Composite temporary plugging construction method for general shearing and fracturing of hot dry rock

Abstract

The present application provides a kind of dry hot rock general shear fracturing composite temporary plugging construction method, it is related to energy exploitation technical field.The method includes: obtaining crack system expansion trend by microseismic real-time monitoring, and the direction needing temporary plugging is demarcated for the purpose of crack system uniform expansion and guaranteeing construction safety;By microseismic, suspend particle temporary plugging agent is used to block longitudinal channeling crack;After longitudinal temporary plugging takes effect, particle temporary plugging agent is used to block transverse temporary plugging position;Then, crosslinking liquid is supplemented to the designated position;Shear fracturing construction is continued, and the above steps are repeated after temporary plugging agent fails.The composite temporary plugging construction method provided by the present application can block multiple expansion directions of crack system that interfere with fracturing construction effect under the condition of general shear fracturing construction in dry hot rock reservoir, while ensuring construction safety and environmental protection.

Description

Technical Field

[0001] This invention relates to the field of energy extraction technology, and in particular to a composite temporary plugging construction method for general shear fracturing of dry hot rock. Background Technology

[0002] Hot dry rock is a geothermal resource with broad development prospects. In the development of hot dry rock, due to the dense nature of the rock and poor fracture conductivity, the formation of artificial reservoirs in deep, low-permeability hot dry rock masses using engineering techniques such as hydraulic fracturing is a crucial step. Fracturing and shearing on existing fractures is the main mechanism for the development of EGS (Enhanced Geotherma System) reservoirs. Shear fracturing causes shear displacement of natural fractures, preventing complete closure and forming a self-supporting fracture network, thereby improving the permeability of the artificial reservoir. Compared to traditional proppant-based hydraulic fracturing, artificial reservoir creation in hot dry rock often uses clear water fracturing to achieve shear displacement. During the general shear fracturing process in hot dry rock, due to the long fracturing section, low fracturing flow rate, and complex fractures, the propagation rate is slow. Microseismic monitoring technology can directly observe the fracture propagation trend.

[0003] To address the challenges of severe vertical heterogeneity in formations and large variability in inter-layer permeability, existing fracturing fluid diversion technologies mainly include mechanical diversion and chemical temporary plugging diversion. Mechanical segmented diversion technology works by using mechanical tools to separate the target layer from other layers, thereby achieving directional flow of the working fluid. Mechanical diversion primarily includes ball-plug diversion and packer segmented diversion, among others. This technology is mature and effective, but its operation is complex and time-consuming. Therefore, to ensure a high success rate and effective fracturing, chemical temporary plugging diversion technology has become a better option. Chemical temporary plugging is mainly achieved through temporary plugging agents.

[0004] Artificial reservoir fracturing connects to natural fractures or involves repeated fracturing to form an artificial fracture network that can provide effective heat exchange over a large area. To create a fracture system of a certain scale, long-term continuous construction is required. Therefore, the continuous construction time for dry hot rock shear fracturing is long, and at least the following problems exist during the construction process:

[0005] (1) In the case of general shear fracturing of hot dry rock, due to the heterogeneity of the fracture system and the influence of geological structure, the hydraulic fractures formed by high net pressure are smoother during the fracturing process, which is not conducive to the formation of fracture network. The hydraulic fractures formed by low net pressure are easy to connect with natural fractures, which is conducive to the formation of complex fracture network. Therefore, the fracture system is prone to uneven expansion during the fracturing process, which affects the transformation effect and creates potential earthquake safety hazards.

[0006] (2) For hot dry rock fracturing, there are no obvious shielding layers above and below the reservoir, so the fracture height is easily out of control.

[0007] (3) Temporary plugging agents are mainly classified into several types: granular, fibrous, and rubber-stopper types; among them:

[0008] Fiber-based temporary plugging agents are primarily used to seal large fractures and can be applied to temporary plugging and diversion operations in low-permeability gas reservoirs. Their fibers have a low specific gravity and high aspect ratio, allowing them to be easily captured by the rough fracture walls after entering the underground, forming a temporary plugging layer. Compared to granular temporary plugging agents, the filter cake formed by fibers has smaller pores, better stability and leak-proof performance, and lower permeability in the underground filter cake, significantly reducing fracturing fluid loss. Simultaneously, their ability to prevent proppant backflow greatly increases the success rate of fracture creation during fracturing operations.

[0009] Particulate temporary plugging agents have good plugging effects and can be used for opening new fractures in old wells, volumetric fracturing of thick oil layers, and diversion fracturing of highly heterogeneous tight reservoirs. However, when plugging larger fractures, the particle packing density of the temporary plugging layer is relatively small, and the structure of the temporary plugging layer is relatively loose, resulting in poor plugging effect.

[0010] Temporary plugging agents, such as gel plugs, are commonly used in directional fracturing operations in reservoirs with fracture apertures in the millimeter or micrometer range. They can be cross-linked and granulated on the surface, then injected underground with the working fluid to form a secondary cross-linking cake for sealing. Alternatively, they can be prepared as a gel solution on the surface, injected underground, and then cross-linked to form a colloidal slug to seal the fractures. After being injected underground, the temporary plugging agent preferentially enters high-permeability layers based on the principle of minimum flow resistance. Subsequently, it cross-links at high temperatures to form a dense filter cake, forcing the subsequent working fluid to deflect and fracture low-permeability layers, thus improving the uniformity of reservoir stimulation. Moreover, the greater the permeability difference between high and low permeability layers, the better the selective sealing effect of the gel plugging agent. This type of temporary plugging agent has advantages such as high sealing compressive strength and good selective sealing effect.

[0011] After fracturing hot dry rock, the fracture width is extremely narrow. When choosing a sealing agent, temporary plugging agents with rubber plugs are the most effective. However, temporary plugging agents with rubber plugs must be mixed with a breaker to break the rubber and remove the plug. The breaking time is difficult to control, and the temperature and salt resistance is poor. It is easy to break the rubber prematurely at high temperatures. If the rubber breaks prematurely but not completely, it will be difficult to induce the flow and remove the plug. If acid is used to remove the plug, it is easy to produce more obvious pollution. Summary of the Invention

[0012] The purpose of this invention is to provide a composite temporary plugging construction method for dry hot rock cage shear fracturing, so as to alleviate the above-mentioned technical problems existing in the prior art. Under the conditions of dry hot rock cage shear fracturing construction, this composite temporary plugging construction method can simultaneously plug multiple expansion directions of the fracture system that interfere with the fracturing construction effect, while ensuring construction safety and environmental protection.

[0013] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0014] This invention provides a composite temporary plugging construction method for general shear fracturing in hot dry rock, comprising the following steps:

[0015] During the process of general shear fracturing of hot dry rock, microseismic instruments are used to monitor and display the propagation of fracturing fractures in real time. Through comparison and calculation of microseismic monitoring, the longitudinal fractures are temporarily plugged if the fractures are significantly extended longitudinally along the wellbore and the fracture height is difficult to control, thus limiting the transverse fracture length. If a certain direction becomes the dominant direction on the transverse plane at different depths, the fractures in that direction on the transverse plane are temporarily plugged. Multiple locations that need to be temporarily plugged are then identified.

[0016] To temporarily plug the upward-growing fracture, the surface of the particulate plugging agent is treated to enhance its suspension performance. Simultaneously, the width of a certain upward-growing fracture is calculated using microseismic inversion to screen the particle size of the plugging agent, resulting in a suspended particulate plugging agent. The injection rate is reduced and the suspended particulate plugging agent is added to the designated location for temporarily plugging the longitudinal fracture. After complete addition, the injection rate is slightly increased, and the onset time of the plugging agent is estimated. The pressure rise and the location of the newly added microseismic time distribution are observed. Once the plugging agent is confirmed to be effective, the injection rate is increased to the shear fracturing injection rate before the addition of the plugging agent, thus completing the sealing of the upward-growing fracture.

[0017] To temporarily plug the transverse fracture, the particle size of the temporary plugging agent is screened by calculating the fracture width at a certain transverse location using microseismic inversion, resulting in a qualified particle size temporary plugging agent. The injection rate is reduced and the qualified particle size temporary plugging agent is added to the designated location for temporarily plugging the transverse fracture. After complete addition, the injection rate is slightly increased, while the onset time of the temporary plugging agent is estimated. The pressure rise and the location of the newly added microseismic time distribution are observed. Once the temporary plugging agent is confirmed to be effective, the injection rate is increased to the shear fracturing injection rate before the addition of the temporary plugging agent, thus completing the sealing of the transverse fracture.

[0018] Add crosslinking liquid to the calibrated location, use crosslinking liquid instead of rubber plugging agent, reduce the flow rate and add crosslinking liquid to the last location that needs temporary plugging, estimate the time when the crosslinking liquid starts to work, reduce the flow rate again after the crosslinking liquid enters the formation, and observe the pressure changes and changes in new microseismic events. After confirming that the crosslinking liquid temporary plugging is effective, gradually increase the flow rate to the normal shear fracturing operation flow rate.

[0019] Continue shear fracturing at normal discharge rate while observing changes in microseismic events. After the temporary plugging agent fails, repeat the above steps to perform temporary plugging at multiple locations.

[0020] In the above steps of this embodiment, more specifically and preferably:

[0021] In the step of determining the temporary plugging location: the criterion for determining whether a longitudinal fracture needs to be temporarily plugged is that the microseismic event point shows that the fracture extends more than a quarter of the fracturing section along the wellbore depth direction and still has an expanding trend; the criterion for determining whether a transverse fracture needs to be temporarily plugged is that the extension of the fracture in the direction of the maximum principal stress in the horizontal direction suddenly accelerates, or the extension of the fracture in a certain direction accelerates while the extension of the fracture in the direction of the maximum principal stress in the horizontal direction is blocked.

[0022] In the step of temporarily plugging the upward-growing fracture: the normal shear fracturing operation displacement is less than 3m³. 3 / min, with a single increase in displacement not exceeding 0.5m 3 / min.

[0023] In the step of temporarily plugging the upward-growing crack, the criteria for determining the effectiveness of the plugging agent include a pressure increase ≥ 2 MPa.

[0024] In the step of temporarily plugging transverse cracks: the qualified particle plugging agent is a particle plugging agent that has not undergone surface treatment to enhance its suspension performance.

[0025] In the step of replenishing the crosslinked liquid at the calibrated location: the viscosity of the crosslinked liquid is ≥150 mPa·s, and the initial injection volume into the formation is ≤1.5 m³. 3 / min; the discharge rate should be reduced again after the cross-linked liquid enters the formation, with a reduction of ≤1.0m³ / min. 3 / min; After confirming the effectiveness of the cross-linked liquid temporary plugging, the first two single-stage increase in discharge rate should be ≤0.5m. 3 / min, the stable injection time for a single injection is generally ≥15min.

[0026] In this embodiment, the criterion for determining whether the temporary plugging agent has failed is whether the original temporary plugging direction has restarted and rapidly expanded, affecting the overall crack system morphology. If so, it has failed.

[0027] In this embodiment, the fractured well is a vertical well, the fractured section is a single long well section with a length ≥ 300m, and the fracture discharge rate is < 3m³. 3 / min.

[0028] In the composite temporary plugging construction method provided in this embodiment, after the step of delineating the temporary plugging location, the location that needs to be temporarily plugged can be determined according to the actual situation of the crack system expansion, thereby making a plan for the type and quantity of the required temporary plugging agent and providing a reference for construction design.

[0029] By temporarily plugging upward-growing fractures, the suspension properties of the plugging agent can be improved. Reducing the injection rate ensures smooth mixing of the plugging agent and facilitates its buoyancy upon entering the formation. Subsequent, continuous low-rate injection helps maintain a low fracture width and forms a bridging effect with the plugging agent, thus successfully sealing the upward-growing fractures. Real-time microseismic monitoring and pressure response verification can enhance the assessment of the plugging agent's effectiveness.

[0030] By temporarily sealing transverse cracks, granular temporary sealant can be used in combination with changes in the construction discharge rate to achieve the same effect as single-segment temporary sealing construction, sealing the first temporary sealing position in the transverse direction.

[0031] By replenishing the marked location with cross-linked liquid, a cross-linked liquid of a certain viscosity can be used instead of a rubber plugging agent for construction. Combined with two consecutive injections to reduce discharge volume, this ensures the smooth addition of the cross-linked liquid rubber plug and the gradual effectiveness of temporary plugging even in narrow fractures. Subsequent precise discharge volume increases and real-time monitoring further enhance the plugging effect. This step, after adding particulate plugging agent to each fracture, replenishes the marked location (the last location to be plugged) with cross-linked liquid instead of the rubber plugging agent. This avoids the disadvantage that cross-linked liquid has a shorter effective time in high-temperature formations than particulate plugging agents, while leveraging the advantages of cross-linked liquid: low cost, no need for a breaker, and no reservoir contamination after high-temperature decomposition.

[0032] By following the steps of "continuing shear fracturing at normal discharge rate while observing changes in microseismic events, and repeating the above steps for temporary plugging at multiple locations after the temporary plugging agent fails," the continuity of the temporary plugging effect can be guaranteed within a construction cycle, and timely measures can be taken after the temporary plugging agent fails.

[0033] Compared with existing temporary damming methods, the composite temporary damming method provided in this invention has at least the following advantages:

[0034] (1) Multiple temporary plugging and turning operations can be performed to simultaneously seal multiple locations of the artificial fracture system in a single fracturing operation;

[0035] (2) By closely combining real-time micro-seismic monitoring and temporary blocking diversion construction, the ability to judge the working conditions is improved, which is conducive to the formulation of construction plans and timely adjustment of construction measures;

[0036] (3) Adding different types of temporary plugging agents in conjunction with changes in displacement can make the temporary plugging agents more stable and effective and continue to play a role.

[0037] (4) Using a cross-linked liquid of a certain viscosity instead of a rubber plugging agent for sealing reduces the cost of using the plugging agent, avoids reservoir pollution caused by the breaking of traditional high-viscosity rubber plugs, and ensures the safety and environmental protection of the temporary plugging construction process.

[0038] (5) Various temporary plugging agents with different properties can be used in combination through specific procedures and processes based on their different performance characteristics, thereby achieving the triple purpose of solving the temporary plugging problem, reducing construction costs, and ensuring safety and environmental protection.

[0039] This method involves processing and combining different types of temporary plugging agents (mainly suspended particulate plugging agents, particulate plugging agents, and cross-linked liquid plugging agents used as substitutes for rubber plugging agents). It leverages the characteristics of hot dry rock shear fracturing operations—high reservoir temperature, small injection volume, long construction period, and small fracture aperture—and, combined with changes in injection volume and real-time microseismic monitoring, to ensure the temporary plugging agents effectively seal multiple locations within the artificial fracture system over a certain period, guaranteeing the scale and uniformity of the thermal reservoir transformation. Simultaneously, the temporary plugging agents automatically decompose under prolonged high temperature and pressure conditions without requiring debonding or backflow, thus avoiding reservoir contamination and making the construction process safer and more environmentally friendly. Attached Figure Description

[0040] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0041] Figure 1 A construction flowchart of the composite temporary plugging construction method for general shear fracturing of dry hot rock provided in an embodiment of the present invention;

[0042] Figure 2 Map showing the location of the temporary blockade;

[0043] Figure 3 This is a graph showing the change in discharge volume during temporary roadblock construction. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0046] It should be noted that similar labels and letters in the accompanying drawings indicate similar items. Therefore, once an item is defined in one accompanying drawing, it does not need to be further defined and explained in subsequent accompanying drawings.

[0047] In the description of this invention, it should be noted that the terms "longitudinal," "lateral," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] Furthermore, in this invention, "longitudinal" refers to the direction along the depth of the wellbore, and "lateral" refers to the direction perpendicular to the plane of the wellbore. The terms "longitudinal" and "lateral" do not imply that the component must be absolutely suspended or horizontal, but rather that it can be slightly tilted. For example, "lateral" simply means that its direction is more horizontal relative to "longitudinal," and does not mean that it must be completely horizontal, but rather that it can be slightly tilted.

[0049] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0051] This invention provides a composite temporary plugging construction method for general shear fracturing in hot dry rock, comprising the following steps:

[0052] During the process of general shear fracturing of hot dry rock, microseismic instruments are used to monitor and display the propagation of fracturing fractures in real time. Through comparison and calculation of microseismic monitoring, the longitudinal fractures are temporarily plugged if the fractures are significantly extended longitudinally along the wellbore and the fracture height is difficult to control, thus limiting the transverse fracture length. If a certain direction becomes the dominant direction on the transverse plane at different depths, the fractures in that direction on the transverse plane are temporarily plugged. Multiple locations that need to be temporarily plugged are then identified.

[0053] To temporarily plug the upward-growing fracture, the surface of the particulate plugging agent is treated to enhance its suspension performance. Simultaneously, the width of a certain upward-growing fracture is calculated using microseismic inversion to screen the particle size of the plugging agent, resulting in a suspended particulate plugging agent. The injection rate is reduced and the suspended particulate plugging agent is added to the designated location for temporarily plugging the longitudinal fracture. After complete addition, the injection rate is slightly increased, and the onset time of the plugging agent is estimated. The pressure rise and the location of the newly added microseismic time distribution are observed. Once the plugging agent is confirmed to be effective, the injection rate is increased to the shear fracturing injection rate before the addition of the plugging agent, thus completing the sealing of the upward-growing fracture.

[0054] To temporarily plug the transverse fracture, the particle size of the temporary plugging agent was screened by calculating the fracture width at a certain transverse location using microseismic inversion, resulting in a qualified particle size temporary plugging agent. The injection rate was reduced and the qualified particle size temporary plugging agent was added to the designated location for temporarily plugging the transverse fracture. After complete addition, the injection rate was slightly increased, and the onset time of the temporary plugging agent was estimated. The pressure rise and the location of the newly added microseismic time distribution were observed. After confirming the effectiveness of the temporary plugging agent, the injection rate was increased to the shear fracturing injection rate before the addition of the temporary plugging agent, thus completing the sealing of the transverse fracture.

[0055] Add crosslinking liquid to the calibrated location, use crosslinking liquid instead of rubber plugging agent, reduce the flow rate and add crosslinking liquid to the last location that needs temporary plugging, estimate the time when the crosslinking liquid starts to work, reduce the flow rate again after the crosslinking liquid enters the formation, and observe the pressure changes and the changes in the micro-vibration time. After confirming that the crosslinking liquid temporary plugging is effective, gradually increase the flow rate to the normal shear fracturing operation flow rate.

[0056] Continue shear fracturing at normal discharge rate while observing changes in microseismic events. After the temporary plugging agent fails, repeat the above steps to perform temporary plugging at multiple locations.

[0057] In the composite temporary plugging construction method provided in this embodiment, after the step of delineating the temporary plugging location, the location that needs to be temporarily plugged can be determined according to the actual situation of the crack system expansion, thereby making a plan for the type and quantity of the required temporary plugging agent and providing a reference for construction design.

[0058] By temporarily plugging upward-growing fractures, the suspension properties of the plugging agent can be improved. Reducing the injection rate ensures smooth mixing of the plugging agent and facilitates its buoyancy upon entering the formation. Subsequent, continuous low-rate injection helps maintain a low fracture width and forms a bridging effect with the plugging agent, thus successfully sealing the upward-growing fractures. Real-time microseismic monitoring and pressure response verification can enhance the assessment of the plugging agent's effectiveness.

[0059] By temporarily sealing transverse cracks, granular temporary sealant can be used in combination with changes in the construction discharge rate to achieve the same effect as single-segment temporary sealing construction, sealing the first temporary sealing position in the transverse direction.

[0060] By replenishing the marked location with cross-linked liquid, a cross-linked liquid of a certain viscosity can be used instead of a rubber plugging agent for construction. Combined with two consecutive injections to reduce discharge volume, this ensures the smooth addition of the cross-linked liquid rubber plug and the gradual effectiveness of temporary plugging even in narrow fractures. Subsequent precise discharge volume increases and real-time monitoring further enhance the plugging effect. This step, after adding particulate plugging agent to each fracture, replenishes the marked location (the last location to be plugged) with cross-linked liquid instead of the rubber plugging agent. This avoids the disadvantage that cross-linked liquid has a shorter effective time in high-temperature formations than particulate plugging agents, while leveraging the advantages of cross-linked liquid: low cost, no need for a breaker, and no reservoir contamination after high-temperature decomposition.

[0061] By following the steps of "continuing shear fracturing at normal discharge rate while observing changes in microseismic events, and repeating the above steps for temporary plugging at multiple locations after the temporary plugging agent fails," the continuity of the temporary plugging effect can be guaranteed within a construction cycle, and timely measures can be taken after the temporary plugging agent fails.

[0062] Compared with existing temporary damming methods, the composite temporary damming method provided in this invention has at least the following advantages:

[0063] (1) Multiple temporary plugging and turning operations can be performed to simultaneously seal multiple locations of the artificial fracture system in a single fracturing operation;

[0064] (2) By closely combining real-time micro-seismic monitoring and temporary blocking diversion construction, the ability to judge the working conditions is improved, which is conducive to the formulation of construction plans and timely adjustment of construction measures;

[0065] (3) Adding different types of temporary plugging agents in conjunction with changes in displacement can make the temporary plugging agents more stable and effective and continue to play a role.

[0066] (4) Using a cross-linked liquid of a certain viscosity instead of a rubber plugging agent for sealing reduces the cost of using the plugging agent, avoids reservoir pollution caused by the breaking of traditional high-viscosity rubber plugs, and ensures the safety and environmental protection of the temporary plugging construction process.

[0067] (5) Various temporary plugging agents with different properties can be used in combination through specific procedures and processes based on their different performance characteristics, thereby achieving the triple purpose of solving the temporary plugging problem, reducing construction costs, and ensuring safety and environmental protection.

[0068] This method involves processing and combining different types of temporary plugging agents (mainly suspended particulate plugging agents, particulate plugging agents, and cross-linked liquid plugging agents used as substitutes for rubber plugging agents). It leverages the characteristics of hot dry rock shear fracturing operations—high reservoir temperature, small injection volume, long construction period, and small fracture aperture—and, combined with changes in injection volume and real-time microseismic monitoring, to ensure the temporary plugging agents effectively seal multiple locations within the artificial fracture system over a certain period, guaranteeing the scale and uniformity of the thermal reservoir transformation. Simultaneously, the temporary plugging agents automatically decompose under prolonged high temperature and pressure conditions without requiring debonding or backflow, thus avoiding reservoir contamination and making the construction process safer and more environmentally friendly.

[0069] In the above steps of this embodiment, more specifically and preferably:

[0070] In the steps of determining the location of temporary plugging: the criterion for determining whether a longitudinal fracture needs to be temporarily plugged is that the microseismic event point shows that the fracture has expanded more than a quarter of the fracturing section along the depth direction of the wellbore and still has an expansion trend; the criterion for determining whether a transverse fracture needs to be temporarily plugged is that the extension of the fracture in the direction of the maximum principal stress in the horizontal direction suddenly accelerates, or the extension of the fracture in a certain direction accelerates while the extension of the fracture in the direction of the maximum principal stress in the horizontal direction is blocked.

[0071] In the process of temporarily plugging upward-growing cracks: the displacement during normal shear fracturing is less than 3m³. 3 / min, with a single increase in displacement not exceeding 0.5m 3 / min; the criteria for judging the effectiveness of the temporary plugging agent include a pressure increase ≥2MPa.

[0072] In the process of temporarily plugging transverse cracks: the qualified particle plugging agent is a particle plugging agent that has not undergone surface treatment to enhance its suspension performance.

[0073] In the step of replenishing the crosslinking liquid to the calibrated location: the viscosity of the crosslinking liquid is ≥150 mPa·s, and the initial injection volume into the formation is ≤1.5 m³. 3 / min; the discharge rate should be reduced again after the cross-linked liquid enters the formation, with a reduction of ≤1.0m³ / min. 3 / min; After confirming the effectiveness of the cross-linked liquid temporary plugging, the first two single-stage increase in discharge rate should be ≤0.5m. 3 / min, with a stable injection time of ≥15min for a single injection. The crosslinked fluid is a widely used fracturing fluid in existing technologies. Its composition is ordinary fracturing fluid thickened with a thickener. The thickener composition varies, for example, but not limited to, using acrylamide (AM) as the main chain monomer, acrylic acid (AA) to provide crosslinking sites, salt-resistant monomer 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and cationic monomer methacryloyloxyethyltrimethylammonium chloride (DMC) in a quaternary copolymerization. In this embodiment, the criterion for determining whether the temporary plugging agent has failed is whether the original plugging direction has restarted its rapid propagation and affected the overall fracture system morphology; if so, it has failed.

[0074] In this embodiment, the fractured well is a vertical well, the fractured section is a single long well section with a length ≥ 300m, and the fracture discharge rate is < 3m³. 3 / min, the reservoir temperature of the dry hot rock is greater than 180℃.

[0075] The following describes the composite temporary plugging construction method for the dry hot rock cage shear fracturing provided by the present invention in more specific terms:

[0076] In one specific embodiment of the present invention, taking a reservoir fracturing section of 200°C as an example, the thickness of the thermal reservoir development section is 360m, the depth is 3000-3360m, the development well type is a vertical well, the main fracturing fluid is slickwater, and the construction is carried out by open-hole completion and general shear fracturing, with real-time monitoring and display by the microseismic network.

[0077] like Figure 1 As shown:

[0078] Step 1: Delineate the temporary blocking location, such as... Figure 2 As shown, real-time microseismic monitoring reveals that the fracture network extends over 100m along the wellbore, affecting fracture length expansion. Furthermore, uneven expansion of transverse fractures is observed at two different depths. Therefore, three directions requiring temporary plugging are identified: the upward-running fracture at 3000m along the wellbore, the dominant main fracture zone at 3100-3150m, and the uneven fracture expansion zone at 3260-3300m.

[0079] Step 2: Temporarily plug the upward crack, such as Figure 3 As shown, the initial shear fracturing displacement is 3m³. 3 / min, reduce construction discharge rate to 1.5m 3 After reaching a flow rate of 100 m³ / min, add a temporary plugging agent containing suspended particles, then increase the flow rate to 2 m³ / min. 3 After 30 minutes, an injection pressure increase of 2 MPa was observed, and the time for new microseismic events along the wellbore depth direction was significantly reduced, confirming the effectiveness of the temporary plugging agent. Subsequently, the injection rate was increased to 3 m³ / min. 3Construction continues at / min;

[0080] Step 3: Temporarily plug the transverse crack (main crack), such as Figure 3 As shown, the construction discharge volume is reduced to 1.5m. 3 After a flow rate of 100 m³ / min, add particulate temporary plugging agent, then increase the discharge rate to 2 m³ / min. 3 After 36 minutes, it was observed that the outward expansion trend of the dominant main fracture in the shallow injection zone of 3100-3150m slowed down, the number of microseismic events decreased significantly, and the injection pressure increased by 3MPa, confirming that the temporary plugging agent was effective at 3100-3150m. Subsequently, the discharge rate was increased to 3m³ / min. 3 Construction continues at / min;

[0081] Step 4: Add crosslinking liquid to the calibration location, and prepare 60 ml of crosslinking liquid with a viscosity of 200 mPa·s. 3 Replaces rubber stopper temporary plugging agent, reducing displacement by 1.5m. 3 After a certain time (in seconds), inject the prepared crosslinking liquid into the calibrated location, i.e., the final temporary plugging location. After 40 minutes, reduce the discharge rate to 1.0 m³ / min. 3 Stable injection was performed at a rate of / min, and the pressure decline trend gradually slowed down and showed a recovery trend. At the same time, the number of new microseismic events in the uneven crack propagation zone of the deep injection layer was significantly reduced, confirming the effectiveness of the cross-linked liquid temporary plugging. Subsequently, the injection rate was increased by 0.5m³ in 15-minute increments. 3 / min, gradually restore displacement to 3.0m 3 / min, to carry out shear fracturing operations;

[0082] Step 5: During this section of shear fracturing, continue to observe the changes in microseismic time and analyze the crack propagation trend. It was found that the temporary plugging agent at each location had not failed, so normal shear fracturing operation can be maintained.

[0083] Finally, it should be noted that:

[0084] 1. In this specification, the estimated time for the temporary plugging agent to enter the formation is calculated using the wellbore volume at the target depth of the temporary plugging location and the fluid injection rate during the addition of the temporary plugging agent; the particle size of the temporary plugging agent is calculated using a formula with corresponding construction parameters; the fracture width can be obtained through advanced microseismic interpretation; the crosslinking fluid is a widely used fracturing fluid in the prior art, and its composition is ordinary fracturing fluid with the addition of a thickener for thickening. The thickener composition varies, for example, but not limited to, using acrylamide (AM) as the main chain monomer, acrylic acid (AA) to provide crosslinking sites, salt-resistant monomer 2-acrylamide-2-methylpropanesulfonic acid (AMPS), and cationic monomer methacryloyloxyethyltrimethylammonium chloride (DMC) in a quaternary copolymerization. This specification only limits its viscosity to ≥150 mPa·s in the preferred embodiment to achieve good rubber-like function; all of the above are directly obtainable in the prior art and are well-known in the industry, and this specification need not elaborate on them;

[0085] 2. The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above embodiments in this specification are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite temporary plugging construction method for overall shear fracturing in hot dry rock, characterized in that: Includes the following steps: During the overall shear fracturing of hot dry rock, microseismic instruments were used to monitor and display the propagation of fracturing fractures in real time. Comparisons and calculations were performed based on microseismic monitoring. The principle was to temporarily plug longitudinal fractures if their longitudinal propagation along the wellbore was significant, fracture height was difficult to control, and transverse fracture length was limited. Conversely, if a certain direction became the dominant direction on a transverse plane at different depths, fractures in that direction on that transverse plane were temporarily plugged. Multiple locations requiring temporary plugging were identified. Specifically: the criterion for determining whether a longitudinal fracture needs temporary plugging was that the microseismic event point showed the fracture propagating more than a quarter of the fracturing section along the wellbore depth and still showing a propagation trend; the criterion for determining whether a transverse fracture needs temporary plugging was a sudden acceleration in fracture extension along the direction of maximum horizontal principal stress, or an acceleration in fracture extension in one direction while the extension of fractures along the direction of maximum horizontal principal stress was hindered. To temporarily plug the upward-growing crack, the surface of the particulate plugging agent is treated to enhance its suspension performance. Simultaneously, the width of a certain upward-growing crack is calculated using microseismic inversion to screen the particle size of the particulate plugging agent, resulting in a suspended particulate plugging agent. The injection rate is reduced and the suspended particulate plugging agent is added to the designated location for temporarily plugging the longitudinal crack. After complete addition, the injection rate is slightly increased, and the onset time of the suspended particulate plugging agent is estimated. Two indicators are observed: pressure rise and the distribution location of new microseismic events. Once the suspension particulate plugging agent is confirmed to be effective, the injection rate is increased to the normal shear fracturing operation injection rate before the addition of the suspension particulate plugging agent, thus completing the sealing of the upward-growing crack. To temporarily seal transverse cracks, the crack width at a specific transverse location is calculated using microseismic inversion. Particle size of the temporary plugging agent is then screened to obtain a suitable particle size. The injection rate is reduced as the suitable particle size is added to the designated location for temporarily sealing the transverse crack. After complete addition, the injection rate is slightly increased. Simultaneously, the onset time of the suitable particle size is estimated, and two indicators—pressure rise and the distribution of new microseismic events—are observed. Once the suitable particle size is confirmed to be effective, the injection rate is increased to the normal shear fracturing injection rate before adding the suitable particle size, thus completing the sealing of the transverse crack. Replenish crosslinking fluid to the calibrated location, then reduce the flow rate and replenish the crosslinking fluid to the last location requiring temporary plugging. Estimate the time it takes for the crosslinking fluid to take effect. After the crosslinking fluid enters the formation, reduce the flow rate again, while observing pressure changes and changes in new microseismic events. Once the temporary plugging effect of the crosslinking fluid is confirmed, gradually increase the flow rate to the normal shear fracturing operation flow rate. The viscosity of the crosslinking fluid is ≥150 mPa•s, and the initial injection flow rate into the formation is ≤1.5 m³. 3 / min; the discharge rate should be reduced again after the cross-linked liquid enters the formation, with a reduction of ≤1.0m³ / min. 3 / min; After confirming the effectiveness of the cross-linked liquid temporary plugging, the first two single increases in displacement should be ≤0.5m. 3 / min, stable injection time for a single increase in displacement ≥15min; Continue shear fracturing operations at the normal shear fracturing displacement, while observing changes in newly added microseismic events. After the suspended particle plugging agent or the qualified particle plugging agent becomes ineffective, repeat the above steps to perform temporary plugging at multiple locations.

2. The composite temporary plugging construction method for coaxial shear fracturing of dry hot rock according to claim 1, characterized in that: In the step of temporarily plugging the upward-cutting crack: The normal shear fracturing operation displacement is less than 3m³. 3 / min, with a single increase in displacement not exceeding 0.5m 3 / min.

3. The composite temporary plugging construction method for coaxial shear fracturing of dry hot rock according to claim 1, characterized in that: In the step of temporarily plugging the upward-growing cracks, the criteria for determining the effectiveness of the suspended particulate plugging agent include a pressure increase ≥ 2 MPa.

4. The composite temporary plugging construction method for coaxial shear fracturing of dry hot rock according to claim 1, characterized in that: In the step of temporarily plugging the transverse crack: The surface of the qualified particle plugging agent was not treated to enhance its suspension performance.

5. The composite temporary plugging construction method for coaxial shear fracturing of dry hot rock according to claim 1, characterized in that: The criterion for determining whether the suspended particulate plugging agent or the qualified particle plugging agent has failed is whether the original plugging direction has restarted and rapidly expanded, affecting the overall crack system morphology. If so, it has failed.

6. The composite temporary plugging construction method for coaxial shear fracturing of dry hot rock according to claim 1, characterized in that: The fractured well is a vertical well.

7. The composite temporary plugging construction method for coaxial shear fracturing of dry hot rock according to claim 1, characterized in that: The fractured section of the fractured well is a single long well section with a length of ≥300m.

8. The composite temporary plugging construction method for coaxial shear fracturing of dry hot rock according to claim 1, characterized in that: The fracturing discharge rate of the fracturing well is <3m³. 3 / min.

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