Leaking stoppage tool and method for drilling leakage formation and drilling fluid leakage model thereof

Abstract

The invention relates to a leaking stoppage tool for a drilling leakage stratum, and relates to the field of petroleum drilling leaking stoppage, the leaking stoppage tool comprises a deformable plugging assembly, a sealing structure is arranged at the end of the deformable plugging assembly, an expansion assembly is arranged in the deformable plugging assembly, and the expansion assembly is in sliding connection with the deformable plugging assembly; and the expansion assembly is used for performing reaming deformation on the deformable plugging assembly in the self-contraction state to be in the expansion state. The anti-leakage plugging device has the advantages that effective plugging can be achieved under the condition that the diameter of a well hole is not reduced, the reliability is high, the cost is low, the period is short, and the number of used machines and tools is small, different measures can be taken for different degrees of leakage working conditions, the good anti-leakage plugging effect is achieved, and the normal drilling effect of well drilling is guaranteed.

Description

Technical Field

[0001] This application relates to the field of oil well plugging, and in particular to a plugging tool, method and drilling fluid loss model for encountering a lost formation. Background Technology

[0002] During the drilling process, lost circulation zones, collapsed zones, and high-pressure zones are frequently encountered, which increases the cost and time of drilling, seriously affects the normal progress of drilling operations, and may even lead to the inability to reach the target layer, thus hindering exploration and production.

[0003] Well leakage treatment methods can generally be divided into: particle bridge plug plugging, static plugging, composite plugging, and casing-assisted isolation. The specific method should be selected based on factors such as the cause of the leakage and the geological characteristics of the affected formation. Medium-volume karst leakage, well leakage in adjustment wells, low-pressure and ultra-low-pressure formations, formations with multiple pressure systems coexisting, and coexisting blowouts are considered catastrophic accidents in the drilling industry.

[0004] Due to the complex and variable underground conditions, there are relatively few effective sealing technologies and materials for dealing with cavern-type leaks. Cement grout is commonly used for sealing, and conventional cement grout is effective for small caverns with low flow velocities. However, when encountering large caverns or high-velocity water caverns, it is necessary to add effective bridging structures and a large amount of filling material to form a sealing layer. Commonly used materials include gravel, sawdust, and cottonseed hulls. While these materials are economical, their drawback is that bridging materials are difficult to form a sealing layer in large caverns, and after cement injection, it is difficult to form a monolithic filler. Sometimes chemical materials are used for sealing, but chemical sealing grouts are expensive and not suitable for large-scale use.

[0005] For explosive plugging technology for fractured wells with leakage, a downhole explosion is used to send a gel-filled syringe tip into the formation. While squeezing the formation fractures, the gel inside the syringe flows out, further sealing and stabilizing the well wall, thus achieving the plugging effect.

[0006] Using electrical imaging technology, the following methods were employed: ① large-particle bridging and filling materials were selected and wrapped with tar paper, such as cottonseed hulls, walnut shells, cement, and quicklime; ② red bricks were selected as bridging materials; ③ long fibrous materials, such as palm rope, were added for bridging; and ④ red clay lumps were selected as bridging and filling materials. These methods successfully sealed the karst leakage in the Koso 1 well.

[0007] To address the aforementioned challenges, in addition to conventional leak-sealing techniques, new leak-sealing processes such as polymer crosslinking agent leak sealing and tool-based leak sealing have been developed. With a deeper understanding of leak prevention and sealing processes, physical leak-sealing methods are receiving increasing attention.

[0008] Regarding the aforementioned technologies, the inventors believe that current technologies are not effective in addressing the problems of poor stability in mudstone, shale, coal seam, and salt gypsum formations, which can easily lead to well collapse, necking, and other complex and severe leakage issues encountered during drilling. Furthermore, these technologies are complex, costly, and time-consuming, and cannot adequately solve the complex wellbore conditions caused by variations in wellbore diameter, azimuth rate, and inclination rate. Summary of the Invention

[0009] In order to achieve effective plugging without reducing the wellbore diameter, and to have the characteristics of high reliability, low cost, short cycle and few tools required, and to be able to take different measures to deal with different degrees of leakage, so as to achieve good leakage prevention and plugging effect and ensure normal drilling, this application provides a plugging tool, method and drilling fluid leakage model for drilling into leakage formations.

[0010] This application provides a plugging tool for encountering lost formations during drilling, employing the following technical solution:

[0011] A plugging tool for drilling into a lost formation includes a deformable plugging component. The end of the deformable plugging component is provided with a closed structure. An expansion component is provided inside the deformable plugging component. The expansion component is slidably connected to the deformable plugging component. The expansion component transforms the deformable plugging component from a contracted state to an expanded state.

[0012] Optionally, the deformable sealing assembly includes a deformable bellows. In its contracted state, the deformable bellows includes oppositely arranged troughs and oppositely arranged crests. Along the circumference of the deformable bellows, the troughs and crests are arranged sequentially and are fixedly connected. In its expanded state, the deformable bellows has an annular structure, and the inner diameter of the annular structure is greater than the maximum distance between the two opposite crests.

[0013] Optionally, the expansion assembly includes a tube expander located inside the deformable plugging assembly. The outer wall of the tube expander abuts against the inner wall of the deformable plugging assembly, and the tube expander enlarges the deformable plugging assembly from a contracted state to an expanded state.

[0014] Optionally, the sealing structure includes a coupling portion located at the end of the deformable sealing assembly, and a plug head is provided at one end of the coupling portion away from the deformable sealing assembly, the plug head sealing the coupling portion and the interior of the deformable sealing assembly.

[0015] Optionally, a transition joint is provided between the coupling and the deformable sealing assembly. One end of the transition joint is fixedly connected to the coupling, and the other end of the transition joint is fixedly connected to the deformable sealing assembly. The shape of the end of the transition joint near the coupling is the same as that of the coupling, and the shape of the end of the transition joint near the deformable sealing assembly is the same as that of the deformable sealing assembly.

[0016] This application also provides a method for plugging leaks encountered during drilling, applied to the aforementioned plugging tool for encountering leaks in a formation, the method comprising:

[0017] S11: Drill through the lost circulation formation to determine the isolation section and wellbore size;

[0018] S12: Determine the enlargement section based on the isolation section, and enlarge the well using an enlarger;

[0019] S13: Insert the deformable sealing component into the eye-expanding position of the eye expander;

[0020] S14: The deformable plugging component is expanded, and the deformable plugging component changes from a contracted state to an expanded state;

[0021] S15: Lower the tube expander for mechanical shaping, trim the deformable plugging component, and press the outer wall of the deformable plugging component tightly against the well wall to seal the formation.

[0022] Optionally, in S14, expanding the deformable plugging assembly includes hydraulic expansion, which brings the outer wall of the deformable plugging assembly tightly against the well wall after the reamer has enlarged the well.

[0023] Optionally, in S15, the mechanical shaping sequentially includes: grinding the upper port of the deformable sealing assembly with a grinding shoe, expanding the tube with a spherical tube expander, expanding the tube with a roller tube expander, milling the lower bottom valve with a grinding shoe, and trimming with a lower milling cone.

[0024] This application also provides a drilling fluid loss model, applied to the aforementioned plugging tool for encountering a loss-prone formation, wherein the drilling fluid loss model includes:

[0025] S21: Determine whether well leakage has occurred and the type of well leakage that has occurred;

[0026] S22: Establish a well leakage model;

[0027] S23: Determine the extent of formation fracturing or fracture extension.

[0028] Optionally, in S21, well leakage occurs when the following formula is satisfied:

[0029] P d (h,t0)>PLs (h)

[0030] Among them, P d (h,t0) represents the drilling fluid pressure at a depth h and time t0 during the drilling process, P Ls (h) represents the leakage initiation pressure at the same depth h.

[0031] Optionally, in S21, after satisfying the well leakage requirement, the well leakage type includes: rupture leakage, fracture leakage, permeability leakage, and cavernous leakage.

[0032] Optionally, the ruptured leakage satisfies the following equation:

[0033] p r ≥p f

[0034] Where, p r p is the bottom hole pressure. f This refers to the formation fracturing pressure.

[0035] Optionally, the crack-like leakage satisfies the following formula:

[0036]

[0037] Where, p fe p is the propagation pressure of the crack. fri This represents the flow resistance of the drilling fluid in the formation. Optionally, the permeability loss satisfies the following equation:

[0038] p sL =p fri+ p lfri

[0039] Where, p fri p is the flow resistance of drilling fluid in the formation. lfri This represents the seepage resistance of drilling fluid in the filter cake.

[0040] Optionally, the fractured leakage: the leakage pressure of the fractured leakage satisfies the following formula:

[0041] p fL =p f

[0042] Where, p f This refers to the formation fracturing pressure.

[0043] Optionally, the leakage pressure of the fissure leakage and the cavernous leakage satisfies the following formula:

[0044] p rL =p p

[0045] Optionally, after leakage starts, the mechanical equilibrium equations needed to maintain leakage are:

[0046] P d (h,t)>P Lf (h,t)+P Le (h)(t>t0,P d (h,t)>P Ls (h));

[0047] Where, p d (h,t) represents the drilling fluid pressure in the wellbore at a certain depth h and time t during drilling, p Lf (h,t) represents the flow resistance of drilling fluid at the same depth t in the lost circulation channel, p Le (h,t) represents the leakage channel extension pressure at time t at the same depth.

[0048] If P cannot be satisfied d (h,t0)>P Ls When (h) is used, it indicates that no omissions will occur;

[0049] If P is satisfied d (h,t0)>P Ls Under the premise of (h), P is not satisfied. d (h,t)>P Lf (h,t)+P Le (h)(t>t0,P d (h,t)>P Ls (h) indicates that the leakage will not continue;

[0050] If both of the above equations are satisfied, it means that not only will leakage occur, but the leakage will continue indefinitely.

[0051] Optionally, in S22, the leakage model is:

[0052]

[0053] Where Q is the leakage velocity of this layer, m 3 / s; D is the inner diameter of the wellbore; m; Ga is the excitation pressure gradient, N / m 3 G e The equivalent density of the drilling fluid circulation is N / m³. 3 G Ls Leakage pressure gradient, N / m 3 G d The pressure gradient caused by the drilling rate, in N / m 3 ρ is the drilling fluid density, kg / m³ 3 φ represents the porosity of the lost section of the formation, which is dimensionless; h1 and h2 are the starting and ending depths of the lost section, respectively; c is a constant.

[0054] Optionally, in S22, when the pressure inside the wellbore exceeds the formation fracturing pressure, the formation is fractured, increasing the cross-sectional area of ​​the leakage channels for drilling fluid flowing into the formation. This leads to an increase in permeability and porosity. The porosity term is a variable that changes over time. The above formula can be:

[0055]

[0056] Where Q is the leakage velocity of this layer, m 3 / s; D is the inner diameter of the wellbore; m; Ga is the excitation pressure gradient, N / m 3 G e The equivalent density of the drilling fluid circulation is N / m³. 3 G Ls Leakage pressure gradient, N / m 3 G d The pressure gradient caused by the drilling rate, in N / m 3 ρ is the drilling fluid density, kg / m³ 3 φ(t) represents porosity, which is dimensionless; h1 and h2 are the starting and ending depths of the leakage layer, respectively.

[0057] In summary, this application includes at least one of the following beneficial technical effects:

[0058] This application presents a corrugated pipe plugging technology, a mechanical plugging method with advantages such as simple construction, low operating cost, and significant plugging effect, effectively addressing severe well leakage problems. This technology achieves effective plugging without reducing the wellbore diameter and features high reliability, low cost, short cycle time, and minimal equipment usage. It can address different leakage conditions with different measures, achieving good leakage prevention and plugging effects and ensuring normal drilling progress. Utilizing this characteristic, the pipe can be smoothly inserted into the well to reach the predetermined well section. Downhole, hydraulic or mechanical methods are used to expand the pipe, transforming its cross-sectional shape into a larger diameter circular pipe that fits tightly against the well wall, achieving the purpose of sealing the formation. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the overall structure of a plugging tool for drilling into a lost formation, as described in an embodiment of this application.

[0060] Figure 2 This is a schematic diagram of a plugging tool for encountering a lost formation during drilling, showing its transformation from an expanded state to a contracted state in an embodiment of this application.

[0061] Figure 3 This is a schematic diagram of a plugging tool for encountering a lost formation during drilling, showing its transformation from a contracted state to an expanded state, according to an embodiment of this application.

[0062] Figure 4This is a schematic diagram of the structure of the eye-expanding device used in a method for plugging leaks in a drilling formation according to an embodiment of this application.

[0063] Figure 5 This is a schematic diagram of the structure of a plugging tool for encountering a lost formation during drilling, as described in an embodiment of this application.

[0064] Figure 6 This is a schematic diagram of the pressure expansion tube structure of a method for plugging leaks in a drilling-encountered formation according to an embodiment of this application.

[0065] Figure 7 This is a schematic diagram of the structure of a method for plugging leaks in a drilling formation according to an embodiment of this application.

[0066] Figure 8 This is a schematic diagram of the upper port of the grinding shoe in a method for plugging leaks in a drilling formation according to an embodiment of this application.

[0067] Figure 9 This is a schematic diagram of the structure of a spherical tube expander for a method of plugging leaks in a drilling-encountered formation according to an embodiment of this application.

[0068] Figure 10 This is a schematic diagram of the structure of a roller expander for a method of plugging leaks in a drilling formation according to an embodiment of this application.

[0069] Figure 11 This is a schematic diagram of the bottom valve of the grinding shoe milling process in a method for plugging leaks in a drilling formation according to an embodiment of this application.

[0070] Figure 12 This is a schematic diagram of the structure of the milling cone trimming in a method for plugging leaks in a drilling formation according to an embodiment of this application.

[0071] Figure 13 This is a schematic diagram of the completed structure of a method for plugging leaks in a drilling-encountered formation according to an embodiment of this application.

[0072] Explanation of reference numerals in the attached drawings: 1. Deformable sealing assembly; 11. Deformable bellows; 111. Valley section; 112. Peak section; 2. Enclosed structure; 21. Joint section; 22. Plug head; 3. Transition assembly; 31. Transition joint; 311. Deformable section; 312. Connecting section. Detailed Implementation

[0073] During the drilling process, lost circulation zones, collapsed zones, and high-pressure zones are frequently encountered, which increases the cost and time of drilling, seriously affects the normal progress of drilling operations, and may even lead to the inability to reach the target layer, thus hindering exploration and production.

[0074] Well leakage treatment methods can generally be divided into: particle bridge plug plugging, static plugging, composite plugging, and casing-assisted isolation. The specific method should be selected based on factors such as the cause of the leakage and the geological characteristics of the affected formation. Medium-volume karst leakage, well leakage in adjustment wells, low-pressure and ultra-low-pressure formations, formations with multiple pressure systems coexisting, and coexisting blowouts are considered catastrophic accidents in the drilling industry.

[0075] Due to the complex and variable underground conditions, there are relatively few effective sealing technologies and materials for dealing with cavern-type leaks. Cement grout is commonly used for sealing, and conventional cement grout is effective for small caverns with low flow velocities. However, when encountering large caverns or high-velocity water caverns, it is necessary to add effective bridging structures and a large amount of filling material to form a sealing layer. Commonly used materials include gravel, sawdust, and cottonseed hulls. While these materials are economical, their drawback is that bridging materials are difficult to form a sealing layer in large caverns, and after cement injection, it is difficult to form a monolithic filler. Sometimes chemical materials are used for sealing, but chemical sealing grouts are expensive and not suitable for large-scale use.

[0076] For explosive plugging technology for fractured wells with leakage, a downhole explosion is used to send a gel-filled syringe tip into the formation. While squeezing the formation fractures, the gel inside the syringe flows out, further sealing and stabilizing the well wall, thus achieving the plugging effect.

[0077] Using electrical imaging technology, the following methods were employed: ① large-particle bridging and filling materials were selected and wrapped with tar paper, such as cottonseed hulls, walnut shells, cement, and quicklime; ② red bricks were selected as bridging materials; ③ long fibrous materials, such as palm rope, were added for bridging; and ④ red clay lumps were selected as bridging and filling materials. These methods successfully sealed the karst leakage in the Koso 1 well.

[0078] To address the aforementioned challenges, in addition to conventional leak-sealing techniques, new leak-sealing processes such as polymer crosslinking agent leak sealing and tool-based leak sealing have been developed. With a deeper understanding of leak prevention and sealing processes, physical leak-sealing methods are receiving increasing attention.

[0079] Regarding the aforementioned technologies, the inventors believe that current technologies are not effective in addressing the problems of poor stability in mudstone, shale, coal seam, and salt gypsum formations, which can easily lead to well collapse, necking, and other complex and severe leakage issues encountered during drilling. Furthermore, these technologies are complex, costly, and time-consuming, and cannot adequately solve the complex wellbore conditions caused by variations in wellbore diameter, azimuth rate, and inclination rate.

[0080] In order to achieve effective plugging without reducing the wellbore diameter, and to have the characteristics of high reliability, low cost, short cycle and few tools required, and to be able to take different measures to deal with different degrees of leakage, so as to achieve good leakage prevention and plugging effect and ensure normal drilling, this application provides a plugging tool, method and drilling fluid leakage model for drilling into leakage formations.

[0081] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0082] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0083] The following is in conjunction with the appendix Figure 1-13 This application will be described in further detail.

[0084] This application discloses a plugging tool for drilling into a lost formation. (Refer to...) Figure 1 , Figure 2 A plugging tool for drilling into a lost formation includes a vertically arranged deformable plugging component 1. A sealing structure 2 is located at each end of the deformable plugging component 1. A transition component 3 is located between the sealing structure 2 and the deformable plugging component 1. One end of the transition component 3 is connected to the end of the deformable plugging component 1, and the other end of the transition component 3 is connected to the end of the sealing structure 2. The sealing structure 2 can seal the end of the deformable plugging component 1. Because the deformable plugging component 1 is a deformable structure, the shape of the transition component 3 near the end of the deformable plugging component 1 is the same as the shape of the end of the deformable plugging component 1, and the shape of the transition component 3 near the end of the sealing structure 2 is the same as the shape of the end of the sealing structure 2.

[0085] The deformable plugging assembly 1 includes a deformable corrugated pipe 11, which is made of a circular pipe through cold pressing to make the cross section corrugated. During the drilling and completion process, the corrugated pipe string is lowered into the well and the string is restored to a circular pipe by hydraulic or mechanical means, so as to plug the complex formation and maintain the original wellbore size.

[0086] Reference Figure 2 , Figure 3 The deformable bellows 11 has a corrugated cross-section in the contracted state, which allows it to be inserted into the wellbore when it is in the contracted state. When the deformable bellows 11 is in the expanded state, its cross-section is circular, which allows the outer wall of the deformable bellows 11 to abut against the inner wall of the wellbore, sealing the inner wall of the wellhead and effectively dealing with severe well leakage.

[0087] When the deformable bellows 11 is in a contracted state, the deformable bellows 11 includes a trough portion 111 and a crest portion 112 arranged opposite to each other. Along the circumference of the deformable bellows 11, the trough portion 111 and the crest portion 112 are arranged sequentially, and the trough portion 111 and the crest portion 112 are fixedly connected. The position where the trough portion 111 and the crest portion 112 are connected is smoothly transitioned.

[0088] The maximum spacing between the opposite troughs 111 is less than the length of the diameter of the deformable bellows 11 before deformation, and the maximum distance between the opposite troughs 111 is less than the length of the diameter of the deformable bellows 11 before deformation.

[0089] This allows the deformable bellows 11 to extend into the wellbore after it is in a contracted state. After the deformable bellows 11 is moved to a predetermined position, it is expanded so that it changes from a contracted state to an expanded state, and the outer wall of the deformable bellows 11 is in close contact with the inner wall of the well.

[0090] In some embodiments, the trough portions 111 and crest portions 112 may be arranged in a group opposite to each other. In other embodiments, the trough portions 111 and crest portions 112 may be arranged in two groups opposite to each other.

[0091] The trough portion 111 of the deformable bellows 11 has an inward concave structure, with a gap between two opposite trough portions 111. The center of the trough portion 111 is located from the two side components of the trough portion 111 toward the side away from the center of the bellows. The center of the trough portion 111 is an arc-shaped structure toward the center of the deformable bellows 11, with the center of the arc located on the side of the trough portion 111 away from the center of the deformable bellows 11.

[0092] The crest portion 112 of the deformable bellows 11 has an outward convex structure. The center of the arc of the outward convex structure is located on the side of the bellows portion close to the center of the deformable bellows 11, and the arc angle of the outward convex structure of the crest portion 112 is smaller than the arc angle of the trough portion 111.

[0093] The connection between the trough portion 111 and the crest portion 112 of the deformable bellows 11 is smoothly transitioned, and the connection between the trough portion 111 and the crest portion 112 of the deformable bellows 11 has an outward convex structure. When the deformable bellows 11 changes from a contracted state to an expanded state, the trough portion 111 expands from the inside out, and the concave structure of the trough portion 111 changes to an outward convex structure. The trough portion 111 and the crest portion 112 form a complete circular structure.

[0094] The diameter of the expanded circular structure is greater than the maximum distance between the two opposite troughs 111 during contraction, and the diameter of the expanded circular structure is greater than the maximum distance between the two opposite crests 112 during contraction.

[0095] Reference Figure 1 , Figure 2 The transition component 3 includes a transition joint 31, one end of which is fixedly connected to the deformable bellows 11, and the other end of which is fixedly connected to the closed structure 2.

[0096] The transition joint 31 includes a deformable part 311 located near one end of the deformable bellows 11, and a connecting part 312 is provided at one end of the transition joint 31 located near the closed structure 2. The deformable part 311 and the connecting part 312 are fixedly connected.

[0097] The deformable portion 311 of the transition joint 31 has the same external structure as the deformable bellows 11, and is fixedly connected to the end of the deformable bellows 11. The connecting portion 312 of the transition joint 31 has a circular shape and is used to connect the connecting portion 312 to the closed structure 2. The connecting portion 312 and the deformable portion 311 have a smooth transition, thereby smoothly connecting the closed structure 2 and the deformable bellows 11 through the transition joint 31.

[0098] The enclosed structure 2 includes a coupling part 21 near one end of the transition joint 31, which is fixedly connected to the transition joint 31. A plug head 22 is fixedly connected to the end of the coupling part 21 away from the transition joint 31, and the plug head 22 completely encloses the interior of the coupling part 21.

[0099] An expansion assembly is provided inside the deformable bellows 11. The outer wall of the expansion assembly abuts against the inner wall of the deformable bellows 11. The expansion assembly can expand the deformable bellows 11 from a contracted state to an expanded state, thereby abutting the outer wall of the deformable bellows 11 against the inner wall of the wellbore.

[0100] After the deformable bellows 11 is placed inside the wellbore, it is initially expanded by hydraulic expansion, so that the concave part of the deformable bellows 11 expands outward and forms a preliminary circular structure.

[0101] After hydraulic expansion, a mechanical expansion component is inserted into the interior of the deformable corrugated pipe 11 to mechanically expand and trim the interior of the deformable corrugated pipe 11, thereby improving the expanded shape of the deformable corrugated pipe 11.

[0102] Reference Figures 4-13This application also discloses a method for plugging leaks encountered during drilling, applied to the aforementioned plugging tool for encountering leaks in a formation. The method for plugging leaks encountered during drilling includes:

[0103] S11: Drill through the lost circulation formation to determine the isolation section and wellbore size;

[0104] S12: Determine the enlarged well section based on the isolation well section, enlarge the well with an enlarger so that the diameter of the enlarged part of the enlarger is larger than the diameter of the inner wall of the wellbore, and make the deformable plugging component placed opposite the enlarged position of the enlarger. The diameter of the deformable plugging component after expansion is larger than the diameter inside the wellbore, and the pipe string can pass through the original size drill bit after expansion.

[0105] S13: Insert the deformable sealing component into the eye-expanding position of the eye expander;

[0106] S14: Expand the deformable sealing component, changing it from a contracted state to an expanded state. First, the interior of the deformable bellows is initially opened by hydraulic expansion, followed by the next step of mechanical expansion and shaping.

[0107] S15: The tube expander is lowered for mechanical shaping, which includes, in sequence, throwing and releasing the ball, grinding and washing the upper end of the tube with a grinding shoe, expanding the tube with a spherical tube expander, expanding the tube with a roller tube expander, grinding and milling the lower bottom valve with a grinding shoe, and trimming the lower milling cone. The deformable plugging component is trimmed, and the outer wall of the deformable plugging component is pressed tightly against the well wall to seal the formation.

[0108] In S12 above, reamers can be classified into two categories based on their reaming principle: fixed-wing reamers and movable-wing reamers. Fixed-wing reamers mainly refer to dual-center drill bits, consisting of a lead drill bit and reaming blades. These drill bits have no moving parts, exhibiting high reliability; they can withstand high drilling pressure and achieve high rotational speeds; and they have no special requirements regarding the solid content of the drilling fluid. Movable-wing reamers typically consist of three parts: the main body, the control mechanism, and the reaming body.

[0109] The RU series emphasizes the structural design of moving parts, enhances the strength of the reaming section and the overall structure, optimizes the water hole structure, rationally distributes water power, and improves the stability of the tool during operation. It can be used in conjunction with downhole power drilling tools.

[0110] During the drilling process, well leakage can occur due to factors such as formation, drilling fluid properties, and drilling parameters. Well leakage during drilling is not a static and constant process, but a dynamic and constantly changing one. For example, during drilling, some wells initially have a high leakage rate, but as drilling continues, the leakage rate gradually decreases and eventually stops; while other wells become increasingly severe as drilling continues.

[0111] Therefore, in order to better prevent and control well leakage, it is necessary to analyze and discuss the evolution of well leakage and the transformation process between different types of well leakage, and establish a dynamic leakage model of well leakage during drilling. This will have important reference value for formulating plans such as optimizing drilling parameters and adjusting drilling fluid performance to prevent well leakage.

[0112] Therefore, based on actual drilling conditions, a dynamic leakage model of drilling fluid is established. The model uses a classification method to represent the actual situation of formation fractures. The construction of a drilling fluid leakage model considering the influence of multiple factors is carried out. Based on the research results of drilling fluid equivalent circulating density and leakage pressure calculation, combined with formation lithology and structural location, a dynamic leakage model during the drilling process is established to reveal the relationship between various parameters during the drilling process and whether leakage occurs. This provides a strong reference or basis for effective leakage prevention and optimization of drilling parameters during the drilling process.

[0113] This application also provides a drilling fluid loss model, applied to the aforementioned plugging tool for encountering a loss-prone formation. The drilling fluid loss model includes:

[0114] S21: Determine whether well leakage has occurred and the type of well leakage that has occurred;

[0115] S22: Establish a well leakage model;

[0116] S23: Determine the extent of formation fracturing or fracture extension.

[0117] In S21, the first step is to establish the dynamic mechanical equilibrium relationship of well leakage;

[0118] The pressure of the drilling fluid in the wellbore is the sole driving force causing leakage. Therefore, to predict whether leakage will occur, it is only necessary to determine whether the pressure of the drilling fluid in the wellbore during drilling reaches the threshold that will cause well leakage. After well leakage occurs, to determine whether it can continue or terminate, the following two conditions are required:

[0119] ① Whether the energy possessed by the drilling fluid can continue to drive the drilling fluid to flow in the leakage channel, that is, whether the energy possessed by the drilling fluid can overcome the resistance encountered by the drilling fluid in the formation leakage channel.

[0120] ②Whether the energy possessed by the drilling fluid can continue to extend and expand the leakage channels, ensuring the continued flow of the drilling fluid and promoting the continued leakage.

[0121] Taking all the above conditions into account, it is not difficult to find that the conditions required for leakage to occur and be maintained during drilling can be summarized into the following two points:

[0122] P d (h,t0)>P Ls (h) (1)

[0123] P d (h,t)>P Lf (h,t)+P Le (h,t)(t>t0,P d (h,t0)>P Ls (h)) (2)

[0124] Among them, P d (h,t0) represents the drilling fluid pressure at a depth h and time t0 during the drilling process, P Ls (h) is the leakage initiation pressure at the same depth h, and leakage can only occur if equation (1) is satisfied.

[0125] When leakage occurs under the condition that equation (1) above is satisfied, the types of leakage include: rupture leakage, crack leakage, seepage leakage and cavern leakage.

[0126] Among them, rupture-related leakage mainly occurs in formations with few natural fractures and poor permeability, that is, the original well wall basically does not contain naturally formed fractures or cracks, and the permeability is low. The cause of leakage is that the drilling fluid pressure at the bottom of the well is greater than the formation rupture pressure, thus leading to pressure leakage.

[0127] p r ≥ p f (3)

[0128] In the formula, p r p is the bottom hole pressure. f This refers to the formation fracture pressure. It means that when the bottom hole pressure exceeds the formation fracture pressure, leakage will occur, and the leakage pressure is:

[0129] p fL = p f (4)

[0130] Where, p f This refers to the formation fracturing pressure.

[0131] Fracture-related leakage refers to leakage that occurs when the original formation already has natural fractures or when a series of fractures are formed in the formation during drilling.

[0132]

[0133] In the formula, p fe Let p be the fracture propagation pressure. This formula indicates that when the bottom hole pressure exceeds the fracture propagation pressure in the formation, complex leakage conditions can occur and be sustained. friThis represents the flow resistance of drilling fluid in the formation. In other words, for microfractures, maintaining leakage requires bottomhole pressure to overcome the flow resistance of the drilling fluid in the formation channel. For terrains or regions with strong tectonic stress, such as steep structures, the propagation pressure of the fracture is the minimum horizontal principal stress.

[0134] Permeability loss often occurs in shallow, loosely cemented sandstone and conglomerate sections. Due to the good permeability of the formation, drilling fluid will leak into the pores of the rock under the action of pressure differential in the well. However, the formation of mud cake will prevent or reduce the degree of leakage, so the leakage rate of permeability loss is not high.

[0135] p sL = p fri+ p lfri (6)

[0136] In the formula, p lfri This represents the seepage resistance of the drilling fluid in the filter cake. This formula indicates that for permeable leakage, if the quality of the mud filter cake is higher, the pressure required to cause leakage is also higher.

[0137] One type of loss is karst cavernous leakage: In certain limestone strata, karst caves are formed through long-term erosion by groundwater. When drilling encounters a karst cave, the drill string may run dry, sometimes reaching a depth of 4-5 meters, followed by circulation failure, with drilling fluid only flowing in and not out. The leakage rate is generally around 100 m / s². 3 A leakage rate exceeding / h often leads to blowouts or well collapses and stuck pipe accidents, constituting the most serious type of well leakage. As long as the bottom hole pressure exceeds the formation fluid pressure within the cavern, leakage is possible. The expression for the leakage pressure is as follows:

[0138] p rL = p p (7)

[0139] In equation (2), p d (h,t) represents the drilling fluid pressure at a certain depth h and time t during drilling.

[0140] p Lf (h,t) represents the flow resistance of drilling fluid at the same depth t in the lost circulation channel, p Le (h,t) represents the leakage channel extension pressure at the same depth at time t. As can be seen from the above, equation (2) is the mechanical equilibrium equation that needs to be maintained after leakage starts.

[0141] According to equation (2), the extension pressure and flow resistance of the leakage channel during the leakage process are both quantities that change with time. However, for common leakage, the extension pressure of the leakage channel is mostly the extension pressure of the fracture, and its value does not change much with time during the drilling process. Therefore, equation (2) can also be simplified to:

[0142] Pd (h,t)>P Lf (h,t)+P Le (h)(t>t0,P d (h,t)>P Ls (h)) (8)

[0143] Equations (1) and (8) constitute the dynamic mechanical equilibrium relationship of well leakage. If equation (1) is not satisfied, it means that leakage will not occur. If equation (2) is not satisfied under the premise of satisfying equation (1), it means that leakage will not continue and will gradually stop. If both equations are satisfied, it means that not only will leakage occur, but leakage will continue indefinitely.

[0144] To characterize the dynamic progression of leakage, let:

[0145] Δp(h,t)=p d (h,t)-p Lf (h)-p Le (h,t) (9)

[0146] Differentiating equation (9) with respect to time t, we get:

[0147]

[0148] Therefore, when Δp(h,t)>0, This indicates that the leakage has worsened. This indicates that the degree of leakage is gradually decreasing.

[0149] In summary, the expression for leakage pressure using pressure gradient is:

[0150]

[0151] In S22, the establishment of the well leakage model includes:

[0152] Basic model:

[0153] According to the momentum principle of fluid mechanics, see the following equation:

[0154] ρQu=ΔpAe (12)

[0155] In the formula, ρ is the drilling fluid density, kg / m³ 3 Q is the leakage velocity, m 3 / s; u is the flow velocity, m / s; p is the pressure, Pa; A e m is the cross-sectional area of ​​the leakage channel. 2 .

[0156] The cross-sectional area of ​​the leakage channel can be expressed by porosity and well wall area as formula (13), and can be expressed by leakage velocity and leakage area as formula (14).

[0157] A e =φA (13)

[0158] In the formula, A is the area of ​​the well wall in the leakage section, in meters. 2 ; This represents the porosity of the lost-flow strata, which is dimensionless.

[0159]

[0160] Substituting formulas (13) and (14) into formula (12), we get:

[0161]

[0162] Further simplification yields:

[0163]

[0164] Dividing the increase in hydraulic column pressure due to the activation pressure generated during tripping in and out of the well by the well depth yields the activation pressure gradient. Let the activation pressure gradient, drilling fluid circulating equivalent density, leakage pressure gradient, and pressure caused by drilling speed be G, respectively. a G e G Ls G d Substituting, we get:

[0165]

[0166] The differential equation for the leakage velocity per unit depth of formation can be expressed as:

[0167]

[0168] By simplification, we can obtain:

[0169]

[0170] Integrating the differential equation (19) for leakage rate yields equation (20):

[0171]

[0172] The simplified model yields the downhole leakage model during drilling:

[0173]

[0174] In the formula, Q is the leakage velocity of that layer, m 3 / s; D is the inner diameter of the well shaft, in meters; G a G e G Ls G dThese are the excitation pressure gradient, drilling fluid circulating equivalent density, leakage pressure gradient, and pressure gradient caused by drilling speed, in N / m³. 3 ρ is the drilling fluid density, kg / m³ 3 φ represents the porosity of the lost section of the formation, which is dimensionless; h1 and h2 are the starting and ending depths of the lost section, respectively; c is a constant.

[0175] In S23, the formation is fractured or the fractures extend.

[0176] When the pressure inside the wellbore exceeds the formation fracturing pressure, the formation is fractured. This increases the cross-sectional area of ​​the leakage channel for drilling fluid to flow into the formation, which can be considered as a significant increase in permeability and porosity. Thus, the porosity term in formula (13) should be a variable value that changes over time.

[0177] Equation (21) can be written as formula (22).

[0178]

[0179] In the formula, φ(t) represents porosity. Considering that the formation is under pressure leakage, the porosity continuously increases.

[0180] By establishing a dynamic model of leakage, the influencing factors affecting leakage were analyzed in depth. A corrugated pipe plugging technology applicable to different working conditions was constructed. A certain length of corrugated pipe was lowered into the leakage zone section of the well. Hydraulic expansion caused radial plastic deformation of the corrugated pipe, restoring its round shape. Mechanical shaping further ensured its fit with the well wall, achieving the purpose of sealing the leakage zone and plugging the leakage. This technology can achieve effective plugging without reducing the wellbore diameter and has the characteristics of high reliability, low cost, short cycle, and minimal equipment usage. It can take different measures to deal with different levels of leakage, achieving good leakage prevention and plugging effects and ensuring normal drilling. Finally, by optimizing the construction displacement, improving drilling fluid performance, and reducing the equivalent pressure gradient of the wellbore, a controlled pressure construction method can effectively control well leakage and scientifically guide on-site production. This achievement has good application prospects.

[0181] In this invention, the term "multiple" refers to at least two or more, unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0182] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A tool for plugging leaks encountered during drilling, characterized in that: It includes a deformable plugging component (1), the end of which is provided with a closed structure (2), and an expansion component is provided inside the deformable plugging component (1). The expansion component is slidably connected to the deformable plugging component (1), and the expansion component transforms the deformable plugging component (1) from a contracted state to an expanded state.

2. The plugging tool for encountering a lost formation during drilling according to claim 1, characterized in that: The deformable sealing assembly (1) includes a deformable bellows (11). When the deformable bellows (11) is in a contracted state, it includes oppositely arranged troughs (111) and oppositely arranged crests (112). Along the circumference of the deformable bellows (11), the troughs (111) and the crests (112) are arranged sequentially and are fixedly connected. When the deformable bellows (11) is in an expanded state, it is an annular structure. The inner diameter of the annular structure is greater than the maximum distance between the two opposite crests (112).

3. The plugging tool for encountering a lost formation during drilling according to claim 2, characterized in that: The expansion assembly includes a tube expander located inside the deformable plugging assembly (1). The outer wall of the tube expander abuts against the inner wall of the deformable plugging assembly (1). The tube expander expands the deformable plugging assembly (1) from a contracted state to an expanded state.

4. The plugging tool for encountering a lost formation during drilling according to claim 1, characterized in that: The closed structure (2) includes a coupling part (21) located at the end of the deformable sealing assembly (1). A plug head (22) is provided at one end of the coupling part (21) away from the deformable sealing assembly (1). The plug head (22) seals the coupling part (21) and the interior of the deformable sealing assembly (1).

5. The plugging tool for encountering a lost formation during drilling according to claim 4, characterized in that: A transition joint (31) is provided between the coupling part (21) and the deformable sealing assembly (1). One end of the transition joint (31) is fixedly connected to the coupling part (21), and the other end of the transition joint (31) is fixedly connected to the deformable sealing assembly (1). The shape of the end of the transition joint (31) near the coupling part (21) is the same as that of the coupling part (21), and the shape of the end of the transition joint (31) near the deformable sealing assembly (1) is the same as that of the deformable sealing assembly (1).

6. A method for plugging leaks encountered during drilling, characterized in that, The method of applying the plugging tool for encountering a lost formation as described in any one of claims 1-5 includes: S11: Drill through the lost circulation formation to determine the isolation section and wellbore size; S12: Determine the enlargement section based on the isolation section, and enlarge the well using an enlarger; S13: Insert the deformable sealing component (1) into the eye-expanding position of the eye expander; S14: The deformable plugging component (1) is expanded, and the deformable plugging component (1) changes from a contracted state to an expanded state; S15: Lower the tube expander for mechanical shaping, trim the deformable plugging component (1), and press the outer wall of the deformable plugging component (1) against the well wall to seal the formation.

7. The method for plugging leaks in drilled formations according to claim 6, characterized in that: In S14, the expansion of the deformable plugging assembly (1) includes hydraulic expansion, which brings the outer wall of the deformable plugging assembly (1) to the well wall after the reamer has expanded the well.

8. The method for plugging leaks in drilled formations according to claim 6, characterized in that: In S15, the mechanical shaping sequentially includes: grinding the upper port of the deformable sealing assembly with a grinding shoe, expanding the tube with a spherical tube expander, expanding the tube with a roller tube expander, milling the lower bottom valve with a grinding shoe, and trimming with a lower milling cone.

9. A drilling fluid loss model, characterized in that: A plugging tool for encountering a lost circulation formation as described in any one of claims 1-5, wherein the drilling fluid loss model comprises: S21: Determine whether well leakage has occurred and the type of well leakage that has occurred; S22: Establish a well leakage model; S23: Determine the extent of formation fracturing or fracture extension.

10. A drilling fluid loss model according to claim 9, characterized in that: In S21, well leakage occurs when the following equation is satisfied: P d (h,t0)>P Ls (h) Among them, P d (h,t0) represents the drilling fluid pressure at a depth h and time t0 during the drilling process. P Ls (h) represents the leakage initiation pressure at the same depth h.

11. The drilling fluid loss model according to claim 10, characterized in that: In S21, after satisfying the well leakage requirement, the well leakage type includes: rupture leakage, fracture leakage, permeability leakage, and cavernous leakage.

12. The drilling fluid loss model according to claim 11, characterized in that: The ruptured leakage satisfies the following equation: p r ≥p f Where, p r p is the bottom hole pressure. f This refers to the formation fracturing pressure.

13. The drilling fluid loss model according to claim 11, characterized in that: The crack-like leakage satisfies the following equation: Where, p fe p is the propagation pressure of the crack. fri This represents the flow resistance of drilling fluid in the formation.

14. The drilling fluid loss model according to claim 11, characterized in that: The permeable leakage satisfies the following equation: p sL =p fri+ p lfri Where, p fri p represents the flow resistance of drilling fluid in the formation. lfri This represents the seepage resistance of drilling fluid in the filter cake.

15. A drilling fluid loss model according to claim 12, characterized in that: The fractured leakage: The leakage pressure of the fractured leakage satisfies the following equation: p fL =p f Where, p f This refers to the formation fracturing pressure.

16. The drilling fluid loss model according to claim 11, characterized in that: The leakage pressure of the fissure leakage and the cavernous leakage satisfies the following formula: p rL =p p 。 17. A drilling fluid loss model according to any one of claims 10-16, characterized in that: After leakage starts, the mechanical equilibrium equations required to maintain leakage are: P d (h,t)>P Lf (h,t)+P Le (h)(t>t0,P d (h,t)>P Ls (h)); Where, p d (h,t) represents the drilling fluid pressure in the wellbore at a certain depth h and time t during drilling, p Lf (h,t) represents the flow resistance of drilling fluid at the same depth t in the lost circulation channel, p Le (h,t) represents the leakage channel extension pressure at time t at the same depth. If P cannot be satisfied d (h,t0)>P Ls When (h) is used, it indicates that no omissions will occur; If P is satisfied d (h,t0)>P Ls Under the premise of (h), P is not satisfied. d (h,t)>P Lf (h,t)+P Le (h)(t>t0,P d (h,t)>P Ls (h) indicates that the leakage will not continue; If both of the above equations are satisfied, it means that not only will leakage occur, but the leakage will continue indefinitely.

18. A drilling fluid loss model according to claim 9, characterized in that: In S22, the leakage model is: Where Q is the leakage velocity of this layer, m 3 / s; D is the inner diameter of the wellbore; m; Ga is the excitation pressure gradient, N / m 3 G e The equivalent density of the drilling fluid circulation is N / m³. 3 G Ls The leakage pressure gradient is N / m. 3 G d The pressure gradient caused by the drilling rate, in N / m 3 ρ is the drilling fluid density, kg / m³ 3 φ represents the porosity of the lost section of the formation, which is dimensionless; h1 and h2 are the starting and ending depths of the lost section, respectively; c is a constant.

19. A drilling fluid loss model according to claim 18, characterized in that: In S22, when the pressure inside the wellbore exceeds the formation fracturing pressure, the formation is fractured, increasing the cross-sectional area of ​​the leakage channels for drilling fluid flowing into the formation. This leads to an increase in permeability and porosity. The porosity term is a variable that changes over time. The above formula can be expressed as: Where Q is the leakage velocity of this layer, m 3 / s; D is the inner diameter of the wellbore; m; Ga is the excitation pressure gradient, N / m 3 G e The equivalent density of the drilling fluid circulation is N / m³. 3 G Ls The leakage pressure gradient is N / m. 3 G d The pressure gradient caused by the drilling rate, in N / m 3 ρ is the drilling fluid density, kg / m³ 3 φ(t) represents porosity, which is dimensionless; h1 and h2 are the starting and ending depths of the leakage layer, respectively.

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