Rock breaking control system and method adapting to formation drillability

Abstract

The rock breaking control system comprises a shell, a pressing cap, a piston and an elastic piece, the piston is arranged in the shell, and the piston can slide in the axial direction of the shell; a first sealing section and a second sealing section of the piston are in sealing fit with an inner cavity of the shell, and the piston divides the inner cavity of the shell into an upper oil cylinder and a lower oil cylinder; the pressing cap is in sealing fit with and fixedly connected with the end of the shell, a center hole is formed in the pressing cap in the axial direction of the pressing cap, and the center hole is used for injecting fluid into the shell; the piston further comprises a third sealing section matched with the center hole in a sealing mode. A fluid channel is arranged in the piston and communicated with a center hole in the pressing cap, the upper oil cylinder and the lower oil cylinder. The elastic piece is arranged in the shell and used for applying force towards the first cavity to the piston. Harmful vibration such as stick-slip vibration of the drill bit can be restrained, and therefore the PDC drill bit is protected.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas mining machinery and equipment, and in particular to a rock breaking control system and method adapted to the drillability of a formation. Background Art

[0002] PDC drill bits are prone to harmful vibrations such as bouncing, oscillation, buckling, and stick-slip when drilling deep into hard formations. When drilling into hard formations or complex strata with alternating hard and soft rock, the bit's cutting teeth penetrate too deeply, requiring significant energy to break the rock. At this point, the drill bit suddenly stops, increasing drillstring torque and accumulating internal energy until the rock in front of the cutting teeth is sheared. This energy is then released, causing the drill bit to rotate at several times the speed of the rotary table, subjecting a neutral point in the drillstring to alternating bidirectional torsion.

[0003] Long-term stick-slip vibration of drill bits can lead to reduced rock-breaking efficiency, shortened drill bit life, and even damage to wellbore integrity, leading to serious accidents such as tool breakage, resulting in significant losses in footage, cycle time, and costs. Therefore, seeking to improve drill bit structure and develop high-efficiency drill bits is the fundamental solution to stick-slip vibration. This has important practical significance for improving drilling efficiency, shortening cycle time, and efficiently developing unconventional resources.

[0004] Currently, the identification and diagnosis of harmful vibration in downhole drilling tools is primarily based on finite element analysis, surface measurements, and downhole instrumentation. Recent research indicates that drill bit design significantly influences the manifestation of stick-slip vibration in drilling tools. The root cause of stick-slip vibration lies in the interaction between the drill bit and the rock. Variations in the rock mechanical properties of the formation and the anisotropy of the rock cause variations in the penetration depth of the drill bit's cutters, which in turn alters the drill bit's rock-breaking efficiency and bottomhole motion.

[0005] Based on research on stick-slip vibration, several papers have proposed solutions, primarily focusing on drilling parameter optimization, vibration damping tools, and drill bit structural design. Kyllingstad and Hasley proposed reducing static friction at the bottom of the well, controlling the rotary table speed, and adjusting the drill bit speed by installing downhole tools. Li Wenfei et al. invented a vibration damper to adjust the relative position of the drill bit to the bottom of the well in real time. Some new drill bits have added structural designs such as stoppers and stop blocks.

[0006] Although the above solutions have reduced the stick-slip vibration of drill tools to a certain extent, the following major technical problems still exist: the mechanism of stick-slip vibration is unclear, and solutions for short sections can often only "treat the symptoms but not the root cause", which greatly reduces their service life and actual effect; the tool structure is complex, and for oil and gas drilling operations, the size of the wellbore and tool and the harsh environment of high temperature and high pressure seriously limit the processing and application of complex components; the application objects and scenarios have strict requirements and strong limitations; while reducing harmful vibrations, it also seriously affects the drilling speed, and there is no substantial economic effect from the perspective of the entire cycle. Summary of the Invention

[0007] The purpose of the present invention is to provide a rock breaking control system and method that adapts to the drillability of the formation. In view of the problem of stick-slip vibration and the defects and limitations of the above solutions, the present invention integrates the entire process from mechanism research, structural design to processing and testing, and proposes a rock breaking control system and method that adapts to the drillability of the formation. The present invention is based on the adaptive adjustment of the drill bit cutting teeth, thereby reducing the harmful vibration of the drill bit and the drill string, which in turn leads to the failure of the drill tool, and realizes efficient drilling in the process of drilling in complex formations, shortens the drilling time, and improves drilling efficiency. Through the adaptive adjustment of the internal structure of the rock breaking control system and the control method of the actual cutting depth of the PDC drill bit, the harmful stick-slip vibration of the drill bit and the drill string and the resulting premature failure of the drill tool are weakened or eliminated, thereby achieving the goal of improving the efficiency of drilling operations and shortening the drilling cycle, as well as improving the quality and efficiency of drilling operations in complex formations. In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0008] A rock breaking control system adapted to the drillability of the formation, the rock breaking control system comprises a housing, a pressure cap, a piston and an elastic member, wherein:

[0009] The piston is arranged in the housing and can slide along the axial direction of the housing;

[0010] The housing is provided with a first cavity, a second cavity, a third cavity, and a fourth cavity with successively increasing inner diameters. The piston includes a first sealing section and a second sealing section. The first sealing section is in sealing engagement with the first cavity, and the second sealing section is in sealing engagement with the second cavity. A first gap is defined between the second sealing section and an end of the second cavity close to the first cavity. A second gap is defined between the piston radially and the third cavity.

[0011] The pressure cap is sealed and fixedly connected to the fourth cavity, and a central hole is provided in the pressure cap along its axial direction, and the central hole is used to inject fluid into the shell; the piston also includes a third sealing section that is sealed and matched with the central hole;

[0012] A fluid channel is provided in the piston, and the fluid channel is connected to the central hole in the pressure cap, the third cavity and the second cavity;

[0013] The elastic member is disposed in the housing and is used to apply a force toward the first cavity to the piston.

[0014] Furthermore, the piston comprises an upper piston portion and a lower piston portion,

[0015] The third sealing section is provided at one end of the upper portion of the piston, and the other end of the upper portion of the piston is fixedly connected to one end of the lower portion of the piston;

[0016] The first sealing section and the second sealing section are both located at the lower part of the piston, and one end of the first sealing section extends out of the housing.

[0017] Furthermore, the fluid channel includes a valve core accommodating cavity provided at one end of the lower portion of the piston close to the upper portion of the piston, and a valve core is provided in the valve core accommodating cavity.

[0018] Furthermore, a limiting tooth is provided on one end of the first sealing section extending out of the housing.

[0019] Furthermore, the fluid channel includes a first central channel and a first cross channel provided at the lower portion of the piston, wherein:

[0020] The first central channel is connected to the valve core accommodating cavity and the first cross-shaped channel.

[0021] When the valve core is located at a specific position, one end of the valve core accommodating cavity close to the first central channel is sealed with the valve core.

[0022] Furthermore, the fluid channel includes a third central channel and a third cross-shaped channel provided in the upper portion of the piston, wherein:

[0023] The third central channel passes through the central axis of the upper part of the piston; the third cross-shaped channel is arranged radially along the upper part of the piston, and the third central channel is connected to the third cross-shaped channel.

[0024] Furthermore, the valve core is provided with a second central channel arranged along its axial direction;

[0025] The outer surface of the valve core is provided with a plurality of grooves arranged along its axial direction;

[0026] Wherein, the second central channel passes through the central axis of the valve core.

[0027] Furthermore, a threaded hole is provided in the central hole on a side away from the piston, and the threaded hole is used to connect an external pipeline or a sealing plunger.

[0028] Furthermore, the shape of the valve core end face is the same as the shape of the end face of the valve core accommodating cavity.

[0029] Furthermore, the elastic member is arranged on the outside of the piston, one end of the elastic member contacts the top surface of the pressure cap, and a limiting protrusion is provided on the upper part of the piston to contact the other end of the elastic member.

[0030] The present invention further provides a rock breaking control method adapted to the drillability of the formation, the method using the rock breaking control system as described above, comprising:

[0031] When the piston moves upward due to the pressure of the rock, the elastic member shortens, and the fluid flows downward from the second gap through the third central channel and the third cross channel of the upper part of the piston, the second central channel of the valve core, and the first central channel and the first cross channel of the lower part of the piston to the first gap; the valve core moves downward under the force of its own gravity and the fluid, causing the conical surface to be pressed into contact with the concave conical surface of the valve core accommodating chamber;

[0032] When the piston moves downward due to the reduction or disappearance of rock pressure, the elastic member stretches, and the fluid flows upward from the first gap through the first central channel and the first cross channel at the bottom of the piston, the second central channel and the groove of the valve core, and the third central channel and the third cross channel at the top of the piston to the third cavity. At this time, the valve core moves upward under the push of the fluid, and the conical surface separates from the concave conical surface of the valve core accommodating cavity.

[0033] Furthermore, when the piston moves upward due to the pressure of the rock and when the piston moves downward due to the reduction or disappearance of the rock pressure,

[0034] The elastic member is in a compressed state throughout the entire process, and the upper and lower end surfaces of the elastic member maintain contact with the pressure cap and the limiting protrusion on the upper part of the piston;

[0035] The length of the elastic member when the piston moves upward due to the pressure of the rock is smaller than the length of the elastic member when the piston moves downward due to the pressure of the rock being reduced or disappearing.

[0036] Technical effects and advantages of the present invention:

[0037] This rock-breaking control system, which adapts to the drillability of the formation, has no gear settings and meets drilling requirements under conditions of any hardness and any penetration depth. Under the dual control mechanism of internal elastic parts and flow-sensing flow, the piston can automatically respond to the retraction and extension length according to the hardness, brittleness, drillability and other formation characteristics of the current drilling formation, that is, dynamically adjust the actual penetration depth of the PDC drill bit's cutting teeth into the formation rock. This prevents the drill bit from stopping when the penetration depth is too deep in the formation rock in difficult-to-drill formations, thereby preventing the drill bit from stopping and torque accumulation between the drill bit and the drill string. After completing the crushing of the current rock portion, the drill bit is rotated at high speed again, causing the drill bit cutting teeth to hit the rock surface at high speed, which can lead to adverse conditions such as tooth collapse and fatigue damage of the drill tool. Therefore, the control system is conducive to suppressing the occurrence of harmful vibrations such as stick-slip vibration of the drill bit, thereby protecting the PDC drill bit; the control system is a fully mechanical structure without electronic components, and has good adaptability to the harsh working conditions of drilling underground; it does not impose additional requirements on the input torque, input speed, input bit pressure, etc. of the drill string, that is, disordered ground control can achieve the function of automatically adapting to different drilling operation conditions and formation lithology characteristics, which is conducive to the comprehensive speed-up, land saving, cost reduction and efficiency improvement of onshore or offshore drilling and completion operations.

[0038] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the structure of a rock breaking control system adapted to the drillability of the formation in a specific embodiment of the present invention;

[0040] Figure 2a This is a schematic diagram of the structural cross-section design of the housing in a specific embodiment of the present invention;

[0041] Figure 2b This is a schematic diagram of the three-dimensional structure of the housing in a specific embodiment of the present invention;

[0042] Figure 3a This is a schematic diagram of the structural cross-section design of the lower part of the piston in a specific embodiment of the present invention;

[0043] Figure 3b This is a schematic diagram of the three-dimensional structure of the lower part of the piston in a specific embodiment of the present invention;

[0044] Figure 4a This is a schematic diagram of the structural cross-sectional design of the valve core in a specific embodiment of the present invention;

[0045] Figure 4b A schematic top view of a valve core in a specific embodiment of the present invention;

[0046] Figure 4c A schematic diagram of the three-dimensional structure of the valve core in a specific embodiment of the present invention;

[0047] Figure 5a This is a schematic diagram of the structural cross-section design of the upper portion of the piston in a specific embodiment of the present invention;

[0048] Figure 5b This is a schematic diagram of the three-dimensional structure of the upper part of the piston in a specific embodiment of the present invention;

[0049] Figure 6a This is a schematic diagram of the structural cross-section design of the pressure cap in a specific embodiment of the present invention;

[0050] Figure 6b It is a schematic top view of the structure of the pressure cap in a specific embodiment of the present invention;

[0051] Figure 6c Schematic diagram of the three-dimensional structure of the pressure cap in a specific embodiment of the present invention;

[0052] Figure 7 Schematic diagram of the relative positions of the rock breaking control system and the PDC drill bit in a specific embodiment of the present invention;

[0053] Figure 8a The internal cross-sectional structure and schematic diagram of the control system in a specific embodiment of the present invention when the limiting teeth are fully extended;

[0054] Figure 8b The internal cross-sectional structure and schematic diagram of the control system in a specific embodiment of the present invention when the limiting teeth are half pressed into the working state;

[0055] Figure 8c It is a cross-sectional structure and schematic diagram of the internal structure of the control system in a specific embodiment of the present invention when the limiting teeth are fully pressed into the working state.

[0056] In the figure: 1. control system; 11. limiting teeth; 12. outer shell; 13. pressure cap; 14. upper oil cylinder; 15. elastic member; 16. lower oil cylinder; 17. upper part of piston; 18. valve core; 19. lower part of piston; 71. third center channel; 72. third cross-shaped channel; 73. external thread; 74. limiting protrusion; 75. second sealing groove; 81. second center channel; 82. groove; 83. conical surface; 91. first center channel; 92. first cross-shaped channel; 93. valve core accommodating chamber; 94. internal thread; 2. drill bit; 21. cutting teeth; 22. drill crown; 23. drill blade. DETAILED DESCRIPTION

[0057] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0058] In order to solve the shortcomings of the existing technology, the present invention discloses a rock breaking control system that adapts to the drillability of the formation, such as Figure 1 As shown, the rock breaking control system 1 includes a housing 12, a pressure cap 13, a piston and an elastic member 15, wherein the piston is arranged in the housing 12 and can slide along the axial direction of the housing 12;

[0059] The housing 12 is provided with a first cavity, a second cavity, a third cavity and a fourth cavity with successively increasing inner diameters. The piston includes a first sealing section and a second sealing section. The first sealing section is sealed with the first cavity, and the second sealing section is sealed with the second cavity. A first gap is formed between the second sealing section and an end of the second cavity close to the first cavity; a second gap is formed between the piston radially and the third cavity; wherein the first gap is smaller than the second gap; in a specific embodiment of the present invention, the first gap is used as Figure 1 As shown in the lower oil cylinder 16, the second gap is Figure 1 The upper oil cylinder 14 shown in ;

[0060] The pressure cap 13 is sealed and fixedly connected to the fourth cavity. A center hole is provided in the pressure cap 13 along its axial direction. The center hole is used to inject fluid into the shell 12. The piston also includes a third sealing section that is sealed with the center hole.

[0061] Combine Figure 1 As shown, the piston is of a split type, consisting of an upper piston portion 17, a lower piston portion 19, and a central valve core 18. The upper piston portion 17 and the lower piston portion 19 are fixedly connected by threads. After the connection, a cavity composed of a nearly cylindrical and conical body is formed in the middle, namely the valve core accommodating chamber 93, which is the location of the valve core 18. The shape of the valve core accommodating chamber 93 is similar to the outer shape of the valve core 18, and the valve core 18 is not fixedly connected to the valve core accommodating chamber 93. The height of the valve core accommodating chamber 93 is greater than the height of the valve core 18, and the inner diameter is slightly larger than the diameter of the valve core 18. Therefore, the valve core 18 can move axially up and down with the flow of oil without changing the relative positions of the upper and lower ends. At the same time, the valve core 18 does not generate significant frictional resistance when moving up and down.

[0062] The third sealing section is provided at one end of the piston upper part 17, and the other end of the piston upper part 17 is fixedly connected to one end of the piston lower part 19; the first sealing section and the second sealing section are both located at the piston lower part 19, and one end of the first sealing section extends out of the outer shell 12; a limiting tooth 11 is provided on the end of the first sealing section extending out of the outer shell 12.

[0063] In a specific embodiment of the present invention, a fluid channel is provided in the piston, and the fluid channel communicates with the central hole, the third cavity and the second cavity in the pressure cap 13; the fluid channel includes a first central channel 91 and a first cross-shaped channel 92 provided in the piston lower portion 19, a third central channel 71 and a third cross-shaped channel 72 provided in the piston upper portion 17, a second central channel 81 provided in the valve core 18, a groove 82 on the outer surface, and a valve core accommodating cavity 93; wherein,

[0064] The first central channel 91 communicates with the valve core accommodating cavity 93 and the first cross-shaped channel 92. When the valve core 18 is located at a specific position, the end of the valve core accommodating cavity 93 close to the first central channel 91 is sealed with the valve core 18.

[0065] The third central channel 71 passes through the central axis of the piston upper portion 17 ; the third cross-shaped channel 72 is radially arranged along the piston upper portion 17 , and the third central channel 71 is connected to the third cross-shaped channel 72 .

[0066] In a specific embodiment of the present invention, the shape of the end face of the valve core 18 is the same as the shape of the end face of the valve core accommodating cavity 93, which is used to ensure that when the oil flows downward, the valve core 18 is completely fitted with the end face of the valve core accommodating cavity 93, so that the four grooves 82 are closed, and the oil can only flow to the lower cylinder 16 through the second center channel 81.

[0067] Combine Figure 1 The elastic member 15 is arranged in the housing 12 and on the outside of the piston. The first end of the elastic member 15 contacts the top surface of the threaded section of the pressure cap 13, and the second end of the elastic member 15 contacts the sealing end of the upper part 17 of the piston.

[0068] In a specific embodiment of the present invention, the piston of the rock breaking control system 1 as a whole performs telescopic reciprocating motion under the action of the pressure formed by the internal elastic member 15 and the external rock.

[0069] A threaded hole is provided in the central hole on a side away from the piston, and the threaded hole is used to connect an external pipeline or a sealing plunger.

[0070] In a specific embodiment of the present invention, the first sealing segment, the second sealing segment and the third sealing segment are all provided with sealing grooves and sealing rings.

[0071] In a specific embodiment of the present invention, the housing 12 of the rock crushing control system 1, along with the piston, elastic member 15, and valve core 18, constitute the internal cylinder of the rock crushing control system 1, i.e., the oil flow space. The entire cylinder is divided into an upper cylinder 14 and a lower cylinder 16 by the piston.

[0072] In a specific embodiment of the present invention, Figure 2a and 2b As shown, the cavity inside the shell 12 is stepped, including a first cavity, a second cavity, a third cavity and a fourth cavity, wherein the inner diameters of the first cavity, the second cavity, the third cavity and the fourth cavity increase in sequence; the first cavity is in sliding sealing cooperation with the second end of the piston lower part 19; the second cavity is in sealing cooperation with the first end of the piston lower part 19; the elastic member 15 is arranged in the third cavity; the fourth cavity is provided with a thread that cooperates with the threaded section of the pressure cap 13, and the pressure cap 13 is sealed and connected to the shell 2. The first gap inside the second cavity serves as a sealing member. Figure 1 The lower oil cylinder 16 shown in FIG, the second gap in the third cavity as Figure 1 The upper oil cylinder 14 shown in the figure; the valve core 18 follows the expansion and contraction movement of the elastic member 15. The upper piston 17 is connected to the pressure cap 13 on the upper part of the rock breaking control system 1 and is sealed.

[0073] In a specific embodiment of the present invention, Figure 1 The housing 12 is fixedly connected to the pressure cap 13 by threads, and the pressure cap 13 is slidingly connected to the piston upper portion 17 via two sealing rings. The elastic member 15 is disposed on the outer side of the piston, with the first end of the elastic member 15 in non-connected contact with the top surface of the threaded section of the pressure cap 13, and the second end of the elastic member 15 in contact with the sealed end of the piston upper portion 17.

[0074] In one embodiment of the present invention, the elastic member 15 is installed so as to be sleeved on the outside of the piston upper portion 17 and in a pre-compressed state. At this time, the piston lower portion 19 and the stopper teeth 11 are fully extended. That is, when the control system 1 is in operation, the elastic member 15 is in a compressed state throughout the entire process. Therefore, the upper and lower end surfaces of the elastic member 15 always maintain contact with the pressure cap 13 and the stopper protrusion 74 of the piston upper portion 17, preventing them from disengaging.

[0075] In a specific embodiment of the present invention, Figure 3a and 3bAs shown, the piston lower part 19 includes an integrated piston column and a limit column; the limit column includes a first sealing groove and a limit tooth 11; the piston column is provided with an internal thread 94, a valve core accommodating chamber 93, a first center channel 91 and a first cross-shaped channel 92 in sequence, wherein the valve core accommodating chamber 93 is used to accommodate the valve core 18, and when the valve core 18 is located at a specific position, the valve core accommodating chamber 93 is close to one end of the first center channel 91 and is sealed with the valve core 18; the first cross-shaped channel 92 includes a plurality of through holes radially arranged along the piston lower part 19, and the end of the first center channel 91 is connected to the first cross-shaped channel 92; the internal thread is used to connect to the first end of the piston upper part 17.

[0076] In a specific embodiment of the present invention, Figures 4a-4c As shown, the valve core 18 includes a second central channel 81 and multiple grooves 82, wherein the second central channel 81 passes through the central axis of the valve core 18; the grooves 82 are arranged on the outside of the valve core 18, and the direction of the grooves 82 is parallel to the central axis of the valve core 18.

[0077] In a specific embodiment of the present invention, Figures 4a-4c The shape of the end face of the valve core 18 is the same as the shape of the end face of the valve core accommodating cavity 93. Preferably, the valve core 18 is approximately cylindrical, with one end being a plane and the other end being a nearly conical surface, and the conical surface can fit with the concave surface of the upper portion 17 of the piston. A second central channel 81 is axially opened at the center of the valve core 18, and four grooves 82 are opened on the outside. The second central channel 81 and the four grooves 82 are both flow channels for the fluid. The four grooves 82 are arranged in a cross in phase, and the angle between two adjacent grooves is 90°. Under different up and down movement states of the piston and the limiting tooth 11, the conical surface 83 of the valve core 18 contacts or disengages from the concave conical surface of the valve core accommodating cavity 93. When the piston moves downward and the fluid flows upward, the valve core 18 moves upward under the push of the fluid, and the conical surface 83 separates from the conical surface 93. At this time, the fluid flows through the second central channel 81 and the four grooves 82. When the piston moves upward and the fluid flows downward, the valve core 18 moves downward under its own weight and the push of the fluid, and makes the conical surface 83 contact the concave conical surface of the valve core accommodating cavity 93, and presses the valve core 18 under the action of the pressure difference. At this time, the fluid can only flow through the second central channel 81. As the valve core 18 moves up and down, the liquid can achieve different flow areas, different pressure differences, and different speeds of the piston's upward and downward extension and retraction when flowing up and down. Under the combined action of the above-mentioned throttling mechanism and the unidirectional thrust of the strong elastic member 15, the upward movement, i.e., the retraction speed of the piston, is significantly lower than the downward movement, i.e., the release speed of the piston.

[0078] In a specific embodiment of the present invention, Figure 5a-5bAs shown, the piston upper portion 17 includes a third central channel 71 and a third cross-shaped channel 72, wherein the third central channel 71 passes through the central axis of the piston upper portion 17; the third cross-shaped channel 72 is arranged radially along the piston upper portion 17, and the third central channel 71 and the third cross-shaped channel 72 intersect at the middle position of the piston upper portion 17; the piston upper portion 17 also includes an external thread 73, a limiting protrusion 74 and a second sealing groove 75, wherein the external thread 73 is arranged on the piston upper portion 17, the limiting protrusion 74 is arranged between the external thread 73 and the second cross-shaped channel 72; the diameter of the limiting protrusion 74 is larger than the external thread 73, one end of the limiting protrusion 74 is fitted with the end of the elastic member 15, and the other end of the limiting protrusion 74 is fitted with the end of the internal thread of the piston lower part 19; the second sealing groove 75 is arranged on the outside of the sealing end of the piston upper part 17, for sealing the outside of the first end of the piston upper part 17 with the inner side of the threaded section of the pressure cap 13.

[0079] In a specific embodiment of the present invention, Figures 6a-6c As shown, the pressure cap 13 includes a threaded section and a limiting section. The diameter of the threaded section of the pressure cap 13 is smaller than that of the limiting section. The pressure cap 13 is provided with a central hole extending through the center of the pressure cap 13. The central hole is a central hole that runs through the pressure cap 13 and enables the up and down movement of the piston. The central hole is connected to the central channel of the piston upper portion 17 and serves as a flow channel for the oil. A threaded hole is provided on the side of the center hole of the pressure cap 13 away from the piston. The threaded hole is used to inject oil after installation. The threaded hole is connected to an external pipeline or a sealing plunger by screws or other components.

[0080] The central axes of the central hole of the pressure cap 13, the third central channel 71, the second central channel 81 and the first central channel 91 coincide with each other.

[0081] In a specific embodiment of the present invention, the piston upper portion 17 has a third central channel 71 opened axially, a third cross-shaped channel 72 opened radially, and the piston lower portion 19 has a first central channel 91 opened axially, and a first cross-shaped channel 92 opened radially. The third central channel 71 extends all the way to the top of the piston upper portion 17, and a pressure cap 13 and a thread 73 are processed to serve as an oil injection hole; the piston upper portion 17 is connected and sealed to the pressure cap 13 on the upper portion of the rock breaking control system 1. The third central channel 71 and the third cross-shaped channel 72 intersect and penetrate in the middle of the piston upper portion 17, so that the lower oil cylinder 16 where the elastic member 15 is located communicates with the upper oil cylinder 14 on the upper portion of the valve core 18, thereby realizing the upward and downward reciprocating motion of the entire piston.

[0082] When the piston as a whole moves upward due to rock pressure, oil flows downward from the upper cylinder 14 through the piston upper portion 17 and lower portion 19, and the central channel 81 of the valve core 18 to the lower cylinder 16. Conversely, when the piston lower portion 19 breaks contact with the rock and moves downward only due to the thrust of the elastic member 15, oil flows upward from the lower cylinder 16 through the entire channel of the valve core 18 to the upper cylinder 14.

[0083] The valve core 18 is approximately cylindrical, with one flat end and a nearly conical surface at the other. The conical surface can fit the concave surface of the piston upper portion 17. A second central channel 81 is axially opened in the center of the valve core 18, and four grooves 82 are opened on the outside. The second central channel 81 and the four grooves 82 are both flow channels for the oil. The four grooves 82 are arranged in a cross pattern, with the phase angle between adjacent grooves being 90°. Under different up and down motion states of the piston and the limit tooth 11, the conical surface 83 of the valve core 18 comes into contact with or disengages from the concave conical surface 93 of the piston lower portion 19. When the piston moves downward and the oil flows upward, the valve core 18 moves upward under the push of the oil, and the conical surface 83 separates from the conical surface 93. At this time, the oil flows through the central channel 81 and the four grooves 82. When the piston moves upward and the oil flows downward, the valve core 18 moves downward under its own weight and the push of the oil, and makes the conical surface 83 contact the conical surface 93, and presses the valve core 18 under the action of the pressure difference. At this time, the oil can only flow through the central channel 81. As the valve core 18 moves up and down, the flow area and pressure difference when the oil flows up and down can be different. Under the combined effect of the above-mentioned throttling mechanism and the unidirectional thrust of the strong elastic member 15, the upward movement, i.e., the retraction speed of the piston, is significantly lower than the downward movement, i.e., the release speed of the piston.

[0084] During oil and gas drilling operations, the drill bit is exposed to a complex and harsh environment with high pressure and temperature, and is surrounded by drilling fluid and rock debris. If the rock breaking control system 1 is exposed to the above environment, its service life may be seriously affected. Therefore, the rock breaking control system 1 must be sealed after being installed in the drill bit blade to prevent drilling fluid from entering the space where the control system 1 is located. Figure 7 As shown, based on the actual use of the drill bit in oil and gas drilling operations, the rock breaking control system 1 is pre-installed at the blade 23 position of the PDC drill bit 2. The spherical stopper teeth 11 at the front end of the piston lower portion 19 extend out of the drill bit crown 22, slightly lower than the exposed height of the drill bit cutting teeth 21. This height difference is a key factor in ensuring that the cutting teeth 21 can continuously, effectively, and stably controllably penetrate and break the fresh rock surface. After the rock breaking control system 1 is installed at the blade 23 position of the PDC drill bit 2, it must be sealed due to the complex and harsh downhole temperature and pressure environment. This prevents drilling fluid, crushed rock cuttings, and other solid and liquid phases from entering the space where the rock breaking control system 1 is located, thereby reducing its service life.

[0085] The housing 12 of the rock breaking control system 1 adapted to the drillability of the formation is fixedly connected to the pressure cap 13 by threads, and the pressure cap 13 is slidably connected to the upper part 17 of the piston. The lower end of the strong elastic member 15 is in non-connected contact with the top surface of the pressure cap 13 of the rock breaking control system 1. When the elastic member 15 is installed, it is sleeved on the outside of the upper part 17 of the piston and is in a pre-compression state. At this time, the lower part 19 of the piston and the limiting tooth 11 are in a fully extended state. That is, when the rock breaking control system 1 is working, the elastic member 15 will be in a compressed state throughout the entire process, so the upper and lower end surfaces of the elastic member 15 always maintain contact with the pressure cap 13 and the limiting protrusion 74 of the upper part 17 of the piston and will not separate.

[0086] This rock-breaking control system, which adapts to the drillability of the formation, has no gear settings and meets drilling requirements under conditions of any hardness and any penetration depth. Under the dual control mechanism of internal elastic parts and flow-sensing flow, the piston can automatically respond to the retraction and extension length according to the hardness, brittleness, drillability and other formation characteristics of the current drilling formation, that is, dynamically adjust the actual penetration depth of the PDC drill bit's cutting teeth into the formation rock. This prevents the drill bit from stopping when the penetration depth is too deep in the formation rock in difficult-to-drill formations, thereby preventing the drill bit from stopping and torque accumulation between the drill bit and the drill string. After completing the crushing of the current rock portion, the drill bit is rotated at high speed again, causing the drill bit cutting teeth to hit the rock surface at high speed, which can lead to adverse conditions such as tooth collapse and fatigue damage of the drill tool. Therefore, the control system is conducive to suppressing the occurrence of harmful vibrations such as stick-slip vibration of the drill bit, thereby protecting the PDC drill bit; the control system is a fully mechanical structure without electronic components, and has good adaptability to the harsh working conditions of drilling underground; it does not impose additional requirements on the input torque, input speed, input bit pressure, etc. of the drill string, that is, disordered ground control can achieve the function of automatically adapting to different drilling operation conditions and formation lithology characteristics, which is conducive to the comprehensive speed-up, land saving, cost reduction and efficiency improvement of onshore or offshore drilling and completion operations.

[0087] The present invention also provides a rock breaking control method adapted to the drillability of the formation, the method comprising:

[0088] In the aforementioned rock breaking control system 1 adapted to formation drillability, the elastic member 15 is installed so that it fits over the outer surface of the piston upper portion 17 and is in a pre-compressed state. At this point, the piston lower portion 19 and the stopper teeth 11 are fully extended. That is, during operation, the elastic member 15 remains in a compressed state, with both its upper and lower end surfaces maintaining contact with the pressure cap 13 and the stopper protrusion 74 on the piston upper portion, preventing it from disengaging.

[0089] When the piston moves upward due to the pressure of the rock, the elastic member 15 shortens, and the fluid flows downward from the second gap through the third central channel 71 and the third cross channel 72 of the piston upper portion 17, the second central channel 81 of the valve core 18, and the first central channel 91 and the first cross channel 92 of the piston lower portion 19 to the first gap. The valve core 18 moves downward under the force of its own gravity and the fluid, causing the conical surface 83 to be pressed into contact with the concave conical surface of the valve core accommodating chamber 93.

[0090] When the piston moves downward due to reduced or absent rock pressure, elastic member 15 extends, and fluid flows upward from the first gap through first central channel 91 and first cross channel 92 of piston lower portion 19, second central channel 81 and groove 82 of valve core 18, and third central channel 71 and third cross channel 72 of piston upper portion 17 to the third chamber. At this point, valve core 18 moves upward under the force of the fluid, and conical surface 83 disengages from the concave conical surface of valve core accommodating chamber 93. Due to the difference in flow channel area, the piston moves downward at a significantly greater speed than it moves upward.

[0091] In a specific embodiment of the present invention, when the piston moves upward due to the pressure of the rock and when the piston moves downward due to the reduction or disappearance of the rock pressure, the elastic member 15 will be in a compressed state throughout the entire process, and the upper and lower end surfaces of the elastic member 15 remain in contact with the pressure cap 13 and the limiting protrusion 74 of the piston upper part 17; the length of the elastic member 15 when the piston moves upward due to the pressure of the rock is greater than the length when the piston moves downward due to the reduction or disappearance of the rock pressure.

[0092] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0093] During oil and gas drilling, the drill bit encounters various soft and hard formations. If the structural parameters of the drill teeth of the drill bit 2 remain unchanged and the operating parameters exhibit significant hysteresis, the drill bit will struggle to achieve maximum rock crushing efficiency, leading to complex accidents such as tooth breakage and fish dropping. A drill bit 2 equipped with a rock crushing and breaking control system 1 adapted to the formation's drillability, when drilling into formations with mixed soft and hard lithologies, dynamically controls the effective cutting depth of the drill teeth through adaptive reciprocating expansion and contraction of its internal piston, preventing the drill bit from becoming stuck.

[0094] Figure 8a-8c The internal cross-sectional structure of the control system 1 of the present invention in three working states is shown. Figure 8a The limit teeth are fully extended. Figure 8b Press the limit tooth halfway in. Figure 8cThe limit teeth are fully pressed in. The specific process is as follows: when the drill bit 2 is drilling in a hard formation or entering a soft formation, the cutting teeth 21 tend to increase the cutting depth, and the limit teeth 11 are subjected to the increased pressure of the rock surface, thereby generating an upward retraction trend. When the piston moves upward as a whole and the flow moves downward, under the action of the flow, the conical surface 83 of the valve core 18 contacts and presses the conical surface 93 of the piston lower part 19, and the flow can only pass through the central channel 81 of the valve core 18. Therefore, the flow area of ​​the valve core 18 is significantly reduced, and the flow is subjected to a large throttling resistance. At the same time, due to the thrust of the pre-compressed elastic member 15, the upward retraction speed of the piston is slow, and the height difference between the cutting teeth 21 and the limit teeth 11 will not increase rapidly, ensuring the stability of the drill bit 2 when drilling in hard formations or soft and hard interlaced formations. The limit teeth 11 always press against the rock surface to prevent the cutting teeth 21 from cutting too deep and causing the drill bit 2 to enter a sticking state ( Figure 8a ); When the drill bit 2 enters a softer formation, the depth of the cutting teeth 21 penetrating into the formation gradually increases, and the pressure exerted on the limit teeth 11 by the rock surface also gradually increases. The oil in the rock breaking control system 1 flows downward from the upper cylinder 14 through the piston to the lower cylinder 16, and is throttled by the valve core 18. The elastic member 15 of the rock breaking control system 1 and the lower part 19 of the piston together with the limit teeth 11 retract inward and upward at a relatively slow speed. The elastic member 15 of the rock breaking control system 1 is finally in a fully or deeply compressed state, the piston and the limit teeth 11 are in a retracted state, the height difference between the cutting teeth 21 and the limit teeth 11 is large, and the cutting teeth 21 cut deeper into the rock ( Figure 8c ), ensuring that the drill bit 2 achieves a higher mechanical penetration rate in soft formations. On the contrary, when the drill bit 2 enters the hard formation from the soft formation, the depth of the cutting teeth 21 cutting into the formation decreases, and the lower part 19 of the piston of the rock breaking control system 1 together with the limiting teeth 11 are extended outward and downward under the thrust of the pre-compressed elastic member 15. The oil in the rock breaking control system 1 flows upward from the lower oil cylinder 16 through the piston to the upper oil cylinder 14. At this time, the valve core 18 is pushed upward by the flow. In addition to the central channel 81 of the valve core 18, the liquid flow will also flow upward through the four grooves 82 on the outer surface of the valve core 18. Therefore, the flow area of ​​the valve core 18 is significantly increased, and the resistance to flow is reduced. The piston moves downward as a whole and extends quickly. The limiting teeth 11 quickly contact the rock surface and support the drill bit to bear the force, thereby quickly improving the stability of the drill bit 2 in cutting and rotating movement after entering the hard formation ( Figure 8a The overall upward and downward movement and position of the piston during this process are as follows ( Figure 8b ), the difference is that due to the one-way thrust of the elastic member 15 and the throttling effect at the valve core 18, the speed of the overall upward and downward movement of the piston is significantly different.

[0095] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A rock breaking control system adapted to the drillability of the formation, characterized in that: The rock breaking control system (1) comprises a housing (12), a pressure cap (13), a piston and an elastic member (15), wherein: The piston is arranged in the housing (12), and the piston can slide along the axial direction of the housing (12); The housing (12) is provided with a first cavity, a second cavity, a third cavity and a fourth cavity with successively increasing inner diameters, the piston comprising a first sealing section and a second sealing section, the first sealing section being in sealing engagement with the first cavity, the second sealing section being in sealing engagement with the second cavity, a first gap being provided between the second sealing section and an end of the second cavity close to the first cavity; and a second gap being provided between the piston radially and the third cavity. The pressure cap (13) is sealed and fixedly connected to the fourth cavity. A central hole is provided in the pressure cap (13) along its axial direction. The central hole is used to inject fluid into the housing (12). The piston also includes a third sealing section that is sealed and matched with the central hole. A fluid channel is provided in the piston, and the fluid channel is connected to the central hole in the pressure cap (13), the third cavity and the second cavity; The elastic member (15) is disposed in the housing (12) and is used to apply a force to the piston toward the first cavity.

2. A rock breaking control system adapted to formation drillability according to claim 1, characterized in that: The piston comprises an upper piston part (17) and a lower piston part (19), The third sealing section is provided at one end of the piston upper portion (17), and the other end of the piston upper portion (17) is fixedly connected to one end of the piston lower portion (19); The first sealing section and the second sealing section are both located at the lower part (19) of the piston, and one end of the first sealing section extends out of the housing (12).

3. A rock breaking control system adapted to formation drillability according to claim 2, characterized in that: The fluid channel comprises a valve core accommodating cavity (93) provided at one end of the piston lower portion (19) close to the piston upper portion (17), and a valve core (18) is provided in the valve core accommodating cavity (93).

4. A rock breaking control system adapted to formation drillability according to claim 3, characterized in that: A limiting tooth (11) is provided on one end of the first sealing section extending out of the housing (12).

5. The rock breaking control system adapted to formation drillability according to claim 3, characterized in that: The fluid channel comprises a first central channel (91) and a first cross channel (92) provided in the lower portion (19) of the piston, wherein: The first central channel (91) is connected to the valve core accommodating chamber (93) and the first cross-shaped channel (92). When the valve core (18) is located at a specific position, one end of the valve core accommodating cavity (93) close to the first central channel (91) is in sealing cooperation with the valve core (18).

6. The rock breaking control system adapted to formation drillability according to claim 3, characterized in that: The fluid passage comprises a third central channel (71) and a third cross-shaped channel (72) provided in the upper portion (17) of the piston, wherein: The third central channel (71) passes through the central axis of the piston upper part (17); the third cross-shaped channel (72) is arranged radially along the piston upper part (17), and the third central channel (71) is connected to the third cross-shaped channel (72).

7. The rock breaking control system adapted to formation drillability according to claim 2, characterized in that: The valve core (18) is provided with a second central channel (81) arranged along its axial direction; The outer surface of the valve core (18) is provided with a plurality of grooves (82) arranged along its axial direction; in, The second central channel (81) passes through the central axis of the valve core (18).

8. The rock breaking control system adapted to formation drillability according to claim 7, characterized in that: A threaded hole is provided in the central hole on a side away from the piston, and the threaded hole is used to connect an external pipeline or a sealing plunger.

9. The rock breaking control system adapted to formation drillability according to claim 3, characterized in that: The shape of the end face of the valve core (18) is the same as the shape of the end face of the valve core accommodating cavity (93).

10. The rock breaking control system adapted to formation drillability according to claim 1, characterized in that: The elastic member (15) is arranged on the outside of the piston, one end of the elastic member (15) contacts the top surface of the pressure cap (13), and a limiting protrusion (74) is provided on the upper part (17) of the piston to contact the other end of the elastic member (15).

11. A rock breaking control method adapted to the drillability of the formation, characterized in that: The method adopts the rock breaking control system according to any one of claims 1 to 10, comprising: When the piston moves upward due to the pressure of the rock, the elastic member (15) shortens, and the fluid flows downward from the second gap through the third central channel (71) and the third cross channel (72) of the piston upper part (17), the second central channel (81) of the valve core (18), and the first central channel (91) and the first cross channel (92) of the piston lower part (19) to the first gap; the valve core (18) moves downward under the force of its own weight and the fluid, and causes the conical surface (83) to be pressed into contact with the concave conical surface of the valve core accommodating chamber (93); When the piston moves downward due to the reduction or disappearance of rock pressure, the elastic member (15) stretches, and the fluid flows upward from the first gap through the first central channel (91) and the first cross channel (92) of the piston lower part (19), the second central channel (81) and the groove (82) of the valve core (18), and the third central channel (71) and the third cross channel (72) of the piston upper part (17) to the third cavity. At this time, the valve core (18) moves upward under the push of the fluid, and the conical surface (83) is separated from the concave conical surface of the valve core accommodating cavity (93).

12. A rock breaking control method adapted to formation drillability according to claim 11, characterized in that: When the piston moves upward due to the pressure of the rock and when the piston moves downward due to the reduction or disappearance of the rock pressure, The elastic member (15) is in a compressed state throughout the entire process, and the upper and lower end surfaces of the elastic member (15) maintain contact with the pressure cap (13) and the limiting protrusion (74) of the upper part of the piston (17); The length of the elastic member (15) when the piston moves upward due to the pressure of the rock is smaller than the length when the piston moves downward due to the pressure of the rock being reduced or eliminated.

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