Experimental measurement method, device and storage medium for evaluating deep foam formation

Abstract

The application provides an experimental measurement method and device for evaluating deep migration of a foamed formation, 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 following steps: adopting a variable-diameter core displacement to simulate the flow condition of a sudden drop of a flow rate and a pressure gradient when a formation injection fluid flows radially from a near-wellbore zone to a deep part of the formation, so as to make up for the defect that a conventional equal-diameter core displacement cannot simulate the flow condition; measuring the steady-state pressure gradient of each part of the variable-diameter core under a certain injection flow rate sequence, so as to effectively measure the critical pressure gradient and the critical flow rate condition required for foam generation, transportation and stable maintenance, and to evaluate the influence mechanism and law of each factor on the critical condition; and the method can be used for predicting the migration distance of the deep part of the foamed formation, and evaluating the feasibility and dynamic behavior law of large-scale foam mobility control, and has important significance for guiding and optimizing the engineering application of the foam mobility control technology in the fields of CO2 flooding and geological storage and deep profile control.

Description

Technical Field

[0001] This invention belongs to the technical fields of oil and gas field development engineering and carbon storage engineering, and specifically relates to an experimental measurement method, device and storage medium for evaluating deep migration in foam formations. Background Technology

[0002] CO2 enhanced oil recovery (EOR) and geological sequestration are key technologies for accelerating the low-carbon development of oil and gas energy. Given the advantageous phase characteristics between the oil phase and CO2, oil washing efficiency can be significantly improved in the affected area of ​​the reservoir crude oil. Simultaneously, some of the injected CO2 is captured in the formation, achieving geological sequestration of CO2 and reducing the environmental impact of carbon emissions. However, three major problems commonly exist during gas injection into the formation: viscous fingering of gas due to the high gas-liquid mobility ratio, gas channeling due to formation heterogeneity, and gravity overlap due to differences in gas-liquid density, resulting in poor volumetric sweep efficiency of the injected gas.

[0003] Indoor experiments and field applications have shown that, compared to other technologies such as co-injection of water and gas, alternating injection of water and gas, stratified injection of water and gas, and supercritical carbon dioxide injection, foam flooding is a highly effective method for improving the formation volume sweep efficiency of injected gas. Its main principle lies in the fact that foam can significantly reduce gas mobility (e.g., by 10⁻¹⁰). 4 This method can overcome or alleviate the aforementioned problems of gas drive, thereby increasing the volumetric sweep efficiency of injected gas, increasing crude oil production, and improving the gas saturation in the swept area, thus increasing the storage capacity of geological carbon sequestration.

[0004] The success of foam-based deep formation mobility control technology hinges on the effective transport of foam to deeper formations. Deep formation migration of foam results from two processes: the transport of near-wellbore generated foam to deeper formations and the generation of new foam at the displacement front. However, significant uncertainties remain regarding whether foam generated under high pressure gradients and high velocities near the wellbore can be successfully transported to deeper formations with low pressure gradients and low velocities, and whether foam can be successfully generated at deep formations at all. These uncertainties greatly limit the prediction and optimization of large-scale foam mobility control technology.

[0005] To effectively control and optimize the effects of foam applications in deep formations, it is essential to determine the pressure gradient and velocity conditions required for foam migration at depth. Core displacement is currently the most commonly used laboratory evaluation method. However, conventional core displacement uses constant-diameter cores, which cannot simulate the flow conditions where the velocity and pressure gradient drop sharply as the injected fluid flows radially from the near-wellbore zone to deeper formations. This limitation prevents conventional constant-diameter core displacement from effectively evaluating whether foam generated under high pressure gradients and high velocities near the wellbore can migrate under low-velocity and low-pressure gradient conditions at deeper formations. Summary of the Invention

[0006] To address the problem of the inability to quantitatively evaluate the migration conditions of foam in deep formations, this invention provides an experimental measurement method, apparatus, and storage medium for evaluating the deep migration of foam in formations.

[0007] To achieve the above objectives, the present invention provides an experimental measurement method for evaluating deep migration in foam formations, comprising:

[0008] 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.

[0009] A preset volumetric flow rate of gas-liquid fluid is injected into the narrow-diameter end of the variable-diameter core model. The pressure gradient of different diameter sections of the core is monitored synchronously at various pressure measurement points. The volumetric flow rate of the injected fluid is gradually increased. When the pressure gradient in the narrow-diameter section of the core jumps, the critical pressure gradient required to trigger foam generation is determined. After foam is generated 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 jumps, the critical pressure gradient required for foam transport is determined. The volumetric flow rate of the injected fluid is gradually reduced. When the pressure gradient in the wide-diameter section of the core drops sharply, the critical pressure gradient required to maintain foam stability is determined.

[0010] The critical flow velocity for foam generation, transport, and stabilization is determined based on the critical pressure gradient required for foam generation, transport, and stabilization. By using the critical pressure gradient and critical flow velocity required for foam generation, transport, and stabilization, the migration distance of foam in deep formations under flow velocity and pressure gradient conditions can be predicted, thereby evaluating the feasibility and effectiveness of large-scale foam mobility regulation.

[0011] Preferably, the variable diameter core model includes a conical variable diameter core model and a stepped variable diameter core model.

[0012] Preferably, when the pressure gradient in the narrow diameter portion of the core increases abruptly, the critical pressure gradient required to trigger foam generation is determined; after foam generation in the narrow diameter portion 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 portion of the core increases abruptly, the critical pressure gradient required for foam transport is determined; the injection fluid volumetric flow rate is gradually reduced; when the pressure gradient in the wide diameter portion of the core decreases abruptly, the critical pressure gradient required for maintaining foam stability is determined. Specific experimental steps include:

[0013] The preset total volumetric flow rate of the injected fluid is and foam dryness That is, gas phase injection volumetric flow rate Qg occupy Q t 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 );

[0014] 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 ;

[0015] Measuring the critical pressure gradient condition that triggers foam formation:

[0016] 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;

[0017] 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 ;

[0018] Critical pressure gradient condition for measuring foam transport:

[0019] 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. ;

[0020] 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. ;

[0021] The critical pressure gradient condition for measuring foam stability:

[0022] 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. .

[0023] Preferably, determining the critical flow velocities for foam generation, transport, and stabilization based on the critical pressure gradient required for foam generation, transport, and stabilization specifically includes:

[0024] 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;

[0025] The total volumetric flow rate of the gas-liquid fluid The Darcy velocity was calculated from the core diameter;

[0026] 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 .

[0027] Preferably, 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.

[0028] Preferably, the method further includes the ability to 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.

[0029] The present invention also provides an experimental method and apparatus for evaluating deep migration in foam formations, comprising:

[0030] 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.

[0031] The critical condition measurement module is used to inject a preset volumetric flow rate of gas-liquid fluid into the narrow-diameter end of the variable-diameter core model, and synchronously monitor the pressure gradient of different diameter sections of the core using various pressure measurement points; gradually increase the injected fluid volumetric flow rate, and when the pressure gradient in the narrow-diameter section of the core jumps, determine the critical pressure gradient required to trigger foam generation; after foam generation in the narrow-diameter section of the core, immediately reduce the injected fluid volumetric flow rate, and then gradually increase the injected fluid volumetric flow rate again; when the pressure gradient in the wide-diameter section of the core jumps, determine the critical pressure gradient required for foam transport; gradually decrease the injected fluid volumetric flow rate; when the pressure gradient in the wide-diameter section of the core drops sharply, determine the critical pressure gradient required to maintain foam stability;

[0032] 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.

[0033] The present invention also provides a computer-readable storage medium storing a computer program that, when loaded by a processor, is capable of performing any of the steps described in the experimental method for evaluating deep migration of foam formations.

[0034] The experimental measurement method for evaluating deep migration in foam formations provided by this invention has the following beneficial effects:

[0035] Based on the porosity, permeability, and wettability parameters of the target oil and gas reservoir rocks, a variable-diameter core model was prepared. This variable-diameter core design more accurately simulates the flow environment where the velocity and pressure gradients of injected fluid drop sharply as it flows radially from the near-wellbore zone to deeper formations. It can directly and effectively simulate the dynamic behavior and seepage patterns of foam migration in deep formations, solving the problem that traditional constant-diameter core displacement cannot accurately reproduce the abrupt changes in flow conditions from near to far wellbore in actual formations. By defining critical conditions for foam generation, transport, and stability, the minimum standards for the occurrence of three foam processes within the formation are precisely determined. Through these critical conditions, the migration distance to deeper foam formations is predicted, and the effect of large-scale foam mobility regulation on improving gas sweep efficiency is evaluated. Experimental measurements of critical values ​​guide the design of operable injection velocity and pressure standards for the field, optimizing the field application effect of foam mobility regulation technology and improving oil recovery and CO2 storage efficiency. Attached Figure Description

[0036] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below. The drawings are only some embodiments of the present invention. Those skilled in the art can obtain other drawings based on the described drawings without any creative effort.

[0037] Figure 1 This is a flowchart of the indoor testing process for evaluating deep migration of foam formations using variable-diameter core displacement according to an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the dynamic transition theory of foam generation, transport, and stabilization in porous media according to an embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram illustrating the design of the variable-diameter core displacement core size and pressure measurement points according to an embodiment of the present invention.

[0040] Figure 4 The critical conditions for the generation, transport, and stability of supercritical carbon dioxide foam in rock samples are described in this embodiment of the invention. Detailed Implementation

[0041] The following embodiments are only used to illustrate the technical solutions of the present invention and should not be used to limit the scope of protection of the present invention.

[0042] This invention provides an experimental measurement method for evaluating deep migration in foam formations, specifically as follows: Figure 1 As shown, it includes:

[0043] This invention proposes for the first time a variable-diameter core displacement experimental measurement method for evaluating deep migration in foam formations. This method can quantitatively evaluate the critical pressure gradient and critical velocity conditions required for foam generation, transport, and stabilization. The variable-diameter core has a larger diameter in the direction of fluid flow, enabling a significant reduction in velocity and pressure gradients from the injection end to the production end at a fixed volumetric flow rate. This variable-diameter core displacement experimental measurement method can successfully simulate the flow environment in vertical or horizontal wells where injected fluid flows radially from the near-wellbore zone to deeper formations, resulting in a significant reduction in velocity and pressure gradients. This method can measure the critical pressure gradient and critical velocity conditions required for foam generation, transport, and stabilization, and reveal the variation patterns and mechanisms between these critical conditions and 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. For the theoretical basis, experimental procedures, and method verification of this foam deep migration measurement method, please refer to the following sections.

[0044] like Figure 2 As shown, the foam jump theory based on the foam quantity balance model reveals the relationship between the apparent viscosity or pressure gradient and the gas-liquid phase velocity during foam generation and transport. Throughout the entire velocity domain of both the gas and liquid phases, the apparent viscosity or pressure gradient of the corresponding foam state exhibits a smooth surface, which folds within the velocity domain. This folding of the surface divides the foam state into three groups: a weak or no-foam state on the lower surface (low apparent viscosity), a strong-foam state on the upper surface (high apparent viscosity), and a foam state on the middle surface (intermediate apparent viscosity).

[0045] According to the theory of transition, the foam state located on the intermediate surface is extremely unstable. Any disturbance (such as flow velocity or pressure gradient) will cause it to jump to a strong or weak foam state. Therefore, a foam state intermediate between strong and weak foam states does not exist in nature. When the gas-liquid phase flow velocity changes from low to high, the foam intensity first increases slowly (lower surface), and then suddenly jumps to a strong foam state (upper surface). This indicates that the formation of strong foam has a critical initiation pressure gradient and a critical initiation flow velocity, i.e. and ( Figure 2 (Right-side jump point). After strong foam is generated, when the gas-liquid flow rate is reduced, the foam strength first weakens slowly (upper curved surface), and then suddenly jumps to a weak or no-foam state (lower curved surface). This indicates that maintaining foam stability requires a critical steady pressure gradient and a critical steady flow rate, i.e. and ( Figure 2 (Left-side drop point). Simultaneously, after foam formation, there is a critical transport pressure gradient and a critical transport velocity in the porous medium, i.e. and .

[0046] The deep formations in the far-wellbore zone possess a flow environment characterized by low flow velocities and low pressure gradients. Whether foam can form in the deep formation, and whether foam generated near the wellbore 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 velocity requirements for foam formation, transport, and stability. Therefore, quantitatively determining the critical conditions for foam transport in porous media is crucial to ensuring the successful application of foam in deep formations.

[0047] Based on the theory of foam transition, this invention proposes a variable-diameter core displacement measurement method for evaluating deep migration of foam formations. This method can effectively measure the critical pressure gradient and critical velocity conditions required for foam migration at depth, i.e., as... Figure 2 shown and , and and For specific testing methods and procedures, please refer to the following sections.

[0048] Unlike conventional constant-diameter core displacement, variable-diameter core displacement uses two types of cores, including conical and stepped variable-diameter cores. Figure 3 This paper presents a design case for a stepped variable-diameter rock core with corresponding pressure measurement point locations. Here, D represents the diameter of each equal-diameter section of the rock core, and L represents the length of sections with different diameters. This represents the distance between adjacent pressure measurement points. This core design case includes three sections of different diameters, which are respectively... D 1 , D 2 and D 3 According to Darcy's Law:

[0049] ;

[0050] In the formula, Q t It is the total volumetric flow rate of the injected fluid. U t It is the total Darcy velocity of the injected fluid. A It is the cross-sectional area of ​​the rock core.

[0051] Fluid from narrow diameter D Part 1 ( Figure 3 During injection (from the left end), the increased diameter of the variable-diameter core causes a decrease in fluid velocity from the injection end to the production end. Times. Meanwhile, multiple pressure measurement points are distributed along the flow direction of the core sample, for example... p 1 arrive p 7 Used to measure the pressure difference between different diameter sections of the rock core. arrive .

[0052] according to Figure 2 The theory of bubble leap and Figure 3 The core of this testing method for variable-diameter core design is to determine the critical pressure gradient required for foam generation, transport, and stability maintenance by measuring the steady-state pressure gradient of different diameter sections of the variable-diameter core under a certain flow velocity sequence. , and The pore flow velocity corresponding to each critical pressure gradient (i.e., U t Dividing by porosity gives the critical flow rate required for foam generation, transport, and stability maintenance. , and .

[0053] In addition to Figure 3 The stepped variable-diameter core shown can also be replaced with a conical variable-diameter core, whose diameter gradually increases from the core injection end to the production end, and the pressure measurement points are set as follows: p 1 arrive p 7 The core samples are evenly distributed along the core. When using a tapered, variable-diameter core, the critical pressure gradient required for foam generation, transport, and stability can be determined. , and However, because the fluid velocity varies along the core length, the corresponding critical velocity condition cannot be accurately determined. Furthermore, the selection of the core diameter for variable-diameter cores can be designed based on the required simulation of the near-wellbore fluid velocity variation.

[0054] Figure 1 A flowchart illustrating the testing process for evaluating deep migration in foam formations using variable-diameter core displacement is presented. The specific steps are as follows:

[0055] (1) Select the dryness of the injected foam f g , which is the volume ratio of the injected gas phase to the injected gas-liquid phase.

[0056] (2) Select a suitable total volumetric flow rate of the injected fluid. Q t To transfer gas and liquid from such Figure 3 The variable-diameter core sample was injected simultaneously at its narrow diameter end. The gas phase flow rate was... Q g =Q t ×f g ， Liquid flow rate is Qw = Q t ×(1– f g ).

[0057] (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.

[0058] 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.

[0059] 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 .

[0060] (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. .

[0061] 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. Qt This is to prevent foam from being transported to the downstream wide-diameter portion of the variable-diameter core, which would make it impossible to measure the critical pressure gradient required for foam transport. .

[0062] (5) in (4) decrease Q t On this basis, gradually increase Q t and measure each Q t steady-state pressure gradient arrive Until the variable diameter rock core D Two-part pressure gradient The jump is at least 2 times or more, at this time D Steady-state pressure gradient in two parts This is the critical pressure gradient for foam transport. The principle is... D The flow rate in section 2 is still below the critical flow rate required for foam formation. Therefore The leap is due to D Part of the generated foam is transported to D Part 2, not in D Two newborns became bubbles.

[0063] (6) Continue to gradually increase based on (5). Q t and measure each Q t steady-state pressure gradient arrive until arrive There is also a jump of at least 2 times, at which point the steady-state pressure gradient... or This also represents the critical pressure gradient for foam transport. .

[0064] (7) After (6), gradually decrease Q t and measure each Q t steady-state pressure gradient arrive until arrive A drop of at least 2 times occurred (i.e., the bubble burst). arrive Steady-state pressure gradient before the jump or This refers to the critical pressure gradient for maintaining foam stability. .

[0065] (8) Measurement , and The corresponding flow velocity is the critical flow velocity required for foam generation, transport, and maintenance of stability. , and .

[0066] (9) Data processing. Each Q t By plotting the measured steady-state pressure gradient data on a foam pressure gradient or apparent viscosity-total velocity diagram, one can obtain... Figure 2 Medium fixed foam dryness f g The following is an "S-shaped" slice. Among them, the apparent viscosity of the foam... µ app This can be obtained from pressure gradient data using Darcy's law:

[0067] ;

[0068] In the formula, k It is the permeability of porous media. It is the steady-state pressure gradient. U t It is the total Darcy velocity of gas and liquid.

[0069] (9) End the experiment. Rinse the core with a suitable solvent to remove foam, and then wash the core with water for reuse.

[0070] For the variable-diameter core model prepared in this embodiment, six pressure measurement points are configured during the experimental testing phase. In practical applications, the number of pressure measurement points should be designed to adapt to the actual division results of different diameter segments of the variable-diameter core model.

[0071] This testing method is universal and can determine the critical conditions for deep migration of different types of foam (such as carbon dioxide, nitrogen, hydrocarbon gases, and steam foam) under different formation conditions, including different foam dryness, medium permeability, foaming agent type and concentration, etc. Simultaneously, this method can also determine the critical conditions for deep formation migration of foam under different injection methods, including simultaneous gas-liquid injection, alternating gas-liquid injection, fixed liquid phase flow rate with varying gas phase flow rate or fixed gas phase flow rate with varying liquid phase flow rate, and pre-generated foam injection.

[0072] This invention adopts Figure 3 Core design shown Figure 1The experimental steps shown measured the critical conditions required for the generation, transport, and stabilization of supercritical carbon dioxide foam. The results verified the effectiveness of the foam deep formation migration measurement method proposed in this invention. This experimental case used gas-liquid co-injection at a fixed foam dryness and employed a specific foaming agent and concentration. Test data are as follows: Figure 4 The figure shows the relationship between the steady-state pressure gradient and the total pore velocity. The data indicates that when foam is injected at a low flow rate, the velocity increases with increasing flow rate. Figure 3 Variable diameter rock core D Part 1 exhibits a low pressure gradient (i.e., no or weak foam). Further increasing the injection flow rate triggers strong foam generation, leading to a jump in the pressure gradient, thus allowing determination of the conditions required for supercritical carbon dioxide foam generation. and .

[0073] according to Figure 1 The experimental steps in the text involve strong foam in variable diameter rock cores. D After the first part is generated, immediately reduce the injection flow rate, and then gradually increase the injection flow rate until the foam is generated from the variable diameter core. D Part 1 is transported downstream. D 2 and D The study used three parts to determine the requirements for supercritical carbon dioxide foam transport. and Then, gradually reduce the injection flow rate until the core diameter is changed. D The bursting of the foam in three parts was used to determine the amount of supercritical carbon dioxide foam required to maintain stability. and .

[0074] The successful determination of the critical conditions for supercritical carbon dioxide foam transport verifies the feasibility of the core displacement experiment method for deep foam formation transport with varying diameters proposed in this invention. Furthermore, the intermediate foam state, located between strong and weak foam, did not appear in the experiment, confirming the predictions of the foam jump theory.

[0075] Figure 4 The experimental conditions (such as pressure and flow rate) used are only provided as an example to verify the effectiveness of this test method. The test method proposed in this invention is generally applicable to porous rock media with different experimental conditions, different permeability ranges, and different sizes of stepped or conical variable diameter rock cores.

[0076] Based on the theory of foam jumps, this invention proposes for the first time a quantitative measurement method for deep migration in foam formations using variable-diameter core displacement experiments. This method can effectively determine the critical pressure gradient and critical velocity conditions required for foam generation, transport, and stabilization, thereby predicting or optimizing the field application effects of large-scale foam mobility control technology. The design of variable-diameter cores can effectively simulate the flow environment where the velocity and pressure gradients drop sharply as the injected fluid flows radially from near to far well, thus achieving direct and effective indoor simulation of deep migration in foam formations. Simultaneously, this measurement method provides a quantitative approach to evaluate the relationship between critical conditions and influencing factors for deep migration in foam formations, including media permeability, foam dryness, foaming agent type and concentration, and residual oil saturation. The determined quantitative relationships not only reveal the mechanism of deep migration in foam formations but also improve the accuracy of deep migration prediction. The foam formation deep migration and variable diameter core displacement measurement method proposed in this invention has universality and can quantitatively evaluate foam migration conditions under different types of foam and different injection methods, including carbon dioxide foam, steam foam, nitrogen foam, hydrocarbon gas foam, gas-liquid co-injection, gas-liquid alternating injection, and injection of pre-generated foam.

[0077] Based on the same inventive concept, the present invention also provides an experimental method and apparatus for evaluating deep migration in foam formations, comprising:

[0078] 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.

[0079] The critical condition measurement module is used to inject a preset volumetric flow rate of gas-liquid fluid into the narrow-diameter end of the variable-diameter core model, and synchronously monitor the pressure gradient of different diameter sections of the core using various pressure measurement points; gradually increase the injected fluid volumetric flow rate, and when the pressure gradient in the narrow-diameter section of the core jumps, determine the critical pressure gradient required to trigger foam generation; after foam generation in the narrow-diameter section of the core, immediately reduce the injected fluid volumetric flow rate, and then gradually increase the injected fluid volumetric flow rate again; when the pressure gradient in the wide-diameter section of the core jumps, determine the critical pressure gradient required for foam transport; gradually decrease the injected fluid volumetric flow rate; when the pressure gradient in the wide-diameter section of the core drops sharply, determine the critical pressure gradient required to maintain foam stability;

[0080] 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.

[0081] The present invention also provides a computer-readable storage medium storing a computer program that can be used to perform the above-described experimental method for evaluating deep migration in foam formations.

[0082] Specific limitations on the computational system for evaluating deep migration in foam formations can be found in the above-mentioned limitations of the experimental method for evaluating deep migration in foam formations, and will not be repeated here. Each module in the above-mentioned experimental method system for evaluating deep migration in foam formations can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0083] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. As long as these combinations of technical features do not contradict each other, they should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed. They should not be construed as limiting the scope of the invention patent. Those skilled in the art can make several modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0084] It should be noted that the specific embodiments described above enable those skilled in the art to more fully understand the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail in this specification and embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention are covered within the protection scope of the patent of the present invention. No reference numerals in the claims should be construed as limiting the scope of 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 transport distance of foam under the flow velocity and pressure gradient conditions in deep formations is predicted, thereby evaluating the feasibility and effectiveness of foam mobility regulation in deep formations. It also includes determining the critical pressure gradient required to trigger foam generation when the pressure gradient in the narrow diameter portion of the core increases abruptly; and immediately reducing the volumetric flow rate of the injected fluid after foam generation in the narrow diameter portion of the core, and then gradually increasing the volumetric flow rate of the injected fluid 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. ; The variable diameter core models include conical variable diameter core models and stepped variable diameter core models.

2. 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 .

3. 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.

4. 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.

5. An experimental method and 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 deeper formation. Multiple pressure measurement points are set along the fluid flow direction of the variable-diameter core model. The variable-diameter core model includes a conical variable-diameter core model and a stepped 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; When the pressure gradient in the wide-diameter section of the core drops sharply, determine the critical pressure gradient required for the foam to maintain stability; preset the total volumetric flow rate of the injected gas-liquid fluid as follows: 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 ;Measure the critical pressure gradient condition that triggers foam formation: If 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 Measure the critical pressure gradient required for foam transport and to maintain stability; if 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 increasing ,when When a jump occurs and exceeds the set threshold of 1, record. This is the critical pressure gradient required for foam transport. ; continued to gradually increase ,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 maintaining foam stability is measured by gradually decreasing it. ,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. ; 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.

6. 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 4.

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