Combination temporary plugging ball and its temporary plugging fracturing operation method

Abstract

The application discloses a combined temporary plugging ball and a temporary plugging and fracturing operation method thereof, and the combined temporary plugging ball comprises a setting ball, at least one group of traction balls and a controllable fracture connecting piece connecting the setting ball and the traction ball; the setting ball is used for plugging a perforation hole, and the outer contour size of the setting ball is larger than the contour size of the perforation hole; the traction ball comprises first and second traction balls which are oppositely arranged on two sides of the setting ball; a monitor is arranged in the traction ball and is used for acquiring a temperature signal and a pressure signal of a plugging position of the setting ball; the outer contour size of the traction ball is smaller than the contour size of the perforation hole; the traction ball comprises a swelling layer made of a swellable composite material, and the density of the traction ball after swelling is smaller than the density of fracturing fluid; and the controllable fracture connecting piece is configured to be automatically fractured after a preset time or to be automatically fractured after downhole temperature and / or pressure reaches a preset fracture condition. The application can realize integration of temporary plugging, monitoring and recycling, thereby supporting efficient exploitation of low-permeability unconventional oil and gas reservoirs.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, and in particular to a combined temporary plugging ball and its temporary plugging fracturing operation method. Background Technology

[0002] Unconventional oil and gas reservoirs (such as shale gas, tight sandstone gas, and coalbed methane) have poor reservoir properties, making it difficult to achieve economically effective production through conventional extraction methods. Therefore, multi-stage temporary plugging fracturing technology has become one of the core processes for enhancing production in these reservoirs. This process involves strategically deploying temporary plugging material into the wellbore to seal the fractured perforations, forcing the fracturing fluid to redirect towards the untreated reservoir. This creates a complex fracture network, thereby expanding the reservoir's stimulation volume, improving fracture conductivity, and ultimately enhancing oil and gas recovery.

[0003] In temporary plugging fracturing operations, real-time temperature and pressure data at the plugging point are crucial for judging the plugging effect, analyzing the fracture propagation pattern, optimizing construction parameters, controlling the timing of unplugging, and ensuring the safety of downhole operations. Therefore, achieving in-situ temperature and pressure monitoring at the plugging point and safe recovery of monitoring devices is of great engineering significance for on-site construction.

[0004] Currently, relevant technologies for downhole temperature and pressure monitoring mainly include wellhead surface monitoring, distributed fiber optic sensing, fixed downhole electronic sensors, and measurement-while-drilling systems. However, there are many insurmountable drawbacks when these technologies are combined with temporary plugging balls. First, existing biodegradable temporary plugging balls are designed to degrade automatically after fracturing, eliminating the need for recovery. If the temperature and pressure monitor is integrated inside the plugging ball, because the monitor's density is greater than that of the well fluid, it is very easy for it to sink to the bottom of the well after unplugging. Furthermore, the monitor is firmly connected to the plugging ball and cannot be separated, making it impossible to recover the monitoring device and data, thus hindering the integrated operation of plugging, monitoring, and recovery. Second, to solve the recovery problem, some sites use mechanical retrieval devices such as mechanical fishing and wire rope jacking. These methods require the pre-planning of complex supporting structures during the well completion stage, resulting in a cumbersome construction process. When facing multiple large-scale temporary plugging operations, the recovery efficiency is extremely low. At the same time, complex working conditions such as downhole sand blockage and scaling can easily lead to recovery failure, resulting not only in the loss of monitoring equipment but also in wellbore blockage and other downhole malfunctions. Third, while distributed fiber optic sensing can acquire continuous wellbore temperature data, the fiber optic cable needs to be pre-laid on the tubing or cable, making it unable to move with the plugging ball to the designated plugging point. Furthermore, its spatial resolution is only at the meter level, unable to accurately locate individual perforation clusters at the centimeter level. Additionally, integrating the fiber optic cable with the plugging ball increases the ball's outer diameter, reducing its mobility within the wellbore. Fourth, if an electronic temperature and pressure sensor is built into the plugging ball, the high-temperature environment of 120°C to 180°C downhole will significantly shorten battery life, failing to meet the requirement of continuous monitoring for several hours. Adding cables and wireless communication modules for real-time data transmission would increase the plugging ball's volume, damage the plugging structure, and the high-pressure downhole environment would affect signal transmission stability. In addition, existing technologies also face difficulties in controlling the timing of plugging removal. Traditional temporary plugging balls rely solely on the inherent properties of their materials to degrade and unblock, resulting in a fixed degradation rate. This makes it impossible to flexibly adjust the unblocking time according to the on-site construction progress. If the unblocking is done too early, it will directly fail, affecting the temporary plugging effect. If the unblocking is done too late, the monitor will remain in the wellbore for a long time, further increasing the risk of equipment loss. The timing of unblocking and the timing of monitor retrieval cannot be effectively matched.

[0005] In summary, existing technologies cannot simultaneously meet the multiple requirements of temporary plugging, in-situ temperature and pressure monitoring at the plugging point, efficient and automatic retrieval of the monitor, and precise control of the timing of plugging removal. Therefore, it is necessary to propose a combined temporary plugging ball and its temporary plugging fracturing operation method to solve the above problems.

[0006] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a combined temporary plugging ball and its temporary plugging fracturing operation method, which integrates temporary plugging, monitoring, and recovery, thereby supporting the efficient exploitation of low-permeability unconventional oil and gas reservoirs.

[0008] The specific technical solution of the embodiments of the present invention is as follows: A combined temporary plugging ball includes: a setting ball, at least one set of traction balls, and a controllable fracture link connecting the setting ball and the traction balls; the setting ball is used to plug a perforation orifice, and the outer contour dimension of the setting ball is larger than the contour dimension of the perforation orifice; the at least one set of traction balls includes a first traction ball and a second traction ball distributed opposite to each other on both sides of the setting ball, and a monitor is installed inside each traction ball to acquire temperature and pressure signals at the plugging position of the setting ball, and the outer contour dimension of the traction ball is smaller. Regarding the profile dimensions of the perforation orifice, the traction ball serves as a guiding element for the setting ball, enabling it to preferentially enter the perforation orifice relative to the setting ball and apply traction force to the setting ball. The traction ball includes a swellable layer made of a swellable composite material, and the density of the swollen traction ball is less than the density of the fracturing fluid. The controllable fracture link is used to transmit the traction force generated by the traction ball to the setting ball. The controllable fracture link is configured to automatically fracture after a preset time, or automatically fracture after the downhole temperature and / or pressure reaches a preset fracture condition.

[0009] Furthermore, the controllable fracture link includes a multi-layer composite structure, which includes an outer protective layer and a biodegradable layer inside the protective layer. The controllable fracture link also has a pressure-sensitive stress weakening part and a temperature-sensitive heat-sensitive part inside.

[0010] Furthermore, the heat-sensitive part is located in the middle of the biodegradable layer, and the stress-weakening part is disposed on the outer surface of the biodegradable layer.

[0011] Furthermore, the stress-reducing portion includes a plurality of notches disposed inward from the outer surface of the degradable layer, the plurality of notches being distributed at intervals along the circumferential direction.

[0012] Furthermore, the setting ball is a biodegradable setting ball made of biodegradable material.

[0013] Furthermore, the aperture of the perforation hole is d, the outer contour of the setting ball is spherical or non-spherical, and the outer contour of the traction ball is spherical or non-spherical. When the outer contours of both the setting ball and the traction ball are spherical, the diameter D1 of the setting ball satisfies: D1≥1.25d; the diameter D2 of the traction ball satisfies: D2≤0.9d.

[0014] Furthermore, the sealing performance coefficient P of the combined temporary plugging ball satisfies the following relationship:

[0015] In the formula, D1 is the diameter of the setting ball; d is the aperture of the perforation orifice; ρ1 is the density of the setting ball; ρ f This represents the density of the fracturing fluid.

[0016] Furthermore, the number of groups of traction balls is 1 to 3.

[0017] A method for temporary plugging fracturing operations based on any of the aforementioned combined temporary plugging balls, the method comprising: The combined temporary plugging ball is inserted into the wellbore and pumped to the target perforation section using fracturing fluid; After the traction ball enters the perforation orifice and pulls the setting ball to complete the setting, the temperature and pressure signals at the sealing position are collected by the monitor inside the traction ball, and at the same time the traction ball continues to swell in contact with the fracturing fluid. After the fracturing operation is completed, the flowback is carried out. The controllable fracture link breaks after the predetermined fracture triggering condition is met, and the setting ball and the traction ball separate from each other. The separated traction ball can float to the wellhead with the flowback fluid. The traction ball is retrieved at the wellhead, and monitoring data is recovered through a monitor inside the traction ball.

[0018] Furthermore, the predetermined fracture triggering conditions include: pressure meeting a preset pressure condition, temperature meeting a preset temperature condition, and usage time meeting a preset fracture duration, and the triggering priorities from high to low are: preset pressure condition, preset temperature condition, and preset fracture duration.

[0019] Furthermore, the pressure meeting the preset pressure conditions includes: the wellbore pressure drop exceeding 30%, or the pressure fluctuation reaching twice the normal operating pressure fluctuation range; the temperature meeting the preset temperature conditions includes: the downhole temperature rising more than 50°C relative to the formation temperature, or the downhole temperature falling below the preset operating temperature lower limit.

[0020] Furthermore, the controllable fracture link is internally provided with a pressure-sensitive stress weakening part and a temperature-sensitive thermal part; when neither the downhole temperature nor the pressure is abnormal, the preset fracture time of the controllable fracture link is controlled between 2 hours and 8 hours; or, when only the pressure is abnormal downhole, the pressure-sensitive stress weakening part inside the controllable fracture link fails preferentially, causing the controllable fracture link to fracture in the first time; or, when only the temperature is abnormal downhole, the temperature-sensitive thermal part inside the controllable fracture link degrades rapidly, causing the controllable fracture link to fracture in the second time; or, when both pressure and temperature are abnormal downhole simultaneously, the pressure-sensitive stress weakening part inside the controllable fracture link fails preferentially, and the temperature-sensitive thermal part inside the controllable fracture link degrades rapidly, causing the controllable fracture link to fracture in the third time, wherein the third time, the first time, the second time, and the preset fracture time increase sequentially.

[0021] The technical solution of the present invention has the following significant beneficial effects: The combined temporary plugging ball provided in this application includes a setting ball, a pair of traction balls, and a controllable fracture connector. The controllable fracture connector enables reliable separation of the setting ball and the traction ball under unplugging conditions. The traction ball contains a monitor and is equipped with a swellable layer made of a swellable composite material. After swelling, its overall density is lower than that of the fracturing fluid. After unplugging and separation, the traction ball can float autonomously and reach the wellhead with the flowback fluid, eliminating the need for complex downhole mechanical retrieval devices. The traction ball and its internal monitor can be retrieved intact, significantly improving the recovery rate and data integrity of downhole in-situ temperature and pressure monitoring devices. The controllable fracture connector enables reliable separation of the setting ball and the traction ball under unplugging conditions. The fractured joint can automatically break after a preset time, or break after the downhole temperature and pressure reach the preset fracture conditions. This allows for precise control of the unplugging timing to match construction needs, effectively avoiding premature or delayed fracture during construction. It ensures stable temporary plugging and sealing effects, continuity of temporary plugging and fracturing operations, and downhole construction safety. The combined temporary plugging ball can be deployed, set, monitored, separated, and retrieved at the wellhead in an integrated process, greatly simplifying the on-site construction process, reducing the investment in supporting equipment and downhole disposal procedures, effectively reducing the overall operating cost, and thus strongly supporting the efficient fracturing development of low-permeability reservoirs and unconventional oil and gas reservoirs.

[0022] Specific embodiments of the invention are disclosed in detail below with reference to the description and accompanying drawings, indicating how the principles of the invention can be employed. It should be understood that the embodiments of the invention are not therefore limited in scope. Features described and / or shown for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments. Attached Figure Description

[0023] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. Those skilled in the art, guided by the teachings of this invention, can select various possible shapes and proportions to implement the invention according to specific circumstances.

[0024] Figure 1 This is a schematic diagram of the structure of a combined temporary blocking ball provided in the embodiments of this application; Figure 2 This is a cross-sectional view of a controllable fracture link in a combined temporary plug ball provided in the embodiments of this application; Figure 3 This is a schematic diagram of a combined temporary plug ball being set up according to an embodiment of this application; Figure 4 This is a schematic diagram of a combined temporary blocking ball return discharge provided in the embodiments of this application; Figure 5 This is a schematic diagram of the controlled fracture link in a combined temporary plug ball provided in this application embodiment when it fractures. Figure 6 This is a schematic diagram of a combined temporary blocking ball system provided in this application, showing the traction ball floating at the inlet. Figure 7 This is a panoramic view of the swelling, floating, and backflow of a traction ball after the controllable fracture link in a combined temporary plug ball provided in this application breaks.

[0025] The reference numerals in the above figures are as follows: 1. Seated ball; 2. Traction ball; 21. First traction ball; 22. Second traction ball; 23. Monitor; 24. Swellable layer; 3. Controllable fracture connection components; 31. Protective layer; 32. Biodegradable layer; 33. Thermal part; 34. Stress-weakened areas; 4. Perforation holes; 5. Shaft; 6. Wellhead. Detailed Implementation

[0026] The details of the present invention can be more clearly understood by referring to the accompanying drawings and the description of specific embodiments. However, the specific embodiments of the present invention described herein are for illustrative purposes only and should not be construed as limiting the invention in any way. Under the teachings of this invention, those skilled in the art can conceive of any possible modifications based on the invention, all of which should be considered within the scope of the invention. It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there may be an intervening element. The terms "mounted," "connected," and "connected" should be interpreted broadly, for example, they can refer to mechanical or electrical connections, or internal communication between two elements, and can be direct or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] Currently, the shortcomings of existing technologies directly lead to the following engineering challenges: Difficulty in acquiring monitoring data; in-situ temperature and pressure data at the plugging point cannot be reliably obtained using existing temporary plugging balls, forcing field engineers to rely on indirect surface data or experience, affecting construction accuracy and safety; Lack of data support for construction optimization; lack of measured data at the plugging point, resulting in a lack of accurate basis for optimizing fracturing parameters, simulating fracture propagation, and evaluating plugging effectiveness, affecting the reproducibility and improvement potential of the process; High monitoring costs; if complex mechanical recovery devices or fiber optic monitoring systems are used, equipment investment and operation and maintenance costs increase significantly, making large-scale application difficult under economically feasible conditions; Increased operational risks; if the monitor cannot be recovered normally, it may cause blockage in the wellbore, affecting subsequent operations, or even causing downhole malfunctions, increasing additional retrieval and disposal costs.

[0029] In summary, existing technologies are insufficient to meet the dual demands of in-situ monitoring of the plugging point and efficient recovery of monitoring equipment during temporary plugging fracturing operations in unconventional oil and gas reservoirs. The industry urgently needs a recoverable monitoring system that can be run along with the plugging ball, collect temperature and pressure data in situ at the plugging point, and automatically separate and discharge with the flowback fluid to the wellhead after unplugging. This system should be characterized by its simple structure, reliable recovery, controllable cost, and strong adaptability, eliminating the need for complex mechanical recovery devices and achieving an organic integration of temporary plugging and monitoring functions.

[0030] This invention proposes a swelling and floating combined temporary plugging ball with a controllable fracture link. Through the innovative swelling and floating mechanism and the design of the controllable fracture link, the efficient recovery of the monitor is achieved, filling the technological gap in the field of integrated temporary plugging, monitoring and recovery. This promotes the development of temporary plugging fracturing technology towards intelligence and precision, thereby supporting the efficient exploitation of low-permeability unconventional oil and gas reservoirs.

[0031] Please refer to the following for comprehensive information. Figures 1 to 7 This application specification provides a combined temporary plugging ball, which may include: a setting ball 1, at least one set of traction balls 2, and a controllable fracture link 3 connecting the setting ball 1 and the traction balls 2; the setting ball 1 is used to plug a perforation orifice 4, and the outer contour dimension of the setting ball 1 is larger than the contour dimension of the perforation orifice 4; the at least one set of traction balls 2 includes a first traction ball 21 and a second traction ball 22 distributed opposite to each other on both sides of the setting ball 1, and a monitor 23 is provided inside the traction ball 2, the monitor 23 being used to acquire temperature and pressure signals at the plugging position of the setting ball 1. The outer contour dimension of the traction ball 2 is smaller than the contour dimension of the perforation hole 4. The traction ball 2 serves as a guiding element for the setting ball 1, enabling it to preferentially enter the perforation hole 4 relative to the setting ball 1 and apply traction force to the setting ball 1. The traction ball 2 includes a swellable layer 24 made of a swellable composite material, and the density of the traction ball 2 after swelling is less than the density of the fracturing fluid. The controllable fracture link 3 is used to transmit the traction force generated by the traction ball 2 to the setting ball 1. The controllable fracture link 3 is configured to automatically fracture after a preset time, or automatically fracture after the downhole temperature and / or pressure reaches a preset fracture condition.

[0032] The combined temporary plugging ball provided in this application includes a setting ball 1, a pair of traction balls 2, and a controllable fracture connector 3. The controllable fracture connector 3 enables reliable separation of the setting ball 1 and the traction ball 2 under unplugging conditions. The traction ball 2 is equipped with a monitor 23 and a swellable layer 24 made of a swellable composite material. After swelling, its overall density is lower than that of the fracturing fluid. After unplugging and separation, the traction ball 2 can float autonomously and reach the wellhead 6 with the flowback fluid. No complex downhole mechanical retrieval and recovery device is required; the traction ball 2 and its internal monitor 23 can be retrieved intact, significantly improving the recovery rate and monitoring data of the downhole in-situ temperature and pressure monitor 23. According to the integrity; the controllable fracture link 3 can automatically fracture after a preset time, or fracture after the downhole temperature and pressure reach the preset fracture conditions, so as to match the construction needs and accurately control the timing of unblocking, effectively avoiding the problems of premature or delayed fracture during construction, and stably ensuring the effect of temporary plugging and sealing, the continuity of temporary plugging fracturing operations, and downhole construction safety; the combined temporary plugging ball can adopt an integrated process of deployment, setting, monitoring, separation, and wellhead 6 retrieval, which greatly simplifies the on-site construction process, reduces the investment in supporting equipment and downhole treatment procedures, effectively reduces the overall operating cost, and thus strongly supports the efficient fracturing development of low-permeability reservoirs and unconventional oil and gas reservoirs.

[0033] The present application will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] like Figure 1 As shown, the combined temporary blocking ball includes a setting ball 1, a pair of traction balls 2, and a controllable breakage link 3.

[0035] The setting ball 1 is used to seal the perforation orifice 4, the diameter of which is d. The outer contour of the setting ball 1 is spherical or non-spherical (e.g., ellipsoidal, irregular, etc.). When the outer contour of the setting ball 1 is spherical, its diameter D1 satisfies: D1 ≥ 1.25d, thereby ensuring that the setting ball 1 has sufficient interference sealing margin and will not be squeezed into the perforation under high-pressure fracturing conditions. When the setting ball 1 is non-spherical, its outer contour dimensions are also sufficient to ensure that the setting ball 1 will not be squeezed into the perforation under high-pressure fracturing conditions.

[0036] Furthermore, the setting ball 1 is a biodegradable setting ball made of biodegradable materials. When the setting ball 1 is made entirely of biodegradable polymer composite material, after the controlled fracture link 3 breaks, the setting ball 1 can degrade on its own in the wellbore 5, eliminating the need for subsequent sand flushing and retrieval operations, thereby simplifying the wellbore 5 production recovery process.

[0037] The number of traction balls 2 is 1 to 3. Theoretically, the more traction balls 2 there are, the higher the data recovery rate. However, as the number of traction balls 2 increases, the resistance to the fluid in the wellbore 5 will also increase accordingly. Therefore, the number of traction balls 2 should not be too many and should be controlled within 3 sets.

[0038] For the same set of traction balls 2, it may include a first traction ball 21 and a second traction ball 22 distributed opposite to each other on both sides of the settling ball 1. The first traction ball 21 and the second traction ball 22 may have the same structure and be symmetrically distributed on both sides of the settling ball 1.

[0039] In this embodiment, taking a set of traction balls 2 as an example, one traction ball 2 serves as a guiding element, preferentially entering the perforation hole 4 relative to the setting ball 1 and applying traction force to the setting ball 1; the other traction ball 2 is located inside the wellbore 5. Each traction ball 2 is equipped with a monitor 23, which is used to acquire temperature and pressure signals at the sealing position of the setting ball 1. The monitor 23 inside the traction ball 2 entering the perforation hole 4 can acquire temperature and pressure data at the setting position outside the wellbore 5; the monitor 23 inside the traction ball 2 located at the setting position inside the wellbore 5 can acquire temperature and pressure data inside the wellbore 5, thereby ensuring that temperature and pressure data both inside and outside the wellbore 5 can be accurately monitored.

[0040] The outer contour of the traction ball 2 is spherical or non-spherical (e.g., ellipsoidal, irregular, etc.). The diameter of the perforation hole 4 is d. When the outer contour of the traction ball 2 is spherical, the diameter D2 of the traction ball 2 satisfies: D2≤0.9d, thereby ensuring that the traction ball 2 can pass through the perforation hole without obstruction, and the dragging action is stable and does not get stuck. When the traction ball 2 is non-spherical, its outer contour size is only sufficient to ensure that the traction ball 2 can pass through the perforation hole without obstruction.

[0041] The traction ball 2 includes a swellable layer 24 made of a swellable composite material. The density of the swelled traction ball 2 is less than that of the fracturing fluid. In use, the traction ball 2 provides traction force to assist the setting ball 1 in sealing after reaching the target perforation section. It adjusts its density by increasing its volume through swelling. After the setting ball 1 seals, it separates and floats upwards. A monitor 23 carrying temperature and pressure data is designed to monitor the temperature and pressure data at the downhole setting position in real time.

[0042] The controllable fracture link 3 is used to connect the setting ball 1 and the traction ball 2. The main body of the controllable fracture link 3 can be made of a biodegradable material.

[0043] The two ends of the controllable fracture connector 3 can be detachably connected to the setting ball 1 and the traction ball 2. For example, it can be detachably connected to the setting ball 1 and the traction ball 2 through a snap-fit ​​structure. If the two ends of the controllable fracture connector 3 are fixed to the setting ball 1 and the traction ball 2 in one piece using an integrated molding process, the molding interface is easily damaged by the fracturing fluid and formation fluid in the wellbore 5 over a long period of time, which may cause the controllable fracture connector 3 to fracture abnormally and prematurely, interfering with the upward floating and recovery process of the traction ball 2 and reducing the integrity and recovery accuracy of downhole monitoring data acquisition. In contrast, the detachable connection method used in this application can avoid the risk of premature failure caused by fluid erosion; in addition, the detachable connection method can also realize the independent batch processing and classified storage of each component. Before construction, different specifications of the setting ball 1, the traction ball 2 and the controllable fracture connector 3 can be flexibly matched according to the target perforation diameter and formation conditions, improving the adaptability of the combined temporary plugging ball to the working conditions.

[0044] like Figure 2 As shown, in one embodiment, the controllable fracture link 3 includes a multi-layer composite structure, comprising an outer protective layer 31, a biodegradable layer 32 within the protective layer 31, and a pressure-sensitive stress-reducing portion 34 and a temperature-sensitive thermosensitive portion 33 disposed internally within the controllable fracture link 3. Specifically, the thermosensitive portion 33 is located in the middle of the biodegradable layer 32, and the stress-reducing portion 34 is disposed on the outer surface of the biodegradable layer 32. The stress-reducing portion 34 includes multiple notches disposed inwardly from the outer surface of the biodegradable layer 32, with the multiple notches spaced circumferentially.

[0045] In this embodiment, the controllable fracture link 3 is formed by a multi-layer composite structure, which may include an outer protective layer 31 and a biodegradable layer 32 disposed inside the protective layer 31. In addition to the above-mentioned matrix layer structure, the controllable fracture link 3 is also equipped with a pressure-sensitive stress weakening part 34 and a temperature-sensitive heat-sensitive part 33, which are used to respond to downhole pressure anomalies and temperature anomalies, respectively, to achieve multi-condition triggered fracture.

[0046] Specifically, the temperature-sensitive thermal element 33 is arranged in the geometric center region of the biodegradable layer 32, and the pressure-sensitive stress-weakening element 34 is arranged circumferentially on the outer surface of the biodegradable layer 32. The two types of sensing structures are arranged independently in separate zones and will not interfere with each other.

[0047] The thermally sensitive part 33 is placed in the middle of the biodegradable layer 32, so that the formation temperature can be uniformly conducted to the thermally sensitive part 33, avoiding misjudgment caused by local temperature fluctuations on the surface and improving temperature response sensitivity and judgment accuracy; the stress weakening part 34 is arranged in close contact with the outer surface of the biodegradable layer 32, and can directly bear the fluid load of the wellbore 5. The downhole pressure change can be applied to the weakened area instantly, and the pressure sensing response speed is faster.

[0048] The stress-weakening portion 34 can be composed of multiple notches formed from the outer surface of the biodegradable layer 32 inwards, with all notches evenly spaced along the circumferential direction of the outer wall of the biodegradable layer 32. The circumferentially distributed notches will form a mechanically weak area on the outer wall of the biodegradable layer 32. When the downhole pressure exceeds a preset threshold, the stress concentration effect will cause structural failure to occur preferentially at the notch location, accurately realizing the graded response logic of pressure-prioritized fracture.

[0049] Please refer to the following: Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 A method for temporary plugging fracturing operations based on any of the aforementioned combined temporary plugging balls, the method comprising: Step S10: Insert the combined temporary plugging ball into the wellbore 5, and use fracturing fluid to pump the combined temporary plugging ball to the target perforation section; Step S12: After the traction ball 2 enters the perforation hole 4 and pulls the setting ball 1 to complete the setting, the temperature and pressure signals at the sealing position are collected by the monitor 23 inside the traction ball 2, and the traction ball 2 continues to swell in contact with the fracturing fluid. Step S14: After the fracturing operation is completed, the flowback is carried out. The controllable fracture link 3 fractures after the predetermined fracture triggering condition is met. The setting ball 1 and the traction ball 2 separate from each other. The separated traction ball 2 can float up to the wellhead 6 with the flowback fluid. Step S16: Retrieve the traction ball 2 at the wellhead 6 and complete the monitoring data recovery through the monitor 23 inside the traction ball 2.

[0050] The predetermined fracture triggering conditions include: pressure meeting a preset pressure condition, temperature meeting a preset temperature condition, and usage time meeting a preset fracture duration, and the triggering priorities from high to low are: preset pressure condition, preset temperature condition, and preset fracture duration.

[0051] Specifically, the pressure meeting the preset pressure conditions includes: the pressure drop in wellbore 5 exceeds 30%, or the pressure fluctuation reaches twice the normal operating pressure fluctuation range; the temperature meeting the preset temperature conditions includes: the downhole temperature rises by more than 50°C relative to the formation temperature, or the downhole temperature is lower than the preset operating temperature lower limit.

[0052] In one embodiment, the controllable fracture link 3 is further provided with a pressure-sensitive stress weakening part 34 and a temperature-sensitive thermal part 33 inside; when neither the downhole temperature nor the pressure is abnormal, the preset fracture time of the controllable fracture link 3 is controlled between 2 hours and 8 hours; or, when only the pressure is abnormal downhole, the pressure-sensitive stress weakening part 34 inside the controllable fracture link 3 fails preferentially, causing the controllable fracture link 3 to fracture in the first time; or, when only the temperature is abnormal downhole, the temperature-sensitive thermal part 33 inside the controllable fracture link 3 degrades rapidly, causing the controllable fracture link 3 to fracture in the second time; or, when both pressure and temperature are abnormal downhole simultaneously, the pressure-sensitive stress weakening part 34 inside the controllable fracture link 3 fails preferentially, and the temperature-sensitive thermal part 33 inside the controllable fracture link 3 degrades rapidly, causing the controllable fracture link 3 to fracture in the third time, wherein the third time, the first time, the second time, and the preset fracture time increase sequentially.

[0053] In practical applications, such as during on-site temporary plugging fracturing operations, the combined temporary plugging ball provided in this application can precisely control the movement path and target perforation cluster of the combined temporary plugging ball by adjusting the initial diameter of the setting ball 1, the initial density of the material of the setting ball 1, and the density of the traction ball 2 after swelling. Using a large-diameter, high-density setting ball 1 increases the probability of the ball moving deep into the wellbore 5 and reaching the toe perforation cluster; using a small-diameter, low-density setting ball 1 makes it easier to remain in the shallow part of the wellbore 5, increasing the probability of sealing the root perforation cluster. Simultaneously, the internal or external surface of the setting ball 1 has a pre-reserved assembly interface connection structure to achieve stable assembly and cooperation between the setting ball 1 and the controllable fracture connector 3.

[0054] The traction ball 2 uses a swelling material as its component. The swelling material can be a hydrophilic polymer, elastomer, or composite material to ensure that the traction ball 2 has buoyancy after swelling. Its swelling rate and final swelling ratio can be controlled by the material formulation, cross-linking degree, and pretreatment process. The internal monitoring device 23 of the traction ball 2 should include at least a temperature sensor and a pressure sensor. The range, temperature tolerance, and pressure resistance of the temperature and pressure sensors should be matched with the on-site construction conditions to stably collect real-time temperature and pressure data at the sealing location.

[0055] The controllable fracture link 3 adopts a multi-layer composite structure, with an outer layer of high-temperature and corrosion-resistant material and an inner layer of controllable degradable polymer material. This ensures the stability of the controllable fracture link 3 in harsh downhole environments while precisely controlling the fracture timing. The controllable fracture link 3 employs an intelligent triggering mechanism that primarily uses time-triggered triggering, supplemented by pressure and temperature anomaly triggering. The specific implementation method is as follows: Time-triggered: Through material formulation design and degradant encapsulation technology, precise time-based fracture control is achieved. The controllable fracture link 3 contains a time-responsive degradant, the degradation rate of which can be precisely controlled by adjusting material thickness, cross-linking degree, and degradant concentration according to a preset operation time (typically 2-8 hours). The degradant utilizes microencapsulation technology, continuously releasing after the operation begins, ensuring that the fracture strength of the controllable fracture link 3 decreases below a critical value after the preset time, guaranteeing reliable separation under the impact of the backflow fluid during normal flowback. This mechanism features time-controllable characteristics and is unaffected by downhole environmental fluctuations, providing a primary guarantee for fracture control. Pressure Anomaly Trigger: To cope with complex downhole conditions and sudden emergencies, the controllable fracture connector 3 incorporates a pressure-sensitive weak structure (e.g., a pressure-sensitive stress weakening part 34). Specifically, a pressure judgment threshold is set: when the pressure drop in wellbore 5 exceeds 30%, or the pressure fluctuation reaches twice the normal operating fluctuation range, it is judged as a pressure anomaly. Under pressure anomaly conditions, the stress-weak structure fails first, accelerating the connector fracture; the pressure trigger threshold is higher than the normal backflow pressure fluctuation range to avoid accidental triggering during normal construction, mainly to achieve emergency unblocking downhole and ensure the safety of the tubing string and wellbore 5 operations.

[0056] Temperature anomaly triggering: The inner layer material of the controllable fracture connector 3 (e.g., temperature-sensitive thermal element 33) is temperature-sensitive. The criteria for determining a temperature anomaly are: a sudden increase in downhole temperature of more than 50°C relative to the original formation temperature, or a temperature in the wellbore 5 falling below the preset lower limit of the construction temperature. When a temperature anomaly occurs, the temperature-sensitive polymer material degrades rapidly, shortening the fracture cycle of the controllable fracture connector 3.

[0057] In practical use, the glass transition temperature of the polymer and the content of heat-sensitive modified components can be adjusted to adapt to the temperature trigger threshold of different formations, so as to cope with extreme working conditions such as high-temperature fluid flow and low formation temperature.

[0058] Pressure anomaly triggers have a higher priority than temperature anomaly triggers. Based on different downhole operating conditions, the fracture response logic is divided into four categories: Normal construction conditions: Downhole pressure and temperature are within the designed construction range, with no abnormal fluctuations. At this time, only the time-based main trigger is active, while the pressure and temperature auxiliary triggers are not activated. The controllable fracture link 3 slowly reduces its strength according to the preset degradation cycle of 2 to 8 hours, and then fractures smoothly under the fluid impact force during the backflow stage, matching the construction rhythm.

[0059] Abnormal pressure conditions: Sudden pressure conditions such as a pressure drop exceeding 30% or pressure fluctuations exceeding twice the normal operating range occur, but temperature parameters remain normal. In this case, the abnormal pressure trigger is activated first, directly accelerating the breakage of connecting parts through the failure of weak structures to achieve emergency unblocking. Temperature conditions are not involved in the trigger judgment, prioritizing the safety of wellbore 5 and equipment.

[0060] Abnormal temperature conditions: Temperature anomalies occur, such as a sudden temperature rise exceeding the formation temperature by more than 50°C, or an operating temperature falling below the design lower limit, but the pressure parameters remain stable. In this case, the abnormal temperature triggers the start-up mechanism, which accelerates the degradation of the inner temperature-sensitive material to shorten the fracture time, preventing the connection structure from becoming uncontrollable or the monitor 23 from failing due to high or low temperatures, and ensuring that the traction ball 2 can separate and float normally.

[0061] Pressure and temperature anomalies: Under extremely complex operating conditions, both pressure and temperature exceed thresholds simultaneously (such as large-scale formation fluid flow, accompanied by a sudden drop in pressure and a sudden change in temperature). In this case, the pressure anomaly triggers a priority response, first achieving instantaneous structural failure through the weakest structure; at the same time, the temperature-sensitive material degrades rapidly, further reducing the remaining strength of the connector. This dual action ensures rapid and complete breakage of the connector, minimizing operational risks.

[0062] In a specific implementation scenario, taking a temporary plugging and fracturing operation in a section of a deep shale gas horizontal well as an example, the target reservoir has a vertical depth of 3800m, a formation temperature of 135℃, a formation pressure coefficient of 1.4, a nominal diameter of d=12mm for the perforation hole 4, and the fracturing fluid in the wellbore 5 is a slickwater system with a density ρ f =1.02g / cm³, the designed temporary plugging construction time is 4 hours, and the goal is to plug a certain cluster of toe-end perforations in this section.

[0063] The above operating conditions directly determine the core parameters of the combined temporary plugging ball. The core parameters of the combined temporary plugging ball are designed to match the operating conditions of this well. A formation temperature of 135℃ will accelerate the reaction rate of the degradation material in the inner layer of the controllable fracture connector 3. Therefore, by increasing the cross-linking degree of the material to 75% and controlling the concentration of the encapsulated degradation agent to 8wt%, the main fracture time of the controllable fracture connector 3 can be precisely matched with the 4-hour construction window. Based on the perforation diameter, the initial diameter of the setting ball 1 is D1=15mm to meet the sealing requirement of D1≥1.25d, and the initial diameter of the traction ball 2 is D2=10.8mm to meet the through-hole requirement of D2≤0.9d. The formation pressure coefficient of 1.4 corresponds to a pressure anomaly trigger threshold set at a sudden pressure drop of 35% in wellbore 5, which is higher than the pressure fluctuation range of ±12% during normal construction, thus avoiding accidental triggering during operation. The fracturing fluid density of 1.02 g / cm³ corresponds to a target density of 0.85 g / cm³ after swelling of the traction ball 2. By adjusting the degree of cross-linking of the swelling material, a swelling ratio of 2.2 times is achieved to ensure sufficient upward floating force after unblocking. Based on historical data from multiple well sites, an empirical formula for the probability of the settling ball 1 being in place can be fitted. Specifically, the sealing performance coefficient P of the combined temporary plugging ball satisfies the following relationship:

[0064] In the formula, D1 is the diameter of the setting ball 1; d is the aperture of the perforation hole 4; ρ1 is the density of the setting ball 1; ρ f This represents the density of the fracturing fluid.

[0065] In this embodiment, ρ1 = 1.18 g / cm³ is taken. Substituting it into the above formula, the probability of the toe-end perforation reaching the target is about 91.2%, which is highly consistent with the actual 92% sealing success rate on site. This formula can optimize the diameter and density parameters of the sealing ball 1 in reverse according to the position of the target perforation cluster, which can significantly improve the accuracy, reliability and construction success rate of the temporary plugging operation.

[0066] The combined temporary plugging ball and its matching temporary plugging fracturing operation method provided in this application firstly, through the structural cooperation of the paired traction ball 2 penetrating the perforation and dragging the setting ball 1 to fit and seal, can stably complete the sealing operation of the perforation hole 4. At the same time, the temperature and pressure sensors integrated inside the traction ball 2 can simultaneously collect in-situ formation data at the sealing point, which solves the industry shortcoming of traditional temporary plugging tools that only have the function of plugging and cannot obtain the real temperature and pressure evolution law downhole. The collected measured data can intuitively reflect the fracture opening and extension state, and provide reliable data support for the dynamic adjustment of fracturing construction parameters on site.

[0067] Based on this, the traction ball 2 is made of a swellable composite material, which can continuously swell and reduce its overall density by relying on the fracturing fluid. After the controllable fracture link 3 is disconnected, it can float up to the wellhead 6 by its own buoyancy with the backflow fluid. Only a simple retrieval operation needs to be completed at the wellhead 6 to completely recover the monitor 23 and all monitoring data. There is no need to lower complex downhole retrieval tools, which fundamentally avoids the problem of the monitor 23 being stuck in the wellbore 5, causing channel blockage and permanent equipment damage, and greatly improves the recovery rate and data integrity of the monitoring device.

[0068] To address the challenge of adapting unblocking timing to varying downhole conditions, this application constructs a graded response system based on timed degradation and supplemented by emergency triggering for abnormal temperature and pressure using a multi-layered composite controllable fracture connector 3. Under normal operating conditions, the connector can steadily reduce its structural strength according to a preset cycle of 2 to 8 hours, matching the standard fracturing operation duration to ensure reliable sealing throughout the entire plugging process. When dangerous situations such as sudden pressure changes or significant temperature deviations from the design range occur downhole, the pressure-sensitive stress weakening part 34 and the temperature-sensitive thermal part 33 can function sequentially or synergistically according to preset priorities, prompting the connector to fracture in a timely manner to achieve emergency unblocking. This greatly enhances the operational safety redundancy of downhole tubing and equipment while ensuring continuous operation.

[0069] Meanwhile, this application can flexibly control the wellbore movement characteristics of the combined temporary plugging balls by adjusting the outer dimensions and density of the setting ball 1 and the density of the traction ball 2 after swelling. Combined with empirical formulas for plugging performance, the ball parameters can be quantitatively matched and designed. This can accurately adapt to the directional plugging requirements of perforation clusters at different positions at the toe and root ends, effectively improving the uniformity of reservoir segmentation. The setting ball 1 is made of biodegradable material, which can remain at the perforation position after separation and degrade on its own in the formation fluid environment. This eliminates the need for wellbore 5 recovery processes such as sand flushing and special retrieval in the later stages of construction, simplifying the overall on-site construction process, reducing the investment in supporting equipment and the consumption of downhole disposal consumables, and ultimately improving construction efficiency and reducing overall operating costs. The entire structure and process system is suitable for high-temperature, high-pressure, deep, low-permeability reservoir conditions, and can strongly support the efficient and economical development of unconventional oil and gas reservoirs such as shale gas and tight oil.

[0070] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from the others. Similar or identical parts between embodiments can be referred to interchangeably. The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be included within the scope of protection of the present invention.

Claims

1. A combined temporary blocking ball, characterized in that, The combined temporary clogging ball includes: a setting ball, at least one set of traction balls, and a controllable breakable connecting piece connecting the setting ball and the traction balls; The setting ball is used to block the perforation orifice, and the outer contour dimension of the setting ball is larger than the contour dimension of the perforation orifice; At least one set of the traction balls includes a first traction ball and a second traction ball distributed opposite to each other on both sides of the setting ball. A monitor is installed inside the traction ball. The monitor is used to acquire temperature and pressure signals at the sealing position of the setting ball. The outer contour dimension of the traction ball is smaller than the contour dimension of the perforation orifice. The traction ball serves as a guiding element for the setting ball, and can preferentially enter the perforation orifice relative to the setting ball and apply traction force to the setting ball. The traction ball includes a swellable layer made of a swellable composite material. The density of the swellable traction ball after swelling is less than the density of the fracturing fluid. The controllable fracture link is used to transmit the traction force generated by the traction ball to the setting ball. The controllable fracture link is configured to automatically fracture after a preset time, or automatically fracture after the downhole temperature and / or pressure reaches a preset fracture condition.

2. The combined temporary blocking ball as described in claim 1, characterized in that, The controllable fracture link includes a multi-layer composite structure, which includes an outer protective layer and a biodegradable layer inside the protective layer. The controllable fracture link also has a pressure-sensitive stress weakening part and a temperature-sensitive heat-sensitive part inside.

3. The combined temporary blocking ball as described in claim 2, characterized in that, The thermally sensitive part is located in the middle of the biodegradable layer, and the stress-reducing part is disposed on the outer surface of the biodegradable layer.

4. The combined temporary blocking ball as described in claim 3, characterized in that, The stress-reducing portion includes a plurality of notches disposed inward from the outer surface of the biodegradable layer, the plurality of notches being distributed at intervals along the circumferential direction.

5. The combined temporary blocking ball as described in claim 1, characterized in that, The setting ball is a biodegradable setting ball made of biodegradable material.

6. The combined temporary blocking ball as described in claim 1, characterized in that, The diameter of the perforation hole is d. The outer contour of the setting ball is spherical or non-spherical, and the outer contour of the traction ball is spherical or non-spherical. When the outer contours of both the setting ball and the traction ball are spherical... The diameter D1 of the settling sphere satisfies: D1 ≥ 1.25d; The diameter D2 of the traction ball satisfies: D2≤0.9d.

7. The combined temporary blocking ball as described in claim 6, characterized in that, The sealing performance coefficient P of the combined temporary plugging ball satisfies the following relationship: In the formula, D1 is the diameter of the setting ball; d is the aperture of the perforation orifice; ρ1 is the density of the setting ball; ρ f This represents the density of the fracturing fluid.

8. The combined temporary blocking ball as described in claim 1, characterized in that, The number of groups of traction balls is 1 to 3.

9. A method for temporary plugging fracturing operations based on the combined temporary plugging ball as described in any one of claims 1 to 8, characterized in that, The temporary plugging fracturing operation method includes: The combined temporary plugging ball is inserted into the wellbore and pumped to the target perforation section using fracturing fluid; After the traction ball enters the perforation orifice and pulls the setting ball to complete the setting, the temperature and pressure signals at the sealing position are collected by the monitor inside the traction ball, and at the same time the traction ball continues to swell in contact with the fracturing fluid. After the fracturing operation is completed, the flowback is carried out. The controllable fracture link breaks after the predetermined fracture triggering condition is met, and the setting ball and the traction ball separate from each other. The separated traction ball can float to the wellhead with the flowback fluid. The traction ball is retrieved at the wellhead, and monitoring data is recovered through a monitor inside the traction ball.

10. The temporary plugging fracturing operation method as described in claim 9, characterized in that, The predetermined fracture triggering conditions include: pressure meeting a preset pressure condition, temperature meeting a preset temperature condition, and usage time meeting a preset fracture duration, and the triggering priority from high to low is as follows: preset pressure condition, preset temperature condition, and preset fracture duration.

11. The temporary plugging fracturing operation method as described in claim 10, characterized in that, The pressure meets the preset pressure conditions, including: the wellbore pressure drop exceeds 30%, or the pressure fluctuation reaches twice the normal operating pressure fluctuation range. The temperature meeting the preset temperature conditions includes: the downhole temperature rising by more than 50°C relative to the formation temperature, or the downhole temperature falling below the preset operating temperature lower limit.

12. The temporary plugging fracturing operation method as described in claim 11, characterized in that, The controllable fracture connector is also provided with a pressure-sensitive stress weakening part and a temperature-sensitive heat-sensitive part inside. When the downhole temperature and pressure are not abnormal, the preset fracture time of the controllable fracture connector is controlled between 2 hours and 8 hours; or, When only an abnormal pressure occurs downhole, the pressure-sensitive stress weakening part inside the controllable fracture connector fails first, causing the controllable fracture connector to fracture in the first time. or, When only a temperature anomaly occurs downhole, the temperature-sensitive thermal element inside the controllable fracture connector degrades rapidly, causing the controllable fracture connector to fracture in a second time. or, When both pressure and temperature abnormalities occur simultaneously downhole, the pressure-sensitive stress weakening part inside the controllable fracture connector fails first, while the temperature-sensitive thermal part inside the controllable fracture connector degrades rapidly, causing the controllable fracture connector to fracture within a third time period. The third time period, the first time period, the second time period, and the preset fracture duration increase sequentially.

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