Method and device for evaluating tight sandstone gas reservoir acidification unblocking liquid

Abstract

The embodiment of the invention provides a method and a device for evaluating tight sandstone gas reservoir acidification blocking removal liquid. The method comprises the following steps: acquiring first three-dimensional scanning data of a target rock core; carrying out acidification unblocking on the target rock core through acidification unblocking liquid to be detected, and obtaining second three-dimensional scanning data of the target rock core after acidification unblocking; according to the first three-dimensional scanning data and the second three-dimensional scanning data, evaluating the acidification unblocking liquid to be tested; the first three-dimensional scanning data and the second three-dimensional scanning data at least comprise the average radius and the communication volume percentage of the three-dimensional pore pipe network. According to the method, the accuracy of obtaining the sandstone acidification unblocking liquid is improved, and scientific guidance is provided for construction design.

Description

Technical Field

[0001] This invention relates to the field of petroleum engineering, and more specifically to a method and apparatus for evaluating acid plugging fluids in tight sandstone gas reservoirs. Background Technology

[0002] Tight sandstone gas reservoirs are characterized by low permeability, low pressure, low production, low abundance, poor reservoir properties, and small pore throats. These characteristics can cause serious contamination and damage during drilling and completion operations (such as solid particle blockage and water lock), which severely affects production. Therefore, it is urgent to take measures to unblock and increase production.

[0003] In existing technologies, acidizing is commonly used to dissolve and erode cementitious materials or blockages in formation pores and fractures generated during drilling. The acidizing and unblocking working fluid is an essential material basis for acidizing operations, and its quality directly affects the success or failure of the operation, playing a crucial role in increasing production. Furthermore, existing methods for evaluating the effectiveness of oil and gas reservoir acidizing (such as static dissolution experiments, acid displacement evaluation, and mercury injection analysis) suffer from significant variations in experimental evaluation results due to various influencing factors. For example, when using petrological analysis methods to analyze changes in core pore structure, the necessary processing of the core inevitably alters or damages its original internal structure to some extent, and the field of observation is relatively narrow. Since the microscopic porosity characteristics of the reservoir rock directly affect the reservoir's storage and permeability, these issues can all influence the final acidizing and unblocking fluid formulation. Therefore, existing technologies cannot accurately evaluate the effectiveness and adaptability of acidizing and unblocking system formulations, and cannot provide accurate and scientific guidance for construction design. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for evaluating acid plugging fluid in tight sandstone gas reservoirs. This method improves the accuracy of obtaining sandstone acid plugging fluid and provides scientific guidance for construction design.

[0005] To achieve the above objectives, embodiments of the present invention provide a method for evaluating acid plugging fluids in tight sandstone gas reservoirs, applicable to sandstone, the method comprising:

[0006] Acquire the first three-dimensional scan data of the target rock core;

[0007] The target core was acidified and unblocked using the acidification and unblocking solution to be tested, and the second three-dimensional scanning data of the target core after acidification and unblocking was obtained.

[0008] The acid-dissolving solution to be tested is evaluated based on the first three-dimensional scan data and the second three-dimensional scan data.

[0009] Both the first and second three-dimensional scan data include at least the average radius and percentage of connected volume of the three-dimensional porous network.

[0010] Optionally, acquiring the first three-dimensional scan data of the target core and acquiring the second three-dimensional scan data of the target core after acid treatment and unblocking include:

[0011] A three-dimensional digital rock sample of the target rock core was obtained using CT equipment;

[0012] Obtain the three-dimensional internal pore network of the three-dimensional digital rock sample;

[0013] The first three-dimensional scan data or the second three-dimensional scan data are obtained by statistically analyzing the three-dimensional internal pore network.

[0014] Optionally, the step of statistically analyzing the three-dimensional internal pore network to obtain the first three-dimensional scan data or the second three-dimensional scan data includes:

[0015] The structural features of the three-dimensional internal pore network are obtained, and the structural features include at least rock pore density, porosity distribution, density variation, internal crack development, pores, joints and bedding, filling material and cementation mode;

[0016] Based on the aforementioned structural features, a multi-component, multi-scale digital core model is constructed. The digital core model includes the quantitative relationship between CT number, pore density, and pore volume.

[0017] The first or second three-dimensional scan data is determined based on the digital core model.

[0018] Optionally, during the acidizing and unblocking test of the target core, the target core is placed on a core acidizing flow experimental device;

[0019] The target core was subjected to a predetermined temperature and pressure using the core acidizing flow experimental device.

[0020] The predetermined temperature is 70℃-120℃;

[0021] The predetermined pressure is 1.5 MPa to 3.5 MPa.

[0022] Optionally, the acid-blocking solution to be tested includes at least one of arginine, citric acid, acidification corrosion inhibitor, sodium dihydrogen phosphate, hydrochloric acid, hydrofluoric acid, and water-locking agent;

[0023] The hydrochloric acid concentration in the acid-based unblocking solution to be tested is 10-15%, and the hydrofluoric acid concentration is 3-8%.

[0024] Optionally, evaluating the acid-blocking solution to be tested based on the first three-dimensional scanning data and the second three-dimensional scanning data includes:

[0025] Comparing the first three-dimensional scan data with the second three-dimensional scan data, if the difference between each data in the first three-dimensional scan data and the second three-dimensional scan data is greater than the difference threshold, then the acid-blocking solution to be tested is beneficial to the pore expansion and permeability enhancement of the rock sample.

[0026] If the difference between any one of the first three-dimensional scan data and the second three-dimensional scan data is not greater than the difference threshold, then the acid-blocking solution to be tested is not conducive to the pore expansion and permeability enhancement of the rock sample.

[0027] On the other hand, the present invention also proposes an apparatus for evaluating acid plugging fluid in tight sandstone gas reservoirs, for use in sandstone, the apparatus comprising:

[0028] The acquisition module is used to acquire the first three-dimensional scan data of the target core.

[0029] The first processing module is used to acidify and deblock the target core with the acid-dissolving and deblocking solution to obtain the second three-dimensional scanning data of the target core after acidification and deblocking.

[0030] The second processing module is used to evaluate the acid unblocking solution to be tested based on the first three-dimensional scanning data and the second three-dimensional scanning data.

[0031] The third processing module is used to ensure that both the first and second three-dimensional scanning data include at least the average radius and the percentage of connected volume of the three-dimensional pore network.

[0032] Optionally, acquiring the first three-dimensional scan data of the target core and acquiring the second three-dimensional scan data of the target core after acid treatment and unblocking include:

[0033] A three-dimensional digital rock sample of the target rock core was obtained using CT equipment;

[0034] Obtain the three-dimensional internal pore network of the three-dimensional digital rock sample;

[0035] The first three-dimensional scan data or the second three-dimensional scan data are obtained by statistically analyzing the three-dimensional internal pore network.

[0036] Optionally, the step of statistically analyzing the three-dimensional internal pore network to obtain the first three-dimensional scan data or the second three-dimensional scan data includes:

[0037] The structural features of the three-dimensional internal pore network are obtained, and the structural features include at least rock pore density, porosity distribution, density variation, internal crack development, pores, joints and bedding, filling material and cementation mode;

[0038] Based on the aforementioned structural features, a multi-component, multi-scale digital core model is constructed. The digital core model includes the quantitative relationship between CT number, pore density, and pore volume.

[0039] The first or second three-dimensional scan data is determined based on the digital core model.

[0040] Optionally, during the acidizing and unblocking test of the target core, the target core is placed on a core acidizing flow experimental device;

[0041] The target core was subjected to a predetermined temperature and pressure using the core acidizing flow experimental device.

[0042] The predetermined temperature is 70℃-120℃;

[0043] The predetermined pressure is 1.5 MPa to 3.5 MPa.

[0044] Optionally, the acid-blocking solution to be tested includes at least one of arginine, citric acid, acidification corrosion inhibitor, sodium dihydrogen phosphate, hydrochloric acid, hydrofluoric acid, and water-locking agent;

[0045] The hydrochloric acid concentration in the acid-based unblocking solution to be tested is 10-15%, and the hydrofluoric acid concentration is 3-8%.

[0046] Optionally, evaluating the acid-blocking solution to be tested based on the first three-dimensional scanning data and the second three-dimensional scanning data includes:

[0047] Comparing the first three-dimensional scan data with the second three-dimensional scan data, if the difference between each data in the first three-dimensional scan data and the second three-dimensional scan data is greater than the difference threshold, then the acid-blocking solution to be tested is beneficial to the pore expansion and permeability enhancement of the rock sample.

[0048] If the difference between any one of the first three-dimensional scan data and the second three-dimensional scan data is not greater than the difference threshold, then the acid-blocking solution to be tested is not conducive to the pore expansion and permeability enhancement of the rock sample.

[0049] This invention discloses a method for evaluating acid-disrupting fluids in tight sandstone gas reservoirs. The method, applied to sandstone, includes: acquiring first three-dimensional scanning data of a target core; acid-disrupting the target core using a test acid-disrupting fluid, and acquiring second three-dimensional scanning data of the target core after acid-disruption; evaluating the test acid-disrupting fluid based on the first and second three-dimensional scanning data; both the first and second three-dimensional scanning data include at least the average radius and percentage of connected volume of the three-dimensional pore network. This invention quantitatively analyzes the core connectivity before and after acid-disruption, thereby evaluating the effectiveness of the acid-disrupting fluid and its adaptability to the reservoir, providing scientific guidance for construction design.

[0050] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0051] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0052] Figure 1 This is a schematic flowchart of a method for evaluating acid dissolution and plugging fluid in tight sandstone gas reservoirs according to the present invention;

[0053] Figure 2 This is a schematic diagram of CT scan data before and after core acidification in Embodiment 2 of the present invention;

[0054] Figure 3 This is a schematic diagram of CT scan data before and after acidification with different formulations in Embodiment 3 of the present invention. Detailed Implementation

[0055] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0056] Example 1

[0057] Figure 1 This is a schematic flowchart of a method for evaluating acidizing and plugging fluids in tight sandstone gas reservoirs according to the present invention, as shown below. Figure 1 As shown, this invention provides a method for evaluating acidizing and plugging fluids in tight sandstone gas reservoirs. The method, applied to sandstone, includes step S101: acquiring first three-dimensional scanning data of the target core. In a specific embodiment, a core acidizing flow experimental device and an industrial CT scanner are combined. A high-pressure resistant glass fiber core holder is used to fix the target core. X-rays penetrate the target core, and a 360° scanning operation is performed. Depending on the core shape and specifications, a suitable scanning method is selected, and an appropriate image acquisition resolution is set, prioritizing image clarity. A rotating connector connects to the fluid supply line, which is placed on the internal test platform of the CT scanner to facilitate rotational scanning.

[0058] Specifically, a three-dimensional digital rock sample of the target core is obtained using CT equipment; the three-dimensional internal pore network of the three-dimensional digital rock sample is obtained; the three-dimensional internal pore network is statistically analyzed to obtain the first three-dimensional scan data. The structural features of the three-dimensional internal pore network are obtained, including at least rock pore density, porosity distribution, density variation, internal fracture development, cavities, joints and bedding, filling material, and cementation method; a multi-component, multi-scale digital core model is constructed based on the structural features, the digital core model including the quantitative relationship between CT count, pore density, and pore volume; the first three-dimensional scan data is determined based on the digital core model.

[0059] For example, before testing, check, debug, and assemble all components of the core acidizing flow experimental device. Select a well-preserved natural core with dimensions of 25.4mm × (40~50)mm and record it. Correctly install the core into the core holder. Turn on the CT scanner, select the appropriate scanning mode based on the chosen core shape and dimensions, and set the appropriate image acquisition resolution, ensuring a clear image. Following the operating procedures of the core acidizing flow experimental device, correctly install the test core into the core holder and assemble the pipelines. Fill the intermediate container with the pre-prepared acid solution. Start the heating system, adjust the temperature to the required simulated formation temperature, and begin heating. Carefully observe the thermometer reading until the predetermined temperature is reached. Adjust the pressure, slowly increasing the confining pressure to 3.5MPa and maintaining it constant to ensure the entire core skeleton particles are in a statically stable state, reducing testing errors. Two-dimensional X-ray scanning was performed by adjusting the parameters of the CT equipment. The scanned data was then used to reconstruct a digital three-dimensional model using CT software, and the porosity, average pore radius, and percentage of connected volume were obtained through analysis.

[0060] Step S102 involves acidifying the target core with the acidizing solution to remove blockages, and obtaining the second three-dimensional scanning data of the target core after acidification. Acidification utilizes the chemical dissolving effect of acid to dissolve formation blockages, enlarge or extend formation fractures and cavities, thereby restoring and improving formation permeability, reducing oil inflow resistance or water injection resistance, and ultimately achieving the goal of increasing oil well production and water well injection.

[0061] The acid-blocking solution to be tested includes at least one of arginine, citric acid, acidification corrosion inhibitor, sodium dihydrogen phosphate, hydrochloric acid, hydrofluoric acid, and water-locking agent; the concentration of hydrochloric acid in the acid-blocking solution to be tested is 10-15%, and the concentration of hydrofluoric acid is 3-8%.

[0062] During the acidizing and unblocking test of the target core, the target core is placed on a core acidizing flow test device; a predetermined temperature and a predetermined pressure are set for the target core using the core acidizing flow test device; the predetermined temperature is 70℃-120℃; and the predetermined pressure is 1.5Mpa-3.5Mpa.

[0063] Specifically, a three-dimensional digital rock sample of the target core is obtained using CT equipment; the three-dimensional internal pore network of the three-dimensional digital rock sample is obtained; and statistical analysis of the three-dimensional internal pore network is performed to obtain second three-dimensional scan data. The structural features of the three-dimensional internal pore network are obtained, including at least rock pore density, porosity distribution, density variation, internal fracture development, cavities, joints and bedding, filling material, and cementation method; a multi-component, multi-scale digital core model is constructed based on the structural features, and the digital core model includes a quantitative relationship between CT count, pore density, and pore volume; the second three-dimensional scan data is determined based on the digital core model.

[0064] For example, the acid injection pump is started, and the injection pressure is maintained at 2.5 MPa to simulate the acid unblocking process for 2 hours. During this period, CT scans are performed continuously to obtain data at different times. A digital three-dimensional model is reconstructed using CT software, and key physical properties such as porosity, average pore radius, and percentage of connected volume are analyzed. After the test, the pressure is released, the test system is shut down, and the test core is carefully removed after cooling to room temperature. The experimental apparatus is then cleaned, maintained, and repaired.

[0065] The acid-repairing and unblocking fluid to be tested is evaluated based on the first and second three-dimensional scanning data. Both the first and second three-dimensional scanning data include at least the average radius and percentage of connected volume of the three-dimensional pore network. According to a specific embodiment, evaluating the acid-repairing and unblocking fluid based on the first and second three-dimensional scanning data includes: comparing the first and second three-dimensional scanning data; if the difference between any data point in the first and second three-dimensional scanning data is greater than a difference threshold, then the acid-repairing and unblocking fluid is beneficial for pore enlargement and permeability enhancement of the rock sample; if the difference between any data point in the first and second three-dimensional scanning data is not greater than the difference threshold, then the acid-repairing and unblocking fluid is not beneficial for pore enlargement and permeability enhancement of the rock sample.

[0066] The present invention also includes changing the acid plugging solution formulation of the test core or the test evaluation, repeating the above steps, filling the test results into a table, and conducting comparative evaluation, optimization and analysis.

[0067] This invention employs a non-destructive method that does not damage the internal structure of rock samples. By using CT scanning digital imaging, it quantitatively analyzes the core connectivity before and after acidizing and unblocking, clarifies the changes in pore throats after acidizing and unblocking, and then evaluates the effect of the acidizing and unblocking fluid. This method is accurate and comprehensive, and can scientifically guide the selection and formulation optimization of the acid system during acidizing and unblocking operations in tight sandstone gas reservoirs, which is beneficial for increasing production and efficiency.

[0068] Example 2

[0069] The present invention provides a second specific embodiment for evaluating the unblocking effect of the same acid-dissolving solution on rock samples at different strata and examining its adaptability to different reservoirs.

[0070] Tight sandstone gas reservoir samples from the TY, SX, H2, and H3 layers of a certain block were selected and prepared into 25.4mm × 50mm core samples for testing. These samples were then labeled and registered. The acidizing and plugging solution formulation was prepared as follows: terpineic acid (12% HCl + 3% HF) + 3% citric acid + 1.5% acidizing corrosion inhibitor + 1% sodium dihydrogen phosphate + 3% water-locking agent. Following the operating procedures of the core acidizing flow test apparatus, all components were debugged and assembled. The test cores were correctly loaded into the core holder and the pipelines were installed, maintaining a constant flow rate. The confining pressure was set at 3.5 MPa; the CT equipment parameters were adjusted, and the core sample before acidizing was scanned; without removing the core sample, the acid injection pump was started, and the injection pressure was maintained at 2.5 MPa to simulate the acidizing and unblocking process for 2 hours, during which CT scans were performed continuously to obtain data at different times; after the test, the pressure was released, the test system was shut down, and the core sample was carefully removed after cooling to room temperature, and the experimental device was cleaned, maintained, and repaired; the above steps were repeated with different core samples, and the test analysis results were filled into a table for comparison, evaluation, and optimization.

[0071] like Figure 2 As shown, the test results indicate that after acid treatment to remove blockages, porosity, average pore radius, and percentage of connected volume increased, confirming that acid treatment to remove blockages is beneficial for expanding pores and increasing permeability. This is manifested in an increase in porosity of 1.65–7.28% and an increase in average pore radius of 0.91–5.34%. Except for the SX group, which remained essentially unchanged, the percentage of connected volume increased in all other formations, indicating that the SX group suffered from severe reservoir damage due to throat blockage, consistent with the result of the lowest relative effectiveness of acid treatment to remove blockages. The H3 formation showed the largest increase in the percentage of connected volume, indicating the highest relative effectiveness of acid treatment to remove blockages.

[0072] After acid etching, the number of pores in the TY and SX cores decreased and the average length of the throats shortened slightly, indicating that the minerals or blockages between the pores caused by acid etching expanded the originally disconnected pores and reduced their number. After acid etching, the number of pores in the H2 and H3 cores increased and the average length of the throats increased slightly, indicating that the cores contained more minerals that were easily acid-etched, forming new pores through acid etching. After acid treatment, the porosity and average pore radius of the TY group cores both increased, with porosity increasing by 2.11%, average pore radius increasing by 4.64%, and the percentage of connected volume increasing by 1.47%. After acid treatment, the porosity and average pore radius of the SX group cores both increased, with porosity increasing by approximately 1.74% and average pore radius increasing by approximately 3.56%, while the percentage of connected volume remained essentially unchanged. The H2 core had relatively high initial porosity, but after acid treatment, porosity increased significantly, and the average pore radius increased slightly, with porosity increasing by approximately 7.28% and average pore radius increasing by approximately 0.91%, while the percentage of connected volume increased by 10.25%. The H3 core had the highest initial porosity, and after acid treatment, both porosity and average pore radius increased, with porosity increasing by approximately 1.65% and average pore radius increasing by approximately 5.34%, while the percentage of connected volume saw the largest increase, reaching 18.31%.

[0073] This demonstrates that the same acidizing and unblocking fluid can have varying effects on core samples from different formations. Different mineral compositions and internal structures in reservoir cores lead to different acidizing and unblocking effects. This evaluation method, by quantitatively assessing the changes in pore size and connectivity before and after acidizing and unblocking, facilitates the selection of highly adaptable acidizing and unblocking fluids and guides the optimization of acidizing fluid formulations for different formations.

[0074] Example 3

[0075] The present invention also provides a specific embodiment three, through analysis of its effects, to select a suitable acid unblocking solution formulation.

[0076] Sandstone is composed of sand grains (quartz and feldspar) and intergranular cement (clay and carbonates). The reservoir space and seepage channels in sandstone are the pores between sand grains that are not completely filled by cement. Hydrochloric acid in soil acid can dissolve iron, aluminum compounds, and carbonates in the formation, and maintain a low pH value to prevent redeposition. Hydrofluoric acid can dissolve clay and silicates. In other words, the acid dissolves the cement between sand grains, some sand grains, or clay plugs in the pores, as well as other scale. After acidification and subsequent drainage, secondary blockage by cement, mud cake, and fouling in the formation can be removed, restoring or improving permeability in the near-wellbore zone. Due to differences in reservoir rock composition and properties, the composition and amount of acid used in actual treatment vary, depending on the clay and carbonate content of the formation and the degree of sandstone cementation. By evaluating the acidification and unblocking effect, a suitable ratio of HCl to HF can be optimized.

[0077] The formulations of the acid-blocking solution to be tested are as follows: A: argyric acid (12% HCl + 3% HF) + 3% citric acid + 1.5% acidification corrosion inhibitor + 1% sodium dihydrogen phosphate + 3% water-locking agent; B: argyric acid (12% HCl + 7% HF) + 3% citric acid + 1.5% acidification corrosion inhibitor + 1.5% sodium dihydrogen phosphate + 3% water-locking agent; C: argyric acid (15% HCl + 3% HF) + 3% citric acid + 1.5% acidification corrosion inhibitor + 1% sodium dihydrogen phosphate + 3% water-locking agent.

[0078] A tight sandstone gas reservoir sample from the TY layer of a certain block was prepared into a 25.4mm × 50mm core sample for testing, and each sample was labeled and registered. Following the operating procedures of the core acidizing flow test apparatus, all components were debugged and assembled. The test core was correctly placed into the core holder and the pipeline was installed, maintaining a constant confining pressure of 3.5MPa. The CT equipment parameters were adjusted, and the core sample was scanned before acidizing. Without removing the core, the acid injection pump was started, and the injection pressure was maintained at 2.5MPa to simulate the acidizing and unblocking process for 2 hours, during which continuous CT scans were performed to obtain data at different stages. After the test, the pressure was released, the test system was shut down, and the core sample was carefully removed after cooling to room temperature. The test apparatus was cleaned, maintained, and repaired. The above steps were repeated with different core samples and prepared acid solutions. The test analysis results were entered into a table for comparison, evaluation, and optimization.

[0079] like Figure 3 The statistical results of CT scans before and after acidification with different formulations show that the porosity, average pore radius, and percentage of connected volume of the TY group cores all increased after acidification, the number of pores decreased, and the average throat length slightly shortened. This indicates that the minerals or blockages between the sandstone pores were dissolved and acidified, the pore throats enlarged, connectivity improved, and seepage capacity increased. Due to the different treatment principles of hydrochloric acid and hydrofluoric acid in soil acid, different ratios and dosages resulted in different effects on the acidification and unblocking of the same rock. The porosity of the TY-2-1 core increased by 2.13%, the average pore radius increased by 3.21%, and the percentage of connected volume increased by 2.78%; the porosity of the TY-2-2 core increased by 5.78%, the average pore radius increased by 5.40%, and the percentage of connected volume increased by 6.34%; the porosity of the TY-2-3 core increased by 4.62%, the average pore radius increased by 4.59%, and the percentage of connected volume increased by 3.07%. The comparison shows that formulation B has a better acid-blocking effect, which also indicates that the TY group core has low carbonate content, high mud content and dense cementation, making it suitable for acid-blocking solution prepared by mixing medium-low concentration hydrochloric acid and high concentration hydrofluoric acid.

[0080] This invention discloses a method for evaluating and selecting optimal acidizing and unblocking fluids for tight sandstone gas reservoirs without damaging the internal structure of the core. A core acidizing flow experimental apparatus combined with a CT scanner is used to simulate the acidizing and unblocking process. Digital imaging via CT scans is used to quantitatively analyze the core connectivity before and after acidizing and unblocking, quantitatively characterizing changes in key physical properties such as porosity, average pore radius, and percentage of connected volume before and after acidizing. This allows for the evaluation of the effectiveness of the acidizing and unblocking fluid and its adaptability to the reservoir, providing accurate and scientific guidance for construction design.

[0081] Example 4

[0082] This invention also proposes an apparatus for evaluating acid-dissolving and unblocking fluids in tight sandstone gas reservoirs. The apparatus comprises: an acquisition module for acquiring first three-dimensional scanning data of a target core; a first processing module for acid-dissolving and unblocking the target core using the test acid-dissolving and unblocking fluid, and acquiring second three-dimensional scanning data of the target core after acid-dissolving and unblocking; a second processing module for evaluating the test acid-dissolving and unblocking fluid based on the first and second three-dimensional scanning data; and a third processing module for ensuring that both the first and second three-dimensional scanning data include at least the average radius and percentage of connected volume of the three-dimensional pore network.

[0083] Optionally, acquiring the first three-dimensional scan data of the target rock core and acquiring the second three-dimensional scan data of the target rock core after acid unblocking include: acquiring a three-dimensional digital rock sample of the target rock core using a CT device; acquiring the three-dimensional internal pore network of the three-dimensional digital rock sample; and statistically analyzing the three-dimensional internal pore network to obtain the first three-dimensional scan data or the second three-dimensional scan data.

[0084] The step of statistically analyzing the three-dimensional internal pore network to obtain either the first or second three-dimensional scanning data includes: acquiring the structural features of the three-dimensional internal pore network, the structural features including at least rock pore density, porosity distribution, density variation, internal fracture development, cavities, joints and bedding, filling materials, and cementation methods; constructing a multi-component, multi-scale digital core model based on the structural features, the digital core model including a quantitative relationship between CT number, pore density, and pore volume; and determining the first or second three-dimensional scanning data based on the digital core model. During the acidizing and unblocking test of the target core, the target core is placed on a core acidizing flow experimental device; a predetermined temperature and pressure are set for the target core using the core acidizing flow experimental device; the predetermined temperature is 70℃-120℃; and the predetermined pressure is 1.5MPa-3.5MPa.

[0085] The acid-blocking solution to be tested includes at least one of arginine, citric acid, acidification corrosion inhibitor, sodium dihydrogen phosphate, hydrochloric acid, hydrofluoric acid, and a water-locking agent; the concentration of hydrochloric acid in the acid-blocking solution to be tested is 10-15%, and the concentration of hydrofluoric acid is 3-8%. The evaluation of the acid-blocking solution to be tested based on the first and second three-dimensional scanning data includes: comparing the first and second three-dimensional scanning data; if the difference between each data point in the first and second three-dimensional scanning data is greater than a difference threshold, then the acid-blocking solution to be tested is beneficial for pore enlargement and permeability enhancement of the rock sample; if the difference between any data point in the first and second three-dimensional scanning data is not greater than the difference threshold, then the acid-blocking solution to be tested is not beneficial for pore enlargement and permeability enhancement of the rock sample.

[0086] This device quantitatively evaluates the changes in pore size and connectivity before and after acidification and unblocking, which helps to evaluate and select acidification and unblocking solutions with strong adaptability and guides the optimization of acid solution formulations for different layers.

[0087] This invention discloses a method for evaluating acid-disrupting fluids in tight sandstone gas reservoirs. The method, applied to sandstone, includes: acquiring first three-dimensional scanning data of a target core; acid-disrupting the target core using a test acid-disrupting fluid, and acquiring second three-dimensional scanning data of the target core after acid-disruption; evaluating the test acid-disrupting fluid based on the first and second three-dimensional scanning data; both the first and second three-dimensional scanning data include at least the average radius and percentage of connected volume of the three-dimensional pore network. This invention quantitatively analyzes the core connectivity before and after acid-disruption, thereby evaluating the effectiveness of the acid-disrupting fluid and its adaptability to the reservoir, providing scientific guidance for construction design.

[0088] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0089] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0090] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0091] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A method for evaluating acid plugging fluids in tight sandstone gas reservoirs, characterized in that, The method includes: Acquire the first three-dimensional scan data of the target rock core; The target core was acidified and unblocked using the acidification and unblocking solution to be tested, and the second three-dimensional scanning data of the target core after acidification and unblocking was obtained. The acid-dissolving solution to be tested is evaluated based on the first three-dimensional scan data and the second three-dimensional scan data. Both the first and second three-dimensional scan data include at least the average radius and percentage of connected volume of the three-dimensional porous network.

2. The method according to claim 1, characterized in that, The acquisition of the first three-dimensional scanning data of the target core and the acquisition of the second three-dimensional scanning data of the target core after acid treatment and unblocking include: A three-dimensional digital rock sample of the target rock core was obtained using CT equipment; Obtain the three-dimensional internal pore network of the three-dimensional digital rock sample; The first three-dimensional scan data or the second three-dimensional scan data are obtained by statistically analyzing the three-dimensional internal pore network.

3. The method according to claim 2, characterized in that, The step of statistically analyzing the three-dimensional internal pore network to obtain the first or second three-dimensional scan data includes: The structural features of the three-dimensional internal pore network are obtained, and the structural features include at least rock pore density, porosity distribution, density variation, internal crack development, pores, joints and bedding, filling material and cementation mode; Based on the aforementioned structural features, a multi-component, multi-scale digital core model is constructed. The digital core model includes the quantitative relationship between CT number, pore density, and pore volume. The first or second three-dimensional scan data is determined based on the digital core model.

4. The method according to claim 1, characterized in that, During the acidizing and unblocking test of the target core, the target core is placed on the core acidizing flow test device; The target core was subjected to a predetermined temperature and pressure using the core acidizing flow experimental device. The predetermined temperature is 70℃-120℃; The predetermined pressure is 1.5 MPa to 3.5 MPa.

5. The method according to claim 1, characterized in that, The acid-blocking solution to be tested includes at least one of the following: arginine, citric acid, acidification corrosion inhibitor, sodium dihydrogen phosphate, hydrochloric acid, hydrofluoric acid, and water-locking agent. The hydrochloric acid concentration in the acid-based unblocking solution to be tested is 10-15%, and the hydrofluoric acid concentration is 3-8%.

6. The method according to claim 1, characterized in that, The evaluation of the acid-blocking solution to be tested based on the first three-dimensional scanning data and the second three-dimensional scanning data includes: Comparing the first three-dimensional scan data with the second three-dimensional scan data, if the difference between each data in the first three-dimensional scan data and the second three-dimensional scan data is greater than the difference threshold, then the acid-blocking solution to be tested is beneficial to the pore expansion and permeability enhancement of the rock sample. If the difference between any one of the first three-dimensional scan data and the second three-dimensional scan data is not greater than the difference threshold, then the acid-blocking solution to be tested is not conducive to the pore expansion and permeability enhancement of the rock sample.

7. An apparatus for evaluating acid-blocking fluids in tight sandstone gas reservoirs, characterized in that, The device includes: The acquisition module is used to acquire the first three-dimensional scan data of the target core. The first processing module is used to acidify and deblock the target core with the acid-dissolving and deblocking solution to obtain the second three-dimensional scanning data of the target core after acidification and deblocking. The second processing module is used to evaluate the acid unblocking solution to be tested based on the first three-dimensional scanning data and the second three-dimensional scanning data. The third processing module is used to ensure that both the first and second three-dimensional scanning data include at least the average radius and the percentage of connected volume of the three-dimensional pore network.

8. The apparatus according to claim 7, characterized in that, The acquisition of the first three-dimensional scanning data of the target core and the acquisition of the second three-dimensional scanning data of the target core after acid treatment and unblocking include: A three-dimensional digital rock sample of the target rock core was obtained using CT equipment; Obtain the three-dimensional internal pore network of the three-dimensional digital rock sample; The first three-dimensional scan data or the second three-dimensional scan data are obtained by statistically analyzing the three-dimensional internal pore network.

9. The apparatus according to claim 8, characterized in that, The step of statistically analyzing the three-dimensional internal pore network to obtain the first or second three-dimensional scan data includes: The structural features of the three-dimensional internal pore network are obtained, and the structural features include at least rock pore density, porosity distribution, density variation, internal crack development, pores, joints and bedding, filling material and cementation mode; Based on the aforementioned structural features, a multi-component, multi-scale digital core model is constructed. The digital core model includes the quantitative relationship between CT number, pore density, and pore volume. The first or second three-dimensional scan data is determined based on the digital core model.

10. The apparatus according to claim 7, characterized in that, During the acidizing and unblocking test of the target core, the target core is placed on the core acidizing flow test device; The target core was subjected to a predetermined temperature and pressure using the core acidizing flow experimental device. The predetermined temperature is 70℃-120℃; The predetermined pressure is 1.5 MPa to 3.5 MPa.

11. The apparatus according to claim 7, characterized in that, The acid-blocking solution to be tested includes at least one of the following: arginine, citric acid, acidification corrosion inhibitor, sodium dihydrogen phosphate, hydrochloric acid, hydrofluoric acid, and water-locking agent. The hydrochloric acid concentration in the acid-based unblocking solution to be tested is 10-15%, and the hydrofluoric acid concentration is 3-8%.

12. The apparatus according to claim 7, characterized in that, The evaluation of the acid-blocking solution to be tested based on the first three-dimensional scanning data and the second three-dimensional scanning data includes: Comparing the first three-dimensional scan data with the second three-dimensional scan data, if the difference between each data in the first three-dimensional scan data and the second three-dimensional scan data is greater than the difference threshold, then the acid-blocking solution to be tested is beneficial to the pore expansion and permeability enhancement of the rock sample. If the difference between any one of the first three-dimensional scan data and the second three-dimensional scan data is not greater than the difference threshold, then the acid-blocking solution to be tested is not conducive to the pore expansion and permeability enhancement of the rock sample.

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