A method for combined fracturing and expansion of horizontal well groups in shale oil production

Abstract

This invention discloses a method for coordinated fracturing with energy replenishment and fracture expansion in shale oil horizontal well groups. It includes the following steps: A: Modeling and simulating to optimize CO2 injection parameters in production wells, and implementing CO2 injection for pressurization and energy replenishment in advance; B: Conducting fracturing operations on new wells in the shale oil horizontal well group, fracturing in sequence from the outside to the inside; C: Performing differentiated fracturing of the horizontal fracturing section of a single well, dividing the horizontal section into three regions, and designing the perforation, segmentation, and scale parameters of each region differently; D: After fracturing each horizontal well in the shale oil horizontal well group, the well is shut down, and production is initiated when the wellhead pressure reaches a stable level. The advantages are: improved energy utilization and stimulation efficiency, successful coordinated fracturing with energy replenishment and fracture expansion in the well group, solving the optimization problem of production wells and wells awaiting fracturing under horizontal well network conditions, maximizing the stimulation effect and reservoir utilization of the horizontal well group, improving the well group recovery rate, and fully releasing the reservoir's potential for increased production.

Description

Technical Field

[0001] This invention relates to a hydraulic fracturing technology for oil and gas field exploration and development, specifically to a shale oil horizontal well group energy supplementation and fracture expansion synergistic fracturing method. Background Technology

[0002] The shale oil reservoirs in the structurally stable Fu-2 Member of the Qintong Depression in the Subei Basin have well-developed laminae, are relatively homogeneous, and range in thickness from 200 to 480 meters. However, they have low permeability and require large-scale fracturing to improve reservoir permeability. This involves creating a hydraulic fracturing network connected to the horizontal wellbore, allowing crude oil in the low-permeability reservoirs to flow more easily into the wellbore to provide production capacity. During development, a single exploration and evaluation well will be deployed first. After a period of production to achieve a breakthrough, multiple horizontal wells will be deployed to form a platform well group for development.

[0003] During well fracturing, the formation pressure deficit caused by production wells significantly alters the in-situ stress field of the reservoir. The artificially created fractures and natural fractures in both production and fracturing wells induce inter-well interference, resulting in varying levels of communication responses. This affects the fracturing effect of the fracturing wells and damages the well network's productivity. After production wells resume production, the wellhead pressure of the fracturing wells drops significantly, production wells experience severe fluid accumulation and high water cut, which can lead to sand blowouts, casing deformation and failure, and limited production capacity. Currently, conventional horizontal well fracturing processes involve similar segment lengths and construction scales. The difficulty and pressure of sand addition decrease from the toe to the root of the horizontal well, exhibiting a certain degree of uniformity in the construction process. There is a lack of systematic and scientific improvement methods, necessitating innovative approaches to achieve technological leaps and advancements. Summary of the Invention

[0004] To address the issue of suppressing inter-well interference induced by well fracturing in well groups, the technical problem this invention aims to solve is to provide a shale oil horizontal well group energy replenishment and fracture expansion co-fracturing method that can simultaneously ensure efficient and coordinated transformation of horizontal well groups and full utilization of well network reserves.

[0005] To solve the above-mentioned technical problems, the present invention provides a shale oil horizontal well group energy replenishment and fracture expansion synergistic fracturing method, comprising the following steps:

[0006] A: Modeling and simulation to optimize CO2 injection parameters for production wells in shale oil horizontal well groups, and implement CO2 injection to boost pressure and replenish energy in production wells in advance;

[0007] In this step, a three-dimensional finite element geomechanical model of the shale oil horizontal well group and a three-dimensional shale gas seepage model are established. Using the three-dimensional pore pressure change as the boundary condition, the changes in geostress at different times after production well pressure are calculated, and the pore pressure and geostress wave range of the production well for long-term production are finally determined. Then, CO2 injection is simulated to enhance the pressure and energy of the production area, the optimal CO2 injection rate is determined, and CO2 injection is implemented in the production well to increase the formation pressure in the production well fracture network and well group area.

[0008] B: Conduct fracturing operations on new horizontal wells in shale oil well groups, fracturing in sequence from the outside to the inside;

[0009] In this step, the outermost horizontal well in the shale oil horizontal well group is selected first for fracturing, and then each well is fracturing sequentially from the outside to the inside. The fracturing processes of the two outer horizontal wells are connected, and the process conversion is achieved through the diversion manifold. A set of fracturing trucks is used to carry out uninterrupted alternating zipper-style fracturing of the two wells.

[0010] C: Conduct differentiated fracturing of the horizontal fracturing section of a single well, dividing the horizontal section into 3 regions, and designing the perforation, segmentation, and scale parameters of each region differently; use a low-viscosity fracturing fluid system, large displacement, and large fluid volume to create a complex fracture network;

[0011] D: After fracturing each horizontal well in the shale oil horizontal well group, the well is shut down. When the wellhead pressure has diffused to a stable level, the well is opened and production is initiated.

[0012] In step A, a small-layer-level structural stratigraphic matrix model of the well group area is established. Seismic inversion porosity volume and saturation volume are used as trend constraints, and the sequential Gaussian method is applied to establish a matrix property model.

[0013] A fracture model was established. Based on seismic data and the properties of ant bodies, the overall distribution of fractures in the well group area was determined. Combined with the fracture development intensity from well logging, large-scale, medium-scale, and small-scale DFN fracture models were established.

[0014] A geostress model was established. Based on the three-dimensional geological model, a geostress field model was constructed using finite element simulation based on the well group brittleness index, rock mechanical characteristic parameters, and fracture distribution and geostress orientation parameters obtained from imaging logging.

[0015] A reservoir-fluid-rock model was established based on monitoring data of fracturing stimulation of production wells, stimulation SRV, and fracture morphology. Considering reservoir damage and fracturing, matrix loss, and the interaction deformation between rock and fracture, a fracture network expansion model for production wells was established. The dynamic evolution of in-situ stress after fracturing of production wells was evaluated, and the pore pressure and in-situ stress sweep range of production wells were determined. The differences in reservoir properties and flow media were characterized by zonal relative permeability, and an equivalent permeability field for fracture distribution was established.

[0016] In step A, the CO2 injection scale is optimized by simulating different injection volumes, and the injection volume that significantly increases oil production is selected. CO2 injection into production wells is then implemented ahead of schedule. After the injection scale is completed, fracturing operations are carried out on the wells in the well group awaiting fracturing. The well-closing time is determined based on pressure diffusion simulation optimization, or well production is initiated after the well-closing pressure has stabilized.

[0017] In step C, an innovative biomimetic fracturing mode is adopted, and the zoned differentiated and efficient transformation is carried out. The differentiated biomimetic fracturing imitates the three-stage flight feather pattern of bird wings and differentiates the process parameters of the horizontal well, which are divided into three zones.

[0018] In step C, Region 1 adopts a short-segment, long-cluster pattern, with segment lengths of 45-60m, 3-5 clusters of perforations per segment, and 24-30 perforations per segment. The perforation method is annular perforation.

[0019] In step C, region two adopts a medium-length, medium-cluster pattern, with segment lengths of 60-80m, 6-8 clusters of perforations per segment, and a perforation method of flow restriction + spiral perforation, with 32-40 perforations per segment.

[0020] In step C, region three adopts a long segment and multiple clusters pattern, with segment lengths of 80-100m, 9-12 clusters of perforations per segment, and the perforation method is flow restriction + spiral perforation, with 45-60 perforations per segment.

[0021] In step C, the differentiated biomimetic fracturing mode gradually increases the amount of fluid injected into the ground and the proppant dosage in each fracturing segment as the fracturing segment depth decreases. For every 60-80 meters decrease in depth, the amount of fluid injected into the ground and the proppant dosage in a single segment increase by 3%-6%.

[0022] In step C, the differentiated biomimetic fracturing mode considers the optimization of single-well fracturing scale to prevent cross-flow between wells. Based on the well group geomechanical model, it imports wellbore, perforation and process parameters to calculate the fracturing fractures and optimizes the critical construction parameters for preventing cross-flow in different well sections as the upper limit of the actual construction scale.

[0023] During fracturing, the differentiated biomimetic fracturing mode requires a composite temporary plugging process in the medium and long-segment multi-cluster patterns of Region 2 and Region 3 to increase the complexity of the fracture network, increase the affected area, and promote the spread of artificial fractures throughout the reservoir, thereby maximizing reservoir control through fractures.

[0024] The advantages of this invention are:

[0025] Compared with existing technologies, this invention addresses the severe interference of new well fracturing in horizontal well groups of shale oil reservoirs with existing production wells. It adopts a method of pre-injecting CO2 to boost pressure and energy in production wells before implementing fracturing in new wells of the well group, proceeding from the outside in. Different fracturing modes are used in individual wells, with different process parameters applied to different areas, improving energy utilization and stimulation efficiency. This achieves coordinated fracturing with energy replenishment and fracture widening of the well group. In particular, CO2 injection to boost pressure and energy replenishment in the depleted areas of production wells in horizontal well groups mitigates the negative effects of inter-well interference. Simultaneously, the viscosity reduction, extraction, and permeability enhancement effects of CO2 significantly increase oil production in production wells and improve the overall recovery rate of the well group. Simultaneously, an innovative biomimetic zonal fracturing mode along the horizontal section of horizontal wells was developed. Based on energy equivalent work, this mode makes differentiated regional transformation of horizontal well groups more grounded and operable, improves energy utilization, and achieves accelerated, cost-effective development. It enables full and effective transformation of the entire area of ​​horizontal well groups under well network conditions, with fractures covering the oil reservoir of the well group and achieving a control level of over 95%. This solves the problem of negative interference between production wells and fracturing wells under well network conditions, maximizes the transformation effect of horizontal well groups and the degree of reservoir utilization, improves the recovery rate of well groups, and fully releases the potential for increased oil production in reservoirs. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the horizontal well group in this invention.

[0027] Figure 2 This is a schematic diagram of the biomimetic differentiated zoning of shale oil horizontal wells in this invention.

[0028] Figure 2 In the middle: 1-Horizontal well vertical section, 2-Horizontal wellbore, 3-Regional boundary line, 4-Region 1 (short section length + few clusters), 5-Region 2 (medium section length + medium clusters), 6-Region 3 (long section length + many clusters) Detailed Implementation

[0029] The following detailed description of the shale oil horizontal well group energy replenishment and fracture expansion synergistic fracturing method of the present invention, with reference to the accompanying drawings and specific embodiments, will be further elaborated.

[0030] As shown in the figure, the shale oil horizontal well group energy replenishment and fracture expansion combined fracturing method of the present invention mainly involves injecting CO2 into the production wells of the shale oil horizontal well group in advance to replenish energy and increase formation pressure during the development of the shale oil reservoir horizontal well group; then fracturing new wells in sequence from the outside to the inside, with two wells fracturing continuously and alternately in a zipper-like manner, and a differentiated zonal fracturing mode for each well; until all wells in the well group have been fracturing, the specific steps include:

[0031] A: Modeling and simulation to optimize CO2 injection parameters for production wells in shale oil horizontal well groups, and implement CO2 injection to boost pressure and replenish energy in production wells in advance;

[0032] Pre-injection of CO2 into production wells for protective pressurization increases stress and pore pressure in existing producing areas, establishes a high-pressure zone to prevent hydraulic fractures from suddenly connecting in new wells, thereby reducing the negative effects of inter-well interference and fully remodeling the reservoir. Compared to water injection for energy replenishment, CO2 has multiple benefits. The pore volume that CO2 can enter is smaller than that of water, enabling diffusion extraction in the dense shale oil matrix. Indoor nuclear magnetic resonance experiments show that while water can enter pore throats larger than 0.1 μm, CO2 can enter pore throats larger than 0.01 μm, improving replacement efficiency.

[0033] CO2 injection has the mechanisms of "expansion and energy enhancement, dissolution and viscosity reduction, hydrocarbon extraction, dissolution and permeability enhancement, and diffusion and replacement". After CO2 injection, the volume of crude oil can expand by 2 times, effectively replenishing the formation energy. After CO2 injection and dissolution, the viscosity of crude oil is reduced by up to 76%, significantly improving the flowability of crude oil. Moreover, after CO2 injection, the content of carbonate minerals in the reservoir is greatly reduced, calcite and dolomite are almost completely dissolved, and the permeability increases by 1-3 orders of magnitude.

[0034] In this step, based on the results of three-dimensional geological modeling, and considering Hooke's law and the effective stress law, a three-dimensional finite element geomechanical model and a three-dimensional shale gas seepage model are established. With the three-dimensional pore pressure change as the boundary condition, the changes in geostress at different times after the production well is pressured are calculated, and finally the pore pressure and geostress wave range of the production well for long-term production are determined.

[0035] Specifically, a small-layer structural stratigraphic matrix model was established for the horizontal well group region. Seismic inversion porosity and saturation volumes were used as trend constraints, and the sequential Gaussian method was applied to establish a matrix property model.

[0036] Specifically, a fracture model is established. Based on seismic data and the properties of ant bodies, the overall distribution of fractures in the well group area is determined. Combined with the fracture development intensity from well logging, large-scale, medium-scale, and small-scale DFN fracture models are established.

[0037] Specifically, a geostress model is established, using the brittleness index of the well group, rock mechanical characteristic parameters, and fracture distribution and geostress orientation parameters obtained from imaging logging. Based on the three-dimensional geological model, a geostress field model is constructed using finite element simulation.

[0038] Specifically, a reservoir-fluid-rock model is established based on monitoring data of fracturing stimulation of production wells, stimulation SRV, and fracture morphology. Considering reservoir damage and fracturing, matrix filtration loss, and interaction deformation between rock and fractures, a fracturing network expansion model for production wells is established. The dynamic evolution of in-situ stress after fracturing of production wells is evaluated, and the pore pressure and in-situ stress sweep range of production wells are determined. The differences in reservoir properties and flow media are characterized by zonal relative permeability, and an equivalent permeability field for fracture distribution is established.

[0039] Specifically, the CO2 injection scale is optimized by simulating different injection volumes and comparing the oil increase effect and oil exchange rate. The injection volume with a significant increase in oil volume is selected, and the bottom hole pressure rises rapidly after gas diffusion, thereby reducing interference. The well stagnation time is optimized by simulating pressure diffusion, or well production is started when the stagnation pressure tends to stabilize. If the stagnation time is too short, the reaction with the formation fluid is insufficient, resulting in waste; if the stagnation time is too long, gas diffusion will be severe, and CO2 will not be able to carry crude oil out, reducing utilization.

[0040] B: Conduct fracturing operations on new horizontal wells in shale oil well groups, fracturing in sequence from the outside to the inside;

[0041] In this step, the outermost horizontal well in the shale oil horizontal well group is selected first for fracturing, and then each well is fracturing sequentially from the outside to the inside; the fracturing processes of the two outer horizontal wells are connected, and the process conversion is achieved through the diversion manifold, and a set of fracturing trucks is used to carry out uninterrupted alternating zipper-style fracturing of the two wells.

[0042] Specifically, sequential fracturing from the outside to the inside concentrates energy within the well group, forming a high-pressure zone, increasing the formation pressure coefficient, reducing the horizontal stress difference, altering the original stress field, and increasing the complexity of the stimulation process.

[0043] C: Conduct differentiated fracturing of the horizontal fracturing section of a single well, dividing the horizontal section into 3 regions, and designing the perforation, segmentation, and scale parameters of each region differently; use a low-viscosity fracturing fluid system, large displacement, and large fluid volume to create a complex fracture network;

[0044] Specifically, based on the principle of energy equivalence, under high-volume fracturing conditions, the fracturing fluid flows at high speed within a 115mm inner diameter pipe, generating significant shear force that is proportional to the velocity gradient. Higher flow velocities result in greater shear force, and high-volume fracturing leads to substantial frictional resistance between the fluid and the pipe wall. Furthermore, longer wellbore lengths increase frictional resistance, leading to greater energy loss and reduced rock-breaking and fracture-creating energy. An innovative biomimetic fracturing model is adopted, employing zoned, differentiated, and efficient fracturing to improve fracture-creating efficiency.

[0045] Specifically, the differentiated biomimetic fracturing process mimics the three-stage flight feather pattern of a bird's wing (outer primary flight feathers - thicker shaft, large and sparse wings; secondary flight feathers - medium shaft, medium wings; tertiary flight feathers - thinner shaft, small and dense wings). The process parameters of the horizontal well are designed in a differentiated biomimetic manner and divided into three regions.

[0046] Furthermore, the differentiated biomimetic fracturing, in Region 1, adopts a short-segment, long-cluster pattern, with segment lengths of 45-60m, 3-5 clusters of perforations per segment, and 24-30 perforations per segment. The perforation method is annular perforation and large-diameter ejection perforation, which reduces the friction of the perforation holes, is conducive to energy accumulation, and improves the ability to create fractures inside the fracture.

[0047] Furthermore, in the differentiated biomimetic fracturing, Region 2 adopts a medium-length, medium-cluster pattern, with segment lengths of 60-80m and 6-8 clusters of perforations per segment. The perforation method is flow restriction + spiral perforation, with 32-40 perforations per segment.

[0048] Furthermore, the differentiated biomimetic fracturing, in Region 3, adopts a long-segment, multi-cluster pattern, with segment lengths of 80-100m and 9-12 clusters of perforations per segment. The perforation method is flow restriction + spiral perforation, with 45-60 perforations per segment.

[0049] Furthermore, in the differentiated biomimetic fracturing mode, as the fracturing depth decreases, the amount of fluid injected into the ground and the proppant dosage in each fracturing stage gradually increase in a stepwise manner. For every 60 to 80 meters decrease in depth, the amount of fluid injected into the ground and the proppant dosage in a single stage increase by 3% to 6%.

[0050] Furthermore, the differentiated biomimetic fracturing mode considers the optimization of single-well fracturing scale by preventing cross-channeling between wells. Based on the well group geomechanical model, the wellbore, perforation and process parameters are imported to calculate the fracturing fractures and optimize the critical construction parameters for preventing cross-channeling in different well sections as the upper limit of the actual construction scale.

[0051] Furthermore, during fracturing, the differentiated biomimetic fracturing mode performs 1-2 composite temporary plugging operations on the medium- and long-section multi-cluster patterns in Regions 2 and 3, promoting the lateral expansion of the fracture layer throughout the reservoir, increasing the density and complexity of the fracture network, realizing biomimetic fracture network transformation, and maximizing the coverage of the fracture network on the inter-well plane transformation area.

[0052] D: After fracturing each horizontal well in the shale oil horizontal well group, the well is shut down. When the wellhead pressure has diffused to a stable level, the well is opened and production is initiated.

[0053] This process enables CO2 injection for energy replenishment and pressure boosting in production wells, and biomimetic differentiated zoning for efficient fracturing wells. It achieves full and efficient transformation of the entire horizontal well group under well network conditions, resulting in good oil production increase in production wells and cost reduction and efficiency improvement in fracturing wells, thereby improving the development efficiency and economic benefits of the well group.

[0054] The following describes the process and effects of applying the design method of this invention in a real-world setting:

[0055] In a shale oil reservoir in the Subei Basin, horizontal well groups were developed. The risk exploration well SQ1HF was deployed first. After fracturing and stimulation, 4mm nozzles were used for blowout production, achieving a peak daily production of 66.3 tons, marking a breakthrough in exploration. Subsequently, two horizontal wells were deployed on each side of the SQ1HF well in the same stratum, with horizontal sections ranging from 1534 to 1804 meters in length.

[0056] First, a CO2 injection study was conducted on the production well SQ1HF. Based on modeling and numerical simulation, CO2 injection simulations were performed to optimize the CO2 injection rate and pressure diffusion time. The designed injection volume was 17,000 tons, the injection rate was 550-650 tons / day, and the injection pressure was 31-38 MPa. After injection, the well entered a shut-in phase. After establishing a high-pressure zone in the fractured area of ​​well SQ1HF, new well construction was carried out on the remaining wells in the well group.

[0057] For new horizontal wells in shale oil well groups, fracturing should be carried out in sequence from the outside to the inside.

[0058] Prioritize connecting the fracturing processes of the two horizontal wells (well 1 and well 4 to be fracturing) on ​​the outside of the well group, and achieve process conversion through the diversion manifold. Share a fracturing truck set to carry out uninterrupted alternating zipper-style fracturing of the two wells.

[0059] A single horizontal well employs a biomimetic zoned fracturing model, divided into three zones:

[0060] Process parameters for Area 1: Section length 45-60m, 4 clusters of perforations per section, total number of perforations 28, large-diameter perforating gun BH42RDX28-2, perforation diameter 16mm, perforation method is annular perforation, single-section fracturing fluid volume 3910-4160 cubic meters, single-section proppant dosage 108-127 cubic meters, injection rate 16-18 cubic meters / minute.

[0061] Process parameters for Zone 2: Section length 60-80m, 8 clusters of flow-limiting perforations per section, total 40 perforations, ultra-deep penetrating perforator SDP36RDX24-2, perforation diameter 9.2mm, 60° phase angle, spiral perforation pattern, single-section fracturing fluid volume 4250-4690 cubic meters, single-section proppant dosage 135-156 cubic meters, injection rate 18-20 cubic meters / minute. One round of composite temporary plugging is employed, using 200kg of plugging agent and 20 plugging balls to promote uniform fracture propagation across multiple perforation clusters.

[0062] Process parameters for Area 3: Section length 80-100m, 10 perforation clusters per section, total 60 perforations, ultra-deep penetrating projectile SDP36RDX24-2, pore diameter 9.2mm, 60° phase angle, spiral perforation pattern, single-section fracturing fluid volume 4870-6060 cubic meters, single-section proppant dosage 160-186 cubic meters, injection rate 18-20 cubic meters / minute. Two-stage composite temporary plugging is employed, with 200kg of plugging agent and 30 plugging balls added each time, promoting uniform fracture modification across multiple perforation clusters.

[0063] After fracturing the two horizontal wells on the outer side of the well group (well 1 and well 4 to be fracturing), the two horizontal wells on the inner side (well 2 and well 3 to be fracturing) are fracturing until all the wells in the well group are fracturing.

[0064] The actual implementation effects of the method of this invention are as follows: After 53 days of well shut-in, the daily pressure drop at the wellhead of well SQ1HF was less than 0.1 MPa, and production was initiated. The wellhead pressure reached 25.7 MPa, with a daily oil production of 30 tons. The average formation pressure increased by 19 MPa compared to before gas injection, resulting in a staged increase in recovery rate of 3.6%. When the daily pressure drop at the wellhead of the fractured well was less than 0.1 MPa, production was initiated with a blowout, and the average daily oil production per well reached 48.9 tons / day, fully realizing the production potential of the reservoir in the well group. Compared with conventional stimulation methods, the hydraulic fractures formed by the combined fracturing and expansion of the well group maximized reservoir control, improving efficiency by 9%, reducing construction costs by 3%, and enhancing the development efficiency and economic benefits of the well group.

Claims

1. A method for combined fracturing and expansion of horizontal well groups in shale oil production, characterized in that, Includes the following steps: A: Modeling and simulation to optimize CO2 injection parameters for production wells in shale oil horizontal well groups, and implement CO2 injection to boost pressure and replenish energy in production wells in advance; In this step, a three-dimensional finite element geomechanical model of the shale oil horizontal well group and a three-dimensional shale gas seepage model are established. Using the three-dimensional pore pressure change as the boundary condition, the changes in geostress at different times after production well pressure are calculated, and the pore pressure and geostress wave range of the production well for long-term production are finally determined. Then, CO2 injection is simulated to enhance the pressure and energy of the production area, the optimal CO2 injection rate is determined, and CO2 injection is implemented in the production well to increase the formation pressure in the production well fracture network and well group area. B: Conduct fracturing operations on new horizontal wells in shale oil well groups, fracturing in sequence from the outside to the inside; In this step, the outermost horizontal well in the shale oil horizontal well group is selected first for fracturing, and then each well is fracturing sequentially from the outside to the inside. The fracturing processes of the two outer horizontal wells are connected, and the process conversion is achieved through the diversion manifold. A set of fracturing trucks is used to carry out uninterrupted alternating zipper-style fracturing of the two wells. C: Conduct differentiated fracturing of the horizontal fracturing section of a single well, dividing the horizontal section into 3 regions, and designing the perforation, segmentation, and scale parameters of each region differently; use a low-viscosity fracturing fluid system, large displacement, and large fluid volume to create a complex fracture network; D: After fracturing each horizontal well in the shale oil horizontal well group, the well is shut down. When the wellhead pressure has diffused to a stable level, the well is opened and production is initiated.

2. The shale oil horizontal well group energy replenishment and fracture expansion combined fracturing method according to claim 1, characterized in that: In step A, a matrix model of the structural strata at the well group level is established. Seismic inversion porosity volume and saturation volume are used as trend constraints, and the sequential Gaussian method is applied to establish a matrix property model. A fracture model was established. Based on seismic data and the properties of ant bodies, the overall distribution of fractures in the well group area was determined. Combined with the fracture development intensity from well logging, large-scale, medium-scale, and small-scale DFN fracture models were established. A geostress model was established. Based on the three-dimensional geological model, a geostress field model was constructed using finite element simulation based on the well group brittleness index, rock mechanical characteristic parameters, and fracture distribution and geostress orientation parameters obtained from imaging logging. A reservoir-fluid-rock model was established based on monitoring data of fracturing stimulation of production wells, stimulation SRV, and fracture morphology. Considering reservoir damage and fracture, matrix loss, and interaction deformation between rock and fracture, a fracturing network expansion model of production wells was established to evaluate the dynamic evolution of in-situ stress after fracturing of production wells and determine the pore pressure and in-situ stress range of production wells. By employing zoned relative permeability to characterize the differences in reservoir properties and flow media, an equivalent permeability field for fracture distribution is established.

3. The shale oil horizontal well group energy replenishment and fracture expansion combined fracturing method according to claim 1, characterized in that: In step A, the CO2 injection scale is optimized, different gas injection volumes are simulated, and the injection volume with a significant increase in oil production is selected. The pressure diffusion is simulated to optimize and determine the well-closing time or the well-closing pressure is stabilized before well-opening and blowout production.

4. The shale oil horizontal well group energy replenishment and fracture expansion combined fracturing method according to claim 1, characterized in that: In step C, an innovative biomimetic fracturing mode is adopted, and the zoned differentiated and efficient transformation is carried out. The differentiated biomimetic fracturing imitates the three-stage flight feather pattern of bird wings and differentiates the process parameters of the horizontal well, which are divided into three zones.

5. The shale oil horizontal well group energy replenishment and fracture expansion combined fracturing method according to claim 4, characterized in that: In step C, Region 1 adopts a short-segment, long-cluster pattern, with segment lengths of 45-60m, 3-5 clusters of perforations per segment, and 24-30 perforations per segment. The perforation method is annular perforation.

6. The shale oil horizontal well group energy replenishment and fracture expansion combined fracturing method according to claim 4 or 5, characterized in that: In step C, region two adopts a medium-length, medium-cluster pattern, with segment lengths of 60-80m, 6-8 clusters of perforations per segment, and a perforation method of flow restriction + spiral perforation, with 32-40 perforations per segment.

7. The shale oil horizontal well group energy replenishment and fracture widening combined fracturing method according to claim 6, characterized in that: In step C, region three adopts a long segment and multiple clusters pattern, with segment lengths of 80-100m, 9-12 clusters of perforations per segment, and the perforation method is flow restriction + spiral perforation, with 45-60 perforations per segment.

8. The shale oil horizontal well group energy replenishment and fracture expansion synergistic fracturing method according to claim 4, 5 or 7, characterized in that: In step C, the differentiated biomimetic fracturing mode gradually increases the amount of fluid injected into the ground and the proppant dosage in each fracturing segment as the fracturing segment depth decreases. For every 60-80 meters decrease in depth, the amount of fluid injected into the ground and the proppant dosage in a single segment increase by 3%-6%.

9. The shale oil horizontal well group energy replenishment and fracture expansion combined fracturing method according to claim 8, characterized in that: In step C, the differentiated biomimetic fracturing mode considers the optimization of single-well fracturing scale to prevent cross-flow between wells. Based on the well group geomechanical model, it imports wellbore, perforation and process parameters to calculate the fracturing fractures and optimizes the critical construction parameters for preventing cross-flow in different well sections as the upper limit of the actual construction scale.

10. The shale oil horizontal well group energy replenishment and fracture expansion combined fracturing method according to claim 9, characterized in that: During fracturing, the differentiated biomimetic fracturing mode requires a composite temporary plugging process in the medium and long-segment multi-cluster patterns of Region 2 and Region 3 to increase the complexity of the fracture network, increase the affected area, and promote the spread of artificial fractures throughout the reservoir, thereby maximizing reservoir control through fractures.

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