Method for evaluating anti-swelling effect of anti-swelling agent

Abstract

The present application relates to a kind of anti-swelling effect evaluation methods of anti-swelling agent, from the angle of micro-pore, by comparing the thickness of adsorption layer and the thickness of swelling layer after core anti-swelling treatment, and combining the occurrence state of anti-swelling agent in core pore throat and the pore throat diameter of core, to evaluate the anti-swelling effect of working fluid anti-swelling agent, and at the same time, the optimal anti-swelling agent addition range can be determined, which provides support for the addition of anti-swelling agent in working fluid and its application in reservoir.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and specifically to a method for evaluating the anti-swelling effect of an anti-swelling agent. Background Technology

[0002] With the continuous development of the petroleum industry, global underground oil and gas reserves are decreasing year by year. Reducing reservoir damage caused by drilling, fracturing, and acidizing operations during development has become a hot research topic. Sensitivity to water, salt, acids, alkalis, and pressure is a major issue facing reservoir damage. Low-permeability oil and gas reservoirs are particularly problematic, as their edge and bottom water are not active and the resistance during seepage is high. Therefore, water injection is often the only option to maintain formation pressure and improve development efficiency. When clay particles come into contact with water molecules, the clay volume increases, clogging the permeable pores. Injected fluids disperse or carry clay particles, causing capillary blockage and further reducing permeability.

[0003] During water injection development in oilfields, the injection of various fluids alters the formation environment. When low-mineralized foreign fluids enter the reservoir and come into contact with clay minerals, they cause the clay minerals to expand, fracture, disperse, or migrate, blocking throats, reducing pore space, and consequently decreasing seepage capacity, permeability, and development effectiveness. Tight sandstone reservoirs, due to their dense lithology, complex structure, and fine pore throats, experience further shrinkage of seepage channels and more complex internal structures after clay mineral expansion and migration, further limiting development space and making effective development of such reservoirs extremely difficult.

[0004] Anti-swelling agents, as reagents to mitigate water-sensitive damage, prevent clay swelling through mechanisms such as reducing surface negative charge, ion exchange, and interaction with hydroxyl groups on the clay surface. Therefore, when developing tight sandstone reservoirs, oilfields often use anti-swelling agents during drilling, completion, and acidizing operations to inhibit the hydration and swelling of clay minerals in the reservoir, reduce reservoir damage, stabilize the reservoir seepage environment, and ensure stable and sustainable oil well productivity.

[0005] CN 108661613A discloses an injection method for developing oil reservoirs by water injection, including the following steps: (1) Selecting the optimal fracturing process based on the reservoir characteristics of the well to be fracturing; (2) Taking water samples from the well site near the well to be fracturing and conducting compatibility tests with the drag-reducing agent. If the compatibility is good, conducting core damage tests and anti-swelling performance tests on the mixed solution of the anti-swelling agent, drag-reducing agent and water sample; (3) Optimizing the injection volume based on the well group deficit; (4) Calculating the expected construction pressure and selecting the injection method; (5) Conducting on-site construction, shutting in all adjacent wells in the same well group and installing pressure gauges; (6) Determining the well shut-in time based on the well group pressure changes, water sample analysis results and / or core test results, and optimizing the well opening sequence.

[0006] CN110776431A discloses a high-efficiency anti-swelling agent, which is prepared by the following steps: dodecyl bromide, tetrabutylammonium bromide and solvent are added to a reaction vessel, stirred evenly, and then heated to 50-70℃. N,N'-bis(3-aminopropyl)-1,4-butanediamine is added dropwise to the reactor. After the addition is complete, the reaction is continued under stirring for 3-5 hours. After the reaction product cools to room temperature, the solvent is removed to obtain the high-efficiency anti-swelling agent.

[0007] The invention disclosed the role of anti-swelling agents in inhibiting the hydration and swelling of clay minerals. However, current research on the application effect of anti-swelling agents mainly focuses on the macroscopic perspective. The volume change and permeability change are measured by static bentonite powder centrifugation experiments and dynamic core flow experiments, and then the anti-swelling rate is calculated to evaluate the application effect of the anti-swelling agent. However, the existing methods for evaluating the anti-swelling effect are relatively limited.

[0008] Therefore, in view of the shortcomings of the existing technology, there is a need to provide a comprehensive and effective method for evaluating the anti-swelling effect of anti-swelling agents. Summary of the Invention

[0009] The purpose of this invention is to provide a method for evaluating the anti-swelling effect of anti-swelling agents. The method evaluates the anti-swelling effect by comparing the thickness of the swelling layer in the rock sample with the thickness of the anti-swelling agent adsorption layer at the microscopic level and the pore throat radius of the core, and determines the dosage range of the anti-swelling agent to be used in the study block. This provides support for the dosage of anti-swelling agents in working fluids and their application in reservoirs.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] This invention provides a method for evaluating the anti-swelling effect of an anti-swelling agent, the method comprising the following steps:

[0012] (1) Select reservoir cores from the target block and determine the basic parameters of the reservoir cores;

[0013] (2) The reservoir core described in step (1) is crushed and sieved, dried and then sampled. The obtained sample is saturated with an anti-swelling agent and then the thickness of the swelling layer df is measured. The reservoir core described in step (1) is subjected to core displacement treatment and then the thickness of the adsorption layer de is measured.

[0014] (3) Compare the adsorption layer thickness de obtained in step (2) with the swelling layer thickness df and the pore throat radius of the reservoir core obtained in step (1) to evaluate the swelling prevention effect of the anti-swelling agent.

[0015] (4) Based on the anti-swelling effect of the anti-swelling agent obtained in step (3) and the relationship between the amount of anti-swelling agent added in step (2) and the thickness df of the swelling layer, determine the range of the amount of anti-swelling agent added.

[0016] The method for evaluating the anti-swelling effect of the anti-swelling agent provided by this invention starts from the perspective of micropores. By comparing the thickness of the adsorption layer and the thickness of the swelling layer after the core anti-swelling treatment, and combining the occurrence state of the anti-swelling agent in the core pore throat and the pore throat radius of the core, the anti-swelling effect of the anti-swelling agent in the working fluid is evaluated, thereby determining the optimal dosage range of the anti-swelling agent, and providing support for the dosage of the anti-swelling agent in the working fluid and its application in the reservoir.

[0017] Preferably, the basic parameters in step (1) include permeability, porosity, pore throat radius, and clay mineral composition.

[0018] Preferably, the clay mineral components are obtained by whole-rock X-ray diffraction analysis.

[0019] The permeability and porosity measurements are taken from the permeability and porosity of the reservoir core under its original state.

[0020] Preferably, the crushing and screening process in step (2) includes: washing the reservoir core with oil, drying it, crushing it to obtain blocks, and then crushing and screening it through a crusher.

[0021] Preferably, the rock powder obtained by the sieving process in step (2) has a mesh size of 200.

[0022] Preferably, the drying temperature in step (2) is 59-61°C, for example, it can be 59°C, 60°C or 61°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the drying time in step (2) is 5.9-6.1h, for example, it can be 5.9h, 6h or 6.1h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, after drying, the product is transferred to a desiccator to cool to room temperature and then stored in a wide-mouth bottle.

[0025] Preferably, the anti-swelling agent in step (2) includes an organic anti-swelling agent.

[0026] Preferably, the organic anti-swelling agent includes an organic cationic anti-swelling agent.

[0027] The anti-swelling agent is prepared by setting different concentration gradients.

[0028] Preferably, the measurement steps of the expansion layer thickness df in step (2) specifically include: crushing and sieving the reservoir core, drying the obtained rock powder and pressing it into a circular thin sheet sample of the target size, adding an anti-swelling agent to the surface of the circular thin sheet sample for saturation treatment, and then measuring the expansion layer thickness df using an atomic force microscope.

[0029] Preferably, an anti-swelling agent is dropped onto different positions on the surface of the circular thin sheet sample for saturation treatment to obtain different test curves. Then, erroneous curves are eliminated, and the statistical average value is calculated as the expansion layer thickness df through statistical analysis.

[0030] Preferably, the target dimensions are a thickness of <1mm and a diameter of <10mm.

[0031] The target size is the size that the stage of the atomic force microscope can measure.

[0032] The thickness of the circular sheet sample is <1mm, for example, it can be 0.8mm, 0.6mm or 0.5mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] The diameter of the circular thin-film sample is <10mm, for example, it can be 9mm, 8mm or 7mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the core displacement treatment in step (2) includes: preparing a solution containing an anti-swelling agent and performing core displacement treatment on the reservoir core until the solution containing the anti-swelling agent is completely displaced.

[0035] Preferably, the determination of the adsorption layer thickness de in step (2) includes: measuring the morphology of the anti-swelling agent on the rock surface using an atomic force microscope, and then performing quantitative analysis.

[0036] Preferably, the reservoir core after the core displacement treatment in step (2) is dried, and the porosity Φ1 and permeability K1 of the reservoir core after displacement by the anti-swelling agent are determined by gas measurement method.

[0037] Preferably, the method for evaluating the anti-swelling effect of the anti-swelling agent in step (3) specifically includes: when the adsorption layer thickness de ≤ min (expansion layer thickness df, 1 / 3 pore throat radius), the anti-swelling effect of the anti-swelling agent is good; when the adsorption layer thickness de > min (expansion layer thickness df, 1 / 3 pore throat radius), the anti-swelling effect of the anti-swelling agent is poor.

[0038] As a preferred embodiment of the anti-swelling effect evaluation method of the present invention, the anti-swelling effect evaluation method includes the following steps:

[0039] (1) Select reservoir cores from the target block and determine the permeability, porosity, pore throat radius and clay mineral composition of the reservoir cores;

[0040] (2) The reservoir core described in step (1) is crushed and sieved. The resulting 200-mesh rock powder is dried at 59-61℃ for 5.9-6.1h and then pressed into circular thin slices with a thickness of <1mm and a diameter of <10mm. An organic anti-swelling agent is dropped onto the surface of the circular thin slices for saturation treatment. Then, the thickness df of the swelling layer is measured using an atomic force microscope. A solution containing the anti-swelling agent is prepared, and the reservoir core described in step (1) is subjected to core displacement treatment until the solution containing the anti-swelling agent is completely displaced. Then, the morphology of the anti-swelling agent on the rock surface is measured using an atomic force microscope, and the thickness de of the adsorption layer is obtained through quantitative analysis.

[0041] (3) Compare the adsorption layer thickness de obtained in step (2) with the expansion layer thickness df and the pore throat radius of the reservoir core obtained in step (1) to evaluate the anti-swelling effect of the anti-swelling agent. The specific method includes: when the adsorption layer thickness de ≤ min (expansion layer thickness df, 1 / 3 pore throat radius), the anti-swelling effect of the anti-swelling agent is good; when the adsorption layer thickness de > min (expansion layer thickness df, 1 / 3 pore throat radius), the anti-swelling effect of the anti-swelling agent is poor.

[0042] (4) Based on the anti-swelling effect of the anti-swelling agent obtained in step (3) and the relationship between the amount of anti-swelling agent added in step (2) and the thickness df of the swelling layer, determine the range of the amount of anti-swelling agent added.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The anti-swelling effect evaluation method provided by the present invention, combined with the microscopic thickness of the anti-swelling agent adsorption layer, more comprehensively and effectively evaluates the effect of the anti-swelling agent, and supplements and improves the evaluation method of the anti-swelling agent.

[0045] (2) The method for evaluating the anti-swelling effect provided by the present invention studies the anti-swelling effect of the anti-swelling agent from the perspective of mechanism, supplements the method for determining the dosage range of the anti-swelling agent, and improves the accuracy of the method. Detailed Implementation

[0046] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0047] Example 1

[0048] This embodiment provides a method for evaluating the anti-swelling effect of an anti-swelling agent, the method comprising the following steps:

[0049] (1) Select reservoir cores from the target block, with a length of 4cm and a diameter of 2.5cm, dry them at 60℃, measure the porosity Φ0 and permeability K0 of the reservoir cores in their original state, measure the pore throat radius of the reservoir cores, and obtain the clay mineral composition of the reservoir cores through X-ray diffraction whole-rock analysis.

[0050] (2) The reservoir core described in step (1) was crushed and sieved. The resulting 200-mesh rock powder was dried at 60°C for 6 hours and then pressed into circular thin slices with a thickness of 0.8 mm and a diameter of 9 mm. Anti-swelling agent was dropped onto different positions on the surface of the circular thin slices for saturation treatment. The thickness df of the swelling layer was measured using an atomic force microscope to obtain different test curves. Erroneous curves were removed, and the thickness df of the swelling layer was obtained through statistical analysis. Solutions of organic anti-swelling agents with different concentration gradients were prepared. The reservoir core described in step (1) was subjected to core displacement treatment until the solution of organic anti-swelling agent was completely displaced. Then, the morphology of the anti-swelling agent on the rock surface was measured using an atomic force microscope, and the thickness de of the adsorption layer was obtained through quantitative analysis. The results are shown in Table 1.

[0051] Table 1

[0052]

[0053]

[0054] (3) Compare the adsorption layer thickness de obtained in step (2) with the expansion layer thickness df and the pore throat radius of the reservoir core obtained in step (1) to evaluate the anti-swelling effect of the anti-swelling agent. The specific method includes: when the adsorption layer thickness de ≤ min (expansion layer thickness df, 1 / 3 pore throat radius), the anti-swelling effect of the anti-swelling agent is good; when the adsorption layer thickness de > min (expansion layer thickness df, 1 / 3 pore throat radius), the anti-swelling effect of the anti-swelling agent is poor.

[0055] (4) Based on the anti-swelling effect of the anti-swelling agent obtained in step (3) and the relationship between the amount of anti-swelling agent added in step (2) and the thickness df of the swelling layer, the optimal addition range of the anti-swelling agent is determined to be 0.5-0.8%.

[0056] Comparative Example 1

[0057] This comparative example provides a method for evaluating the anti-swelling effect of an anti-swelling agent. The method for evaluating the anti-swelling effect is based on the method disclosed in CN114839101A for evaluating the effect of anti-swelling agents on the inhibition of hydration swelling in shale reservoirs.

[0058] In this comparative example, four rock samples with different clay contents were selected for displacement experiments. By measuring the changes in porosity and permeability, rock sample volume, and sand production before and after displacement with organic anti-swelling agent solution, the effect of organic anti-swelling agent under different clay contents was determined, thereby determining the dosage of organic anti-swelling agent in reservoirs with different clay contents. This yielded an evaluation method for the anti-swelling agent's effect on inhibiting hydration and swelling in shale reservoirs. However, this evaluation method is based on a macroscopic perspective and cannot reflect the changes in pore throats inside the reservoir before and after anti-swelling treatment. It also cannot incorporate the microscopic effects of the anti-swelling agent, thus having certain limitations.

[0059] In summary, the anti-swelling effect evaluation method provided by this invention, by combining the microscopic thickness of the swelling layer and the microscopic thickness of the anti-swelling agent adsorption layer, more comprehensively and effectively evaluates the effect of the anti-swelling agent, and supplements and improves the evaluation method of the anti-swelling agent.

[0060] The method for evaluating the anti-swelling effect provided by this invention studies the anti-swelling effect of anti-swelling agents from the perspective of mechanism, supplements the method for determining the dosage range of anti-swelling agents, and improves the accuracy of the method.

[0061] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for evaluating the anti-swelling effect of an anti-swelling agent, characterized in that, The method for evaluating the anti-swelling effect includes the following steps: (1) Select reservoir cores from the target block and determine the basic parameters of the reservoir cores; (2) The reservoir core described in step (1) is crushed and sieved, dried and then sampled. The obtained sample is saturated with an anti-swelling agent and then the thickness of the swelling layer df is measured. The reservoir core described in step (1) is subjected to core displacement treatment and then the thickness of the adsorption layer de is measured. (3) Compare the thickness de of the adsorption layer obtained in step (2) with the thickness df of the expansion layer and the pore throat radius of the reservoir core obtained in step (1) to evaluate the anti-swelling effect of the anti-swelling agent; (4) Based on the anti-swelling effect of the anti-swelling agent obtained in step (3) and the relationship between the amount of anti-swelling agent added in step (2) and the thickness df of the swelling layer, determine the range of the amount of anti-swelling agent to be added; The method for evaluating the anti-swelling effect of the anti-swelling agent in step (3) specifically includes: when the adsorption layer thickness de ≤ the smaller value between the expansion layer thickness df and 1 / 3 pore throat radius, the anti-swelling effect of the anti-swelling agent is good; when the adsorption layer thickness de > the smaller value between the expansion layer thickness df and 1 / 3 pore throat radius, the anti-swelling effect of the anti-swelling agent is poor.

2. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, The basic parameters mentioned in step (1) include permeability, porosity, pore throat radius, and clay mineral composition.

3. The method for evaluating the anti-swelling effect according to claim 2, characterized in that, The clay mineral composition was obtained by whole-rock X-ray diffraction analysis.

4. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, The rock powder obtained by the sieving process in step (2) has a mesh size of 200.

5. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, The drying temperature in step (2) is 59-61℃.

6. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, The drying time in step (2) is 5.9-6.1 hours.

7. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, The anti-swelling agent in step (2) includes an organic anti-swelling agent.

8. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, The specific steps for measuring the thickness df of the expansion layer in step (2) include: crushing and sieving the reservoir core, drying the resulting rock powder and pressing it into a circular thin sheet sample of the target size, adding an anti-swelling agent to the surface of the circular thin sheet sample for saturation treatment, and then measuring the thickness df of the expansion layer using an atomic force microscope.

9. The method for evaluating the anti-swelling effect according to claim 8, characterized in that, The target dimensions are: thickness < 1 mm and diameter < 10 mm.

10. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, Step (2) of the core displacement treatment includes: preparing a solution containing an anti-swelling agent and performing core displacement treatment on the reservoir core until the solution containing the anti-swelling agent is completely displaced.

11. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, The determination of the adsorption layer thickness de in step (2) includes: measuring the morphology of the anti-swelling agent on the rock surface using an atomic force microscope, and then performing quantitative analysis.

12. The method for evaluating the anti-swelling effect according to claim 1, characterized in that, The method for evaluating the anti-swelling effect includes the following steps: (1) Select reservoir cores from the target block and determine the permeability, porosity, pore throat radius and clay mineral composition of the reservoir cores; (2) The reservoir core described in step (1) is crushed and sieved. The resulting 200-mesh rock powder is dried at 59-61℃ for 5.9-6.1h and then pressed into circular thin slices with a thickness of <1mm and a diameter of <10mm. Organic anti-swelling agent is dripped onto the surface of the circular thin slices for saturation treatment. Then, the thickness df of the swelling layer is measured using an atomic force microscope. A solution containing anti-swelling agent is prepared, and the reservoir core described in step (1) is subjected to core displacement treatment until the solution containing anti-swelling agent is completely displaced. Then, the morphology of the anti-swelling agent on the rock surface is measured using an atomic force microscope, and the thickness de of the adsorption layer is obtained through quantitative analysis. (3) Compare the adsorption layer thickness de obtained in step (2) with the expansion layer thickness df and the pore throat radius of the reservoir core obtained in step (1) to evaluate the anti-swelling effect of the anti-swelling agent. The specific method includes: when the adsorption layer thickness de ≤ the smaller value between the expansion layer thickness df and 1 / 3 pore throat radius, the anti-swelling effect of the anti-swelling agent is good; when the adsorption layer thickness de > the smaller value between the expansion layer thickness df and 1 / 3 pore throat radius, the anti-swelling effect of the anti-swelling agent is poor. (4) Based on the anti-swelling effect of the anti-swelling agent obtained in step (3) and the relationship between the amount of anti-swelling agent added in step (2) and the thickness df of the swelling layer, determine the range of the amount of anti-swelling agent added.

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