Multi-cluster interlayer / in-crack temporary plugging diversion fracturing process and product preparation method

Abstract

The invention discloses a multi-cluster interlayer / in-fracture temporary plugging diversion fracturing process and a product preparation method, and particularly relates to the technical field of petroleum and natural gas exploitation, the fracturing process comprises the steps of dividing fracturing sections according to the physical property of a horizontal section reservoir of a coal-bed gas well, monitoring and automatically adjusting parameters during drifting, injecting prepad fluid to form a main fracture, and injecting sand adding fluid in a stepped mode. Preparing and injecting a temporary plugging material, injecting prepad fluid again to form a new crack, injecting sand-adding fluid into the new crack, replacing the sand-carrying fluid with clear water after fracturing, discharging the fluid and monitoring. The preparation method of the temporary plugging material comprises the steps of raw material mixing, extrusion granulation, drying, secondary extrusion granulation and the like, and the performance of the temporary plugging material is ensured through the measures of a specially designed screw structure, accurate control of temperature and humidity, addition of an auxiliary agent and the like. According to the method, the longitudinal crack coverage rate and the oil and gas recovery rate are increased, accurate control is achieved, the formation damage rate and the accident rate are reduced, it is ensured that the quality of the temporary plugging material is stable, and the formation permeability recovery rate is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and natural gas exploitation, and more specifically to a multi-cluster interlayer / intra-fracture temporary plugging and diverting fracturing process and a product preparation method. Background Art

[0002] At present, the transformation ideas of shale oil and gas reservoirs at home and abroad are mainly based on large-scale volume fracturing with multi-cluster perforation, low-viscosity fracturing fluid, large displacement and large scale. This process improves the production capacity after fracturing by significantly increasing the volume of fracture transformation. Its core principle is to shorten the distance of fluid in the matrix to flow into the fracture, reduce the driving pressure difference, and increase the contact area between the matrix and the fracture, so as to give full play to the dominant path role of natural fractures. For example, in the fracturing operations of some conventional oil and gas wells, the fracture network is made more complex by increasing the number of perforation clusters and increasing the displacement of fracturing fluid, in the hope of increasing oil and gas production.

[0003] Data-driven production in fracturing has gradually become the mainstream, such as regional geological conditions, fracture network distribution patterns, core analysis and imaging logging technology combined to determine fracture layers, etc. The parameters in production are imported into the numerical model to systematically study the production blocks. However, although these technologies help to optimize fracturing plans to a certain extent, there are still many problems in practical applications.

[0004] For coalbed methane wells, the geological conditions are different from those of shale oil and gas reservoirs. Coalbed methane wells are generally shallow and the underground temperature is relatively low (usually around 20°C), while general temporary plugging agents must be at least 60°C to dissolve, which makes conventional temporary plugging agents unsuitable for coalbed methane well fracturing operations. For example, in some coalbed methane well fracturing attempts, after using conventional temporary plugging agents, it was found that the temporary plugging agents could not be degraded in time under low temperature conditions, causing formation blockage, affecting oil and gas extraction efficiency, and even causing permanent damage to the formation.

[0005] In addition, the existing fracturing technology is still not precise enough in controlling fracture diversion. For example, some fracture diversion technologies are mostly used in conventional and unconventional oil and gas wells with relatively deep wells in China, and their application effect in coalbed methane wells is not good. The method of achieving fracture diversion by changing the injection pressure and rate of fracturing fluid is relatively simple and difficult to control accurately, which cannot meet the complex geological requirements of coalbed methane wells, resulting in unsatisfactory fracturing effects and limited improvement in oil and gas recovery rates.

[0006] Therefore, a multi-cluster interlayer / intra-fracture temporary plugging and diverting fracturing process and a product preparation method are proposed. Summary of the invention

[0007] In order to overcome the above-mentioned defects of the prior art, the present invention provides a multi-cluster interlayer / intra-fracture temporary plugging diverting fracturing process and a product preparation method to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a multi-cluster interlayer / intra-fracture temporary plugging and diverting fracturing process, comprising the following steps: S1: According to the reservoir properties of the horizontal section of the coalbed methane well, the coalbed methane well is divided into multiple fracturing sections. The fracturing sections from the bottom of the well to the wellhead are the first fracturing section, the second fracturing section, the third fracturing section...the Nth fracturing section, and then the casing is lowered into the wellbore; the method of dividing the fracturing sections is based on the three-dimensional imaging analysis of the reservoir properties of the horizontal section of the coalbed methane well, combined with the artificial intelligence algorithm to accurately identify and predict the porosity, permeability, gas content and other parameters of the reservoir, determine the optimal length and position of each fracturing section, so that the fracturing sections can achieve the maximum mutual influence and synergy to improve the fracturing effect.

[0009] S2: Use a well-draining gauge to drain the well to the bottom of the artificial well to ensure that the wellbore is clean. Use clean water as the fracturing fluid to displace the liquid in the wellbore at a rate of 0.6-1.0m³ per minute. During the well-draining process, high-precision sensors are used to monitor the changes in parameters such as pressure, temperature, and humidity in the wellbore in real time, and the data is transmitted to the ground control system. The running speed and strength of the well-draining gauge are automatically adjusted according to the feedback information to ensure that the well-draining effect is optimal and there is no damage to the wellbore.

[0010] S3: Inject pre-fluid into the wellbore at a displacement of 8.0-12.0m³ / min to form a main fracture in the coal seam; a special surfactant and nanoparticle mixture is added to the pre-fluid, which can form a protective film with extremely low surface tension on the surface of the coal seam, reducing the resistance of the fracturing fluid to enter the coal seam, while promoting the uniform expansion of the fracture and improving the quality and stability of the main fracture.

[0011] S4: The main fractures formed in step S2 are injected with sand-adding fluid in a stepped manner, and the sand-adding ratios are 3%, 5%, 10% and 15% respectively; the sand particles in the sand-adding fluid are treated with a special surface coating, and the coating material contains a degradable polymer and a metal oxide. The degradable polymer automatically decomposes after a certain period of time to avoid long-term blockage of the formation, and the metal oxide can enhance the adsorption force between the sand particles and the fracturing fluid, and improve the suspension stability of the sand particles in the fractures.

[0012] S5: Equipped with temporary plugging materials; the temporary plugging materials adopt a new composite formula, which is composed of a variety of degradable polymer materials and special additives. These degradable polymer materials include but are not limited to polylactic acid-glycolic acid copolymer (PLGA), polycaprolactone (PCL), etc. They have controllable degradation rates under different temperatures and formation conditions. Special additives can adjust the plugging strength and degradation time of the temporary plugging materials to meet different fracturing requirements.

[0013] S6: Inject the prepared temporary plugging materials into the wellbore, and the temporary plugging materials gradually enter the wellbore and the seam to form a bridge plugging. During the injection of the temporary plugging materials, the intelligent flow control system is used to accurately control the injection speed and pressure, and the injection parameters are adjusted in real time according to the pressure changes in the wellbore to ensure that the temporary plugging materials can accurately enter the predetermined position and form a stable bridge plugging structure, while avoiding unnecessary pressure shocks to the wellbore and formation.

[0014] S7: A certain amount of pre-fluid is injected again. The bridge formed by S6 causes the pre-fluid to be diverted to other holes to form new fractures. The pre-fluid injected in this step is added with tracers, which can accurately track the formation and expansion paths of new fractures in the subsequent monitoring process, providing a basis for evaluating the fracturing effect.

[0015] S8: Inject sand-adding fluid into the formed new fractures, with the sand-adding ratios being 3%, 5%, 10% and 15% respectively, to complete the fracturing of the first fracturing section, and then repeat the above steps for the subsequent fracturing sections in sequence; after the fracturing of each fracturing section is completed, use the downhole microseismic monitoring equipment to monitor the expansion of the fractures in real time, and adjust the fracturing parameters of the next fracturing section in time according to the monitoring results, so as to achieve efficient and accurate fracturing of the entire coal seam.

[0016] S9: After fracturing in each fracturing stage, use clean water to displace the sand-carrying fluid to the uppermost hole and stop pumping. During the displacement process, use layered displacement technology to accurately control the injection volume and displacement speed of clean water according to the characteristics and requirements of different fracturing stages to ensure that the sand-carrying fluid can be completely displaced to the predetermined position while avoiding damage to the already formed cracks and formations.

[0017] S10: Start the pump to discharge the sand-adding liquid and clean water in the wellbore. With the drainage and suction process, the temporary plugging material in the fracture can be completely dissolved and then discharged. During the drainage process, the online monitoring equipment is used to detect the concentration of temporary plugging materials, sand content, chemical composition and other parameters in the discharged liquid in real time. The dissolution of the temporary plugging materials and the cleanliness of the formation are judged according to the test results. When it is detected that the temporary plugging materials are completely dissolved and the various indicators of the discharged liquid meet the requirements, the drainage operation is stopped.

[0018] A method for preparing temporary plugging materials used in the above-mentioned multi-cluster interlayer / fracture temporary plugging steering fracturing process, the specific steps are: S1: Mix polyhydroxyalkanoates, polyamides, polylactic acid, chitosan, nano-silica-modified polyvinyl alcohol, compatibilizers, lubricants, antioxidants and shear thickening liquid in a high-speed mixer for 20 minutes at a speed of 300-500 rpm to obtain raw material A; wherein the polyhydroxyalkanoates are copolymers of specific structures and compositions, such as poly (3-hydroxybutyrate-co-3-hydroxyvalerate), which have unique crystallization properties and biodegradability, can achieve slow and stable degradation under low-temperature formation conditions, and have good compatibility with other components; polyamides are selected from polyamide varieties with special molecular structures, such as block copolymers of polyamide 6 and polyamide 66, which can improve the mechanical strength and heat resistance of temporary plugging materials; the nano-silica content in nano-silica-modified polyvinyl alcohol is precisely controlled between 3.5-5.5%, and this content range can significantly enhance its compressive strength and plugging performance while ensuring the flexibility of the material.

[0019] S2: Raw material A is added into a parallel twin-screw extruder from the main feeding port for granulation. The barrel temperature is 170-195°C, the screw speed is 200-300rpm, and water ring pelletizing is adopted. Cyclone separation and drying are performed to obtain granular raw material B. During the extrusion granulation process, the screw structure is specially designed, and a new screw element combination with mixing, shearing and dispersing functions is adopted to ensure that the components are fully mixed and uniformly during the extrusion process to avoid phase separation. At the same time, the temperature distribution of each section of the barrel is accurately controlled to plasticize and mix the raw materials under the optimal temperature conditions, thereby improving the quality and performance stability of the granules.

[0020] S3: Place raw material B in a vacuum drying oven, control the drying temperature to 80-95 degrees, the drying time to 8-12 hours, and control the moisture content to less than 160ppm to obtain raw material C; during the drying process, introduce an automatic humidity adjustment system to adjust the drying parameters in real time according to the humidity changes in the drying oven to ensure that the moisture in raw material B can evaporate evenly and quickly to avoid degradation of raw material performance due to local overheating or insufficient drying. At the same time, inert gas protection measures are adopted to prevent oxidation and deterioration of the raw material during the drying process.

[0021] S4: adding raw material C from the main feeding port into a parallel twin-screw extruder for granulation, with a barrel temperature of 170-195°C and a screw speed of 200-300rpm, adopting water ring granulation and cyclone separation and drying to obtain a temporary plugging material; when extruding and granulating again in this step, adding a small amount of cross-linking agent and dispersant to raw material C, the cross-linking agent can enhance the interaction between the molecular chains of the temporary plugging material, improve its stability and plugging ability under high temperature and high pressure conditions, and the dispersant helps to further improve the dispersibility of each component, so that the performance of the temporary plugging material is more uniform, and the particle size distribution of the obtained temporary plugging material is within a specific range, with good fluidity and operability.

[0022] Preferably, the compatibilizer further comprises an auxiliary compatibilizer, and the auxiliary compatibilizer is one or more of polycaprolactone, ethylene-glycidyl methacrylate copolymer, and glycidyl methacrylate.

[0023] Preferably, the chitosan is obtained by partially deacetylation of natural chitosan, and the chitosan is in granular or powder form, with a mesh size of 50 to 1800 meshes, a deacetylation degree of 40 to 85%, and a viscosity of 0.2 to 2.5 Pa.s.

[0024] Preferably, the polyhydroxyalkanoate is one or more of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), 3-hydroxybutyrate-3-hydroxyhexanoate copolyester, and poly-3-hydroxybutyrate-4-hydroxybutyrate.

[0025] Preferably, the polyamide is one or more of polyamide 6, polyamide 66, polyamide 11 and polyamide 12.

[0026] Preferably, the lubricant is a mixture of polyethylene wax and glycerin in a weight ratio of 1:1.3, and the antioxidant is composed of 1010 and 168 in a weight ratio of 1:1.2.

[0027] Technical effects and advantages of the present invention: By adding temporary plugging materials during the fracturing process of each fracturing stage, the ends of the fractures can be temporarily plugged, forcing the fracturing fluid to turn in the wellbore. Multiple fracturing stages are divided according to the reservoir properties of the horizontal section of the coalbed methane well, and the fracturing process of each fracturing stage is accurately controlled. For example, during the fracturing of the first fracturing stage, temporary plugging materials are injected after the main fracture is formed, and then the pre-fluid is injected to turn the pre-fluid to other holes to form new fractures. The subsequent fracturing stages are analogous. This method allows the fractures to be more fully expanded in the vertical and horizontal directions, and improves the coverage rate and transformation range of the vertical fractures. Compared with the traditional fracturing process, it can not only improve the coverage rate of the vertical fractures, but also expand the scope of transformation, thereby providing more seepage channels for oil and gas and improving the oil and gas recovery rate.

[0028] By using high-precision sensors to monitor the parameters in the wellbore in real time during the well clearing process and automatically adjusting the operating parameters of the well clearing gauge, optimizing the composition of the pre-fluid, specially treating the sand particles in the sand-adding fluid, accurately controlling the injection of temporary plugging materials, using tracers to track the formation and expansion paths of new cracks, and using downhole microseismic monitoring equipment to monitor the expansion of cracks in real time, precise control of the fracturing process is achieved. Through these precise control measures, the fracturing parameters can be adjusted in time according to the actual situation of the formation to ensure that the cracks expand in the expected direction and shape, avoiding problems such as excessive extension or uneven expansion of cracks, and improving the effectiveness and reliability of the fracturing operation.

[0029] Through intelligent control during the well-draining process, damage to the wellbore can be avoided. Special additives in the pre-fluid reduce the resistance of the fracturing fluid to enter the coal seam and reduce damage to the formation. Precise control of the injection of temporary plugging materials avoids pressure shock to the formation. The layered displacement technology ensures that the sand-carrying fluid displacement process does not cause damage to the formed cracks and formations. Online monitoring during the drainage process ensures the cleanliness of the formation, etc. Compared with traditional processes, it can not only reduce the formation damage rate, but also reduce the incidence of fracturing operations. It effectively protects the integrity of the formation and is conducive to the long-term stable production of oil and gas wells.

[0030] Through the specific selection and precise proportioning of raw materials such as polyhydroxyalkanoates, polyamides, and nano-silica-modified polyvinyl alcohol, the temporary plugging material has good degradation performance, mechanical strength and plugging performance under low-temperature formation conditions. By selecting polyhydroxyalkanoates with specific structures and polyamides with special molecular structures, and controlling the content of nano-silica in nano-silica-modified polyvinyl alcohol within a specific range, compared with traditional temporary plugging materials, the prepared temporary plugging material not only improves the compressive strength under simulated coal seam conditions, but also improves the plugging efficiency, so that the degradation rate within the specified time is more in line with the needs of fracturing operations.

[0031] The stability of the quality of temporary plugging materials is ensured through measures such as special screw structure design and precise barrel temperature control during extrusion granulation, automatic humidity adjustment and inert gas protection during drying, and adding additives and controlling particle size distribution during secondary extrusion. The specially designed screw structure allows each component to be fully mixed and evenly mixed to avoid phase separation. The precisely controlled drying process prevents oxidation and deterioration of the raw materials. The secondary extrusion after adding additives improves the stability and dispersibility of the material under high temperature and high pressure. This makes the performance of each batch of temporary plugging materials more consistent, reduces the risk of fracturing operations caused by fluctuations in material properties, and improves the reliability and repeatability of the fracturing process.

[0032] By combining a variety of degradable polymer materials and special additives in the composite formula of temporary plugging materials, it is possible to achieve a controllable degradation rate and good plugging strength under different temperatures and formation conditions. By adjusting the proportion of each component in the formula or adding specific additives, the temporary plugging material can adapt to the formation characteristics of different coalbed methane wells. Whether it is the change in formation temperature or the difference in formation pore structure, it can effectively play a temporary plugging and diversion role. At the same time, it can be degraded in time after the fracturing operation is completed, reducing the long-term impact on the formation, improving the permeability recovery rate of the formation, and is beneficial to the long-term production capacity maintenance of oil and gas wells. DETAILED DESCRIPTION

[0033] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention. Example 1

[0034] This embodiment 1 provides a multi-cluster interlayer / intra-fracture temporary plugging and diverting fracturing process, and the specific implementation steps are as follows: S1: Use advanced 3D imaging equipment to conduct detailed scanning and analysis of the reservoir properties of the horizontal section of the coalbed methane well to obtain 3D distribution data of parameters such as porosity, permeability, and gas content. Input these data into the artificial intelligence algorithm model, and after complex calculations and simulations, divide the coalbed methane well into 5 fracturing sections, which are marked as the first fracturing section, the second fracturing section, the third fracturing section, the fourth fracturing section, and the fifth fracturing section from the bottom of the well to the wellhead. Then, a carefully designed high-strength, corrosion-resistant casing is lowered into the wellbore to ensure that the casing fits tightly against the wellbore wall, providing a stable channel for subsequent fracturing operations.

[0035] S2: Use a high-precision well-drilling gauge for well-drilling operations. The well-drilling gauge is equipped with multiple high-precision sensors to monitor the pressure, temperature, humidity and other parameters in the wellbore in real time during the well-drilling process. When the well-drilling gauge is lowered to the bottom of the artificial well, the ground control system determines whether there is any abnormality in the wellbore based on the data fed back by the sensor. If it is found that the pressure in a certain section of the wellbore is abnormally high, the system automatically adjusts the running speed of the well-drilling gauge to make it pass through the section slowly, and at the same time increases the rotation force of the well-drilling gauge to ensure that the debris in the wellbore can be effectively removed and the wellbore is kept clean. Use clean water as the fracturing fluid, and stably displace the liquid in the wellbore at a displacement of 0.8m³ per minute. During the displacement process, continuously monitor the flow and pressure of the liquid to ensure the smooth displacement process.

[0036] S3: Prepare a specially configured pre-fluid, in which a new surfactant and nanoparticle mixture are added. The pre-fluid is injected into the wellbore at a displacement of 10.0m³ per minute. With the injection of the pre-fluid, main fractures begin to form in the coal seam. The formation process of the main fractures is observed in real time using downhole fracture monitoring instruments. It is found that due to the effect of the surfactant and nanoparticle mixture, the expansion of the main fracture is more uniform, the fracture surface is smoother, and the resistance of subsequent fracturing fluid entering the fracture is reduced.

[0037] S4: The main fractures formed were injected with sanding fluid in a step-by-step manner, with the sanding ratios being 3%, 5%, 10% and 15% respectively. The sand in the sanding fluid was treated with a special surface coating containing degradable polymers and metal oxides. During the injection of the sanding fluid, the injection speed and pressure of the sanding fluid were precisely controlled by special injection equipment to ensure that the sand could be evenly distributed in the fractures. As the fracturing operation progressed, it was observed that the suspension stability of the sand in the fractures was good, and there was no sand precipitation or aggregation, which effectively supported the fractures.

[0038] S5: Equipped with temporary plugging materials, which are made of degradable polymer materials such as polylactic acid-glycolic acid copolymer (PLGA), polycaprolactone (PCL) and special additives. These materials have undergone rigorous performance testing in the laboratory and can achieve controllable degradation rates under different temperatures and formation conditions. For example, under the condition of a simulated coal seam temperature of 25°C, the temporary plugging material begins to degrade within 72 hours, and the degradation rate reaches 80% within 168 hours, meeting the needs of formation recovery after fracturing operations.

[0039] S6: The prepared temporary plugging material is injected into the wellbore through the intelligent injection system, which can adjust the injection speed and pressure in real time according to the pressure changes in the wellbore. The temporary plugging material gradually enters the wellbore and the seam opening, forming a stable bridge plugging structure at the predetermined position. During the injection process, the downhole camera observed that the temporary plugging material was accurately filled in the cracks and holes, forming an effective plugging.

[0040] S7: A certain amount of pre-fluid with tracer added was injected again. Due to the bridge blockage formed previously, the pre-fluid was smoothly diverted to other holes to form new fractures. Using ground monitoring equipment to track the tracer signal, the formation and expansion path of new fractures were clearly observed. It was found that the new fractures were intertwined with the main fractures to form a complex fracture network, which increased the oil and gas seepage channels.

[0041] S8: Inject sand-adding fluid into the new fractures, and the sand-adding ratio is also 3%, 5%, 10% and 15% respectively. After completing the fracturing of the first fracturing stage, use the downhole microseismic monitoring equipment to comprehensively evaluate the crack expansion, and adjust the fracturing parameters of the subsequent fracturing stages according to the evaluation results. If it is found that the crack expansion in a certain area is not ideal, appropriately increase the amount of pre-fluid injection and the concentration of sand-adding fluid in that area to optimize the fracturing effect. Then follow the same steps to perform fracturing operations on the subsequent fracturing stages in turn.

[0042] S9: After each fracturing stage is completed, the layered displacement technology is used to displace the sand-carrying fluid with clean water. According to the characteristics of different fracturing stages, the injection volume and displacement speed of clean water are accurately controlled. For fracturing stages with low permeability, the injection speed of clean water is reduced and the displacement time is extended to ensure that the sand-carrying fluid can be completely displaced to the uppermost hole. During the displacement process, the pressure changes in the wellbore are monitored through the downhole pressure sensor to ensure stable pressure and avoid damage to the already formed cracks and formations.

[0043] S10: Start pumping to discharge the sand-adding liquid and clean water in the wellbore. During the drainage and suction process, use online monitoring equipment to detect the temporary plugging material concentration, sand content, chemical composition and other parameters in the discharged liquid in real time. When the concentration of the temporary plugging material is gradually reduced until it is completely dissolved, and the sand content and chemical composition in the discharged liquid meet environmental protection requirements, stop the drainage operation. At this time, the cracks in the formation form stable oil and gas seepage channels, laying a good foundation for subsequent oil and gas production. Example 2

[0044] This embodiment 2 provides a multi-cluster interlayer / intra-fracture temporary plugging and diverting fracturing process, and the specific implementation steps are: S1: Comprehensively evaluate the reservoir properties of the horizontal section of the coalbed methane well, combine geological data and field test data, and use more complex artificial intelligence algorithms to divide the fracturing sections. This time, the coalbed methane well is divided into 8 fracturing sections, and the length and position of each fracturing section are precisely adjusted according to the subtle changes in the reservoir properties to achieve refined fracturing of the coal seam. The casing with a special sealing structure is lowered into the wellbore. This casing can effectively prevent the leakage of liquid and gas in the wellbore and improve the safety of the fracturing operation.

[0045] S2: Use a high-precision well gauge to clear the well to the bottom of the artificial well. The sensor on the well gauge transmits the parameters in the wellbore to the ground control system in real time. During the well clearing process, if a slightly deformed area is found in the wellbore, the ground control system automatically adjusts the shape of the well gauge to better adapt to the shape of the wellbore to ensure that the wellbore is clean. Use clean water at a displacement of 0.9m³ per minute to displace the liquid in the wellbore, and install a flow stabilizer at the wellhead to ensure the stability of the flow during the displacement process.

[0046] S3: A pre-fluid with a special surfactant and nanoparticle mixture was added and injected into the wellbore at a rate of 11.0 m³ / min. During the injection process, the temperature change of the coal seam was monitored by the downhole temperature sensor, and the concentration of the surfactant and nanoparticles in the pre-fluid was adjusted according to the temperature change to ensure that the best crack formation effect can be achieved under different temperature conditions. It was observed that the width and length of the main cracks formed in the coal seam were in line with expectations, and the crack wall was relatively flat.

[0047] S4: The main fractures are injected with sanding fluid in a stepped manner, with the sanding ratios being 3%, 5%, 10% and 15% respectively. The surface coating of the sand particles in the sanding fluid is a combination of degradable polymers and metal oxides, which can maintain stable performance under different formation pressures. When injecting the sanding fluid, the downhole pressure monitoring system is used to monitor the pressure changes in the fractures in real time, and the injection speed of the sanding fluid is adjusted according to the pressure changes, so that the sand particles can be evenly distributed in the fractures to form an effective support structure.

[0048] S5: Temporary plugging materials are used. The ratio of polylactic acid-co-glycolic acid (PLGA) and polycaprolactone (PCL) in the composite formula of the temporary plugging materials has been optimized, and a small amount of biological enzymes have been added as special additives. This biological enzyme can accelerate the degradation of the temporary plugging materials under specific formation conditions. Tests conducted under laboratory simulated formation conditions have shown that the plugging strength of the temporary plugging materials can remain stable during the fracturing operation. After the fracturing operation is completed, as the formation environment changes, the biological enzymes begin to play a role, and the degradation rate of the temporary plugging materials is significantly accelerated.

[0049] S6: Inject temporary plugging materials into the wellbore. During the injection process, an intelligent flow control system is used, which can automatically adjust the injection parameters of the temporary plugging materials according to the changes in the pressure and flow in the wellbore. Through the downhole camera, it is observed that the temporary plugging materials quickly form a bridge plugging structure in the wellbore and the seam, and the bridge plugging structure has good stability and can withstand certain pressure shocks.

[0050] S7: Pre-fluid with tracers added was injected, and the distribution of tracers was tracked using high-precision ground monitoring equipment. It was found that the formation direction and expansion range of the new fractures were consistent with expectations. The new fractures were interconnected with the main fractures, forming a more complex fracture network, which greatly improved the seepage capacity of oil and gas.

[0051] S8: Inject sand-adding fluid into the new fracture, and the sand-adding ratio is 3%, 5%, 10% and 15% respectively. After completing the first fracturing stage, the fracture expansion is analyzed in detail, including the length, width, height, direction and other parameters of the fracture. According to the analysis results, the fracturing parameters of the subsequent fracturing stages are optimized and adjusted, such as adjusting the injection sequence and injection volume of the pre-fluid and the sand-adding fluid. Then, the subsequent fracturing stages are fracturing in sequence according to the optimized plan.

[0052] S9: After fracturing, the layered displacement technology is used to replace the sand-carrying fluid with clean water. According to the formation characteristics of different fracturing sections, a personalized displacement plan is formulated. For example, for the fracturing section with larger porosity, the injection volume of clean water is appropriately increased to ensure that the sand-carrying fluid can be completely displaced. During the displacement process, the downhole acoustic wave monitoring technology is used to monitor the flow state of the liquid in the wellbore in real time to ensure that the displacement process proceeds smoothly and avoid damage to the formation.

[0053] S10: Start pumping to discharge the sand-adding liquid and clean water in the wellbore. During the discharge process, the online monitoring equipment detects various parameters of the discharged liquid in real time. When the concentration of temporary plugging material in the discharged liquid drops to an extremely low level, the sand content meets the discharge standard, and the chemical composition is stable, the discharge operation is stopped. At this time, the temporary plugging material in the formation has been basically completely dissolved, and the fracture system is in the best state for oil and gas production. Example 3

[0054] This embodiment 3 provides a method for preparing a temporary plugging material, and the steps for preparing the temporary plugging material are as follows: S1: Accurately weigh 18g of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) as polyhydroxyalkanoate, 28g of block copolymer of polyamide 6 and polyamide 66 as polyamide, 42g of polylactic acid, 22g of chitosan, 18g of nanosilica-modified polyvinyl alcohol with a nanosilica content of 4.5%, 12g of compatibilizer (including 8g of polycaprolactone and 4g of ethylene-methacrylate copolymer), 0.6g of lubricant composed of polyethylene wax and glycerol in a weight ratio of 1:1.3, 0.6g of antioxidant composed of 1010 and 168 in a weight ratio of 1:1.2, and the remainder of shear thickening liquid. Add these raw materials into a high-speed mixer and mix at a speed of 400rpm for 20min to obtain raw material A. During the mixing process, the special stirring paddle design allows the raw materials to form strong convection and shearing effects in the mixer to ensure that the components are fully mixed and uniform.

[0055] S2: Add raw material A from the main feed port to the parallel twin-screw extruder for granulation. The barrel temperature is set to 180°C (the temperature of the front section of the barrel is 170°C, the temperature of the middle section is 180°C, and the temperature of the rear section is 190°C), and the screw speed is 250rpm. A water ring pelletizing device with a special flow channel structure is used for pelletizing. The flow channel structure can make the pelletizing process smoother and reduce the adhesion and deformation of the particles. The pelletized pellets are dried by a cyclone separation drying system to obtain pelletized raw material B. During the extrusion granulation process, the material parameters such as temperature, pressure and torque are monitored in real time by online monitoring equipment to ensure the stability of the extrusion process.

[0056] S3: Place the raw material B in a vacuum drying oven, turn on the automatic humidity adjustment system, control the drying temperature at 90 degrees, and set the drying time to 10 hours. During the drying process, continuously introduce inert gas (such as nitrogen) into the drying oven to prevent oxidation and deterioration of the raw material. After drying, the moisture content of raw material B is controlled at 120ppm, and raw material C is obtained.

[0057] S4: Add 0.5% (mass fraction) of cross-linking agent and 0.3% (mass fraction) of dispersant to raw material C, and then add it to the parallel twin-screw extruder from the main feed port for granulation again. The barrel temperature is still 180°C (the temperature of the front section of the barrel is 175°C, the temperature of the middle section is 180°C, and the temperature of the rear section is 185°C), and the screw speed is 280rpm. The optimized water ring pelletizing process is used for pelletizing to obtain temporary plugging materials. The performance of the prepared temporary plugging material was tested, and the results showed that its compressive strength was 30% higher than that of traditional temporary plugging materials, and the plugging efficiency under simulated formation conditions reached more than 95%, and it began to degrade within 72 hours, and the degradation rate reached 70% within 144 hours, meeting the requirements of coalbed methane well fracturing operations for the performance of temporary plugging materials. Example 4

[0058] This embodiment 4 provides a method for preparing a temporary plugging material, and the steps for preparing the temporary plugging material are as follows: S1: Weigh 15g of poly-3-hydroxybutyrate-4-hydroxybutyrate as polyhydroxyalkanoate, 25g of polyamide 11, 38g of polylactic acid, 18g of chitosan, 16g of nanosilica-modified polyvinyl alcohol with a nanosilica content of 5.0%, 10g of compatibilizer (including 6g of ethylene-glycidyl methacrylate copolymer and 4g of glycidyl methacrylate), 0.5g of lubricant composed of polyethylene wax and glycerol in a weight ratio of 1:1.3, 0.5g of antioxidant composed of 1010 and 168 in a weight ratio of 1:1.2, and the remainder of shear thickening liquid. These raw materials were placed in a high-speed mixer and mixed at a speed of 350rpm for 20min to obtain raw material A. During the mixing process, ultrasonic assisted mixing technology was used to further improve the mixing uniformity of each component.

[0059] S2: Raw material A is added to the parallel twin-screw extruder from the main feed port for granulation. The barrel temperature is set to 175°C (the barrel front section temperature is 170°C, the middle section temperature is 175°C, and the rear section temperature is 180°C), and the screw speed is 220rpm. A new water ring pelletizing die is used for pelletizing, which can make the pellet size more uniform after pelletizing. The pelletized pellets are dried by a cyclone separation drying device to obtain pelletized raw material B. During the extrusion granulation process, the screw pitch and thread depth are adjusted to optimize the material conveying and mixing effects.

[0060] S3: Place the raw material B in a vacuum drying oven, start the automatic humidity adjustment system, control the drying temperature at 85 degrees, and set the drying time to 11 hours. During the drying process, maintain a stable supply of inert gas to prevent oxidation of the raw material. After drying, the moisture content of raw material B reaches 100ppm, and raw material C is obtained.

[0061] S4: Add 0.4% (mass fraction) of cross-linking agent and 0.2% (mass fraction) of dispersant to raw material C, and then add it from the main feed port to a parallel twin-screw extruder for secondary granulation. The barrel temperature is maintained at 175°C (the temperature of the front section of the barrel is 172°C, the temperature of the middle section is 175°C, and the temperature of the rear section is 178°C), and the screw speed is 260rpm. The temporary plugging material is obtained by pelletizing using the improved water ring pelletizing method. The performance of the temporary plugging material was evaluated, and it was found that its stability under high temperature and high pressure conditions was improved by 25%, and its plugging ability was enhanced by 20%. When the simulated formation temperature was 20°C, the degradation rate reached 80% within 96 hours, which effectively solved the problems existing in traditional temporary plugging materials in coalbed methane well fracturing operations.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. Multi-cluster interlayer / intra-fracture temporary plugging and diversion fracturing process, characterized by: The following steps are involved: S1: According to the reservoir physical properties of the horizontal section of the coalbed methane well, the coalbed methane well is divided into multiple fracturing sections, and the fracturing sections from the bottom of the well to the wellhead are the first fracturing section, the second fracturing section, the third fracturing section...the Nth fracturing section, and then the casing is lowered into the wellbore; the method of dividing the fracturing sections is based on the three-dimensional imaging analysis of the reservoir physical properties of the horizontal section of the coalbed methane well, combined with the artificial intelligence algorithm to accurately identify and predict the porosity, permeability, gas content and other parameters of the reservoir, and determine the optimal length and position of each fracturing section; S2: Use a well-draining gauge to drain the well to the bottom of the artificial well to ensure that the wellbore is clean. Use clean water as the fracturing fluid to displace the liquid in the wellbore at a rate of 0.6-1.0m³ per minute. During the well-draining process, use high-precision sensors to monitor the changes in parameters such as pressure, temperature, and humidity in the wellbore in real time, and transmit the data to the ground control system. According to the feedback information, the running speed and strength of the well-draining gauge are automatically adjusted to ensure that the well-draining effect is optimal and there is no damage to the wellbore; S3: Inject pre-fluid into the wellbore at a rate of 8.0-12.0 m³ / min to form main fractures in the coal seam; S4: the main cracks formed in step S2 are injected with sand-adding liquid in a stepwise manner, and the sand-adding ratios are 3%, 5%, 10% and 15% respectively, and the sand particles in the sand-adding liquid are treated with a special surface coating, and the coating material includes a degradable polymer and a metal oxide; S5: Temporary plugging materials are provided. The temporary plugging materials are composed of a variety of degradable polymer materials and special additives. The degradable polymer materials include but are not limited to polylactic acid-glycolic acid copolymer (PLGA) and polycaprolactone (PCL). The special additives are used to adjust the plugging strength and degradation time of the temporary plugging materials to meet different fracturing requirements. S6: Inject the prepared temporary plugging material into the wellbore, and the temporary plugging material gradually enters the wellbore and the seam to form a bridge plug. During the injection of the temporary plugging material, the intelligent flow control system is used to accurately control the injection speed and pressure, and the injection parameters are adjusted in real time according to the pressure changes in the wellbore to ensure that the temporary plugging material can accurately enter the predetermined position and form a stable bridge plugging structure, while avoiding unnecessary pressure shocks to the wellbore and formation; S7: inject a certain amount of pre-fluid again. The bridge formed by S6 causes the pre-fluid to be diverted to other holes to form new fractures. The pre-fluid injected in this step is added with a tracer to accurately track the formation and expansion path of new fractures in the subsequent monitoring process, providing a basis for evaluating the fracturing effect; S8: injecting sand-adding fluid into the formed new fractures, with the sand-adding ratios being 3%, 5%, 10% and 15% respectively, to complete the fracturing of the first fracturing stage, and then repeating the above steps to use the subsequent fracturing stages in sequence. After the fracturing of each fracturing stage is completed, the expansion of the fractures is monitored in real time using the downhole microseismic monitoring equipment, and the fracturing parameters of the next fracturing stage are adjusted in time according to the monitoring results, so as to achieve efficient and accurate fracturing of the entire coal seam; S9: After fracturing at each fracturing stage, the sand-carrying fluid is displaced to the uppermost hole with clean water, and pumping is stopped. During the displacement process, the layered displacement technology is adopted to accurately control the injection volume and displacement speed of clean water according to the characteristics and requirements of different fracturing stages to ensure that the sand-carrying fluid can be completely displaced to the predetermined position and avoid damage to the formed cracks and formations; S10: Start the pump to discharge the sand-adding liquid and clean water in the wellbore. With the process of drainage and suction, the temporary plugging material in the seam can be completely dissolved and then discharged. During the drainage process, the online monitoring equipment is used to detect the concentration of temporary plugging materials, sand content, chemical composition and other parameters in the discharged liquid in real time. The dissolution of the temporary plugging material and the cleanliness of the formation are judged according to the test results. When it is detected that the temporary plugging material is completely dissolved and the various indicators of the discharged liquid meet the requirements, the drainage operation is stopped.

2. The multi-cluster interlayer / intra-fracture temporary plugging and diverting fracturing process according to claim 1 is characterized in that: The S3 prefluid contains a mixture of special surfactants and nanoparticles, which is used to form a protective film with extremely low surface tension on the surface of the coal seam, reducing the resistance of the fracturing fluid entering the coal seam, while promoting uniform expansion of the cracks and improving the quality and stability of the main cracks.

3. The multi-cluster interlayer / intra-fracture temporary plugging and diverting fracturing process according to claim 1 is characterized in that: The degradable polymer in S4 can automatically decompose after a certain period of time to avoid long-term blockage of the formation, and cooperates with metal oxides to enhance the adsorption force between sand particles and fracturing fluid to improve the suspension stability of sand particles in the cracks.

4. A method for preparing temporary plugging materials for use in the multi-cluster interlayer / intra-fracture temporary plugging diversion fracturing process according to any one of claims 1 to 3, characterized in that: The specific steps are: S1: Mix polyhydroxyalkanoate, polyamide, polylactic acid, chitosan, nano-silica modified polyvinyl alcohol, compatibilizer, lubricant, antioxidant and shear thickening liquid in a high-speed mixer for 20 minutes at a speed of 300-500rpm to obtain raw material A; wherein the polyhydroxyalkanoate is a copolymer with a specific structure and composition for achieving slow and stable degradation under low-temperature formation conditions and has good compatibility with other components; the polyamide is used to improve the mechanical strength and heat resistance of the temporary plugging material; the nano-silica content in the nano-silica modified polyvinyl alcohol is precisely controlled between 3.5-5.5%, so as to significantly enhance its compressive strength and plugging performance while ensuring the flexibility of the material within this content range; S2: Raw material A is added into a parallel twin-screw extruder from the main feed port for granulation. The barrel temperature is 170-195°C, the screw speed is 200-300rpm, water ring granulation is adopted, and cyclone separation and drying are performed to obtain granular raw material B. During the extrusion granulation process, the screw structure is specially designed; S3: placing raw material B in a vacuum drying oven, controlling the drying temperature to 80-95 degrees, the drying time to 8-12 hours, and controlling the moisture content to be less than 160ppm, to obtain raw material C; during the drying process, introducing an automatic humidity adjustment system, and adjusting the drying parameters in real time according to the humidity changes in the drying oven, so as to ensure that the moisture in raw material B can evaporate evenly and quickly, and avoid the degradation of raw material performance due to local overheating or insufficient drying, and at the same time adopting inert gas protection measures to prevent the raw material from oxidation and deterioration during the drying process; S4: adding raw material C from the main feeding port into a parallel twin-screw extruder for granulation, with a barrel temperature of 170-195°C and a screw speed of 200-300rpm, adopting water ring granulation, and cyclone separation and drying to obtain a temporary plugging material; when extruding and granulating again in this step, adding a small amount of cross-linking agent and dispersant to raw material C, the cross-linking agent is used to enhance the interaction between the molecular chains of the temporary plugging material, improve its stability and plugging ability under high temperature and high pressure conditions, and the dispersant is used to further improve the dispersibility of each component, so that the performance of the temporary plugging material is more uniform, and the particle size distribution of the obtained temporary plugging material is within a specific range, with good fluidity and operability.

5. The method for preparing temporary plugging material according to claim 4, characterized in that: The specially designed screw structure adopts a new screw element combination with mixing, shearing and dispersing functions to ensure that the components are fully mixed and evenly during the extrusion process to avoid phase separation. At the same time, the temperature distribution of each section of the barrel is accurately controlled to plasticize and mix the raw materials under the optimal temperature conditions, thereby improving the quality and performance stability of the pellets.

6. The method for preparing temporary plugging material according to claim 4, characterized in that: The compatibilizer further comprises an auxiliary compatibilizer, and the auxiliary compatibilizer is one or more of polycaprolactone, ethylene-glycidyl methacrylate copolymer, and glycidyl methacrylate.

7. The method for preparing temporary plugging material according to claim 4, characterized in that: The chitosan is obtained by partially deacetylation of natural chitosan. The chitosan is granular or powdery, with a mesh number of 50 to 1800 meshes, a deacetylation degree of 40 to 85%, and a viscosity of 0.2 to 2.5 Pa.s.

8. The method for preparing temporary plugging material according to claim 4, characterized in that: The polyhydroxyalkanoate is one or more of poly (3-hydroxybutyrate-co-3-hydroxyvalerate), 3-hydroxybutyrate-3-hydroxyhexanoate copolyester, and poly-3-hydroxybutyrate-4-hydroxybutyrate.

9. The method for preparing temporary plugging material according to claim 4, characterized in that: The polyamide is one or more of polyamide 6, polyamide 66, polyamide 11 and polyamide 12.

10. The method for preparing temporary plugging material according to claim 4, characterized in that: The lubricant is a mixture of polyethylene wax and glycerin in a weight ratio of 1:1.3, and the antioxidant is composed of 1010 and 168 in a weight ratio of 1:1.2.