A coring apparatus and method for shale gas, tight sand gas exploration

Abstract

This invention relates to the field of geological exploration coring equipment technology, specifically to a coring device and method for shale gas and tight sandstone gas exploration. The coring device includes an outer tube, an inner tube, a reduced-diameter sleeve, a clamp-type core claw, a guide cylinder, a guide rod, a core break cutter, and a linkage assembly. The reduced-diameter sleeve is located at the bottom of the inner tube and inside the outer tube; the clamp-type core claw is installed on the reduced-diameter surface; the guide cylinder is inclined upwards and mounted on the reduced-diameter sleeve; the guide rod passes through the guide cylinder; the core break cutter is located at the bottom of the guide rod; when the clamp-type core claw moves downwards, it drives multiple sets of guide rods to move inwards synchronously through the linkage assembly. The multiple sets of guide rods and the core break cutter of this invention form a bottoming structure inwards, which supports the core inside the inner tube, enabling the relatively complete extraction of cores from interlayered shale reservoirs and tight sandstone reservoirs.

Description

Technical Field

[0001] This invention relates to the field of geological exploration coring equipment technology, and in particular to a coring equipment and method for shale gas and tight sandstone gas exploration. Background Technology

[0002] Currently, multiple oil and gas basins have achieved the co-production of three gases. Studies have found that shale gas reservoirs and tight sandstone reservoirs are often located very close to each other and have a co-existing relationship. However, due to the huge differences in the petrological properties between shale reservoirs and tight sandstone reservoirs, shale has low hardness, is brittle and easily broken, while tight sandstone layers have high hardness and are not easily broken. When obtaining cores, shale core segments are very easy to break, which often results in only cores from tight sandstone layers being obtained, with low core yields from adjacent shale layers, or even no cores from adjacent shale reservoirs being obtained at all.

[0003] Most conventional core-retrieving equipment can only obtain relatively complete cores from strata with relatively homogeneous lithology and hardness, and cannot obtain cores from strata with varying hardness and interbedded layers. Existing technology includes a dual-core-claw composite core-cutting mechanism. This device consists of an inner cylinder, connecting sleeve, inner cylinder shoe, and fully enclosed core claws connected sequentially. The inner cylinder shoe is equipped with slip-type core claws, and the lower part of the drill bit's inner cavity has an inclined surface. Using this dual-core-claw composite core-cutting mechanism, core-cutting operations can be successfully performed in fractured and alternating hard and soft strata. However, when core-cutting in shale and tight sandstone interbedded strata, this core-cutting mechanism is still prone to core breakage in shale reservoir sections, making it impossible to obtain complete cores from interbedded shale and tight sandstone reservoir sections. The core recovery rate is low, failing to meet the requirement of obtaining as complete cores as possible during the exploration of interbedded shale and tight sandstone reservoir sections.

[0004] Therefore, there is an urgent need to provide a core sampling device suitable for shale and tight sandstone interbedded formations with high core recovery rates to meet the exploration needs of shale gas and tight sandstone gas. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a core sampling device and method for shale gas and tight sandstone gas exploration, in order to solve the technical problem in the prior art that the cores of shale reservoir sections are easily broken, and the cores of interbedded shale reservoirs and tight sandstone reservoir sections cannot be extracted relatively completely.

[0006] The objective of this invention is achieved as follows:

[0007] On the one hand, a coring device for shale gas and tight sandstone gas exploration is provided, comprising:

[0008] outer tube;

[0009] Inner tube, which is coaxially disposed inside the outer tube;

[0010] A drill bit, wherein the drill bit is located at the bottom of the outer tube;

[0011] A reducing sleeve, wherein the reducing sleeve is disposed at the bottom of the inner tube and located inside the outer tube;

[0012] A clamp-type core claw, wherein the clamp-type core claw is located inside the reduced-diameter sleeve and is configured to grip the core to be cut;

[0013] Multiple cutting mechanisms are evenly arranged on the reducing sleeve along the circumference of the reducing sleeve; each cutting structure includes a core-breaking cutter, a guide cylinder, and a guide rod; wherein, the guide cylinder is inclined upward on the reducing sleeve, and the guide rod is movably arranged inside the guide cylinder; the core-breaking cutter is arranged at the bottom of the guide rod and can move towards the axis of the inner tube under the drive of the guide rod to cut the outer wall of the rock core to be cut.

[0014] A linkage component is disposed on the reduced-diameter sleeve and connected between the clamp-type core claw and the guide rod. The linkage component is configured to drive multiple sets of guide rods together with the core-breaking cutter to move obliquely downward in the axial direction of the reduced-diameter sleeve when the clamp-type core claw moves downward. After cutting the core to be cut, a bottom-catching structure is formed at the bottom opening of the inner tube.

[0015] Furthermore, the inner wall surface of the reducing sleeve, from top to bottom, consists of a first vertical circumferential surface, a reducing surface, and a second vertical circumferential surface; the top end of the reducing surface has a first diameter and the bottom end has a second diameter, the first diameter being larger than the diameter of the first vertical circumferential surface and the second diameter; the top end of the reducing surface and the first vertical circumferential surface have a horizontal end face; the bottom end of the reducing surface is transitionally connected to the second vertical circumferential surface, the second diameter being equal to the diameter of the second vertical circumferential surface; the clamp-type core claw is installed within the reducing space enclosed by the reducing surface, and can be sleeved on the core to be cut and can move up and down within the reducing space; when the clamp-type core claw moves from the top to the bottom within the reducing surface, the clamp-type core claw can retract under the restriction of the reducing surface to grip the core to be cut.

[0016] Furthermore, an annular groove is provided on the lower inner wall surface of the reduced diameter sleeve. The annular groove is located at the lower part of the second vertical circumferential surface. An opening is provided on the groove wall of the annular groove. The lower end of the guide cylinder is fixedly connected to the opening. The core-breaking cutter is located inside the annular groove.

[0017] Furthermore, the linkage component includes a fixing block, a connecting cable, and a guide; the fixing block is disposed on the top of the guide rod; the guide is disposed on the outer wall of the reduced diameter sleeve and is located directly above the connection between the guide cylinder and the outer wall of the reduced diameter sleeve; multiple sets of through holes are provided on the side wall of the reduced diameter sleeve, and the through holes are located directly above the guide; one end of the connecting cable is connected to the outer wall of the clamp-type core claw, and the other end of the connecting cable passes through the through hole and the guide in sequence and is connected to the fixing block.

[0018] Furthermore, the guide component is a guide ring, through which the connecting cable can pass; the ring opening of the guide ring and the through hole opening of the reduced diameter surface are rounded to prevent the connecting cable from forming an approximately right angle with the ring opening of the guide ring and the through hole of the reduced diameter sleeve, thus hindering the movement of the connecting cable.

[0019] Furthermore, the inner wall of the guide ring and the wall of the through hole of the reduced diameter surface are provided with balls, rollers or similar rolling components.

[0020] Furthermore, the centerline of the through hole is perpendicular to the axis of the locking sleeve, and the through hole is located at the top of the reduced diameter surface.

[0021] Furthermore, the through hole has an arc-shaped channel, and the center line of the arc-shaped channel is C-shaped, with the vertex of the C-shaped center line located at the midpoint of the wall thickness at the position of the through hole on the reduced-diameter sleeve.

[0022] Furthermore, the guide includes a pulley and a support base. The pulley is mounted on the support base via a pivot, and the connecting cable passes over the pulley.

[0023] Furthermore, the bottom of the core-breaking cutter has an arc-shaped plate that extends outward from the lower end of the reducing sleeve to the outer side of the reducing sleeve. When multiple sets of guide rods and the core-breaking cutter move obliquely downward toward the axis of the reducing sleeve, the cutting edge of the core-breaking cutter converges on or near the center line of the reducing sleeve, forming a primary blocking structure. Multiple arc-shaped plates move toward the center line of the reducing sleeve under the drive of the core-breaking cutter, forming a secondary blocking structure below the primary blocking structure. The two blocking structures together form a bottom-covering structure.

[0024] Furthermore, the arc-shaped plate has a first end and a second end, the first end being narrow and the second end being wide; the first end is connected to the bottom end of the core-breaking cutter, and arcs upward from the first end to the second end, the second end being arc-shaped, and the projection of the arc-shaped plate onto the horizontal plane is fan-shaped.

[0025] Furthermore, the connecting cable is woven from multiple strands of steel wire.

[0026] Furthermore, the drill bit is connected to the bottom of the outer tube; the reducing sleeve is threadedly connected to the bottom of the inner tube.

[0027] Furthermore, it also includes a spring clip stop, a spring clip chamber, a cylinder, a spring clip, and a suspension ring; the spring clip chamber is located at the top of the outer tube, the spring clip stop is located at the top of the spring clip chamber, and the spring clip stop is connected to the bottom of the drill string; the cylinder is located at the top of the inner tube, and a retrieval spearhead is located at the top of the cylinder, which is connected to the rope retrieval device; the spring clip is located on the cylinder and unfolds to fit into the groove on the inner wall of the spring clip chamber; the suspension ring is located on the outer peripheral wall of the cylinder, and a seat ring is located on the inner wall of the outer tube, with the suspension ring resting against the seat ring.

[0028] Furthermore, the bottom of the spring clip chamber is threaded to the top of the outer tube, the top of the spring clip chamber is threaded to the bottom of the spring clip stop, and the top of the inner tube is threaded to the bottom of the cylinder.

[0029] On the other hand, a coring method for shale gas and tight sandstone gas exploration is also provided, which uses the aforementioned coring equipment for shale gas and tight sandstone gas exploration to perform coring in the target exploration area; the coring method includes the following steps:

[0030] The outer tube rotates under the driving force of the drill string and continuously drills downward into the target rock layer. The drill bit forms a cylindrical rock core to be cut in the target rock layer. The rock core to be cut enters the inner tube and is collected.

[0031] The inner tube is raised by the rope retrieval device, the clamp-type core claw moves downward along the narrowing surface and continuously grips the core to be cut, and at the same time, under the action of the linkage component, the guide rod moves obliquely downward along the guide cylinder, and the guide rod drives the core cutting cutter to cut into the outer surface of the core to be cut; the rotary drill string causes the core to be cut to break at the cutting mark; multiple sets of guide rods and core cutting cutters continue to move inward, and the core cutting cutter forms a bottom catch structure at the bottom opening of the inner tube;

[0032] The downhole equipment is moved to the surface wellhead using a drill string, and the core sample is extracted from the inner tube.

[0033] Compared with the prior art, the present invention has the following beneficial technical effects:

[0034] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0035] a) The core sampling equipment for shale gas and tight sandstone gas exploration provided by the present invention, by setting multiple sets of cutting mechanisms on the reduced diameter sleeve, allows the cutting edge of the core cutter to cut into the outer peripheral surface of the rock core, forming a cut mark on the outer peripheral surface of the rock core. During the core sampling process, the friction between the core claw and the rock core and the conical surface of the reduced diameter sleeve make it easier for the rock core to break at the cut mark.

[0036] (b) The coring equipment for shale gas and tight sandstone gas exploration provided by this invention achieves linkage between the guide rods and the core cutter through a linkage component. Specifically, when the clamp-type core claw on the reduced-diameter sleeve moves downward, the linkage component drives multiple sets of guide rods to move inward synchronously. The guide rods, together with the core cutter, move obliquely downward in the axial direction of the reduced-diameter sleeve. In this way, multiple sets of guide rods and the core cutter form a bottom-covering structure inward. The bottom-covering structure is formed at the bottom opening of the inner tube, which can at least partially block the bottom opening of the inner tube, thereby supporting the core inside the inner tube and preventing the core, or broken core segments, from leaking out from the bottom opening of the inner tube during the coring process, thus significantly improving the core recovery rate.

[0037] c) The core sampling equipment for shale gas and tight sandstone gas exploration provided by this invention has an arc-shaped plate at the bottom of each core-breaking cutter, which extends outward from the lower end of the reduced-diameter sleeve to the outer side of the reduced-diameter sleeve. In this way, when multiple sets of guide rods and core-breaking cutters move obliquely downward in the axial direction of the reduced-diameter sleeve, the cutting edges of the core-breaking cutters converge to form a primary blocking structure. At the same time, multiple arc-shaped plates form a secondary blocking structure below the primary blocking structure. The two blocking structures together form a bottom-covering structure. The mesh area of ​​the bottom-covering structure is smaller, which can reduce the leakage of broken core fragments and further improve the core acquisition rate.

[0038] d) The core sampling method for shale gas and tight sandstone gas exploration provided by this invention has a simple structure and is easy to operate. During the core sampling process, a bottom-filling structure can be formed at the bottom opening of the inner tube to prevent core leakage. It can basically extract the cores of interbedded shale reservoirs and tight sandstone reservoirs relatively completely, thereby improving the core acquisition rate. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings.

[0040] Figure 1 This is a schematic diagram of the structure of a coring device for shale gas and tight sandstone gas exploration provided by the present invention.

[0041] Figure 2 for Figure 1 A schematic diagram of the structure after removing the cartridge stop;

[0042] Figure 3 for Figure 1 A schematic diagram of the structure after removing the outer tube;

[0043] Figure 4 This is a schematic diagram of the structure of the reducing sleeve provided by the present invention;

[0044] Figure 5 for Figure 4 A partial cross-sectional diagram of the structure;

[0045] Figure 6 for Figure 5 Enlarged diagram of point A in the diagram;

[0046] Figure 7 A top view of an arc-shaped plate provided by the present invention;

[0047] Figure 8A schematic diagram of the connection structure between the arc-shaped plate and the core-breaking cutter provided by the present invention;

[0048] Figure 9 A schematic diagram of the structure of a guide ring provided by the present invention;

[0049] Figure 10 A schematic diagram of the structure of the reduced-diameter sleeve provided by the present invention, showing the C-shaped through hole provided;

[0050] Figure 11 This is a schematic diagram of a linkage component using pulleys provided by the present invention.

[0051] Figure label:

[0052] 1. Spring-loaded stop; 2. Spring-loaded chamber; 3. Outer tube; 4. Drill bit; 5. Retrieving spearhead; 6. Cylindrical part; 7. Spring-loaded stop; 8. Suspension ring; 9. Inner tube; 10. Reduction sleeve; 11. Clamp-type core claw; 12. Guide cylinder; 13. Guide rod; 14. Core cutting tool; 15. Annular groove; 16. Arc plate; 17. Reduction surface; 18. First vertical circumferential surface; 19. Second vertical circumferential surface; 20. Fixing block; 21. Connecting cable; 22. Guide ring; 23. Through hole; 24. Cutting edge; 25. Connecting plate; 26. First end; 27. Second end; 28. Pulley; 29. ​​Support base; 30. Roller. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. It should be noted that, unless otherwise specified, the implementation methods and features in the implementation methods in this disclosure can be combined, separated, interchanged, and / or rearranged. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0054] In the accompanying drawings, the dimensions and relative dimensions of components may be exaggerated for clarity and / or descriptive purposes. When exemplary embodiments can be implemented differently, the specific process sequence may be performed in a different order than that described. Furthermore, the same reference numerals denote the same components.

[0055] The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms “a” and “the” are intended to include the plural forms as well. Furthermore, when the terms “comprising” and / or “including” and variations thereof are used in this specification, it indicates the presence of the stated features, integrals, steps, operations, parts, components, and / or groups thereof, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, parts, components, and / or groups thereof.

[0056] Example 1

[0057] A specific embodiment of the present invention, such as Figures 1 to 5 As shown, a coring device for shale gas and tight sandstone gas exploration is disclosed, comprising:

[0058] Outer tube 3;

[0059] Inner tube 9, which is coaxially disposed inside outer tube 3;

[0060] Drill bit 4, which is located at the bottom of the outer tube 3;

[0061] A reducing sleeve 10 is provided at the bottom of the inner tube 9 and located inside the outer tube 3;

[0062] The clamp-type core claw 11 is located inside the reduced-diameter sleeve 10 and is configured to hold the core to be cut.

[0063] Multiple cutting mechanisms are evenly arranged on the reducing sleeve 10 along the circumference of the reducing sleeve 10. Each cutting mechanism includes a core-breaking cutter 14, a guide cylinder 12, and a guide rod 13. Multiple guide cylinders 12 are evenly arranged along the circumference of the reducing sleeve 10. The guide cylinders 12 are inclined upward on the reducing sleeve 10, and the guide rods 13 are movably arranged inside the guide cylinders 12. Optionally, the angle between the axis of the guide cylinder 12 and the axis of the reducing sleeve 10 is 30°-45°. The core-breaking cutter 14 is located at the bottom of the guide rod 13 and can move towards the axis of the inner tube 9 under the drive of the guide rod 13 to cut the outer wall of the rock core to be cut.

[0064] A linkage component is disposed on the reduced-diameter sleeve 10 and connected between the clamp-type core claw 11 and the guide rod 13. The linkage component is configured to drive multiple sets of guide rods 13 together with the core cutting blade 14 to move obliquely downward in the axial direction of the reduced-diameter sleeve 10 when the clamp-type core claw 11 moves downward. After cutting the core to be cut, a bottom-catching structure is formed at the bottom opening of the inner tube 9.

[0065] In this embodiment, the inner wall diameter of the reduced-diameter sleeve 10 is not uniform and can be divided into three segments from top to bottom. That is, the inner wall surface of the reduced-diameter sleeve 10, from top to bottom, consists of a first vertical circumferential surface 18, a reduced-diameter surface 17, and a second vertical circumferential surface 19. The top end of the reduced-diameter surface 17 has a first diameter, and the bottom end has a second diameter. The first diameter is larger than the diameter of the first vertical circumferential surface 18 and the second diameter. It can also be understood that the shape of the reduced-diameter surface 17 is a conical surface with the larger opening facing upwards. The top end of the reduced-diameter surface 17 has a horizontal end face with the first vertical circumferential surface 18. The bottom end of the reduced-diameter surface 17 is transitionally connected to the second vertical circumferential surface 19, and the second diameter is equal to that of the second vertical circumferential surface 19. The diameter of the core clamp 11; the clamp-type core claw 11 is installed within the reduced diameter space enclosed by the reduced diameter surface 17, and can be fitted over the core to be cut and can move up and down within the reduced diameter space; when the clamp-type core claw 11 is at the top of the reduced diameter surface 17, the outer diameter of the top of the clamp-type core claw 11 is larger than the diameter of the first vertical circumferential surface 18 and also larger than the diameter of the second vertical circumferential surface 19; the top of the clamp-type core claw 11 can abut against the end face formed between the top of the reduced diameter surface 17 and the first vertical circumferential surface 18; when the clamp-type core claw 11 moves from the top to the bottom within the reduced diameter surface 17, the clamp-type core claw 11 can contract under the restriction of the reduced diameter surface 17 to hold the core to be cut tightly.

[0066] In this embodiment, an annular groove 15 is provided on the lower inner wall surface of the reduced-diameter sleeve 10. The annular groove 15 is located at the lower part of the second vertical circumferential surface 19. An opening is provided on the groove wall of the annular groove 15, and the lower end of the guide cylinder 12 is fixedly connected to the opening, such as by welding. The core-cutting cutter 14 is movably disposed within the annular groove 15. Before performing the core-cutting operation, the core-cutting cutter 14 is located within the annular groove 15. During the core-cutting operation, the core-cutting cutter 14 moves inward and extends out of the annular groove 15 under the drive of the guide rod 13, forming a cut on the peripheral wall surface of the core to be cut. During the core extraction process, the friction between the clamp-type core claw and the core, as well as the conical surface of the reduced-diameter sleeve 10, are used to make the claw grip the core and pull it off. The cutting edge 24 of the core cutter 14 can cut into the outer circumferential surface of the core, forming a cut on the outer circumferential surface of the core, making it easier for the core to break at the cut. After the core is cut, the core cutter 14 moves further inward to form a bottom-covering structure. The bottom-covering structure can at least partially block the bottom opening of the inner tube 9, thus catching the entire broken core and preventing the broken core from falling off during the process of taking it out from downhole.

[0067] In this embodiment, the linkage component includes a fixing block 20, a connecting cable 21, and a guide member. The fixing block 20 is disposed on the top of the guide rod 13. The guide member is disposed on the outer wall of the reduced-diameter sleeve 10 and is located directly above the connection between the guide cylinder 12 and the outer wall of the reduced-diameter sleeve 10, and is used to guide the movement of the connecting cable 21. Multiple sets of through holes 23 are provided on the side wall of the reduced-diameter sleeve 10, with the through holes 23 located directly above the guide member and on the side wall of the reduced-diameter sleeve 10 corresponding to the reduced-diameter surface 17. One end of the connecting cable 21 is connected to the outer wall of the clamp-type core claw 11, and the other end of the connecting cable 21 passes through the through hole 23 and the guide member in sequence and is connected to the fixing block 20. The number of through holes 23, guide members, and connecting cables 21 are the same.

[0068] In one alternative embodiment, the fixing block 20 is hinged to the top of the guide rod 13. The fixing block 20 can rotate at a certain angle when the connecting cable 21 is moved and pulled, which is beneficial to the smooth operation of the linkage component.

[0069] In this embodiment, the linkage assembly is configured as a set with the clamp-type core claw 11 and the guide rod 13. The linkage assembly includes, but is not limited to, the following two structures, the main difference between the two structures being the structure of the guide component.

[0070] The first type of linkage component, such as Figures 5 to 6 As shown, its guide component is a guide ring 22, through which the connecting cable 21 can pass; the ring opening of the guide ring 22 and the opening of the through hole 23 of the reduced diameter surface 17 are rounded to prevent the connecting cable 21 from forming an approximately right angle with the ring opening of the guide ring 22 and the through hole 23 of the reduced diameter sleeve 10, thus hindering the movement of the connecting cable 21.

[0071] Furthermore, the inner wall of the guide ring 22 and the wall of the through hole 23 on the reduced-diameter sleeve 10 are provided with balls, rollers 30, or similar rolling components. When the connecting cable 21 moves within the annular opening of the guide ring 22, it can drive the balls or rollers 30 to rotate. Figure 9 The diagram shows a structure with roller 30, which greatly reduces the friction between the connecting cable 21 and the guide ring 22 and the through hole 23 on the reduced diameter surface 17. The presence of the ball or roller 30 allows the connecting cable 21 to pass smoothly through the guide ring 22, resulting in better linkage between the clamp-type core claw 11, the guide rod 13 and the core cutter 14.

[0072] The second type of structural linkage component, such as Figure 11As shown, its guide component includes a pulley 28 and a support base 29. The pulley 28 is mounted on the support base 29 via a pivot, and the connecting cable 21 passes around the pulley 28. The support base 29 includes two legs, the bottom ends of which are fixedly connected to the outer walls of the guide cylinder 12 and the reduced-diameter sleeve 10, respectively. The top ends of the two legs are rotatably connected to the pulley 28. The connecting cable 21 passes through the gap between the two legs and wraps around the pulley 28, thus making the movement of the connecting cable 21 smoother.

[0073] In this embodiment, the through hole 23 can be a straight channel or a curved arc channel.

[0074] For example, the through hole 23 is a straight channel, the center line of the through hole 23 is perpendicular to the axis of the locking sleeve 10, and the through hole 23 is located at the top of the reduced diameter surface 17.

[0075] For example, the through hole 23 has an arc-shaped channel, and the centerline of the arc-shaped channel is C-shaped, such as... Figure 10 As shown, the vertex of the C-shaped centerline is located at or near the midpoint of the wall thickness of the reduced-diameter sleeve 10 where the through hole is located. This arrangement ensures that the included angle between the connecting cable 21 and the two ends of the through hole 23 is acute, improving the smoothness of the connecting cable 21 passing through the through hole 23.

[0076] In one alternative embodiment, after the multiple sets of guide rods 13 and the core-breaking cutter 14 move inward, the cutting edges 24 of the core-breaking cutter 14 converge on or near the center line of the reduced-diameter sleeve 10. For example, a circular hole is formed between the cutting edges 24 of the core-breaking cutter 14. The diameter of this circular hole is smaller than the diameter of the inner tube 9 and also smaller than the diameter of the drilled rock core. For example, the diameter of the circular hole is 1 / 8 to 1 / 4 of the diameter of the inner tube 9, and the drilled rock core will not leak out from this circular hole.

[0077] To better contain the bottom opening of the inner tube 9, in one optional embodiment, an arc-shaped plate 16 is provided at the bottom of each core-breaking cutter 14. The arc-shaped plate 16 extends outward from the lower port of the reducing sleeve 10 to the outer side of the reducing sleeve 10. Thus, when multiple sets of guide rods 13 and core-breaking cutters 14 move obliquely downward toward the axis of the reducing sleeve 10, the cutting edge 24 of the core-breaking cutter 14 converges on or near the center line of the reducing sleeve 10, forming a primary blocking structure. Multiple arc-shaped plates 16 move toward the center line of the reducing sleeve 10 under the drive of the core-breaking cutter 14, forming a secondary blocking structure below the primary blocking structure. The two blocking structures together form a bottom-containing structure, which can be understood as an approximate mesh-like bottom-containing structure.

[0078] Furthermore, such as Figure 7As shown, the arc-shaped plate 16 has a first end 26 and a second end 27. The first end 26 is narrow, and the second end 27 is wide. The first end 26 is connected to the bottom end of the core-breaking cutter 14. The position of the arc-shaped plate 16 does not affect the use of the blade 24. It curves upwards from the first end 26 to the second end 27, and the second end 27 is arc-shaped. The horizontal projection of the arc-shaped plate 16 is fan-shaped. In this way, when the arc-shaped plate moves inward, the secondary blocking structure formed has smaller gaps between the arc-shaped plates, that is, the mesh area of ​​the grid-like bottom-covering structure is smaller, thereby reducing the leakage of small pieces of broken rock core and further improving the core recovery rate.

[0079] In one alternative implementation, such as Figure 8 As shown, the arc-shaped plate 16 is connected to the bottom end face of the core-breaking cutter 14 via a connecting plate 25. The connecting plate 25 can be a flat plate, and it is perpendicular to the bottom end face of the core-breaking cutter 14. The connection point between the connecting plate 25 and the core-breaking cutter 14 is located in the middle of the bottom end face of the core-breaking cutter 14. This allows the cutting edge 24 to protrude, avoiding interference with the cutting edge 24's ability to cut the rock core sidewall. Furthermore, both the connecting plate 25 and the arc-shaped plate 16 are elastic steel plates.

[0080] In this embodiment, the connecting cable 21 is a rigid rope with high strength, sufficient to meet actual requirements. Optionally, the connecting cable 21 is a rigid rope woven from multiple strands of steel wire.

[0081] In this embodiment, the drill bit 4 is connected to the bottom of the outer tube 3; for example, the drill bit 4 is threadedly connected to the bottom of the outer tube 3, or the drill bit 4 is threadedly inserted into the bottom of the outer tube 3 for fixed connection. In one optional embodiment, a fixing pin is also provided between the drill bit 4 and the outer tube 3, and the fixing pin is inserted into the inner wall of the drill bit 4 and the outer tube 3 to prevent the drill bit 4 from disengaging from the outer tube 3 when rotating down for drilling.

[0082] In this example, the reducing sleeve 10 is located at the bottom of the inner tube 9 and inside the outer tube 3, and the reducing sleeve 10 is threadedly connected to the bottom of the inner tube 9. A fixing pin can also be provided between the reducing sleeve 10 and the inner tube 9. The fixing pin is inserted into the inner wall of the reducing sleeve 10 and the inner tube 9 to prevent the reducing sleeve 10 from separating from the inner tube 9 when rotating and drilling.

[0083] The coring equipment for shale gas and tight sandstone gas exploration in this embodiment further includes a spring clip stop 1, a spring clip chamber 2, a cylinder 6, a spring clip 7, and a suspension ring 8. The spring clip chamber 2 is located on the top of the outer tube 3, and the spring clip stop 1 is located on the top of the spring clip chamber 2, connected to the bottom of the drill string. The cylinder 6 is located on the top of the inner tube 9, and a retrieval spearhead 5 is located on the top of the cylinder 6, connected to a rope retrieval device. The spring clip 7 is located on the cylinder 6 and unfolds to fit into a groove on the inner wall of the spring clip chamber 2. The suspension ring 8 is located on the outer peripheral wall of the cylinder 6, and a seat ring is located on the inner wall of the outer tube 3. The suspension ring 8 rests against the seat ring, thus fixing the suspension ring 8 between the outer tube 3 and the spring clip chamber 2. The bottom of the spring clip chamber 2 is threadedly connected to the top of the outer tube 3, the top of the spring clip chamber 2 is threadedly connected to the bottom of the spring clip stop 1, and the top of the inner tube 9 is threadedly connected to the bottom of the cylinder 6. During the core retrieval process, the inner tube 9 is raised by the rope retrieval device, and the clamp-type core claw 11 moves downward along the narrowing surface 17 to continuously clamp the core to be cut. At the same time, under the pull of the connecting cable 21, the guide rod 13 moves downward along the guide cylinder 12. Under the action of the clamp-type core claw 11 and multiple sets of core cutting blades 14, the core to be cut can be separated from the original formation. Moreover, the multiple sets of guide rods 13 and core cutting blades 14 form a bottoming structure at the bottom opening of the inner tube 9, which supports the core inside the inner tube 9 and effectively prevents leakage during the process of moving it from the downhole to the surface wellhead.

[0084] It should be noted that the top structure of the outer tube 3, the top structure of the inner tube 9, and the mating structure of the inner tube 9 and the outer tube 3 in this embodiment are existing technologies. For details, please refer to the Chinese utility model patent with announcement number CN213573981U. It will not be repeated here.

[0085] Using the coring equipment for shale gas and tight sandstone gas exploration according to this embodiment to perform coring in the target exploration area includes the following steps:

[0086] S1. Drilling down to the target rock stratum in the exploration area, the outer tube 3 rotates under the driving force of the drill string and continuously drills downward into the target rock stratum. The drill bit 4 forms a cylindrical rock core in the target rock stratum. One end of the cylindrical rock core is connected to the stratum and has not yet broken. It is the rock core to be cut. The cylindrical rock core to be cut enters the inner tube 9 and is collected. During the process of the inner tube 9 collecting the rock core to be cut, the guide rod 13 moves upward to the highest point, and the clamp-type rock core claw 11 is limited by the bottom end face of the first vertical circumferential surface 18.

[0087] S2. The inner tube 9 is raised by the rope retrieval device. The clamp-type core claw 11 moves downward along the narrowing surface 17 and continuously clamps the core to be cut. At the same time, under the pull of the connecting cable 21 of the linkage component, the guide rod 13 moves obliquely downward along the guide cylinder 12. The guide rod 13 drives the core cutting cutter 14 to cut into the outer surface of the core to be cut. The cutting edge of the core cutting cutter 14 forms a cut mark on the outer circumference of the core to be cut. The drill string is slowly rotated, and the drill string provides power for the core to be cut to twist. The core to be cut is cut at the cut mark under the combined action of the clamp-type core claw 11 and multiple sets of core cutting cutters 14. The multiple sets of guide rods 13 and core cutting cutters 14 move inward. The core cutting cutter 14 forms a bottoming structure at the bottom opening of the inner tube 9, which supports the core cut inside the inner tube 9 and prevents the broken core from falling off during the process of taking it out from downhole.

[0088] S3. After the core is cut, the downhole equipment is moved to the surface wellhead using the drill string, and the core is retrieved. Specifically, after reaching the surface wellhead, the inner tube 9 is separated from the outer tube 3. The inner tube 9 is removed, and multiple sets of guide rods 13 are manually pulled upwards and outwards at an angle. The guide rods 13 and the core-breaking cutter 14 move outwards away from the axis of the reducing sleeve 10. The core-breaking cutter 14 moves into the annular groove 15 of the reducing sleeve 10, causing the bottom cover structure to disappear. The bottom opening of the inner tube 9 is now open, and the core can be poured out completely from the open bottom opening of the inner tube 9. During the core-pouring process, if necessary, the outer wall of the inner tube 9 can be tapped for rapid core extraction.

[0089] Compared with the prior art, the coring equipment and method for shale gas and tight sandstone gas exploration provided in this embodiment have at least one of the following beneficial effects:

[0090] 1. By setting multiple cutting mechanisms on the reduced diameter sleeve, the cutting edge of the core cutter can cut into the outer circumference of the rock core, forming a cut mark on the outer circumference of the rock core. During the core extraction process, the friction between the core claw and the rock core, as well as the conical surface of the reduced diameter sleeve, make it easier for the rock core to break at the cut mark.

[0091] 2. It can form a catch-the-bottom structure at the bottom opening of the inner tube to prevent core leakage. Specifically, when the clamp-type core claw on the reduced-diameter sleeve moves downward, multiple sets of guide rods move inward synchronously through the linkage component. The guide rods, along with the core-breaking cutter, move obliquely downward in the direction of the axis of the reduced-diameter sleeve. In this way, multiple sets of guide rods and core-breaking cutters form a catch-the-bottom structure at the bottom opening of the inner tube, which can at least partially block the bottom opening of the inner tube, thereby supporting the core inside the inner tube and preventing the core, either whole or broken, from leaking out from the bottom opening of the inner tube during the core extraction process. It can basically extract cores from interbedded shale reservoirs and tight sandstone reservoirs relatively intact, significantly improving the core recovery rate.

[0092] 3. By installing an arc-shaped plate at the bottom of each core-breaking cutter, extending outward from the lower end of the reduced-diameter sleeve to the outer side of the sleeve, when multiple sets of guide rods and the core-breaking cutter move obliquely downward towards the axis of the reduced-diameter sleeve, the cutting edge of the core-breaking cutter converges on or near the center line of the reduced-diameter sleeve, forming a primary blocking structure. Simultaneously, multiple arc-shaped plates move towards the center line of the reduced-diameter sleeve under the drive of the core-breaking cutter, forming a secondary blocking structure below the primary blocking structure. The two blocking structures together form a bottom-covering structure, which has a smaller mesh area, thereby reducing the leakage of small fragments of rock core and further improving the core recovery rate.

[0093] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto. Various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention.

Claims

1. A coring device for shale gas and tight sandstone gas exploration, characterized in that, include: Outer tube (3); Inner tube (9), which is coaxially disposed inside the outer tube (3); Drill bit (4), the drill bit (4) is located at the bottom of the outer tube (3); A reducing sleeve (10) is provided at the bottom of the inner tube (9) and located inside the outer tube (3); Clamp-type core claw (11), the clamp-type core claw (11) is located inside the reduced diameter sleeve (10) and is configured to clamp the core to be cut; Multiple cutting mechanisms are evenly arranged on the reducing sleeve (10) along the circumference of the reducing sleeve (10); each cutting mechanism includes a core-breaking cutter (14), a guide cylinder (12) and a guide rod (13); wherein, the guide cylinder (12) is inclined upward on the reducing sleeve (10), and the guide rod (13) is movably arranged inside the guide cylinder (12); the core-breaking cutter (14) is arranged at the bottom of the guide rod (13) and can move towards the axis of the inner tube (9) under the drive of the guide rod (13) to cut the outer wall of the rock core to be cut; The linkage component is disposed on the reduced diameter sleeve (10) and connected between the clamp-type core claw (11) and the guide rod (13). The linkage component is configured to drive multiple sets of guide rods (13) together with the core cutting blade (14) to move obliquely downward in the axial direction of the reduced diameter sleeve (10) when the clamp-type core claw (11) moves downward. After cutting the core to be cut, a bottom-filling structure is formed at the bottom opening of the inner tube (9). The linkage component includes a fixing block (20), a connecting cable (21), and a guide; the fixing block (20) is set on the top of the guide rod (13); the guide is set on the outer wall of the reduced diameter sleeve (10) and is located directly above the connection between the guide cylinder (12) and the outer wall of the reduced diameter sleeve (10); multiple sets of through holes (23) are provided on the side wall of the reduced diameter sleeve (10), and the through holes (23) are located directly above the guide; one end of the connecting cable (21) is connected to the outer wall of the clamp-type core claw (11), and the other end of the connecting cable (21) passes through the through hole (23) and the guide in sequence and is connected to the fixing block (20); The bottom of the core-breaking cutter (14) has an arc-shaped plate (16), which extends outward from the lower port of the reducing sleeve (10) to the outside of the reducing sleeve (10). When multiple sets of guide rods (13) and core cutter (14) move obliquely downward in the direction of the axis of the reduced diameter sleeve (10), the cutting edge (24) of the core cutter (14) converges to form a primary blocking structure; multiple arc plates (16) form a secondary blocking structure below the primary blocking structure, and the two blocking structures together form a bottoming structure.

2. The coring equipment for shale gas and tight sandstone gas exploration according to claim 1, characterized in that, The connecting cable (21) is woven from multiple strands of steel wire.

3. The coring equipment for shale gas and tight sandstone gas exploration according to claim 1 or 2, characterized in that, The inner wall surfaces of the reduced diameter sleeve (10) are, from top to bottom, the first vertical circumferential surface (18), the reduced diameter surface (17), and the second vertical circumferential surface (19). The top end of the reduced diameter surface (17) has a first diameter and the bottom end has a second diameter. The first diameter is larger than the diameter of the first vertical circumferential surface (18) and the second diameter. The top end of the reduced diameter surface (17) has a horizontal end face between it and the first vertical circumferential surface (18); the bottom end of the reduced diameter surface (17) is connected to the second vertical circumferential surface (19), and the second diameter is equal to the diameter of the second vertical circumferential surface (19). The clamp-type core claw (11) is installed in the narrowed space enclosed by the narrowed surface (17), and can be fitted on the outside of the core to be cut and can move up and down in the narrowed space.

4. The coring equipment for shale gas and tight sandstone gas exploration according to claim 3, characterized in that, An annular groove (15) is provided on the lower inner wall surface of the reduced diameter sleeve (10). The annular groove (15) is opened at the lower part of the second vertical circumferential surface (19). An opening is provided on the groove wall of the annular groove (15). The lower port of the guide cylinder (12) is fixedly connected to the opening. The core cutter (14) is located in the annular groove (15).

5. The coring equipment for shale gas and tight sandstone gas exploration according to claim 1, characterized in that, The drill bit (4) is connected to the bottom of the outer tube (3); the reducing sleeve (10) is threaded to the bottom of the inner tube (9).

6. The coring equipment for shale gas and tight sandstone gas exploration according to claim 1, characterized in that, It also includes a spring clip stop (1), a spring clip chamber (2), a cylinder (6), a spring clip (7), and a suspension ring (8); the spring clip chamber (2) is located on the top of the outer tube (3), the spring clip stop (1) is located on the top of the spring clip chamber (2), and the spring clip stop (1) is connected to the bottom of the drill string; the cylinder (6) is located on the top of the inner tube (9), and a retrieval spearhead (5) is located on the top of the cylinder (6), and the retrieval spearhead (5) is connected to the rope retrieval device; the spring clip (7) is located on the cylinder (6) and is deployed and locked in the groove on the inner wall of the spring clip chamber (2); the suspension ring (8) is located on the outer peripheral wall of the cylinder (6), and a seat ring is located on the inner wall of the outer tube (3), and the suspension ring (8) rests on the seat ring.

7. The coring equipment for shale gas and tight sandstone gas exploration according to claim 6, characterized in that, The bottom of the spring clip chamber (2) is threaded to the top of the outer tube (3), the top of the spring clip chamber (2) is threaded to the bottom of the spring clip stop (1), and the top of the inner tube (9) is threaded to the bottom of the cylinder (6).

8. A core sampling method for shale gas and tight sandstone gas exploration, characterized in that, Core sampling is performed in the target exploration area using the coring equipment for shale gas and tight sandstone gas exploration as described in any one of claims 1 to 7. The core extraction method includes the following steps: The outer tube (3) rotates under the driving force of the drill string and continuously drills downward into the target rock layer. The drill bit (4) forms a cylindrical rock core to be cut in the target rock layer. The rock core to be cut enters the inner tube (9) and is collected. The inner tube (9) is raised by the rope retrieval device, and the clamp-type core claw (11) moves downward along the narrowing surface (17) and continuously hugs the core to be cut. At the same time, under the action of the linkage component, the guide rod (13) moves obliquely downward along the guide cylinder (12). The guide rod (13) drives the core cutting cutter (14) to cut into the outer surface of the core to be cut. The rotary drill string causes the core to be cut to twist and break at the cut mark. Multiple sets of guide rods (13) and core cutting cutter (14) continue to move inward. The core cutting cutter (14) forms a bottom-holding structure at the bottom opening of the inner tube (9). The downhole equipment was moved to the surface wellhead using the drill string, and the core was taken out from the inner tube (9).

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