Core processing method of simulated stratum fracture net for reservoir damage and protection evaluation

Abstract

The invention belongs to the technical field of oil and gas production specialty, and relates to a rock core processing method of a simulated formation fracture net for reservoir damage and protection evaluation, which comprises the following steps: preparing a plurality of rock core columns for reflecting and evaluating formation components of an oil and gas reservoir; taking the prepared rock core column, and forming forces in three directions of two horizontal principal stresses and overlying strata pressure on the rock core column according to a preset loading mode and interval time, so that a crack-micro crack network which is the same as the stratum rock of the oil and gas reservoir is formed in the rock core; and acquiring a three-dimensional graph of the fracture network in a digital rock core scanning mode, calculating the fracture degree and high-density mineral data of the fracture body, and establishing the fracture distribution condition of the rock core after fracture forming until the fracture degree and the high-density mineral data of the rock core column are consistent with the fracture degree and the high-density mineral data of the stratum rock core. According to the invention, the stratum rock core consistent with the stratum seepage channel can be produced, the established rock core can better simulate the stratum condition, and the evaluation result is more reliable.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas production, and specifically relates to a core processing method for simulating a formation fracture network for reservoir damage and protection evaluation. Background Art

[0002] Damage to oil and gas reservoirs during drilling and completion mainly refers to the phenomenon that when the liquid column pressure of the working fluids such as drilling fluid, cementing fluid, completion fluid and perforating fluid far exceeds the pore pressure of the reservoir, the working fluid is squeezed into the oil and gas reservoir, causing the oil and gas channels to become smaller or blocked, and the permeability of the oil and gas layer to decrease. The result of reservoir damage is reduced production capacity and inaccurate reserve and production capacity estimation; it affects the formulation of development plans; increases the workload of oil testing, acidizing, fracturing, well repair, etc., increases costs; affects the final recovery rate, and damages oil and gas resources. Therefore, in the drilling and completion operations, every effort should be made to reduce reservoir damage and protect the oil and gas layer as much as possible.

[0003] In the development of a certain layer, in order to protect the oil and gas layer from damage during drilling and completion, it is necessary to evaluate the damage of the fluids that need to be introduced in each process of drilling and completion, and to conduct experimental evaluation on the effectiveness of the protection treatment measures used in each stage to ensure that each drilling and completion process causes the least damage to the oil and gas reservoir and the protection measures used are optimal. Therefore, it is crucial to accurately test the damage of each drilling and completion process, fluid system and reservoir protection formula to the oil and gas reservoir.

[0004] For general oil and gas reservoirs (such as average, medium porosity, medium permeability oil and gas reservoirs), the existing technology is to obtain the degree of damage to the oil and gas reservoirs during the drilling and completion process and the effect of protective measures by measuring the core sensitivity (including velocity sensitivity, water sensitivity, salt sensitivity, alkali sensitivity, acid sensitivity, etc.) and the permeability recovery value after the working fluid damages the reservoir. The core steps of the core sensitivity evaluation experiment are: drilling rock cores from the oil and gas reservoir, using fluids (clean water, formation brine, acid, alkali, etc.) that simulate different drilling and completion processes to conduct displacement experiments on the rock cores, allowing the fluids to interact with the rocks of the oil and gas reservoir, and using the permeability changes before and after the fluids interact with the rocks to define the sensitivity of the oil and gas reservoir to external fluids. The core of the drilling and completion working fluid damage and protection evaluation experiment is to use the working fluid to directly interact with the formation cores taken from the oil and gas reservoir, measure the core permeability values ​​before and after the action, and judge the degree of reservoir damage and the protective effect of the reservoir protection formula by the change in the values. According to the above experimental evaluation, one of the core factors in the damage and protection evaluation of oil and gas reservoirs is the formation rock core taken from the oil and gas reservoir. First, it is required to have the same composition as the formation rock of the oil and gas reservoir, and the physical and chemical reactions when different drilling and completion fluids act on it are consistent; second, it is required to have the same pore and permeability conditions as the formation rock of the oil and gas reservoir, that is, the seepage channels in oil and gas development and production are the same after the reaction. For general oil and gas reservoirs, their seepage channels are mainly pores, so the core taken from the formation has the same composition as the formation and the same porosity as the formation, so this method can simulate the formation conditions and the evaluation results are reliable.

[0005] In recent years, with the rapid development of the world economy, the global demand for oil and natural gas has also increased rapidly. With the increasing reduction of conventional oil and gas resources, unconventional oil and gas resources have become the main battlefield for exploration and development. Their efficient development and utilization are of great significance to maintaining stable economic growth and ensuring national energy security. In the development process of unconventional oil and gas resources, the development of tight sandstone gas reservoirs with developed micro-fractures occupies an important position.

[0006] In the development of tight sandstone gas reservoirs with developed fractures and micro-fractures, one of the core issues of sensitivity evaluation of oil and gas reservoirs and damage evaluation of working fluids is to process and manufacture rock cores that are consistent with the formation composition and seepage channels of the oil and gas layers. For tight sandstone with developed fractures and micro-fractures, the rock core taken from the formation has the same composition as the formation, but there is no way to simulate the fractures and micro-fractures of the formation through the core. Due to the development of fractures and micro-fractures in the formation, a complete core cannot be formed when drilling the core. Therefore, a rock core with the same porosity and permeability structure as the oil and gas formation cannot be formed.

[0007] To address this problem, the existing technology is to take a rock core of an oil and gas reservoir without formation cracks or microcracks, ensure that the core is the same as the formation composition, and then use the Brazilian fracturing test to fracture the formation cracks, or use the cutting and splitting methods to establish a crack on the formation core to simulate the formation porosity and permeability conditions. The Brazilian splitting test, the splitting test, and the cutting test can only establish linear cracks in the core, and the crack shape is single, and in most cases there is only one crack. Since the crack opening is difficult to control, the seepage channel of the processed formation rock core is larger than the actual seepage channel at the bottom of the well, so it is not easy to simulate the formation conditions. Summary of the invention

[0008] The purpose of the present invention is to provide a core processing method for simulating a formation fracture network for reservoir damage and protection evaluation, which solves the problem that the core of fractures and micro-fractures consistent with the formation cannot be taken out.

[0009] The present invention is achieved through the following technical solutions:

[0010] A core processing method for simulating a formation fracture network for reservoir damage and protection evaluation comprises the following steps:

[0011] S1. Using a digital core scanning method, a numerical three-dimensional graph of the core fractures of the simulated reservoir formation is obtained, and the fracture degree and high-density mineral content of the simulated reservoir formation are calculated;

[0012] S2. Prepare several core columns reflecting the composition of the reservoir formation for evaluation;

[0013] S3, taking the core column prepared in S2, and forming forces in three directions of two horizontal principal stresses and overburden stratum pressure on the core column according to a preset loading mode and interval time, so that a fracture-microfracture network identical to that of the reservoir stratum rock is formed in the core;

[0014] S4. Use the digital core scanning method to establish the fracture distribution of the core after fracture creation, until the fracture degree and high-density mineral content of the core column are consistent with the fracture degree and high-density mineral content of the simulated reservoir formation core, and the core processing is completed.

[0015] Further, S2 specifically includes the following steps:

[0016] S21. Drill several circular columnar cores from rocks without cracks or microcracks and flatten them in two sections;

[0017] If there are few or no cores taken from the formation to be evaluated, and it is impossible to drill cylindrical cores, a round cylindrical core can be drilled from the outcrop core of the formation with the same stratigraphic level;

[0018] S22. Naturally dry the round columnar core in a drying oven to obtain a qualified core column.

[0019] Furthermore, the diameter of the circular columnar core is 24.5 mm and the length is 40 to 60 mm.

[0020] Further, in S22, if the mass change between two weighings before and after drying is less than 1%, a qualified core column is obtained.

[0021] Further, S3 specifically includes the following steps:

[0022] S31, take the core column prepared in S2, and wrap it with several layers of transparent tape, and reserve a certain length when wrapping the tape to control the tension;

[0023] S32, take the core column wrapped with transparent tape in S31, put it into the stress clamp, and shake the handle to clamp the core;

[0024] S33. After shaking the stress clamp handle, stop for 3 to 5 minutes;

[0025] S34, observe the core column surface and two end faces in the stress clamp, and stop loading when visible cracks appear on the core column surface or end faces;

[0026] S35. Release the clamping force of the stress clamp, remove the core column, rotate the core column 45°, and repeat steps S21-S24 to ensure that the cracks in the core are evenly distributed.

[0027] Furthermore, in S31, 2 to 5 layers of transparent tape are used for wrapping.

[0028] Furthermore, in S3, when the permeability of the formation fracture is 0.1-10 mD, the number of layers of transparent tape is 5, the reserved length of the tape is controlled within 2 mm, the pressure angle of the stress clamp handle is 45°, and the interval time after a single pressure application is 5 min;

[0029] When the permeability of the formation crack is 10-100mD, the number of layers of transparent tape is 4, the reserved length of the tape is controlled at 4-8mm, the pressure angle of the stress clamp handle is 60°-90°, and the interval time after a single pressure application is 4-5min;

[0030] When the permeability of the formation crack is 100-1000mD, the number of transparent tape winding layers is 3, the reserved length of the tape is controlled at 10-14mm, the pressure angle of the stress clamp handle is 90°, and the interval time after single pressure application is 3-4min.

[0031] Furthermore, in S33, the shaking angle is 45 to 90 degrees.

[0032] Further, S4 specifically includes the following processes:

[0033] Take the core column that has completed the fracture processing in S3, establish the fracture distribution of the core after the fracture creation, use the digital core scanning method again to obtain the reconstructed three-dimensional figure of the fracture network of the small core after the fracture creation, and calculate the fracture degree and high-density mineral content of the fracture network;

[0034] If the fracture degree and high-density mineral content of a fracture network are less than the requirements of the simulated reservoir formation, the core column is placed in the stress clamp and continues to be loaded until the requirements are met.

[0035] Furthermore, the digital core scanning method is specifically as follows:

[0036] After X-rays penetrate the rock, they attenuate, and two-dimensional X-ray imaging is performed according to the different degrees of attenuation. The sample is then rotated for a 360° scan to obtain a series of two-dimensional projection images, which are filtered and contrast enhanced to reconstruct the rock's surrounding structure and obtain a three-dimensional model of the rock sample.

[0037] Compared with the prior art, the present invention has the following beneficial technical effects:

[0038] The present invention discloses a core processing method for simulating formation fracture networks for reservoir damage and protection evaluation. According to the preset loading mode and interval time, a fracture-micro-fracture network identical to the formation rock of the oil and gas reservoir is formed in the core, and a core consistent with the pore and permeability of the oil and gas reservoir rock can be formed. The specific reason is that the fracture travel of the oil and gas reservoir rock is the result of the action of geological stress. According to the research results, the geological stress can be divided into two horizontal principal stresses and overburden pressure in three directions according to its action effect. In the present invention, the pressure applied by the two end faces of the stress clamp is used to simulate the horizontal principal stress in the geological action process, and the tension provided by the winding tape is used to simulate the overburden pressure. Therefore, under this action mode, the cracks-micro-fractures generated are the same as the cracks-micro-fractures generated in the geological process.

[0039] Furthermore, after the X-rays penetrate the rock, attenuation occurs, and two-dimensional X-ray imaging is performed according to different attenuation degrees; then the sample is rotated for 360° scanning, a series of two-dimensional projection images are obtained, filtering and contrast enhancement are performed, the rock perimeter structure is reconstructed, and a three-dimensional model of the rock sample is obtained. Different grayscales are used to represent the fracture pore space, and the fracture degree and high-density mineral content are calculated. The fracture degree and high-density mineral content of the core of a fracture network are retrieved, which are consistent with the simulated reservoir formation. If the digital core scanning fracture degree and high-density mineral content are less than the formation requirements, the core column is placed in the stress clamp and continues to be loaded until the requirements are met.

[0040] The present invention can produce formation rock cores that are consistent with formation seepage channels, and can be used for evaluating damage to oil and gas reservoirs caused by drilling and completion working fluids in fractured and micro-fractured formations and studying protective countermeasures. The cores established by the method disclosed in the present invention better simulate formation conditions, and the evaluation results are more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A three-dimensional image of a fracture network obtained by digital scanning and reconstruction of a stratum core in the embodiment;

[0042] Figure 2 This is a three-dimensional image of the fracture network obtained by digital scanning and reconstruction of the core after coring and fracture creation in the embodiment. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0044] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0045] It should be noted that the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, so that a process, element, method, article or equipment that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or equipment.

[0046] The present invention discloses a core processing method for simulating formation fracture networks for reservoir damage and protection evaluation, which can process experimental cores that are consistent with the rock composition and porosity and permeability of oil and gas reservoir formations, and can be used for reservoir damage and protection evaluation experiments in the development of fractured and micro-fractured oil and gas reservoirs.

[0047] The present invention provides a method for processing experimental cores with consistent rock composition and porosity and permeability in the above-mentioned oil and gas reservoir formation, comprising the following steps:

[0048] S1. Using a digital core scanning method, a numerical three-dimensional graph of the core fractures of the simulated reservoir formation is obtained, and the fracture degree and high-density mineral content of the simulated reservoir formation are calculated;

[0049] S2. Prepare several small core columns reflecting the composition of the reservoir formation for evaluation;

[0050] S3, taking the small core column prepared in S2, using stress clamps, and forming forces in three directions of two horizontal principal stresses and overburden stratum pressure on the core column according to a predetermined loading method and interval time, so that a fracture-microfracture network identical to that of the reservoir stratum rock is formed in the core;

[0051] S4. Use the digital core scanning method to establish the fracture distribution of the core after fracture creation, until the fracture degree and high-density mineral content of the core column are consistent with the fracture degree and high-density mineral content of the simulated reservoir formation core, and the core processing is completed.

[0052] Furthermore, step S2 specifically includes:

[0053] S21. Drill a small round columnar core with a diameter of 24.5 mm and a length of 40 to 60 mm from a rock without cracks or microcracks, and flatten the two sections.

[0054] S22. Dry the small round columnar core naturally in a drying oven. The core is qualified if the mass change between two weighings is less than 1%;

[0055] In this way, the use of small circular cylindrical cores can simulate the situation of formation rocks. Small circular cylindrical cores can be taken from the formation to be evaluated to ensure that the displacement medium is the same as the formation. If the formation to be evaluated has less or no cores, and small cylindrical cores cannot be drilled, small circular cylindrical cores can be drilled from the outcrop cores of the formation with the same stratum as the formation. Since the formations are the same, the properties of the formation rocks are basically the same. In addition, the length of the small circular cylindrical core must be greater than 40 mm. If it is too small, it is not enough to simulate the formation medium.

[0056] Furthermore, step S3 specifically includes:

[0057] S31, take the small core column prepared in S2, and wrap it with 2 to 5 layers of transparent tape, and reserve a certain length when wrapping the tape to control the tension;

[0058] S32. Take the small core column wrapped with transparent tape in S31, put it into the stress clamp, and shake the handle to clamp the core.

[0059] S33. Slowly shake the handle of the stress clamp. The shaking angle should be 45 to 90 degrees. After shaking the handle, stop for 3 to 5 minutes.

[0060] S34. Observe the cylindrical surface and two end faces of the small core column in the stress clamp. When cracks visible to the naked eye appear on the cylindrical surface or end faces, stop loading.

[0061] S35, release the clamping force of the stress clamp, remove the small core column, rotate the core column 45 degrees, and repeat steps S31-S34.

[0062] The reason for using transparent tape to wrap the small core column is that the core of the dense formation is relatively brittle and is prone to collapse during loading, causing core damage. Wrapping with transparent tape can prevent the collapse of some rocks during core pressurization. At the same time, by adjusting the tightness of the transparent tape, cracks are formed in the core to increase the volume for control. Use stress clamps to load the small core column, slowly load and clamp the small core column, and at a certain interval, to generate cracks inside the core, and allow the cracks to expand and form a crack network; the reason for adjusting the core by 45° is to ensure that the cracks in the core are evenly distributed.

[0063] The reason why the above method can form the same pore and permeability as the reservoir rock is: the fracture of the reservoir rock is the result of geological stress. According to the research results, geological stress can be divided into two horizontal principal stresses and overburden pressure in three directions according to its effect. In this experiment, the pressure applied by the two ends of the stress clamp is used to simulate the horizontal principal stress in the geological process, and the tension provided by the winding tape is used to simulate the overburden pressure. Therefore, under this mode of action, the cracks and microcracks generated are the same as the cracks and microcracks generated in the geological process.

[0064] Furthermore, step S4 specifically includes:

[0065] Take the small core column that has completed the crack processing in S3, and establish the crack distribution of the core after cracking according to the digital core scanning method;

[0066] The fracture degree and high-density mineral content of the core of a certain fracture network are retrieved, which are consistent with the fracture degree and high-density mineral content of the formation core. If the fracture degree and high-density mineral content are less than those of the formation core, the small core column can be placed in the stress clamp and continued to be loaded until the requirements are met.

[0067] Digital core scanning method: X-rays attenuate after penetrating the rock, and two-dimensional X-ray imaging is performed according to different attenuation degrees; then the sample is rotated for 360° scanning to obtain a series of two-dimensional projection images, which are filtered and contrast enhanced to reconstruct the rock perimeter structure and obtain a three-dimensional model of the rock sample. Different grayscales are used to represent the crack pore space, and the crack degree and high-density mineral content are calculated.

[0068] With this setting, the formation fissure degree and high-density mineral content are compared with the actual fracture creation results to determine whether they can be kept consistent within the error range.

[0069] The present invention also provides a method for controlling the parameters of the seam network consistent with the evaluated formation rock core, specifically including the number of layers of transparent tape winding, the reserved length of tape, the rotation angle of the single stress clamp handle, the interval time after single pressurization, etc. The operation can be performed according to the following table.

[0070]

[0071]

[0072] In this way, the controllable condition parameters of fracture network formation are quantified, which is easy for practical operation. The above parameters are derived based on the basic knowledge of fracture mechanics and are formed after being improved and modified in actual operation. Different formation core loading may be slightly different.

[0073] The method disclosed in the present invention has been applied to the research on reservoir damage evaluation and protection technology of Bozi and Dabei blocks of PetroChina Tarim Oilfield Company. The reservoirs in this area are dense and have developed fractures and microfractures. All experimental evaluations require the manufacture of rock cores consistent with the formations.

[0074] like Figure 1 As shown, a three-dimensional image of the fracture network is obtained by digitally scanning the simulated stratum core, and the calculated fracture degree is 1.12%, and the high-density mineral content is 0.52%. Through the method provided by the present invention, a core equivalent to the stratum is processed, such as Figure 2 As shown, the core digital scanning and reconstruction after coring and fracture creation obtains a three-dimensional image of the fracture network. The calculated fracture degree is 1.41%, and the high-density mineral content is 0.71%. The fracture degree and high-density mineral content of the core column are basically consistent with the fracture degree and high-density mineral content of the simulated reservoir formation core, and the core processing is completed.

[0075] Then, the damage evaluation experiment was carried out using the manufactured core. The experimental results were reasonable and reliable, and achieved good results. The experimental process is as follows:

[0076] Experiment name: Experiment on damage rate of drilling fluid to dual media in Bozi Dabei block

[0077] (1) Experimental purpose

[0078] Evaluate the permeability recovery value of drilling fluid and understand its reservoir protection performance.

[0079] (2) Experimental instruments

[0080] Experimental instruments: high-speed stirrer, beaker, 100mL measuring cylinder, 1000mL measuring cylinder, low-speed stirrer, electronic scale, glass rod, porcelain cylinder, timer, core displacement experimental device.

[0081] Stratigraphic core: cores of oil and gas reservoirs in Bozi and Dabei areas

[0082] Experimental evaluation of damaging fluids

[0083] 1#: Water-based drilling fluid for Bozi and Dabei reservoir sections, density 1.84g / cm3.

[0084] 2#: High-density oil-based drilling fluid for Bozi and Dabei reservoir sections, density 1.81g / cm3

[0085] (3) Experimental procedures

[0086] ① Use stress clamps to control the pressure of the core taken from the oil and gas reservoir to create a fracture network and control the permeability to 40-100mD.

[0087] ② Gas testing of core permeability;

[0088] ③Prepare simulated formation water and saturated core

[0089] The simulated formation water formula is: 2.0% potassium chloride + 5.5% sodium chloride + 0.45% magnesium chloride + 0.55% calcium chloride, which is prepared into a simulated formation water with a concentration of 8.5%. The core is placed in the brine for saturation for 24 hours, the mass of the core before and after saturation is weighed, and the pore volume is calculated.

[0090] ④ Determine the core permeability K1 before damage

[0091] The simulated formation water was injected into the core at a rate of 2.52 mL / min for 5 PV, and the flow rate and pressure difference were kept stable for 60 min. The pressure difference and flow rate were recorded, and the permeability K1 before damage was calculated.

[0092] ⑤Injury process

[0093] The drilling fluid is placed in a high-pressure container and pressurized with a pressure pump to reversely inject the drilling fluid into the core at a rate of 0.50 mL / min. When the drilling fluid solution begins to flow out, record the time and the cumulative filtration loss of the drilling fluid solution. During the measurement process, the measurement time is 36 minutes, and the temperature fluctuation is allowed to be ±5°C. After the injection is completed, close the valves at both ends of the clamp to allow the foaming agent solution to displace in the core for 3 hours at a confining pressure of 5.0 MPa and a constant pressure of 3.0 MPa.

[0094] ⑥ Determination of core permeability K2 after damage

[0095] According to the method in ④, the permeability K2 of the core after being damaged by the drilling fluid solution is measured, and the damage rate of the drilling fluid to the reservoir and the permeability recovery value are calculated.

[0096] (4) Experimental data

[0097] In the experiment, cores from Bozi and Dabei formations were taken. Since the formations were dense and the pressure was too high during liquid displacement, the cores were crushed by pressure clamps to increase their permeability for the permeability recovery value determination of the drilling fluid damage experiment. The core information used for the experimental determination is shown in Table 1, and the experimental results are shown in Table 2.

[0098] Table 1 Drilling fluid damage test core information

[0099]

[0100] Table 2 Drilling fluid core damage experimental data

[0101]

[0102] (5) Experimental conclusion

[0103] Water-based drilling fluids damage the permeability of the cores in the Bozi and Dabei blocks by 60% to 70%, while the damage to the permeability of oil-based drilling fluids is 40% to 50%. In comparison, oil-based drilling fluids do less damage. The degree of damage in Bozi and Dabei is basically the same, which is related to the core permeability. The greater the core permeability, the less damage.

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A core processing method for simulating a formation fracture network for reservoir damage and protection evaluation, characterized in that: The steps include: S1. Using a digital core scanning method, a numerical three-dimensional graph of the core fractures of the simulated reservoir formation is obtained, and the fracture degree and high-density mineral content of the simulated reservoir formation are calculated; S2. Prepare several core columns reflecting the composition of the reservoir formation for evaluation; S3, taking the core column prepared in S2, and forming forces in three directions of two horizontal principal stresses and overburden stratum pressure on the core column according to a preset loading mode and interval time, so that a fracture-microfracture network identical to that of the reservoir stratum rock is formed in the core; S4. Use the digital core scanning method to establish the fracture distribution of the core after fracture creation, until the fracture degree and high-density mineral content of the core column are consistent with the fracture degree and high-density mineral content of the simulated reservoir formation core, and the core processing is completed.

2. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 1 is characterized in that: S2 specifically includes the following steps: S21. Drill several circular columnar cores from rocks without cracks or microcracks and flatten them in two sections; If there are few or no cores taken from the formation to be evaluated, and it is impossible to drill cylindrical cores, a round cylindrical core can be drilled from the outcrop core of the formation with the same stratigraphic level; S22. Naturally dry the round columnar core in a drying oven to obtain a qualified core column.

3. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 2 is characterized in that: The diameter of the round columnar core is 24.5 mm and the length is 40 to 60 mm.

4. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 2 is characterized in that: In S22, if the mass change between the two weighings before and after drying is less than 1%, a qualified core column is obtained.

5. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 1 is characterized in that: S3 specifically includes the following steps: S31, take the core column prepared in S2, and wrap it with several layers of transparent tape, and reserve a certain length when wrapping the tape to control the tension; S32, take the core column wrapped with transparent tape in S31, put it into the stress clamp, and shake the handle to clamp the core; S33. After shaking the stress clamp handle, stop for 3 to 5 minutes; S34, observe the cylindrical surface and two end faces of the core column in the stress clamp, and stop loading when visible cracks appear on the cylindrical surface or end faces; S35. Release the clamping force of the stress clamp, remove the core column, rotate the core column 45°, and repeat steps S21-S24 to ensure that the cracks in the core are evenly distributed.

6. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 5 is characterized in that: In S31, the transparent tape is wound in 2 to 5 layers.

7. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 6 is characterized in that: In S3, when the permeability of the formation fracture is 0.1-10mD, the number of layers of transparent tape is 5, the reserved length of the tape is controlled within 2mm, the pressure angle of the stress clamp handle is 45°, and the interval time after a single pressure application is 5min; When the permeability of the formation crack is 10-100mD, the number of layers of transparent tape is 4, the reserved length of the tape is controlled at 4-8mm, the pressure angle of the stress clamp handle is 60°-90°, and the interval time after a single pressure application is 4-5min; When the permeability of the formation crack is 100-1000mD, the number of transparent tape winding layers is 3, the reserved length of the tape is controlled at 10-14mm, the pressure angle of the stress clamp handle is 90°, and the interval time after single pressure application is 3-4min.

8. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 5, characterized in that: In S33, the shaking angle is 45 to 90 degrees.

9. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 1, characterized in that: S4 specifically includes the following processes: Take the core column that has completed the fracture processing in S3, establish the fracture distribution of the core after fracture creation, use the digital core scanning method again to obtain the reconstructed three-dimensional figure of the fracture network of the small core after fracture creation, and calculate the fracture degree and high-density mineral content of the fracture network; If the fracture degree and high-density mineral content of a fracture network are less than the requirements of the simulated reservoir formation, the core column is placed in the stress clamp and continues to be loaded until the requirements are met.

10. The core processing method for simulating formation fracture network for reservoir damage and protection evaluation according to claim 9, characterized in that: The digital core scanning method is as follows: After X-rays penetrate the rock, they attenuate, and two-dimensional X-ray imaging is performed according to the different degrees of attenuation. The sample is then rotated for a 360° scan to obtain a series of two-dimensional projection images, which are filtered and contrast enhanced to reconstruct the rock's surrounding structure and obtain a three-dimensional model of the rock sample.

Images