound water saturation with the electron microscope. Then scan the image with Image software. (4) Select an appropriate pressure to maintain constant pressure conditions and inject CO2 to displace the formation water and crude oil. Scan the image with Image software to record the oil and water distribution under different CO2 injection amounts. (6) Scan the image with Image software and determine the position of the CO2 component front by the difference in oil and water distribution before and after displacement.

[0079] like Figure 3 As shown, Figure 3 (a) is a two-dimensional planar scale model. Figure 3 (b) is the model after initial saturation with oil and water. Figure 3 (c) is an oil-water distribution diagram with 10% carbon dioxide injection; Figure 3 (d) is the oil-water distribution diagram under 30% carbon dioxide injection.

[0080] Step S3: Perform numerical simulation based on the frontal position of carbon dioxide components at the one-dimensional scale and the frontal distribution position of carbon dioxide components at the two-dimensional scale to obtain the setting parameters for the one-dimensional numerical simulation and the setting parameters for the two-dimensional numerical simulation.

[0081] One-dimensional planar numerical simulation:

[0082] A numerical model of a core of the same size was established and improved based on CMG simulation software for online nuclear magnetic resonance core CO2 displacement physical simulation experiment, such as... Figure 4 As shown, the main steps of the CO2 displacement numerical simulation process are as follows: (1) Based on high-temperature and high-pressure PVT experiments such as constant mass expansion experiment, multi-stage degassing experiment, and gas injection expansion experiment, the fluid composition of the formation crude oil is analyzed and obtained. The fluid composition of the formation crude oil is imported into the Winprop module of the CMG numerical simulation software, and adjustable variables (such as component interaction coefficient, C 30+(1) Fit the experimental data of numerical simulation and physical simulation (e.g., molar mass and crude oil viscosity). When the fitting accuracy of the simulation data with the PVT experimental results is greater than 95%, output the fluid model and calculate the minimum miscibility pressure of the fluid components; (2) Establish a core numerical model of the same size based on CMG simulation software and set parameters such as temperature, pressure, porosity, permeability, oil saturation, pressure coefficient, and saturation pressure. Then set production parameters such as relative permeability curve, CO2 injection amount, CO2 injection rate, injection pressure, and production pressure during the CO2 displacement process. (3) The CO2 displacement process of long core was carried out based on the GEM module of the CMG simulation software, and the pressure distribution, crude oil saturation distribution, and gas phase saturation distribution in the operation results were analyzed. (4) The steps of "component fitting, minimum miscibility pressure, and relative permeability curve fitting" of the CMG simulation software were continuously adjusted until the error between all parameters of all numerical simulation results and the results of long core gas drive experiments was less than 1%. (5) Based on the pressure field map, gas phase mass fraction field map and oil-gas interface tension field map in the numerical simulation results, the CO2 saturation distribution value from the injection end to the production end under different gas injection conditions was analyzed using the CMG numerical simulation software. The position where CO2 is initially zero is identified as the CO2 component front, and the crude oil recovery rate and gas-oil ratio at the production end in the numerical simulation results are derived. (6) The results of the CO2 component front position, crude oil recovery rate and gas-oil ratio at the production end are compared with those of the improved cross-sectional scanning online nuclear magnetic resonance core gas drive physical simulation experiment. (7) Adjust the fitting steps of the numerical simulation software such as “component fitting, minimum miscibility pressure, relative permeability curve fitting” until the error between all parameters of all numerical simulation results and the results of online nuclear magnetic resonance core gas drive physical simulation experiment is less than 1%, then the numerical simulation result is considered accurate.

[0083] In this embodiment, all parameters include oil recovery rate, gas-oil ratio, temperature distribution along the injection end to the production end, pressure distribution along the injection end to the production end, porosity, permeability, oil saturation along the injection end to the production end, gas saturation along the injection end to the production end, pressure coefficient, saturation pressure, and other parameters.

[0084] Two-dimensional planar numerical simulation:

[0085] ①Based on the GEM module of the reservoir numerical simulation software CMG, a model with the same size as the two-dimensional flat plate in the two-dimensional planar scale gas drive physical simulation experiment was established, and the same parameters such as porosity, permeability, oil saturation, initial temperature, and initial pressure were set.

[0086] ② Import the results of “component fitting, minimum miscibility pressure, and relative permeability curve fitting” established during the one-dimensional core-scale numerical simulation into the initial parameter settings of the two-dimensional planar-scale numerical simulation.

[0087] ③ Conduct two-dimensional planar scale gas drive numerical simulations under different gas injection rates. Based on the CO2 saturation distribution values ​​in the two-dimensional planar scale numerical simulation results, the location where CO2 is initially zero is identified as the CO2 component front, and parameters such as oil recovery rate and gas-oil ratio at the production end are derived from the numerical simulation results. These results are then compared with the CO2 component front location results from two-dimensional planar scale gas drive physical simulation experiments. Figure 5 As shown.

[0088] ④ If the error of all parameters is less than 1%, the fitting process of the numerical simulation method is considered to be accurate and error-free. The fitting process of "component fitting, minimum miscibility pressure, and relative permeability curve" can be directly applied to the numerical model at the three-dimensional reservoir scale.

[0089] If any parameter error exceeds 1%, the fitting process for "component fitting, minimum miscibility pressure, and relative permeability curves" established during the one-dimensional core-scale numerical simulation is returned and readjusted until the output results simultaneously satisfy the results of both the one-dimensional core-scale numerical simulation and the two-dimensional planar-scale numerical simulation. Once both are satisfied, the fitting process for "component fitting, minimum miscibility pressure, and relative permeability curves" can be applied to the three-dimensional reservoir-scale numerical simulation.

[0090] Step S4: Based on the set parameters of the one-dimensional numerical simulation and the set parameters of the two-dimensional numerical simulation, the parameters of the three-dimensional reservoir-scale numerical simulation are corrected to obtain a three-dimensional reservoir model. Based on the results of the three-dimensional reservoir numerical simulation, the characteristics of the miscible pressure front, component front, and phase front in the gas drive displacement process are determined, and the cross-scale characterization of the spatiotemporal characteristics of the front migration in the carbon dioxide displacement process is completed.

[0091] (1) A three-dimensional reservoir model was established based on CMG simulation software, and parameters such as reservoir depth, reservoir temperature, reservoir pressure, reservoir porosity, reservoir permeability, reservoir oil saturation, reservoir temperature gradient, reservoir pressure coefficient, and saturation pressure were set. (2) The results of "component fitting, minimum miscibility pressure, and relative permeability curve fitting" established in the "one-dimensional core-scale numerical simulation" were imported into the three-dimensional reservoir model. (3) Based on the pressure field map, gas phase mass fraction field map, and oil-gas interface tension field map in the numerical simulation results of the three-dimensional reservoir model, the characteristics of the miscibility pressure front, component front, and phase front in the three-dimensional reservoir-scale gas drive process were determined, such as... Figure 6 As shown.

[0092] Example 2:

[0093] A multi-scale characterization system for the spatiotemporal features of frontal transport during carbon dioxide displacement, comprising:

[0094] The one-dimensional leading edge position acquisition module is used to acquire the NMR T2 signal along the path of the fluid in the core from the injection end to the production end under the original conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment, and to acquire the NMR T2 signal along the path of the fluid in the core from the injection end to the production end under different gas injection conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment. Based on the NMR T2 signal under the original conditions and the NMR T2 signal under different gas injection conditions, the one-dimensional carbon dioxide component leading edge position is obtained.

[0095] The two-dimensional front position acquisition module is used to record the oil-water distribution characteristics under the original conditions after creating bound formation water and saturated crude oil in a two-dimensional flat-plate scale physical model, conduct two-dimensional planar scale gas drive physical simulation experiments under different gas injection rates, obtain the oil-water distribution characteristics under different gas injection rates, and obtain the two-dimensional scale carbon dioxide component front distribution position based on the oil-water distribution characteristics under the original conditions and the oil-water distribution characteristics under different gas injection rates.

[0096] The numerical simulation module is used to perform numerical simulations based on the leading edge position of carbon dioxide components at the one-dimensional scale and the leading edge distribution position of carbon dioxide components at the two-dimensional scale, so as to obtain the setting parameters for the one-dimensional numerical simulation and the setting parameters for the two-dimensional numerical simulation.

[0097] The cross-scale characterization module is used to correct the parameters of the three-dimensional reservoir-scale numerical simulation based on the set parameters of the one-dimensional numerical simulation and the set parameters of the two-dimensional numerical simulation, so as to obtain a three-dimensional reservoir model. Based on the results of the three-dimensional reservoir numerical simulation, the module judges the characteristics of the miscible pressure front, component front, and phase front in the gas drive displacement process, and completes the cross-scale characterization of the spatiotemporal characteristics of the front migration in the carbon dioxide displacement process.

[0098] In the one-dimensional front position acquisition module, the specific method for obtaining the one-dimensional carbon dioxide component front position is as follows: After adding bound formation water and saturated crude oil to the core in the online nuclear magnetic resonance core gas drive physical simulation experiment with improved cross-section scanning, the nuclear magnetic resonance T2 signal under the original conditions is obtained; gas drive experiments under different gas injection rates are carried out to obtain the along-path nuclear magnetic resonance T2 signal spectrum of the core from the injection end to the production end under different gas injection rates; the along-path nuclear magnetic resonance T2 signal spectrum is compared with the nuclear magnetic resonance T2 signal under the original conditions, and when the difference between the along-path nuclear magnetic resonance T2 signal spectrum and the nuclear magnetic resonance T2 signal under the original conditions is greater than 1%, the one-dimensional carbon dioxide component front position is obtained.

[0099] In the numerical simulation module, the process of obtaining one-dimensional simulation values ​​is as follows: Basic parameters of the core samples from the nuclear magnetic resonance (NMR) experiment are collected; a model with the same dimensions as the basic parameters is established using the GEM module of the reservoir numerical simulation software CMG; initial core parameters are set for the model, and the carbon dioxide saturation distribution from the injection end to the production end under different gas injection rates is analyzed using the CMG numerical simulation software to obtain numerical simulation results; the numerical simulation results are compared with the CO2 component front position, oil recovery rate, and gas-oil ratio results from the improved cross-sectional scanning online NMR core gas drive physical simulation experiment; the fitting process of the numerical simulation software is adjusted based on the comparison results. This fitting process includes component fitting, minimum miscibility pressure, and relative permeability curve fitting until the error between all parameters of the numerical simulation results and the results of the online NMR core gas drive physical simulation experiment is less than 1%, thus obtaining one-dimensional simulation values.

[0100] In the numerical simulation module, the process of obtaining two-dimensional simulation values ​​is as follows: Based on the GEM module of the reservoir numerical simulation software CMG, a model with the same size as the two-dimensional flat plate in the two-dimensional planar scale gas drive physical simulation experiment is established, and the same parameters such as porosity, permeability, oil saturation, initial temperature, and initial pressure are set; the results of the fitting process are imported into the initial parameter settings of the two-dimensional planar scale numerical simulation; two-dimensional planar scale gas drive numerical simulations are carried out under different gas injection rates; based on the carbon dioxide saturation distribution value in the two-dimensional planar scale numerical simulation results, the position where CO2 is initially zero is identified as the CO2 component front, and parameters such as oil recovery rate and gas-oil ratio at the production end are derived from the numerical simulation results; the oil recovery rate and gas-oil ratio at the production end in the numerical simulation results are compared with the CO2 component front position, oil recovery rate, and gas-oil ratio at the production end in the two-dimensional planar scale gas drive physical simulation experiment, and the two-dimensional simulation values ​​are obtained based on the parameter comparison error.

[0101] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A cross-scale characterization method for the spatiotemporal features of leading-edge transport during carbon dioxide displacement, characterized in that, The method includes: Step S1: Obtain the fluid NMR T2 signal of the core before carbon dioxide displacement under the original conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment; obtain the fluid NMR T2 signal of the core after carbon dioxide displacement under different gas injection conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment; obtain the one-dimensional carbon dioxide component front position based on the NMR T2 signal under the original conditions and the NMR T2 signal under different gas injection conditions. Step S2: After creating bound formation water and saturated crude oil in the two-dimensional flat-plate scale physical model, record the oil-water distribution characteristics under the original conditions, carry out two-dimensional planar scale gas drive physical simulation experiments under different gas injection rates, obtain the oil-water distribution characteristics under different gas injection rates, and obtain the frontal distribution position of carbon dioxide components at the two-dimensional scale based on the oil-water distribution characteristics under the original conditions and the oil-water distribution characteristics under different gas injection rates. Step S3: Perform numerical simulation based on the frontal position of carbon dioxide components at the one-dimensional scale and the frontal distribution position of carbon dioxide components at the two-dimensional scale to obtain the setting parameters for the one-dimensional numerical simulation and the setting parameters for the two-dimensional numerical simulation. Step S4: Based on the set parameters of the one-dimensional numerical simulation and the set parameters of the two-dimensional numerical simulation, the parameters of the three-dimensional reservoir-scale numerical simulation are corrected to obtain a three-dimensional reservoir model. Based on the three-dimensional reservoir numerical simulation results, the characteristics of the miscible pressure front, component front, and phase front in the gas drive displacement process are judged, and the cross-scale characterization of the spatiotemporal characteristics of the front migration in the carbon dioxide displacement process is completed.

2. The cross-scale characterization method for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement according to claim 1, characterized in that, In step S1, the specific method for obtaining the leading edge position of the carbon dioxide component at a one-dimensional scale is as follows: After adding bound formation water and saturated crude oil to the core of an online nuclear magnetic resonance core gas drive physical simulation experiment with improved cross-section scanning, the friction NMR T2 signal of the fluid in the core under the original conditions from the injection end to the production end was obtained. Gas drive experiments were conducted under different gas injection rates to obtain the T2 NMR signal of the fluid in the core from the injection end to the production end under different gas injection rates. The magnitudes of the T2 NMR signals along the path under different gas injection conditions are compared with those under the original conditions. When the difference between the T2 NMR signals along the path under different gas injection conditions and those under the original conditions is greater than 1%, the position of the carbon dioxide component front on a one-dimensional scale is obtained.

3. The cross-scale characterization method for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement according to claim 1, characterized in that, In step S3, the process of obtaining the setting parameters for the one-dimensional numerical simulation is as follows: Collect basic parameters from core samples used in nuclear magnetic resonance experiments; Using reservoir numerical simulation software, a model with the same dimensions as the basic parameters was established; The initial parameters of the core were set for the model, and the carbon dioxide saturation distribution from the injection end to the production end under different gas injection rates was analyzed using numerical simulation software to obtain the numerical simulation results. The results of numerical simulation and improved cross-sectional scanning online nuclear magnetic resonance core gas drive physical simulation experiments were compared to the CO2 component front location, oil recovery rate at the production end, and gas-oil ratio. The fitting process of the numerical simulation software is adjusted based on the comparison results. The fitting process includes component fitting, minimum miscibility pressure and relative permeability curve fitting, until the error between all parameters of the numerical simulation results and the results of the online nuclear magnetic resonance core gas drive physical simulation experiment is less than 1%, thus obtaining the set parameters for the one-dimensional numerical simulation.

4. The cross-scale characterization method for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement according to claim 3, characterized in that, In step S3, the process of obtaining the setting parameters for the two-dimensional numerical simulation is as follows: Based on reservoir numerical simulation software, a model with the same size as the two-dimensional flat plate in the two-dimensional planar scale gas drive physical simulation experiment was established, and the same porosity, permeability, oil saturation, initial temperature, and initial pressure parameters were set. Import the results of the fitting process into the initial parameter settings of the two-dimensional planar numerical simulation; Two-dimensional planar scale gas drive numerical simulations were carried out under different gas injection rates. Based on the carbon dioxide saturation distribution values ​​in the two-dimensional planar scale numerical simulation results, the position where CO2 is initially zero was identified as the CO2 component front, and the oil recovery rate and gas-oil ratio parameters at the production end in the numerical simulation results were derived. The oil recovery rate and gas-oil ratio parameters at the production end in the numerical simulation results are compared with the CO2 component front position, oil recovery rate and gas-oil ratio parameters at the production end in the two-dimensional planar scale gas drive physical simulation experiment. Based on the parameter comparison error, the setting parameters for the two-dimensional numerical simulation are obtained.

5. The cross-scale characterization method for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement according to claim 4, characterized in that, The process of obtaining the set parameters for the two-dimensional numerical simulation based on the parameter comparison error is as follows: If the error of all parameters is less than 1%, then the fitting process of the numerical simulation method is considered to be accurate. If any parameter error is greater than or equal to 1%, the fitting process of "component fitting, minimum miscibility pressure and relative permeability curve" will be readjusted until the output results simultaneously satisfy the results of one-dimensional numerical simulation and two-dimensional numerical simulation.

6. The cross-scale characterization method for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement according to claim 5, characterized in that, The process of obtaining the three-dimensional reservoir model is as follows: An initial three-dimensional reservoir model was established, and reservoir depth, reservoir temperature, reservoir pressure, reservoir porosity, reservoir permeability, reservoir oil saturation, reservoir temperature gradient, reservoir pressure coefficient, and saturation pressure parameters were set. The results of the adjusted "component fitting, minimum miscibility pressure and relative permeability curves" are imported into the initial three-dimensional reservoir model to obtain the three-dimensional reservoir model.

7. A cross-scale characterization system for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement, used to implement the method described in any one of claims 1-6, characterized in that the system include: The one-dimensional leading edge position acquisition module is used to acquire the fluid NMR T2 signal of the core before carbon dioxide displacement under the original conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment, and to acquire the fluid NMR T2 signal of the core after carbon dioxide displacement under different gas injection conditions in the improved cross-sectional scanning online NMR core gas drive physical simulation experiment. Based on the NMR T2 signal under the original conditions and the NMR T2 signal under different gas injection conditions, the one-dimensional carbon dioxide component leading edge position is obtained. The two-dimensional front position acquisition module is used to record the oil-water distribution characteristics under the original conditions after creating bound formation water and saturated crude oil in the two-dimensional flat plate scale physical model, carry out two-dimensional planar scale gas drive physical simulation experiments under different gas injection conditions, obtain the oil-water distribution characteristics under different gas injection conditions, and obtain the two-dimensional scale carbon dioxide component front distribution position based on the oil-water distribution characteristics under the original conditions and the oil-water distribution characteristics under different gas injection conditions. The numerical simulation module is used to perform numerical simulations based on the frontal position of carbon dioxide components at the one-dimensional scale and the frontal distribution position of carbon dioxide components at the two-dimensional scale, so as to obtain the setting parameters for the one-dimensional numerical simulation and the setting parameters for the two-dimensional numerical simulation. The cross-scale characterization module is used to correct the parameters of the three-dimensional reservoir-scale numerical simulation based on the set parameters of the one-dimensional numerical simulation and the set parameters of the two-dimensional numerical simulation, so as to obtain a three-dimensional reservoir model. Based on the three-dimensional reservoir numerical simulation results, the module judges the characteristics of the miscible pressure front, component front, and phase front in the gas drive displacement process, and completes the cross-scale characterization of the spatiotemporal characteristics of the front migration in the carbon dioxide displacement process.

8. The cross-scale characterization system for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement according to claim 7, characterized in that, In the one-dimensional leading edge position acquisition module, the specific position of the carbon dioxide component leading edge at the one-dimensional scale is obtained as follows: After adding bound formation water and saturated crude oil to the core of an online nuclear magnetic resonance core gas drive physical simulation experiment with improved cross-section scanning, the friction NMR T2 signal of the fluid in the core under the original conditions from the injection end to the production end was obtained. Gas drive experiments were conducted under different gas injection rates to obtain the T2 NMR signal of the fluid in the core from the injection end to the production end under different gas injection rates. The T2 NMR signal along the path under different gas injection conditions is compared with the T2 NMR signal along the path under the original conditions. When the difference between the T2 NMR signal along the path and the T2 NMR signal under the original conditions is greater than 1%, the position of the carbon dioxide component front on a one-dimensional scale is obtained.

9. The cross-scale characterization system for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement according to claim 7, characterized in that, In the numerical simulation module, the process of obtaining the set parameters for the one-dimensional numerical simulation is as follows: Collect basic parameters from core samples used in nuclear magnetic resonance experiments; Using reservoir numerical simulation software, a model with the same dimensions as the basic parameters was established; The initial parameters of the core were set for the model, and the carbon dioxide saturation distribution from the injection end to the production end under different gas injection rates was analyzed using numerical simulation software to obtain the numerical simulation results. The results of numerical simulation and improved cross-sectional scanning online nuclear magnetic resonance core gas drive physical simulation experiments were compared to the CO2 component front location, oil recovery rate at the production end, and gas-oil ratio. The fitting process of the numerical simulation software is adjusted based on the comparison results. The fitting process includes component fitting, minimum miscibility pressure and relative permeability curve fitting, until the error between all parameters of the numerical simulation results and the results of the online nuclear magnetic resonance core gas drive physical simulation experiment is less than 1%, thus obtaining the set parameters for the one-dimensional numerical simulation.

10. The cross-scale characterization system for the spatiotemporal characteristics of leading-edge transport during carbon dioxide displacement according to claim 9, characterized in that, In the numerical simulation module, the process of obtaining the set parameters for the two-dimensional numerical simulation is as follows: Based on reservoir numerical simulation software, a model with the same size as the two-dimensional flat plate in the two-dimensional planar scale gas drive physical simulation experiment was established, and the same porosity, permeability, oil saturation, initial temperature, and initial pressure parameters were set. The results of the fitting process are imported into the initial parameter settings for the two-dimensional planar numerical simulation. Two-dimensional planar scale gas drive numerical simulations were carried out under different gas injection rates. Based on the carbon dioxide saturation distribution values ​​in the two-dimensional planar scale numerical simulation results, the position where CO2 is initially zero was identified as the CO2 component front, and the oil recovery rate and gas-oil ratio parameters at the production end in the numerical simulation results were derived. The oil recovery rate and gas-oil ratio parameters at the production end in the numerical simulation results are compared with the CO2 component front position, oil recovery rate and gas-oil ratio parameters at the production end in the two-dimensional planar scale gas drive physical simulation experiment. Based on the parameter comparison error, the setting parameters for the two-dimensional numerical simulation are obtained.

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