Experimental measurement method and device for evaluating deep migration of foam stratum and storage medium

Abstract

The invention provides an experimental measurement method and device for evaluating foam stratum deep migration and a storage medium, and belongs to the technical field of oil and gas field development engineering and carbon storage engineering.The method comprises the steps that variable-diameter rock core displacement is adopted, and the flow condition that the flow speed and the pressure gradient are suddenly decreased when stratum injection fluid radially flows from a near wellbore area to the stratum deep part is simulated; the defect that the flow condition cannot be simulated by conventional equal-diameter rock core displacement is overcome; the steady-state pressure gradient of each part of the variable-diameter rock core under a certain injection flow velocity sequence is measured, the critical pressure gradient and critical flow velocity conditions required by foam generation, transportation and stability maintenance can be effectively measured, and the influence mechanism and rule of each factor on the critical conditions can be evaluated; the method can be used for predicting the migration distance of the deep part of the foam stratum and evaluating the feasibility and dynamic behavior rule of large-scale foam mobility regulation and control, and has important significance in guiding and optimizing engineering application of a foam mobility regulation and control technology in the fields of CO2 oil displacement, geological sequestration and deep profile control.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas field development engineering, carbon storage engineering, and the like, and particularly relates to an experimental measurement method and device for evaluating deep formation foam migration, and a storage medium. BACKGROUND

[0002] CO2 flooding and geological storage is one of the important technologies for accelerating low-carbon development of oil and gas energy. In view of the phase state characteristics between the oil phase and CO2, the oil washing efficiency in the swept area of the reservoir crude oil can be greatly improved. At the same time, part of the injected CO2 is trapped in the formation, achieving the geological storage of CO2 to reduce the impact of carbon emissions on the environment. However, there are three major problems in the process of gas injection into the formation, namely, gas viscous fingering due to large gas-liquid mobility ratio, gas channeling due to formation heterogeneity, and gravity override caused by the difference between gas and liquid densities, thereby resulting in poor volume sweep efficiency of the injected gas.

[0003] Laboratory experiments and field applications show that, compared with other technologies such as water-gas co-injection, water-gas alternating injection, water-gas layered injection, and supercritical carbon dioxide injection, foam flooding is an extremely effective method for improving the volume sweep efficiency of the injected gas in the formation. The main principle is that foam can greatly reduce the mobility of gas (for example, 10-10 4 times), overcome or alleviate the above problems of gas flooding, increase the volume sweep efficiency of the injected gas, increase the production of crude oil, and increase the gas saturation in the swept area, thereby increasing the storage capacity of geological carbon storage.

[0004] The key to the success of the foam formation deep mobility control technology depends on whether the foam can be effectively transported to the deep formation. The deep formation migration of foam is the result of two processes: the transportation of the foam generated in the near-wellbore zone to the deep formation and the generation of new foam at the displacement front. However, there is still great uncertainty as to whether the foam generated under the conditions of high pressure gradient and high flow rate in the near-wellbore zone can be successfully transported to the deep formation with low pressure gradient and low flow rate, and whether the foam can be successfully generated in the deep formation. These uncertainties greatly limit the behavior prediction and optimization of large-scale foam mobility control technology.

[0005] In order to effectively control and optimize the effect of foam deep formation application, it is necessary to determine the pressure gradient and flow rate conditions required for the deep migration of foam. Core flooding is the most commonly used laboratory evaluation method at present. However, conventional core flooding uses equal-diameter cores, which cannot simulate the flow conditions of the sudden drop of flow rate and pressure gradient when the injected fluid flows radially from the near-wellbore zone to the deep formation. This limitation results in the fact that conventional equal-diameter core flooding cannot effectively evaluate whether the foam generated under the conditions of high pressure gradient and high flow rate in the near-wellbore zone can be transported to the deep formation under the conditions of low flow rate and low pressure gradient. SUMMARY

[0006] In order to solve the problem that the deep formation migration condition of the foam cannot be quantitatively evaluated, the application provides an experimental measurement method and device for evaluating the deep formation migration of foam and a storage medium.

[0007] In order to achieve the above-mentioned purpose, the application provides an experimental measurement method for evaluating the deep formation migration of foam, comprising the following steps: According to the rock porosity parameters, permeability parameters and wettability parameters of the target oil and gas reservoir, a variable-diameter core model is prepared; the diameter of the variable-diameter core model increases from the injection end to the production end, simulating the flow environment of the sudden drop of flow rate and pressure gradient when the formation injection fluid flows radially from the near-wellbore zone to the deep formation; a plurality of pressure measuring points are arranged along the flow direction of the variable-diameter core model.

[0008] A gas-liquid fluid with a preset volume flow rate is injected into the narrow-diameter end of the variable-diameter core model, and the pressure gradient of the core at different diameters is synchronously monitored by using each pressure measuring point; the volume flow rate of the injection fluid is gradually increased, and when the pressure gradient of the narrow-diameter part of the core jumps, the critical pressure gradient required for triggering foam generation is determined; after the foam is generated in the narrow-diameter part of the core, the volume flow rate of the injection fluid is immediately reduced, and the volume flow rate of the injection fluid is again gradually increased; when the pressure gradient of the wide-diameter part of the core jumps, the critical pressure gradient required for foam transport is determined; the volume flow rate of the injection fluid is gradually reduced; when the pressure gradient of the wide-diameter part of the core drops, the critical pressure gradient required for maintaining the stability of the foam is determined.

[0009] The critical flow rate required for foam generation, transport and stability is determined according to the critical pressure gradient required for foam generation, transport and stability; the migration distance of the foam under the flow rate and pressure gradient conditions of the deep formation is predicted through the critical pressure gradient and the critical flow rate required for foam generation, transport and stability, and then the feasibility and effect of the large-scale foam mobility control are evaluated.

[0010] Preferably, the variable-diameter core model comprises a tapered variable-diameter core model and a stepped variable-diameter core model.

[0011] Preferably, when the pressure gradient of the narrow-diameter part of the core jumps, the critical pressure gradient required for triggering foam generation is determined; after the foam is generated in the narrow-diameter part of the core, the volume flow rate of the injection fluid is immediately reduced, and the volume flow rate of the injection fluid is again gradually increased; when the pressure gradient of the wide-diameter part of the core jumps, the critical pressure gradient required for foam transport is determined; the volume flow rate of the injection fluid is gradually reduced; when the pressure gradient of the wide-diameter part of the core drops, the critical pressure gradient required for maintaining the stability of the foam is determined, and the specific experimental steps comprise: The total volume flow rate of the injection fluid is preset as and the foam dryness is that is, the volume flow rate of the gas phase is Q g accounts for Qt The proportion, based on and Determine the gas injection volumetric flow rate Q g = Q t × f g and liquid phase injection volume flow rate Q w = Q t × (1 – f g ); The diameters of the variable-diameter core models are respectively increased sequentially. , and Six pressure measurement points are set along the flow direction of the variable-diameter core model; a preset volumetric flow rate is simultaneously injected into the narrow end of the variable-diameter core model. Q g gas phase and Q w The liquid phase, pressure gradient is collected in real time. to ; Measuring the critical pressure gradient condition that triggers foam formation: like exist When the initial injection surge exceeds a set threshold of 1, the core is cleaned, and a flow rate less than the preset total volumetric flow rate is selected. Remeasure and gradually increase the total volumetric flow rate of the injected fluid. Q t Simultaneously measure the pressure gradient of each diameter section of the variable-diameter rock core to determine the critical pressure gradient required to trigger foam formation; or choose to abandon measuring the critical conditions for foam formation and immediately reduce the pressure gradient. Then gradually increase To measure the critical pressure gradient required for foam transport and to maintain stability; like When the pressure gradient is close to that of gas-liquid injection without surfactant, gradually increase until A jump of at least 2 times occurred; records were kept prior to the jump. This refers to the critical pressure gradient required to trigger foam formation. immediately reduce ; Critical pressure gradient condition for measuring foam transport: Gradually increase ,when When a jump occurs and exceeds the set threshold of 1, record. critical pressure gradient required for foam transport ; continuously increasing , when to all pressure gradients jump and are greater than a set threshold 1, record or critical pressure gradient required for foam transport ; measuring the critical pressure gradient condition for foam stability: continuously decreasing , when to all pressure gradients jump and are less than a set threshold 2, record to steady state pressure gradient before jump down or critical pressure gradient required for foam stability .

[0012] Preferably, the critical flow rates of foam generation, transport and stability are determined according to the critical pressure gradients required for foam generation, transport and stability, specifically comprising: record the total gas-liquid fluid volume flow rate corresponding to the foam generation critical pressure gradient , foam transport critical pressure gradient and foam stability critical pressure gradient respectively; and the current recorded pressure gradient corresponding core diameter; calculate Darcy flow rate from the total gas-liquid fluid volume flow rate and core diameter; obtain the porosity of the variable diameter core model; obtain the pore flow rate from the ratio of Darcy flow rate and core porosity; thus determine , and foam generation critical flow rate , foam transport critical flow rate and foam stability critical flow rate .

[0013] Preferably, the gas-liquid fluid comprises: gas phase and liquid phase; the gas phase comprises: carbon dioxide, steam, nitrogen, air and hydrocarbon gas; the liquid phase is a foaming agent solution.

[0014] Preferably, the experimental method can quantitatively evaluate deep migration conditions of different types of foams and different injection modes; the different types of foams include carbon dioxide foam, steam foam, nitrogen foam, air foam and hydrocarbon gas foam; and the different injection modes include gas-liquid simultaneous injection, gas-liquid alternating injection and injection of pre-generated foam.

[0015] The application further provides an experimental method device for evaluating deep migration of a foam formation, comprising: A core model preparation module is configured to prepare a variable-diameter core model according to rock porosity parameters, permeability parameters and wettability parameters of a target oil and gas reservoir; the variable-diameter core model has a diameter that increases from an injection end to a production end, simulating a flow environment in which flow velocity and pressure gradient suddenly decrease when injection fluid flows radially from a near-wellbore zone to a deep formation; and a plurality of pressure measurement points are arranged along a fluid flow direction of the variable-diameter core model. A critical condition measurement module is configured to inject a gas-liquid fluid with a preset volume flow rate into a narrow-diameter end of the variable-diameter core model, and simultaneously monitor pressure gradients of different diameter portions of the core by using the pressure measurement points; gradually increase the volume flow rate of the injection fluid, and determine a critical pressure gradient required for triggering foam generation when the pressure gradient of the narrow-diameter portion of the core jumps; immediately reduce the volume flow rate of the injection fluid after the foam is generated in the narrow-diameter portion of the core, and again gradually increase the volume flow rate of the injection fluid; determine a critical pressure gradient required for foam transport when the pressure gradient of the wide-diameter portion of the core jumps; gradually reduce the volume flow rate of the injection fluid; and determine a critical pressure gradient required for foam stability maintenance when the pressure gradient of the wide-diameter portion of the core drops. A data application module is configured to determine critical flow rates required for foam generation, transport and stability maintenance according to the critical pressure gradients required for foam generation, transport and stability maintenance; and predict migration distances of the foam under flow velocity and pressure gradient conditions in the deep formation by using the critical pressure gradients and the critical flow rates required for foam generation, transport and stability maintenance, and further evaluate the feasibility and effect of large-scale foam mobility control.

[0016] The application further provides a computer readable storage medium, wherein the storage medium stores a computer program, and the computer program can execute any step of the experimental method for evaluating deep migration of a foam formation when loaded by a processor.

[0017] The experimental measurement method for evaluating deep migration of a foam formation provided by the application has the following beneficial effects: According to the target oil and gas reservoir rock porosity parameters, permeability parameters and wettability parameters, a variable diameter core model is prepared, the variable diameter core design more accurately simulates the flow environment of the sudden drop of flow velocity and pressure gradient when the formation injection fluid flows radially from the near wellbore to the deep part of the formation, which can directly and effectively simulate the dynamic behavior and seepage law of foam deep migration in the formation, and solve the problem that the traditional equal diameter core displacement cannot restore the actual formation near well to far well flow condition sudden change; through the foam generation critical condition, transport critical condition and stable critical condition, the minimum standard of the three processes of foam in the formation is accurately determined; through the foam generation, transport and stable critical conditions, the foam deep migration distance in the formation is predicted, and the effect of large-scale foam mobility regulation on improving gas sweep is evaluated; the critical value measured by experiment is used to guide the design of the injection flow rate and pressure standard which is operable in the field, the application effect of foam mobility regulation technology in the field is optimized, and the oil recovery efficiency and CO2 storage efficiency are improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present application and the design scheme thereof, the drawings required by the present embodiments will be briefly introduced as follows. The drawings are only part of the embodiments of the present application. Those skilled in the art can obtain other drawings according to the drawings without paying creative labor.

[0019] Figure 1 The indoor test flow chart of the variable diameter core displacement of the embodiments of the present application for evaluating foam deep migration in the formation; Figure 2 The schematic diagram of the foam generation, transport and stable kinetics jump theory in the porous medium of the embodiments of the present application; Figure 3 The variable diameter core displacement core size and pressure measuring point design case schematic diagram of the embodiments of the present application; Figure 4 The critical condition of supercritical carbon dioxide foam generation, transport and stability in the rock sample of the embodiments of the present application. DETAILED DESCRIPTION

[0020] The following embodiments are only used to assist in describing the technical scheme of the present application, and cannot limit the protection scope of the present application.

[0021] The present application provides an experimental measurement method for evaluating foam deep migration in the formation, specifically as shown in Figure 1 , comprising: The present application first proposes a variable-diameter core displacement experiment measurement method for evaluating deep formation foam migration, which can quantitatively evaluate the critical pressure gradient and critical flow rate conditions required for foam generation, transportation and stability. The variable-diameter core has a larger diameter in the fluid flow direction, which can realize the flow conditions of a large decrease in flow rate and pressure gradient from the core injection end to the production end under a fixed volumetric flow rate. The variable-diameter core displacement experiment measurement method can successfully simulate the flow environment of a large decrease in flow rate and pressure gradient in the radial flow process of the injected fluid from the near-wellbore zone to the deep formation in the vertical well or horizontal well. Through this method, the critical pressure gradient and critical flow rate conditions required for foam generation, transportation and stability maintenance can be measured, and the variation law and mechanism between the critical conditions and the influencing factors, including medium permeability, foam dryness (i.e. the volume fraction of gas in the foam), foam stabilizer type and concentration, and residual oil saturation, are revealed. For the theoretical basis, experimental steps and method verification of the foam deep formation migration measurement method, please refer to the following sections.

[0022] As shown in Figure 2 , the foam jump theory based on the foam mass balance model reveals the relationship between the apparent viscosity or pressure gradient and the gas-liquid phase flow rate in the process of foam generation and migration. In the entire flow rate domain of the gas phase and the liquid phase, the apparent viscosity or pressure gradient of the corresponding foam state presents a smooth surface, and the surface is folded in the flow rate domain. The folding of the surface divides the foam state into three groups: the lower surface weak or no foam state (low apparent viscosity), the upper surface strong foam state (high apparent viscosity) and the middle surface foam state (intermediate intensity apparent viscosity).

[0023] According to the jump theory, the foam state in the middle surface is extremely unstable, and any disturbance (such as flow rate, pressure gradient) will make it jump to the strong or weak foam state, so the foam state between the strong and weak foam states does not exist in nature. When the gas-liquid phase flow rate changes from low to high, the foam strength first slowly increases (lower surface), and then suddenly jumps to the strong foam state (upper surface), indicating that there is a critical startup pressure gradient and a critical startup flow rate for the generation of strong foam, i.e. and . Figure 2 right jump point). After the generation of strong foam, when the gas-liquid flow rate decreases, the foam strength first slowly weakens (upper surface), and then suddenly jumps to the weak or no foam state (lower surface), indicating that there is a critical stable pressure gradient and a critical stable flow rate required for the stability maintenance of foam, i.e. and . Figure 2 left jump-down point). At the same time, there is a critical transportation pressure gradient and a critical transportation flow rate for the transportation of foam in the porous medium after the generation of foam, i.e. and .

[0024] The deep formation in the far-wellbore zone has a low flow rate and low pressure gradient flow environment. Whether the foam can be generated in the deep formation and the foam generated in the near-wellbore zone can be transported to the deep formation depends on whether the flow conditions in the deep formation can meet the critical pressure gradient and critical flow rate required for foam generation, transportation and stable maintenance. Therefore, quantitatively determining the critical conditions for foam migration in porous media is the key to ensuring the success of foam deep application.

[0025] Based on the foam jump theory, the present application proposes a variable-diameter core displacement measurement method for evaluating the deep formation migration of foam. The method can effectively measure the critical pressure gradient and critical flow rate conditions required for foam migration in the deep formation, that is, the critical pressure gradient and critical flow rate conditions required for foam migration in the deep formation, as shown in Figure 2 and , and and . For specific test methods and steps, please refer to the following sections.

[0026] Unlike conventional constant-diameter core displacement, variable-diameter core displacement selects two types of cores, including tapered and stepped variable-diameter cores. Figure 3 A design case of stepped variable-diameter core size and pressure point position is shown, where D represents the diameter of each constant-diameter part of the variable-diameter core, L represents the length of the different diameter parts of the core, represents the distance between adjacent pressure points. The core design case includes three different diameter parts, which are D 1 , D 2 and D 3 According to Darcy's law: ; wherein, Q t is the total volumetric flow rate of the injected fluid, U t is the total Darcy flow rate of the injected fluid, A is the cross-sectional area of the core.

[0027] When the fluid is injected from the narrow-diameter D 1 part ( Figure 3 left end) of the variable-diameter core, the increase in the diameter of the core causes the fluid flow rate to decrease times from the injection end to the production end of the core. At the same time, multiple pressure points are distributed in the flow direction of the core, for example p 1 to p 7 , which are used to measure the pressure difference to of different diameter parts of the core.​

[0028] According to the foam jump theory of Figure 2 and the variable diameter core design of Figure 3 , the core of this test method is to determine the critical pressure gradient required for foam generation, transport and maintenance of stability by measuring the steady-state pressure gradient of different diameter parts of the variable diameter core under a certain flow rate sequence, that is , and . The pore flow rate corresponding to each critical pressure gradient (i.e. U t divided by porosity) is the critical flow rate required for foam generation, transport and maintenance of stability, that is , and .

[0029] In addition to the stepped variable diameter core as shown in Figure 3 , a tapered variable diameter core can also be selected, whose diameter gradually increases from the core injection end to the production end, and the pressure measuring points, for example p 1 to p 7 , are distributed equidistantly along the core. When using a tapered variable diameter core, the critical pressure gradients required for foam generation, transport and maintenance of stability , and can be measured, but due to the change of fluid flow rate along the length of the core, the corresponding critical flow rate conditions cannot be accurately determined. In addition, regarding the selection of the diameter of the variable diameter core, the amplitude of the change of the near-wellbore fluid flow rate to be simulated can be designed according to the needs.

[0030] Figure 1 The test flow chart of the variable diameter core displacement evaluation of foam deep migration in the formation is shown. The specific steps are as follows: (1) Select the injected foam dryness f g , that is, the volume ratio of the injected gas phase in the injected gas-liquid.

[0031] (2) Select a suitable total volume flow rate of the injected fluid Q t , and inject gas and liquid from the narrow diameter end of the variable diameter core as shown in Figure 3 . Among them, the gas phase flow rate is Q g =Q t ×f g ， The liquid phase flow rate is Q w = Q t ×(1–f g ).

[0032] (3) Determine whether strong foam is generated. Compared with the wide diameter part of the variable diameter core, the narrow diameter D1 part has a higher flow velocity, so it is most likely to generate foam first.

[0033] if D 1 Partial pressure gradient If the pressure gradient is close to that of gas-liquid injection without surfactant, it indicates that no strong foam is generated, and the next step should be performed sequentially.

[0034] If at the beginning Q t A strong bubble has already formed (such as) If the pressure increases by more than two times, the critical pressure gradient that triggers foam formation cannot be determined. At this point, the core sample needs to be cleaned and the process returned to step (2), while selecting a lower [temperature]. Q t Retest. Or, give up. The measurement immediately decreased Q t , making Q t Can maintain D Part 1 of the foam is insufficient to transport the foam to the downstream wide-diameter section of the variable-diameter core, and proceeds directly to (5) and subsequent steps to determine... and .

[0035] (4) When no strong foam is generated in (3), at a fixed foam dryness f g Gradually increase the volumetric flow rate. Q t and measure each Q t Steady-state pressure gradients in different parts of the variable-diameter core arrive . Q t Increase to When the price jumps by at least 2 times (i.e., a strong bubble forms), in Before the leap D The steady-state pressure gradient of part 1 is the critical pressure gradient required for foam formation. .

[0036] At the same time, once strong foam is present in narrow diameter core samples with varying diameters... D Part 1 generated, needs to be reduced immediately. Q tto avoid foam transport to the wider downstream section of the variable diameter core, resulting in a critical pressure gradient required for foam transport that cannot be measured .

[0037] (5) On the basis of (4) reducing Q t , then gradually increasing Q t , and measuring the steady-state pressure gradient Q t at each , until the pressure gradient D 2 section of the variable diameter core jumps at least 2 times or more, at which point the steady-state pressure gradient D 2 section is the critical pressure gradient for foam transport . The principle is D 2 section of the flow rate is still below the critical flow rate required for foam generation , so jump is due to the foam generated in D 1 section transport to D 2 section, rather than new foam generated in D 2 section.

[0038] (6) On the basis of (5), continue to gradually increase Q t , and measure the steady-state pressure gradient Q t at each , until also jumps at least 2 times or more, at which point the steady-state pressure gradient or is also the critical pressure gradient for foam transport .

[0039] (7) After (6), gradually reduce Q t , and measure the steady-state pressure gradient Q t at each , until jumps at least 2 times or more (i.e. foam collapse). The steady-state pressure gradient or before jumps is the critical pressure gradient for maintaining foam stability . ​​​​​​

[0040] (8) measured , and The corresponding flow rate is the critical flow rate required for foam generation, transport and stability , and .

[0041] (9) Data processing. The steady-state pressure gradient data measured in each Q t The steady-state pressure gradient data measured in each Figure 2 The steady-state pressure gradient data measured in each f g A "S-shaped" slice of the foam pressure gradient or apparent viscosity-total flow rate graph can be obtained, in which the foam apparent viscosity µ app The foam apparent viscosity ; In the formula, k is the permeability of the porous medium, is the steady-state pressure gradient, U t is the total Darcy flow rate of gas and liquid.

[0042] (9) End the experiment. Flush the core with a suitable solvent to remove the foam in the core, and then clean the core with water for reuse.

[0043] For the variable-diameter core model prepared in this embodiment, 6 pressure measurement points are configured in the experimental test stage; in actual application, the number of pressure measurement points should be adaptively designed according to the actual division result of different diameter sections of the variable-diameter core model.

[0044] This test method is universal and can be used to measure the deep migration critical conditions of different types of foam (such as carbon dioxide, nitrogen, hydrocarbon gas and steam foam) under different formation conditions, including different foam dryness, medium permeability, foaming agent type and concentration. At the same time, this method can also be used to measure the deep migration critical conditions of foam under different injection modes, including gas-liquid co-injection, gas-liquid alternating injection, fixed liquid phase flow rate and changed gas phase flow rate or fixed gas phase flow rate and changed liquid phase flow rate, and pre-generated foam injection.

[0045] The present application adopts Figure 3 The core design shown in and the experimental steps shown in Figure 1 The critical conditions required for supercritical carbon dioxide foam generation, transport and stability are measured, and the results verify the effectiveness of the above-mentioned foam deep formation migration measurement method proposed by the present application. This experimental case uses gas-liquid co-injection under fixed foam dryness, and uses a specific foaming agent and concentration. The test data are as follows:Figure 4 The steady-state pressure gradient versus total pore velocity is shown. The data show that when foam is injected from low flow rates, the pressure gradient increases with increasing flow rate, Figure 3 Variable diameter core D 1 The pressure gradient is low (i.e. no or weak foam). Further increase in injection rate triggers strong foam generation, resulting in a jump in pressure gradient, which determines the foam generation threshold pressure gradient and .

[0046] According to the experimental procedure in Figure 1 , strong foam is generated in the variable diameter core D 1 immediately after the injection rate is decreased, and then gradually increased until foam is transported from the variable diameter core D 1 to the downstream D 2 and D 3 sections, which determines the foam transport threshold pressure gradient and . Then, the injection rate is gradually decreased until foam in the variable diameter core D 3 section breaks, which determines the foam stability threshold pressure gradient and .

[0047] The successful determination of the foam migration threshold conditions verifies the feasibility of the foam deep migration variable diameter core displacement experiment measurement method proposed in the present application. At the same time, the intermediate foam state between strong and weak foam did not appear in the experiment, which confirms the prediction results of the foam jump theory.

[0048] Figure 4 The experimental conditions (such as pressure, flow rate) used in are only a case to verify the effectiveness of the test method. The test method proposed in the present application is generally applicable to rock porous media with different experimental conditions, different permeability ranges, and variable diameter cores with different sizes and shapes.

[0049] Based on the foam jump theory, the application first proposes a variable-diameter core displacement experiment measurement method for quantitatively evaluating deep migration of foam formation. The method can effectively determine the critical pressure gradient and critical flow rate conditions required for foam generation, transportation and stability, so as to predict or optimize the field application effect of large-scale foam mobility control technology. The design of the variable-diameter core can effectively simulate the flow environment of the sudden drop of flow rate and pressure gradient when the formation injection fluid flows radially from the near well to the far well, thereby realizing the direct and effective laboratory simulation of deep migration of foam formation. At the same time, the measurement method provides a quantitative method for evaluating the relationship between the critical conditions and influencing factors of deep migration of foam formation, including medium permeability, foam dryness, foaming agent type and concentration, and residual oil saturation. The determined quantitative relationship can not only reveal the mechanism of deep migration of foam formation, but also improve the accuracy of the prediction of deep migration of foam formation. The variable-diameter core displacement measurement method for deep migration of foam formation proposed by the application has universality, and can quantitatively evaluate the foam migration conditions under different types of foam and different injection modes, including carbon dioxide foam, steam foam, nitrogen foam, hydrocarbon gas foam, gas-liquid simultaneous injection, gas-liquid alternating injection, and injection of pre-generated foam.

[0050] Based on the same inventive concept, the application further provides an experimental method device for evaluating deep migration of foam formation, comprising: A core model preparation module is used to prepare a variable-diameter core model according to the rock porosity parameters, permeability parameters and wettability parameters of a target oil and gas reservoir. The diameter of the variable-diameter core model increases from the injection end to the production end, simulating the flow environment of the sudden drop of flow rate and pressure gradient when the formation injection fluid flows radially from the near well zone to the deep formation. A plurality of pressure measurement points are arranged along the fluid flow direction of the variable-diameter core model. A critical condition measurement module is used to inject a preset volume flow rate of gas-liquid fluid into the narrow-diameter end of the variable-diameter core model, and simultaneously monitor the pressure gradient of different diameter parts of the core by using each pressure measurement point. The volume flow rate of the injection fluid is gradually increased, and when the pressure gradient of the narrow-diameter part of the core jumps, the critical pressure gradient required for triggering foam generation is determined. After the foam is generated in the narrow-diameter part of the core, the volume flow rate of the injection fluid is immediately reduced, and the volume flow rate of the injection fluid is again gradually increased. When the pressure gradient of the wide-diameter part of the core jumps, the critical pressure gradient required for foam transportation is determined. The volume flow rate of the injection fluid is gradually reduced. When the pressure gradient of the wide-diameter part of the core drops, the critical pressure gradient required for foam to maintain stability is determined. A data application module is used to determine the critical flow rate of foam generation, transportation and stability maintenance according to the critical pressure gradient required for foam generation, transportation and stability maintenance. Through the critical pressure gradient and critical flow rate required for foam generation, transportation and stability, the migration distance of foam under the flow rate and pressure gradient conditions in the deep formation is predicted, and the feasibility and effect of large-scale foam mobility control are evaluated.

[0051] The application further provides a computer readable storage medium, which stores a computer program, and the computer program can be used to execute the experimental method for evaluating deep migration of foam in a formation.

[0052] The specific limitations of the experimental method system for evaluating deep migration of foam in a formation can refer to the limitations of the experimental method for evaluating deep migration of foam in a formation described above, which will not be repeated here. Each module in the experimental method system for evaluating deep migration of foam in a formation described above can be realized by software, hardware and combinations thereof, in whole or in part. Each module described above can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory in the computer device in software form, so as to be called and executed by the processor to perform the operations corresponding to each module.

[0053] Each technical feature of the above embodiments can be combined arbitrarily, and in order to make the description concise, each technical feature in the above embodiments is not described in all possible combinations, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application. The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, and should not be understood as a limitation on the scope of the patent. Those skilled in the art can make some modifications and improvements without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the patent protection scope of the present application should be subject to the appended claims

[0054] It should be noted that the above specific embodiments can enable those skilled in the art to more fully understand the present application, but in no way limit the present application. Therefore, although the present application has been described in detail in the specification and examples, those skilled in the art should understand that the present application can still be modified or replaced by equivalents; all technical solutions and improvements that do not depart from the spirit and scope of the present application are covered in the protection scope of the present application. Any reference signs in the claims should not be considered as limiting the claims.

Claims

1. An experimental measurement method for evaluating deep migration in foam formations, characterized in that, include: Based on the rock porosity, permeability, and wettability parameters of the target oil and gas reservoir, a variable-diameter core model is prepared. The diameter of the variable-diameter core model increases from the injection end to the production end, simulating the flow environment where the velocity and pressure gradient of the injected fluid decreases sharply when it flows radially from the near-wellbore zone to the deep formation. Multiple pressure measurement points are set along the flow direction of the variable-diameter core model. A gas-liquid fluid with a preset volumetric flow rate is injected into the narrow end of the variable-diameter core model, and the steady-state pressure gradient of different diameter parts of the core is measured synchronously at each pressure measuring point. The injection fluid volumetric flow rate is gradually increased. When the pressure gradient in the narrow diameter section of the core increases abruptly, the critical pressure gradient required to trigger foam generation is determined. After foam generation in the narrow diameter section of the core, the injection fluid volumetric flow rate is immediately reduced, and then gradually increased again. When the pressure gradient in the wide diameter section of the core increases abruptly, the critical pressure gradient required for foam transport is determined. Gradually reduce the volumetric flow rate of the injected fluid; Determine the critical pressure gradient required for foam to maintain stability when the pressure gradient in the wide-diameter portion of the core drops abruptly. Based on the critical pressure gradient required for foam generation, transport, and maintenance of stability, the critical flow velocity for foam generation, transport, and maintenance of stability is determined. By using the critical pressure gradient and critical flow velocity required for foam generation, transport, and maintenance of stability, the migration distance of foam under the conditions of flow velocity and pressure gradient in deep formations is predicted, thereby evaluating the feasibility and effectiveness of foam mobility regulation in deep formations.

2. The experimental measurement method for evaluating deep migration in foam formations according to claim 1, characterized in that, The variable diameter core models include conical variable diameter core models and stepped variable diameter core models.

3. The experimental measurement method for evaluating deep migration in foam formations according to claim 1, characterized in that, When the pressure gradient in the narrow diameter section of the core increases abruptly, the critical pressure gradient required to trigger foam generation is determined; after foam generation in the narrow diameter section of the core, the volumetric flow rate of the injected fluid is immediately reduced, and then gradually increased again. When the pressure gradient in the wide diameter section of the core increases abruptly, the critical pressure gradient required for foam transport is determined. Gradually reduce the volumetric flow rate of the injected fluid; When the pressure gradient in the wide-diameter portion of the core drops abruptly, the critical pressure gradient required for the foam to maintain stability is determined. The specific experimental steps include: The preset total volumetric flow rate of the injected gas-liquid fluid is and foam dryness The foam dryness is the ratio of the gas phase injection volumetric flow rate to the total gas-liquid fluid volumetric flow rate, based on... and Determine the gas injection volumetric flow rate Q g = Q t × f g and liquid phase injection volume flow rate Q w = Q t × (1 – f g ); The diameters of the variable-diameter core models are respectively increased sequentially. , and ; Six pressure measurement points were set along the flow direction of the variable-diameter core model; a preset volumetric flow rate was simultaneously injected into the narrow end of the variable-diameter core model. Q g gas phase and Q w The liquid phase, pressure gradient is collected in real time. to ; Measuring the critical pressure gradient condition that triggers foam formation: like exist When the initial injection surge exceeds a set threshold of 1, the core is cleaned, and a flow rate less than the preset total volumetric flow rate is selected. Remeasure and gradually increase the total volumetric flow rate of the injected fluid. Q t Simultaneously measure the pressure gradient of each diameter section of the variable-diameter rock core to determine the critical pressure gradient required to trigger foam formation; or choose to abandon measuring the critical conditions for foam formation and immediately reduce the pressure gradient. Then gradually increase To measure the critical pressure gradient required for foam transport and to maintain stability; like When the pressure gradient is close to that of gas-liquid injection without surfactant, gradually increase until A jump of at least 2 times occurred; records were kept prior to the jump. This refers to the critical pressure gradient required to trigger foam formation. immediately reduce ; Critical pressure gradient condition for measuring foam transport: Gradually increase ,when When a jump occurs and exceeds the set threshold of 1, record. This is the critical pressure gradient required for foam transport. ; Continue to rise gradually ,when to When all pressure gradients in the middle suddenly increase and exceed the set threshold of 1, record. or This is the critical pressure gradient required for foam transport. ; The critical pressure gradient condition for measuring foam stability: Gradually reduce ,when to When all pressure gradients in the middle drop sharply and fall below the set threshold of 2, in arrive Steady-state pressure gradient before the jump or This is the critical pressure gradient required for the foam to maintain stability. .

4. The experimental measurement method for evaluating deep migration in foam formations according to claim 1, characterized in that, The determination of the critical flow velocities for foam generation, transport, and stability based on the critical pressure gradient required for foam generation, transport, and stability specifically includes: Record the critical pressure gradient for foam formation respectively. Critical pressure gradient for foam transport And the foam maintains a stable critical pressure gradient The corresponding total volumetric flow rate of gas-liquid fluid and the core diameter corresponding to the current recorded pressure gradient; The total volumetric flow rate of the gas-liquid fluid The Darcy velocity was calculated from the core diameter; The porosity of the variable-diameter core model is obtained; the pore flow velocity is obtained from the ratio of the Darcy flow velocity to the core porosity; thus determining... , and The corresponding critical flow rate for foam formation Critical velocity for foam transport and the critical velocity for foam stability .

5. The experimental measurement method for evaluating deep migration in foam formations according to claim 1, characterized in that, The gas-liquid fluid comprises a gas phase and a liquid phase; the gas phase comprises carbon dioxide, steam, nitrogen, air, and hydrocarbon gases; and the liquid phase is a foaming agent solution.

6. The experimental measurement method for evaluating deep migration in foam formations according to claim 1, characterized in that, Furthermore, this experimental method can quantitatively evaluate the deep migration conditions of foam formations under different types of foam and different injection methods; The different types of foam include: carbon dioxide foam, steam foam, nitrogen foam, air foam, and hydrocarbon gas foam; the different injection methods include: simultaneous gas-liquid injection, alternating gas-liquid injection, and injection of pre-generated foam.

7. An experimental apparatus for evaluating deep migration in foam formations, characterized in that, include: The core model preparation module is used to prepare a variable-diameter core model based on the rock porosity, permeability, and wettability parameters of the target oil and gas reservoir. The diameter of the variable-diameter core model increases from the injection end to the production end, simulating the flow environment where the velocity and pressure gradient of the injected fluid decreases sharply as it flows radially from the near-wellbore zone to the deep formation. Multiple pressure measurement points are set along the fluid flow direction of the variable-diameter core model. The critical condition measurement module is used to inject a gas-liquid fluid with a preset volumetric flow rate into the narrow end of the variable diameter rock core model, and to simultaneously monitor the pressure gradient of different diameter parts of the rock core using each pressure measurement point. The injection fluid volumetric flow rate is gradually increased. When the pressure gradient in the narrow diameter section of the core increases abruptly, the critical pressure gradient required to trigger foam generation is determined. After foam generation in the narrow diameter section of the core, the injection fluid volumetric flow rate is immediately reduced, and then gradually increased again. When the pressure gradient in the wide diameter section of the core increases abruptly, the critical pressure gradient required for foam transport is determined. Gradually reduce the volumetric flow rate of the injected fluid; Determine the critical pressure gradient required for foam to maintain stability when the pressure gradient in the wide-diameter portion of the core drops abruptly. The data application module is used to determine the critical flow velocity required for foam generation, transport, and stability based on the critical pressure gradient. By using the critical pressure gradient and critical flow velocity required for foam generation, transport, and stability, the module predicts the migration distance of foam under the conditions of flow velocity and pressure gradient in deep formations, thereby evaluating the feasibility and effectiveness of large-scale foam mobility regulation.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is loaded by the processor, it is able to perform the steps of the method according to any one of claims 1 to 6.

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