Flexible coring equipment, flexible coring system and in-well coring methods

Abstract

This application relates to the field of drilling technology, and particularly to a flexible coring device, a flexible coring system, and a method for coring in wells. An embodiment of this application provides a flexible coring device, which includes a flexible coring cylinder, a flexible frame, and multiple articulated members. Each articulated member has a cavity, and the multiple articulated members are sequentially arranged along a first direction. Adjacent articulated members are movably connected, and the cavities of each articulated member are interconnected to form a coring channel for core movement. By using multiple articulated members, this application enables the flexible coring cylinder to bend, adapting to complex conditions such as short-radius wells, small curvature radii, and small wellbore diameters. This improves the flexibility of the flexible coring device in short-radius wells, allowing for efficient and stable coring operations. Furthermore, it can reveal detailed information such as near-wellbore sand body connectivity, residual oil distribution, and contamination zone characteristics, improving the accuracy of reservoir assessment.

Description

Technical Field

[0001] This application relates to the field of drilling technology, and in particular to a flexible coring device, a flexible coring system, and an in-well coring method. Background Technology

[0002] Most of my country's oilfields have entered the medium-to-high water-cut stage, while a large number of old wells have been shut down due to reasons such as damaged downhole tubing, high water cut, and production capacity below economic limits. In order to re-understand the distribution patterns of remaining underground oil and tap the development potential of remaining oil in old areas, it is necessary to further obtain reservoir physical parameters and formation oil-water dynamic information, and coring is one of the most direct and economical technical means.

[0003] Conventional directional coring technology is mainly used to evaluate the basic physical and mechanical properties of oil reservoirs and their hydrocarbon content. However, it struggles to obtain detailed reservoir information such as near-wellbore sand body connectivity, remaining oil distribution, and contamination zone distribution. In contrast, short-radius horizontal drilling coring technology, through window-side drilling in shut-in wells, leverages its small turning radius and short target distance to control the coring equipment's entry position and target distance. Under short-radius conditions, it obtains representative core samples from the near-wellbore zone of the target formation, analyzes changes in formation rock properties and oil-water dynamics after long-term water injection, clarifies the distribution patterns of remaining oil in older wells, and provides a basis for optimizing development plans. Compared to conventional directional coring, short-radius horizontal drilling coring technology more easily obtains detailed reservoir information such as oil reservoir connectivity and near-wellbore contamination zone distribution.

[0004] However, existing coring equipment generally suffers from insufficient throughput when applied to horizontal borehole coring technology with short curvature radius, making it difficult to meet the requirements for high-quality coring under complex well conditions. As a result, it is difficult to obtain detailed reservoir information such as oil layer connectivity and near-wellbore contamination zone distribution, which seriously affects the accuracy of reservoir assessment. Summary of the Invention

[0005] This application provides a flexible coring device. By setting multiple joint components, the flexible coring cylinder has bending ability to adapt to complex working conditions such as short-radius wells, small curvature radii, and small wellbore, thereby improving the passability of the flexible coring device in short-radius wells. This enables the flexible coring device to achieve efficient and stable coring operations, and further reveals detailed information such as the connectivity of sand bodies in the near-wellbore zone, the distribution of remaining oil, and the characteristics of contamination zones, thereby improving the accuracy of reservoir assessment.

[0006] In a first aspect, embodiments of this application provide a flexible coring device, which includes a flexible coring cylinder, a flexible skeleton, a plurality of joints, each joint having a cavity, the plurality of joints being arranged sequentially along a first direction, adjacent joints being movably connected, and the cavities of each joint being interconnected to form a coring channel for core movement.

[0007] This application provides a flexible coring device. The flexible frame includes multiple articulated components, with movable connections between adjacent articulated components. This allows the flexible frame to bend flexibly, giving the flexible coring cylinder bending capability. This effectively avoids problems such as jamming, top jamming, or uneven wear that are common in traditional coring cylinders, improving the flexibility of the flexible coring device in short-radius wells. The flexible coring device can achieve efficient and stable coring operations, thereby revealing detailed information such as near-wellbore sand body connectivity, residual oil distribution, and contamination zone characteristics, improving the accuracy of reservoir assessment.

[0008] In some embodiments, along the direction of movement of the core in the core sampling channel, the joint has an upstream end and a downstream end, the upstream end having a first connecting arm and the downstream end having a second connecting arm;

[0009] The joint is movably connected to the second connecting arm of the adjacent upstream joint via the first connecting arm, and the joint is movably connected to the first connecting arm of the adjacent downstream joint via the second connecting arm.

[0010] In some embodiments, the first connecting arm and the second connecting arm are distributed circumferentially at intervals along the joint.

[0011] In some embodiments, two adjacent joint members have a hollowed-out area at the connection position;

[0012] The flexible skeleton also includes a flexible filler, the hollow area is filled with the flexible filler, and the flexible filler has a connecting cavity, through which the cavities of adjacent joints are connected.

[0013] In some embodiments, the flexible core tube further includes a sealing sleeve, which is fitted onto the circumferential outer wall of the flexible skeleton.

[0014] In some embodiments, the flexible coring device further includes a coring drill bit movably connected to the first joint of the flexible frame at the upstream end, and the flexible coring cylinder is configured to be located inside a rotatable outer cylinder connected to the drill bit.

[0015] The core drill bit is constructed to rotate under the drive of the outer cylinder.

[0016] In some embodiments, the flexible coring device further includes a coring alignment assembly, a first bearing member, a second bearing member, and a lower connector assembly;

[0017] One end of the coring and straightening assembly is movably connected to the first joint of the flexible skeleton at the upstream end, and the other end is connected to the first bearing component, which is installed on the coring drill bit.

[0018] One end of the lower connector assembly is movably connected to the last joint of the flexible skeleton at the downstream end, and the other end is configured to be suspended from the drill string and fixed relative to the drill string.

[0019] The second bearing is sleeved on the outside of the lower connector assembly, and the second bearing is configured to connect to the outer cylinder.

[0020] In some embodiments, the core-retrieving and straightening assembly includes a blade straightener, a core-retrieving claw, and a limiting member. The blade straightener is connected to a first bearing member, and the core-retrieving claw is movably disposed within the blade straightener. One end of the limiting member is disposed within the blade straightener and together with the blade straightener, defines a space within the blade straightener for the core-retrieving claw to move upward.

[0021] The knife-edge stabilizer has a knife-edge structure. The core-taking claw is designed to cooperate with the knife-edge structure when falling in space to form a clamping structure, which is used to clamp the rock core.

[0022] In some embodiments, the inner cavity of the blade stabilizer is formed with a guide mating surface, which is configured to engage with the circumferential outer wall of the core claw when the core enters the flexible core tube, so as to push the core claw upward in space.

[0023] In some embodiments, the core retrieval channel contains a sealing liquid, and a piston is provided within the core retrieval channel. The piston can move within the core retrieval channel to push the sealing liquid toward the end of the core retrieval channel, and the end of the core retrieval channel has a liquid outlet.

[0024] The flexible core tube and the outer tube have an annular channel, which is connected to the liquid outlet. The core drill bit has a liquid outlet that is connected to the annular channel, and the liquid outlet has a sealing component.

[0025] Secondly, embodiments of this application provide a flexible core sampling system, comprising:

[0026] Drilling tools;

[0027] The outer cylinder comprises multiple outer cylinder segments arranged sequentially, with adjacent outer cylinder segments being movably connected.

[0028] As provided in any embodiment of the first aspect above, the flexible coring device includes a flexible coring cylinder and a coring drill bit. The flexible coring cylinder is located inside the outer cylinder. The flexible coring cylinder includes a flexible frame. One end of the flexible frame is suspended from the drill bit and fixed relative to the drill bit. The other end of the flexible frame is movably connected to the coring drill bit. The flexible frame has a coring channel inside.

[0029] The outer cylinder is connected to the drill string so that the core drill bit can be rotated under the drive of the drill string.

[0030] The flexible coring system provided in this application adopts the flexible coring equipment provided in any of the embodiments of the first aspect above, and thus has the beneficial effects of the flexible coring equipment, namely, improving the passability of the flexible coring equipment in short-radius wells, enabling the flexible coring equipment to achieve efficient and stable coring work, thereby revealing detailed information such as the sand body connectivity, residual oil distribution and pollution zone characteristics in the near-wellbore zone, and improving the accuracy of reservoir assessment.

[0031] Thirdly, embodiments of this application provide a method for in-well coring, applied to the flexible coring system provided in any of the embodiments of the second aspect above. The in-well coring method includes the following steps:

[0032] The drill string is controlled to rotate the outer cylinder so that the rock core inside the well enters the core sampling channel of the flexible skeleton in the flexible core sampling cylinder and moves towards the end of the core sampling channel.

[0033] The in-well coring method provided in this application embodiment is applied to the flexible coring system provided in any of the embodiments of the second aspect above. Therefore, it has the beneficial effects of the flexible coring system, namely, improving the passability of the flexible coring equipment in short-radius wells, enabling the flexible coring equipment to achieve efficient and stable coring work, thereby revealing detailed information such as the sand body connectivity, residual oil distribution and pollution zone characteristics in the near-wellbore zone, and improving the accuracy of reservoir assessment.

[0034] In some embodiments, an annular channel is provided between the flexible core sampling cylinder and the outer cylinder, a piston is provided inside the core sampling channel, and a sealing liquid is provided on the side of the core sampling channel facing the end of the core sampling channel;

[0035] The piston is configured to move within the coring channel under the push of the core, thereby propelling the sealing fluid toward the end of the coring channel.

[0036] The end of the coring channel has a liquid outlet hole, which is connected to the annular channel; the coring drill bit has a liquid outlet that is connected to the annular channel, and the liquid outlet has a sealing component.

[0037] In some embodiments, the flexible coring system further includes a blade stabilizer, a coring claw, and a limiting member. The blade stabilizer is connected to a first bearing member, and the coring claw is movably disposed within the blade stabilizer. One end of the limiting member is disposed within the blade stabilizer and together with the blade stabilizer, defines a space within the blade stabilizer for the coring claw to move upward. The blade stabilizer has a blade structure.

[0038] After obtaining the required core sample, the in-well coring method also includes the following steps:

[0039] The core-collecting claw is controlled to fall within the space and cooperates with the cutting edge structure to form a clamping structure to clamp the rock core. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of this application 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 some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the flexible skeleton of the flexible coring device provided in the embodiments of this application;

[0042] Figure 2 This is a schematic diagram of the flexible coring device provided in the embodiments of this application;

[0043] Figure 3 A cross-sectional view (AA) of the flexible coring device provided in the embodiments of this application;

[0044] Figure 4 This is a schematic diagram of the assembly of the flexible coring device and the drill string outer cylinder provided in the embodiments of this application;

[0045] Figure 5 A partial cross-sectional view of the flexible coring device and drill string outer cylinder provided in the embodiments of this application;

[0046] Figure 6 This is a schematic diagram of the structure of the first bearing component of the flexible coring device provided in the embodiments of this application;

[0047] Figure 7 A BB cross-sectional view of the first bearing component of the flexible coring device provided in the embodiments of this application;

[0048] Figure 8 This is a schematic diagram of the coring and straightening assembly of the flexible coring device provided in the embodiments of this application;

[0049] Figure 9 An exploded view of the coring and straightening assembly of the flexible coring device provided in the embodiments of this application;

[0050] Figure 10 A CC cross-sectional view of the coring and straightening component of the flexible coring device provided in this application embodiment;

[0051] Figure 11 This is a schematic diagram of the core drill bit of the flexible core sampling device provided in the embodiments of this application;

[0052] Figure 12 A schematic diagram of the core drill bit of the flexible core sampling device provided in this application embodiment;

[0053] Figure 13This is a schematic diagram of the lower connector assembly of the flexible coring device provided in the embodiments of this application;

[0054] Figure 14 An exploded view of the lower connector assembly of the flexible coring device provided in this application embodiment;

[0055] Figure 15 This is a schematic diagram of the structure of the flexible filler in the flexible coring device provided in the embodiments of this application;

[0056] Figure 16 This is a structural schematic diagram of the flexible filler of the flexible coring device provided in the embodiments of this application from another perspective.

[0057] Figure label:

[0058] 100 - Flexible skeleton; 110 - Joint component; 111 - Upstream end; 1111 - First connecting arm; 112 - Downstream end; 1121 - Second connecting arm; 113 - First joint component; 114 - Second joint component; 120 - Hollowed-out area; 130 - Flexible filler; 140 - Sealing sleeve; 150 - First liquid outlet; 160 - Piston;

[0059] 200 - Core drill bit; 210 - Flat teeth; 220 - Tapered teeth; 230 - Diameter-maintaining teeth; 240 - Centering block; 250 - Liquid outlet;

[0060] 300 - Outer cylinder; 310 - Outer cylinder section; 320 - Outer cylinder connector;

[0061] 400 - Core extraction and straightening assembly; 410 - Blade straightener; 420 - Core extraction claw; 430 - Limiting component; 440 - Guide mating surface;

[0062] 500 - First bearing component; 510 - Fluid guide hole;

[0063] 600 - Second bearing component; 610 - First sub-bearing housing; 620 - First sub-bearing component; 630 - Second sub-bearing component;

[0064] 700 - Lower connector assembly; 710 - Suspension bearing housing; 720 - Suspension connector; 730 - Second liquid outlet;

[0065] X - First direction;

[0066] Y - First radial direction;

[0067] Z - Second radial direction. Detailed Implementation

[0068] 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. 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.

[0069] Most of my country's oilfields have entered the medium-to-high water-cut stage, while a large number of old wells have been shut down due to reasons such as damaged downhole tubing, high water cut, and production capacity below economic limits. In order to re-understand the distribution patterns of remaining underground oil and tap the development potential of remaining oil in old areas, it is necessary to further obtain reservoir physical parameters and formation oil-water dynamic information, and coring is one of the most direct and economical technical means.

[0070] Conventional directional coring technology is mainly used to evaluate the basic physical and mechanical properties of oil reservoirs and their hydrocarbon content, but it is difficult to obtain detailed reservoir information such as near-wellbore sand body connectivity, remaining oil distribution, and contamination zone distribution.

[0071] In contrast, the short radius of curvature horizontal coring technology, by performing window-side drilling in shut-down wells, utilizes its small turning radius and short target distance to control the entry position and target distance of the coring equipment. Under short radius conditions, it can obtain representative core samples from the near-wellbore zone of the target formation, analyze the changes in formation rock properties and oil-water dynamics after long-term water injection, clarify the distribution pattern of remaining oil in old wells, and provide a basis for optimizing development plans.

[0072] Therefore, horizontal drilling with short curvature radius coring technology is more likely to obtain detailed reservoir information such as reservoir connectivity and near-wellbore contamination zone distribution, and is a key means to further obtain reservoir physical parameters and formation oil-water dynamic information.

[0073] Specifically, to gain a new understanding of the distribution patterns of remaining oil, coring is typically performed on shut-in wells. The obtained core samples are then used to analyze changes in formation rock properties and oil-water dynamics after long-term water injection. For example, detailed information such as near-wellbore sand body connectivity, remaining oil distribution, and contamination zone characteristics is analyzed to clarify the distribution patterns of remaining oil in older wells, determine development strategies favorable to the remaining oil and gas, maximize the production of remaining oil and gas in older well areas, improve recovery rates, and achieve the oilfield's goal of increasing reserves and production. During coring operations, sidetracking is often required in short-radius wells with small radii of curvature.

[0074] For example, the wellbore diameter of a shut-in well is typically between 114 mm and 149 mm. When performing ultra-short radius sidetracking, the turning radius is controlled within the range of 3 m to 5 m. Ultimately, core samples with a diameter of 30 mm to 50 mm are obtained.

[0075] It should be noted that short-radius wells refer to wells with a small radius of curvature. Compared to conventional vertical wells, short-radius wells can more quickly transition from the vertical section to the horizontal section or the target oil layer, making them suitable for traversing thinner oil layers.

[0076] In related technologies, coring equipment typically includes a coring drill bit and a rigid coring cylinder. The coring drill bit has a central hole through which the rock core passes. The drill string drives the coring drill bit to break up the rock strata, and the rock core enters the rigid coring cylinder through the central hole of the coring drill bit, thereby achieving coring.

[0077] However, the relevant coring equipment is generally suitable for conventional directional coring techniques. When applied to short-radius or ultra-short-radius wells, rigid coring tubes cannot adapt to complex wellbore conditions (such as irregular wellbore walls, wellbore curvature, etc.). They are prone to problems such as top sticking, wear, or obstruction, which can lead to insufficient mobility of the coring equipment in curved well sections. This makes it difficult to carry out horizontal side-drilling coring operations with short curvature radii, thus failing to reveal detailed information such as near-wellbore sand body connectivity, residual oil distribution, and contamination zone characteristics, seriously affecting the accuracy of reservoir assessment.

[0078] Furthermore, during the coring process, the rigid coring barrel rotates along with the outer barrel of the drill string, causing shear disturbance and frictional damage to the core sample inside the barrel, which can easily lead to core breakage. Additionally, drilling fluid can easily infiltrate the rigid coring barrel, contaminating the core sample and affecting the accuracy of reservoir properties and oil-water dynamics analysis. Moreover, the lack of reliable mechanisms for separating the core from the formation and for core retrieval after coring makes core detachment and recovery failures common.

[0079] Therefore, there is an urgent need for a coring device that can adapt to short-radius wells, improve its permeability in short-radius wells, and achieve efficient and stable coring operations, so as to provide representative core samples for oil reservoir assessment and improve the accuracy of the assessment.

[0080] In view of this, embodiments of this application provide a flexible coring device, a flexible coring system, and a bottom-hole coring method. The flexible frame includes multiple articulated components, with movable connections between adjacent articulated components, allowing the flexible frame to bend flexibly, thus enabling the flexible coring cylinder to bend. When the flexible coring cylinder is penetrating deep into the borehole or rock formation, it can bend flexibly according to the borehole trajectory or rock formation strike, adapting to complex conditions such as irregular wellbore walls and curved wellbore. This effectively avoids problems such as jamming, top-jamming, or uneven wear that are common with traditional rigid coring cylinders, thereby improving the passability of the flexible coring device in short-radius wells. This allows the flexible coring device to achieve efficient and stable coring operations, revealing detailed information such as near-wellbore sand body connectivity, residual oil distribution, and contamination zone characteristics, thus improving the accuracy of reservoir assessment.

[0081] See Figure 1, Figure 2 and Figure 3 This application provides a flexible coring device, which includes a flexible coring cylinder. The interior of the flexible coring cylinder forms a channel for accommodating and transporting rock cores.

[0082] Specifically, the flexible coring cylinder includes a flexible frame 100, which serves as the main support structure for the flexible coring cylinder. The flexible frame 100 includes multiple joint members 110, each with a cavity, and the multiple joint members 110 are arranged sequentially along a first direction X. The first direction X is the extension direction of the flexible coring cylinder and also the direction in which the core enters and moves.

[0083] The two adjacent joint components 110 are movably connected, and the cavities of each joint component 110 are interconnected to form a core sampling channel for core movement.

[0084] When two adjacent joint components 110 are movably connected, the cavities of the multiple joint components 110 are interconnected. After the multiple joint components 110 are connected sequentially along the first direction X, the cavities of the multiple joint components 110 together form a continuous and interconnected internal space, which serves as a core sampling channel for core movement.

[0085] For example, two adjacent joint members 110 can be combined together by means of a hinge or a ball joint.

[0086] By movably connecting two adjacent joints 110, each joint 110 can deflect at a certain angle relative to the adjacent joint 110, resulting in relative movement. This allows the flexible skeleton 100, composed of multiple joints 110 connected in series, to bend flexibly, thereby enabling the flexible core tube to bend and adapt to complex working conditions.

[0087] Specifically, when the flexible coring equipment penetrates deep into complex conditions such as boreholes or rock formations, the inner wall of the borehole or rock formation will compress the flexible coring cylinder. Under the force provided by the inner wall, the flexible coring cylinder can bend to adapt to the borehole trajectory or the direction of the rock formation, thereby adjusting its shape so that the flexible coring equipment can pass through the borehole or rock formation.

[0088] As the flexible coring equipment moves, the core enters the coring channel. Even when the flexible coring cylinder bends, the coring channel inside remains open, ensuring the core can move along the channel and ultimately complete the coring process.

[0089] By setting the joint 110, the flexible coring cylinder has the ability to bend, which effectively avoids the problems of jamming, top jamming or uneven wear that are prone to occur in traditional rigid coring cylinders. This improves the passability of the flexible coring equipment in complex working conditions, realizes efficient and stable coring work, and can provide representative core samples for oil reservoir assessment, thereby improving the accuracy of the assessment.

[0090] See Figure 1 , Figure 2 and Figure 3 This application provides a flexible coring device. The flexible frame 100 includes multiple articulated members 110, with adjacent articulated members 110 being movably connected. This allows the flexible frame 100 to bend flexibly, thus enabling the flexible coring cylinder to bend. When the flexible coring cylinder is penetrating deep into the borehole or rock formation, it can bend flexibly according to the borehole trajectory or the rock formation's orientation, effectively avoiding problems such as jamming, top-jamming, or uneven wear that easily occur with traditional rigid coring cylinders. This improves the flexibility of the flexible coring device in complex working conditions, achieving efficient and stable coring operations. Consequently, it can provide representative core samples for oil reservoir assessment, improving the accuracy of the assessment.

[0091] For example, the inner diameter of the flexible core tube can be 30mm-50mm, such as 30mm, 35mm, 39mm, 42mm, 45mm, 47mm, 49mm, 50mm, etc.

[0092] When the inner diameter of the flexible coring tube is 30mm-50mm, it can ensure both the structural strength of the coring tube and the coring results to meet the needs of subsequent core experiments.

[0093] See Figure 1 , Figure 2 and Figure 3 In some embodiments, along the direction of movement of the core in the core sampling channel, the joint 110 has an upstream end 111 and a downstream end 112, the upstream end 111 having a first connecting arm 1111 and the downstream end 112 having a second connecting arm 1121.

[0094] The joint 110 is movably connected to the second connecting arm 1121 in the adjacent upstream joint 110 via the first connecting arm 1111, and the joint 110 is movably connected to the first connecting arm 1111 in the adjacent downstream joint 110 via the second connecting arm 1121.

[0095] For example, the upstream end 111 is the end facing the core input direction, and the downstream end 112 is the end facing the core output direction.

[0096] During assembly, the first connecting arm 1111 of a joint 110 is movably connected to the second connecting arm 1121 of the adjacent joint 110 located upstream of it, while its own second connecting arm 1121 is movably connected to the first connecting arm 1111 of the adjacent joint 110 located downstream of it.

[0097] Among them, the active connection can be a hinge.

[0098] By cooperating with the first connecting arm 1111 and the second connecting arm 1121 between adjacent joint members 110, multiple joint members 110 are connected in series along the first direction X. Furthermore, each joint member 110 can deflect at a certain angle relative to the adjacent joint member 110 around the connection point, thereby enabling the flexible skeleton 100 to bend flexibly, and thus enabling the flexible core tube to have bending capability.

[0099] In some embodiments, the first connecting arm 1111 and the second connecting arm 1121 are distributed circumferentially at intervals along the joint member 110.

[0100] For example, two joint members 110 constitute a joint member unit, and multiple joint member units are arranged sequentially along the first direction X to form a flexible skeleton 100.

[0101] In one joint unit, one joint 110 is a first joint 113, and the other joint 110 is a second joint 114. The upstream end 111 of the second joint 114 is adjacent to the downstream end 112 of the first joint 113.

[0102] The upstream end 111 of the first joint member 113a has two first connecting arms 1111a, which are distributed on both sides of the first joint member 113a along the first radial direction Y and extend in a direction opposite to the first direction X. The first connecting arms 1111a of the first joint member 113a are movably connected to the second connecting arms 1121c of the second joint member 114c of the joint member unit adjacent to its upstream end 111.

[0103] The downstream end 112 of the first joint member 113a has two second connecting arms 1121a, which are distributed on both sides of the first joint member 113a along the second radial direction Z and extend along the first direction X.

[0104] The upstream end 111 of the second joint member 114b has two first connecting arms 1111b. The two first connecting arms 1111b of the second joint member 114b are correspondingly arranged with the two second connecting arms 1121a of the first joint member 113a. That is, the two first connecting arms 1111b of the second joint member 114b are distributed on both sides of the second joint member 114b along the second radial direction Z and extend in a direction away from the first direction X.

[0105] The two second connecting arms 1121a of the first joint member 113a are movably connected to the two first connecting arms 1111b of the second joint member 114b.

[0106] The downstream end 112 of the second joint member 114b has two second connecting arms 1121b, which are also distributed along the first radial direction Y on both sides of the second joint member 114b and extend along the first direction X. The second connecting arms 1121b of the second joint member 114b are movably connected to the first connecting arm 1111d of the first joint member 113d of the joint member unit adjacent to its downstream segment.

[0107] The first radial direction Y intersects with the second radial direction Z.

[0108] By arranging the first connecting arm 1111 and the second connecting arm 1121 circumferentially spaced along the joint 110, the overall connection strength and stability of the flexible skeleton 100 are significantly improved. Furthermore, the bending flexibility of the flexible skeleton 100 is enhanced. Specifically, the bending of the flexible skeleton 100 is no longer limited to a single plane, but can achieve multi-dimensional and omnidirectional deflection, thereby enabling the flexible core-taking cylinder to better adapt to complex working conditions and efficiently and stably complete the core-taking work.

[0109] See Figure 1 , Figure 2 , Figure 3 , Figure 15 and Figure 16 In some embodiments, two adjacent joint members 110 have a hollowed-out area 120 at the connection position.

[0110] Specifically, when two adjacent joint members 110 are movably connected by the first connecting arm 1111 and the second connecting arm 1121, a hollow area 120 is naturally formed around the connection position of the two. The hollow area 120 is the space defined by the gap between the end contours of the adjacent joint members 110 and the gap between the connecting arms.

[0111] To ensure the sealing of the core extraction channel, the flexible skeleton 100 also includes a flexible filler 130. The hollow area 120 is filled with the flexible filler 130, and the flexible filler 130 has a communicating cavity, through which the cavities of adjacent joint members 110 are connected.

[0112] For example, the flexible filler 130 may be made of a material with good elasticity and deformability, such as rubber, polyurethane or other polymeric elastomers, so that the flexible filler 130 can adapt to the relative movement between the joint members 110 without causing interference.

[0113] For example, the flexible filler 130 can be a flexible tube made of a high-pressure resistant material. The contour shape of the tube matches the contour of the hollow area 120, allowing the tube to fill the hollow area 120, thereby ensuring the sealing of the core extraction channel. The connecting cavity inside the tube connects to the cavity of the adjacent joint 110, ensuring the continuity of the core extraction channel.

[0114] The phrase "the shape of the hose matches the outline of the hollow area 120" means that the shape of the hose is the same as or similar to the outline of the hollow area 120.

[0115] The flexible filler 130 ensures the sealing of the core sampling channel and provides a continuous and smooth channel wall for core movement, preventing the core from getting stuck in the gaps at the connection of adjacent joints 110 or scraping against the edge of the hollow area 120 during movement, thus ensuring the smooth movement of the core within the core sampling channel.

[0116] See Figure 1 , Figure 2 and Figure 3 In some embodiments, the flexible core tube further includes a sealing sleeve 140, which is fitted onto the circumferential outer wall of the flexible skeleton 100.

[0117] For example, the sealing sleeve 140 is typically made of a material with a certain degree of flexibility and sealing properties. The sealing sleeve 140 is an integral structure that can tightly wrap around the circumferential outer wall of the flexible skeleton 100 formed by multiple joints 110 connected in series, thereby sealing the connection gaps that may exist between the joints 110 and the hollow area 120.

[0118] The sealing sleeve 140 further ensures the airtightness of the core sampling channel. This prevents rock cuttings and fluids from entering the core sampling channel from the borehole or rock strata, ensuring the reliability of core movement.

[0119] In addition, the sealing sleeve 140 may be fitted only on the circumferential outer wall of the flexible filler 130 and the area where the flexible filler 130 contacts the joint member 110.

[0120] Alternatively, the sealing sleeve 140 may have a partial structure capable of filling the hollow area 120. Specifically, when the sealing sleeve 140 is tightly wrapped around the circumferential outer wall of the flexible skeleton 100, which is composed of multiple articulated members 110 connected in series, it can simultaneously fill the hollow area 120, thus eliminating the need for an additional flexible filler 130.

[0121] See Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 11 and Figure 12 In some embodiments, the flexible coring device also includes a coring drill bit 200, which is a component that directly acts on the rock, breaks the rock core, and forms a borehole.

[0122] For example, the core drill bit 200 has a ring-shaped structure, with a central hole formed in the middle of the ring for the core to pass through. Eight blades are evenly distributed along the circumferential direction of the core drill bit 200, and planar teeth 210 and conical teeth 220 are mixed on the blades. The planar teeth 210 are mainly used for shearing and scraping the rock, while the conical teeth 220 are mainly used for crushing and grinding harder formations.

[0123] By arranging the planar teeth 210 and the conical teeth 220 together on the same core drill bit 200, the core drill bit 200 can simultaneously exert the rock-breaking advantages of both tooth types when facing rock formations of different hardness or properties, thereby maintaining a high mechanical drilling speed and stable drilling effect.

[0124] In addition, a diameter-maintaining tooth 230 is provided on the outer wall of the cutter wing. The diameter-maintaining tooth 230 protrudes from the outer wall surface of the cutter wing. When the drill bit rotates, the diameter-maintaining tooth 230 contacts the rock of the hole wall, which plays the role of trimming the hole wall and maintaining the diameter of the drill bit, thereby reducing the radial wear of the drill bit during the drilling process and ensuring the consistency of the borehole diameter.

[0125] Furthermore, a centering block 240 is provided on the inner wall of the cutter wing. The centering block 240 protrudes inward, and when the core passes through the center hole of the drill bit, the inner side of the centering block 240 forms a sliding contact with the circumferential outer wall of the core, thereby limiting and guiding the core in the circumferential direction and preventing the core from deviating or breaking before entering the core barrel, thus ensuring that the core can smoothly enter the subsequent core straightening assembly 400 and the flexible core barrel.

[0126] The core drill bit 200 is movably connected to the first joint 110 of the flexible skeleton 100 at the upstream end 111. The flexible core cylinder is constructed to be located inside the rotatable outer cylinder 300, which is connected to the drill bit.

[0127] The core drill bit 200 is configured to rotate under the drive of the outer cylinder 300. Specifically, the outer cylinder 300 of the drill bit is sleeved outside the flexible core tube. One end of the outer cylinder 300 is connected to the core drill bit 200, and the other end is configured to be connected to the rotation shaft of the drill bit so as to drive the core drill bit 200 to rotate under the drive of the rotation shaft.

[0128] When the drill string's rotating shaft begins to rotate and applies torque, the rotating shaft drives the entire outer cylinder 300 to rotate. The outer cylinder 300 transmits the torque to the core drill bit 200, causing the core drill bit 200 to rotate as well, thereby achieving drilling and rock breaking. During drilling, the outer cylinder 300 is used to transmit torque to the core drill bit 200, and the flexible core tube located inside the outer cylinder 300 is used to contain and protect the obtained rock core.

[0129] To accommodate the curved trajectory of the borehole, the outer cylinder 300 is also designed to be flexible along the first direction X, i.e., the extension direction of the flexible core cylinder. Specifically, along the first direction X, the outer cylinder 300 includes a plurality of sequentially arranged outer cylinder 300 segments, with adjacent outer cylinder 300 segments being movably connected.

[0130] As the outer cylinder 300 advances deeper into the borehole and encounters a curved section, the adjacent sections of the outer cylinder 300 will deflect relative to each other at the movable connection, allowing the outer cylinder 300 to bend in accordance with the direction of the borehole. This ensures that the flexible core tube and core sampling channel can also smoothly enter the curved borehole, thus realizing the core sampling function in non-linear boreholes.

[0131] For example, adjacent outer cylinder segments 300 can be connected by hinges or ball joints.

[0132] For example, along the first direction X, the length of one outer cylinder segment 300 is the same as that of one joint unit, that is, the length of one outer cylinder segment 300 is the same as the length of two adjacent joint units 110.

[0133] See Figure 1 , Figure 2 , Figure 3 , Figure 8 , Figure 9 and Figure 10 In some embodiments, the flexible coring device further includes a coring alignment component 400, a first bearing component 500, a second bearing component 600, and a lower connector component 700.

[0134] One end of the core-harvesting and straightening assembly 400 is movably connected to the first joint 110 of the flexible skeleton 100 at the upstream end 111, and the other end is connected to the first bearing 500, which is mounted on the core drill bit 200.

[0135] For example, the core-aligning assembly 400 and the flexible skeleton 100 are movably connected at the first joint 110 at the upstream end 111 by threads. For instance, one end of the core-aligning assembly 400 has internal threads, and the first joint 110 at the upstream end 111 of the flexible skeleton 100 has external threads.

[0136] See Figure 6 and Figure 7 The first bearing component 500 is mounted on the core drill bit 200. The core drill bit 200 has a receiving cavity, and the first bearing component 500 is disposed in the receiving cavity. The other end of the core straightening assembly 400 is fixed to the first bearing component 500 by a threaded connection or a snap-fit ​​method.

[0137] The first bearing component 500 can be a roller bearing. The outer ring or rollers of the roller bearing are connected to the core drill bit 200, and the inner ring of the roller bearing is connected to the core straightening assembly 400.

[0138] When the outer cylinder 300 transmits torque to the core drill bit 200, the outer ring or roller of the roller bearing rotates together with the core drill bit 200, thereby driving the core drill bit 200 to break the rock. At the same time, the inner ring of the roller bearing remains stationary, thus effectively blocking the transmission path of torque to the core straightening assembly 400, thereby preventing torque from being transmitted to the flexible core cylinder and ensuring that the flexible core cylinder is not affected by the rotational movement of the core drill bit 200 during the core extraction process.

[0139] See Figure 13 and Figure 14 One end of the lower connector assembly 700 is movably connected to the last joint 110 of the flexible skeleton 100 at the downstream end 112, and the other end is configured to be suspended from the drill string and fixed relative to the drill string.

[0140] For example, the lower connector assembly 700 includes a suspension bearing housing 710 and a suspension connector 720. Both the suspension bearing housing 710 and the suspension connector 720 may have pin holes, and the suspension bearing housing 710 and the suspension connector 720 may be connected by pins.

[0141] The end of the suspension bearing housing 710 opposite to the end connected to the suspension joint 720 is connected to the drill string, thereby achieving relative fixation with the drill string. The end of the suspension joint 720 opposite to the end connected to the suspension bearing housing 710 is connected to the last joint member 110 at the downstream end 112 of the flexible skeleton 100 via a thread.

[0142] The second bearing component 600 is sleeved on the outside of the lower connector assembly 700, and the second bearing component 600 is connected to the outer cylinder 300.

[0143] For example, the second bearing member 600 includes a first sub-bearing member 620 and a second sub-bearing member 630, and the lower connector assembly 700 also includes a first sub-bearing housing 610. The first sub-bearing member 620 is installed in the first sub-bearing housing 610, and the first sub-bearing housing 610 abuts against the suspension bearing housing 710.

[0144] The first sub-bearing component 620 and the second sub-bearing component 630 can be ball bearings, each including an inner ring, an outer ring, and balls disposed between the inner and outer rings. The balls of the first sub-bearing component 620 can contact the first sub-bearing housing 610. The outer rings of the first sub-bearing component 620 and the second sub-bearing component 630 are in contact. The balls of the second sub-bearing component 630 are in contact with the outer cylinder 300. Specifically, the outer cylinder 300 has an outer cylinder connector 320 inside, which contacts the balls of the second sub-bearing component 630.

[0145] When the outer cylinder 300 rotates, the outer cylinder connector 320 drives the balls of the second sub-bearing component 630 to roll between the inner and outer rings, thereby enabling the outer cylinder 300 to maintain its rotation. Due to the isolation effect of the ball bearing, the rotational torque is blocked and will not be transmitted to the lower connector assembly 700 through the suspension bearing housing 710, thus preventing torque transmission to the flexible core barrel.

[0146] At the same time, the first sub-bearing component 620 remains relatively stationary or slightly moving in the first sub-bearing housing 610, playing a balancing and stabilizing role and preventing the lower joint assembly 700 from tilting or shaking when subjected to off-center load.

[0147] Therefore, the flexible coring device provided in this application embodiment has a flexible frame 100 with one end rotatably connected to the coring drill bit 200 via a first bearing 500, and the other end fixedly connected to the drill string via a lower connector assembly 700. The outer cylinder 300 is supported on the lower connector assembly 700 via a second bearing 600 and rotates relative to the lower connector assembly 700. This configuration ensures that when the coring drill bit 200 and the outer cylinder 300 rotate and drill under the drive of the drill string, the flexible coring cylinder inside the outer cylinder 300 remains stationary. This avoids torsion, wear, or jamming of the core entering the coring channel due to rotation, ensuring that the core can be collected and preserved completely and smoothly, thus improving the stability and success rate of coring operations.

[0148] In some embodiments, the core-harvesting and straightening assembly 400 includes a blade straightener 410, a core-harvesting claw 420, and a limiting member 430. The blade straightener 410 is connected to a first bearing member 500, and the core-harvesting claw 420 is movably disposed within the blade straightener 410. One end of the limiting member 430 is disposed within the blade straightener 410, and together with the blade straightener 410, defines a space within the blade straightener 410 for the core-harvesting claw 420 to move upward.

[0149] The knife-edge stabilizer 410 has a knife-edge structure, and the core-taking claw 420 is configured to cooperate with the knife-edge structure when falling in space to form a clamping structure, which is used to clamp the rock core.

[0150] For example, one end of the blade straightener 410 is connected to the inner ring of the first bearing member 500 by a threaded connection or snap-fit. The core extractor 420 is movably disposed within the blade straightener 410. The limiting member 430 is assembled at the other end of the blade straightener 410, and the inner wall of the blade straightener 410 and the limiting member 430 together define a space for the core extractor 420 to move upward.

[0151] The knife-edge stabilizer 410 has a knife-edge structure at its end facing the rock core, which is usually an inwardly tapered cone.

[0152] In the initial stage of the coring operation, the core claw 420 is confined by the inner wall of the blade centralizer 410 and the limiting member 430 to create a space for the core claw 420 to move upward. The core enters the flexible coring cylinder through the blade centralizer 410 and pushes the core claw 420. The blade centralizer 410 provides guidance for the entry of the core.

[0153] When the core has reached the predetermined length and a core extraction operation is required, the core extraction claw 420 is moved toward the end of the cutterhead centralizer 410 connected to the first bearing 500 by pulling the drill bit. That is, the core extraction claw 420 falls within the space jointly defined by the limiting member 430 and the cutterhead centralizer 410.

[0154] When the core-taking claw 420 descends to contact the blade structure of the blade stabilizer 410, the outer edge of the core-taking claw 420 and the inner edge of the blade structure cooperate with each other and gradually wedge tightly. As the core-taking claw 420 descends and wedges in, the blade structure forces the core-taking claw 420 to retract inward and hold the rock core tightly, thus forming a clamping structure under the combined action of the core-taking claw 420 and the blade structure.

[0155] The clamping structure applies force to the core, causing it to eventually break. This enables reliable clamping and retrieval of the core after core sampling, allowing it to be extracted from the bottom of the borehole to the surface. This reduces the probability of core loss, short cores, or hollow cores during retrieval, and improves the core recovery rate and retrieval reliability.

[0156] In addition, a chamfer is provided at one end of the blade stabilizer 410 near the core drill bit 200 to guide the core into the flexible core tube.

[0157] In some embodiments, the inner cavity of the blade straightener 410 is formed with a guide mating surface 440, which is configured to engage with the circumferential outer wall of the core claw 420 when the core enters the flexible core tube, so as to push the core claw 420 upward in space.

[0158] For example, the guide mating surface 440 can be a conical surface. The guide mating surface 440 provides guidance for the core claw 420, thereby ensuring that the core can smoothly enter and pass through the cutter head centralizer 410, and then enter the flexible core barrel.

[0159] In some embodiments, the core retrieval channel contains a sealing liquid and a piston 160 is provided within the core retrieval channel. The piston 160 can move within the core retrieval channel to push the sealing liquid toward the end of the core retrieval channel, and the end of the core retrieval channel has an outlet hole.

[0160] For example, the last joint 110 of the flexible skeleton 100 at the downstream end 112 has a first liquid outlet 150, and the end of the lower connector assembly 700 connected to the last joint 110 of the flexible skeleton 100 at the downstream end 112 is correspondingly provided with a second liquid outlet 730. When the lower connector assembly 700 is connected to the last joint 110 of the flexible skeleton 100 at the downstream end 112, the first liquid outlet 150 and the second liquid outlet 730 correspond to and communicate with each other, together forming the liquid outlet at the end of the core extraction channel.

[0161] There is an annular channel between the flexible core tube and the outer tube 300. The annular channel is connected to the liquid outlet. The core drill bit 200 has a liquid outlet 250 connected to the annular channel. The liquid outlet 250 has a sealing element inside.

[0162] For example, the plugging element can be a soluble plug.

[0163] By setting the sealing element, the outlet 250 is sealed, so that the annular channel and the outlet 250 together form a closed space for filling the sealing liquid.

[0164] The annular channel is connected to the liquid outlet and is filled with sealed liquid. When the core enters the coring channel, the core pushes the piston 160 to move within the channel. Then, the piston 160 pushes the sealed liquid within the channel toward its end. Since the end of the channel has a liquid outlet, the sealed liquid is discharged through this outlet.

[0165] The flexible core sampling cylinder and the outer cylinder 300 have an annular channel that communicates with the liquid outlet. The annular channel also contains a sealed liquid. Therefore, when the sealed liquid is discharged through the liquid outlet, the sealed liquid in the core sampling channel is discharged into the annular channel.

[0166] In the initial state, a soluble plug is installed inside the outlet 250 to seal the outlet 250 and prevent the sealed fluid in the annular channel from flowing out. When the sealed fluid in the core sampling channel is discharged into the annular channel, the pressure in the annular channel increases, the soluble plug falls off from the outlet 250, and the sealed fluid in the annular channel flows into the outlet 250 on the drill bit.

[0167] At this time, the pressurized sealed fluid in the annular channel is ejected from the outlet 250 of the coring drill bit 200, which coats the core entering the coring channel. This forms a continuous isolation and coating protection for the core during the coring process, preventing drilling fluid from invading the interior of the flexible coring tube, contaminating the core sample, and affecting the accuracy of reservoir properties and oil-water dynamic analysis.

[0168] In addition, the first bearing 500 installed in the cavity of the core drill bit 200 may have a liquid guide hole 510. When the sealed liquid in the core channel is discharged into the annular channel, the pressure in the annular channel increases, the soluble plug falls off from the liquid outlet 250, and the sealed liquid in the annular channel flows into the liquid outlet 250 of the drill bit through the liquid guide hole 510.

[0169] The end of the first bearing component 500 facing away from the flexible core tube may also be provided with a chamfer to guide the rock core into the flexible core tube.

[0170] Meanwhile, this application provides a flexible coring system, including a drill bit, an outer cylinder 300, and a flexible coring device as described in any of the embodiments above.

[0171] Drilling tools are rotary drive and suspension support devices located on the ground surface or above the borehole, used to provide the torque required for drilling and to provide suspension support for the outer casing 300 and flexible coring equipment.

[0172] The outer cylinder 300 includes a plurality of sequentially arranged outer cylinder 300 segments, which are movably connected to each other. For example, adjacent outer cylinder 300 segments can be connected by hinges or ball joints, thereby giving the outer cylinder 300 as a whole good flexibility and enabling it to bend and deform in accordance with the bending trajectory of the borehole.

[0173] The flexible coring equipment includes a flexible coring cylinder and a coring drill bit 200, with the flexible coring cylinder located inside an outer cylinder 300. The flexible coring cylinder includes a flexible frame 100, one end of which is suspended from and fixed relative to the drill string. The other end of the flexible frame 100 is movably connected to the coring drill bit 200. The flexible frame 100 has a coring channel within it. The coring channel is used to receive and protect the core sample retrieved from the borehole.

[0174] For example, the downstream end 112 of the flexible skeleton 100 is suspended from the drill string, and the upstream end 111 of the flexible skeleton 100 is movably connected to the core drill bit 200.

[0175] The outer cylinder 300 is connected to the drill string so as to drive the core drill bit 200 to rotate under the drive of the drill string. When the outer cylinder 300 rotates, the core drill bit 200 rotates under the drive of the outer cylinder 300, thereby realizing the rock breaking drilling.

[0176] When the flexible coring system is in operation, the drill string drives the outer cylinder 300 to rotate, which in turn drives the coring bit 200 to rotate and drill. As the coring bit 200 rotates, the rock is broken up. Exemplarily, the coring bit 200 has a central hole through which the core passes. The core enters the coring channel through the central hole.

[0177] As the borehole extends, the outer cylinder 300 can bend along the borehole trajectory. Since the flexible coring cylinder is located inside the outer cylinder 300 and includes a flexible frame 100, the flexible coring cylinder can bend along with the outer cylinder 300 to adapt to the borehole trajectory, thereby enabling the flexible coring equipment to perform coring in short-radius wells.

[0178] The flexible coring system provided in this application adopts the flexible coring equipment provided in any of the above embodiments, and thus has the beneficial effects of the aforementioned flexible coring equipment. That is, it improves the passability of the flexible coring equipment in short-radius wells, enabling the flexible coring equipment to achieve efficient and stable coring work, thereby revealing detailed information such as the sand body connectivity, residual oil distribution and pollution zone characteristics in the near-wellbore zone, and improving the accuracy of reservoir assessment.

[0179] Furthermore, this application also provides a method for in-well coring, applied to the flexible coring system provided in any of the above embodiments. The in-well coring method includes the following steps:

[0180] Control the drill string to rotate the outer cylinder 300 so that the rock core in the well enters the core sampling channel of the flexible skeleton 100 in the flexible core sampling cylinder and moves towards the end of the core sampling channel.

[0181] Specifically, the drill bit acts as a rotary drive device, and the torque output by the drill bit is transmitted to the outer cylinder 300, driving the outer cylinder 300 to rotate around its axis. Since the outer cylinder 300 is composed of multiple movably connected outer cylinder 300 segments, the outer cylinder 300 can bend and deform in accordance with the bending trajectory of the borehole while rotating.

[0182] As the outer cylinder 300 rotates, the core drill bit 200 connected to the outer cylinder 300 is driven to rotate as well. The rotating core drill bit 200 breaks and cuts the rock at the bottom of the borehole, causing the rock to continuously break and form a cylindrical rock core.

[0183] As drilling continues, newly formed core samples enter the flexible core barrel through the central hole of the core drill bit 200. Specifically, the core sample first passes through the upstream end 111 of the flexible frame 100, which is movably connected to the core drill bit 200, and then enters the core sampling channel. Under the continuous pushing of subsequently formed core samples, the core samples already in the core sampling channel are propelled towards the end of the channel, thus ensuring that the core samples continuously enter and are preserved inside the flexible core barrel.

[0184] Through the above steps, the application of flexible coring equipment in short-radius wells was realized. This allows the core to be successfully entered and preserved in the flexible coring cylinder while the drill string drives the outer cylinder to rotate 300 degrees and the coring drill bit 200 breaks the rock and drills. This completes continuous coring operations in short-radius wells, thereby revealing detailed information such as the connectivity of sand bodies in the near-wellbore zone, the distribution of remaining oil, and the characteristics of contamination zones, thus improving the accuracy of reservoir assessment.

[0185] The in-well coring method provided in this application is applied to the flexible coring system provided in any of the above embodiments. Therefore, it has the beneficial effects of the above-mentioned flexible coring system, namely, improving the passability of the flexible coring equipment in short-radius wells, enabling the flexible coring equipment to achieve efficient and stable coring work, thereby revealing detailed information such as the sand body connectivity, residual oil distribution and pollution zone characteristics in the near-wellbore zone, and improving the accuracy of reservoir assessment.

[0186] In some embodiments, an annular channel is provided between the flexible core tube and the outer tube 300, and a piston 160 is provided in the core tube, with a sealing liquid on the side of the core tube facing the end of the core tube.

[0187] Piston 160 is configured to move within the coring channel under the push of the core to move the sealing fluid toward the end of the coring channel.

[0188] The core sampling channel has a liquid outlet at its end, which is connected to the annular channel. The core drill bit 200 has a liquid outlet 250 that is connected to the annular channel, and the liquid outlet 250 has a sealing element inside.

[0189] Specifically, when the core enters the coring channel from the coring bit 200, the core contacts the piston 160 and exerts a pushing force on it. Under the continuous pushing of the core, the piston 160 moves away from the coring bit 200 within the coring channel, i.e., towards the end of the coring channel. The movement of the piston 160, in turn, pushes the sealing fluid towards the end of the coring channel towards the end as well.

[0190] As piston 160 moves, the sealing fluid is pushed to the end of the core extraction channel and discharged through the outlet hole. The discharged sealing fluid enters the annular channel connected to the outlet hole. As piston 160 continues to move, more and more sealing fluid enters the annular channel, causing the liquid pressure inside the annular channel to gradually increase.

[0191] When the liquid pressure within the annular channel rises sufficiently to overcome the sealing force of the plugging component, the plugging component is forced open, and the outlet 250 opens. At this point, the pressurized sealing fluid within the annular channel is ejected from the outlet 250 of the coring bit 200, encapsulating the core entering the coring channel. This provides continuous isolation and protection for the core during the coring process, reducing contamination caused by drilling fluid intrusion, improving the core's original state preservation and representativeness, and meeting the sampling requirements for detailed evaluation of reservoir oil-water dynamics and physical properties.

[0192] In some embodiments, the flexible coring system further includes a blade stabilizer 410, a coring claw 420, and a limiting member 430. The blade stabilizer 410 is connected to the first bearing member 500, and the coring claw 420 is movably disposed within the blade stabilizer 410. One end of the limiting member 430 is disposed within the blade stabilizer 410, and together with the blade stabilizer 410, defines a space within the blade stabilizer 410 for the coring claw 420 to move upward. The blade stabilizer 410 has a blade structure.

[0193] After obtaining the required core sample, the in-well coring method also includes the following steps:

[0194] The core-collecting claw 420 is controlled to fall in space and cooperate with the cutting edge structure to form a clamping structure to clamp the rock core.

[0195] To ensure reliable clamping and retrieval after core sampling, so that the core can be extracted from the bottom of the borehole to the surface, this scheme further supplements the in-well coring method.

[0196] Specifically, when the core enters the core sampling channel to a predetermined length and a core sampling operation is required, the core sampling claw 420 moves downward under the action of gravity within the space jointly defined by the limiting member 430 and the cutting edge stabilizer 410, that is, it falls towards the core sampling drill bit 200.

[0197] As the core-retrieving claw 420 descends, its outer edge gradually contacts and engages with the blade structure of the blade stabilizer 410. During its descent, the claw 420 is guided and constrained by the blade structure, forcing it to retract inwards. When the claw 420 continues to descend until it is wedged tightly against the blade structure, its inner edge grips the core, thus forming a clamping structure under the combined action of the claw 420 and the blade structure. This clamping structure applies radial clamping force and axial tensile force to the core.

[0198] Subsequently, an upward pulling force is applied by pulling the drill string. When the pulling force is transmitted to the core through the clamping structure and exceeds the tensile strength of the core, the core is clamped at the clamping structure and eventually breaks. The clamped core is held by the core claw 420 and lifted to the surface along with the flexible coring system.

[0199] Through the above steps, the core can be snapped and reliably retrieved after coring, ensuring that the core can be extracted intact from the bottom of the borehole, thereby improving the yield of coring work.

[0200] In addition, the flexible coring system also includes a first bearing component 500, a second bearing component 600, and a lower connector assembly 700.

[0201] One end of the core-taking and straightening assembly 400 is movably connected to the flexible skeleton 100, and the other end is connected to the first bearing component 500, which is mounted on the core drill bit 200.

[0202] See Figure 6 and Figure 7 The first bearing component 500 is mounted on the core drill bit 200. The core drill bit 200 has a receiving cavity, and the first bearing component 500 is disposed in the receiving cavity. The end of the blade straightener 410 facing away from the flexible skeleton is connected to the first bearing component 500.

[0203] The first bearing component 500 can be a roller bearing. The outer ring or rollers of the roller bearing are connected to the core drill bit 200, and the inner ring of the roller bearing is connected to the tool edge stabilizer 410.

[0204] When the outer cylinder 300 transmits torque to the core drill bit 200, the outer ring or roller of the roller bearing rotates together with the core drill bit 200, thereby driving the core drill bit 200 to break the rock. At the same time, the inner ring of the roller bearing remains stationary, thus effectively blocking the transmission path of torque to the cutter head centralizer 410, thereby preventing torque transmission to the flexible core cylinder and ensuring that the flexible core cylinder is not affected by the rotational movement of the core drill bit 200 during the core extraction process.

[0205] See Figure 13 and Figure 14One end of the lower connector assembly 700 is movably connected to one end of the flexible skeleton 100 at the downstream end 112, and the other end is configured to be suspended from the drill string and fixed relative to the drill string.

[0206] For example, the lower connector assembly 700 includes a suspension bearing housing 710 and a suspension connector 720. Both the suspension bearing housing 710 and the suspension connector 720 may have pin holes, and the suspension bearing housing 710 and the suspension connector 720 may be connected by pins.

[0207] The end of the suspension bearing housing 710 opposite to the end connected to the suspension joint 720 is connected to the drill string, thereby achieving relative fixation with the drill string. The end of the suspension joint 720 opposite to the end connected to the suspension bearing housing 710 is connected to the last joint member 110 at the downstream end 112 of the flexible skeleton 100 via a thread.

[0208] The second bearing component 600 is sleeved on the outside of the lower connector assembly 700, and the second bearing component 600 is connected to the outer cylinder 300.

[0209] For example, the second bearing member 600 includes a first sub-bearing member 620 and a second sub-bearing member 630, and the lower connector assembly 700 also includes a first sub-bearing housing 610. The first sub-bearing member 620 is installed in the first sub-bearing housing 610, and the first sub-bearing housing 610 abuts against the suspension bearing housing 710.

[0210] The first sub-bearing component 620 and the second sub-bearing component 630 can be ball bearings, each including an inner ring, an outer ring, and balls disposed between the inner and outer rings. The balls of the first sub-bearing component 620 can contact the first sub-bearing housing 610. The outer rings of the first sub-bearing component 620 and the second sub-bearing component 630 are in contact. The balls of the second sub-bearing component 630 are in contact with the outer cylinder 300. Specifically, the outer cylinder 300 has an outer cylinder connector 320 inside, which contacts the balls of the second sub-bearing component 630.

[0211] When the outer cylinder 300 rotates, the outer cylinder connector 320 drives the balls of the second sub-bearing component 630 to roll between the inner and outer rings, thereby enabling the outer cylinder 300 to maintain its rotation. Due to the isolation effect of the ball bearing, the rotational torque is blocked and will not be transmitted to the lower connector assembly 700 through the suspension bearing housing 710, thus preventing torque transmission to the flexible core barrel.

[0212] At the same time, the first sub-bearing component 620 remains relatively stationary or slightly moving in the first sub-bearing housing 610, playing a balancing and stabilizing role and preventing the lower joint assembly 700 from tilting or shaking when subjected to off-center load.

[0213] The flexible skeleton 100 is rotatably connected to the core drill bit 200 at one end via a first bearing 500, and is relatively fixedly connected to the drill string at the other end via a lower connector assembly 700. The outer cylinder 300 is supported on the lower connector assembly 700 and rotates relative to the lower connector assembly 700 via a second bearing 600. This configuration ensures that when the core drill bit 200 and the outer cylinder 300 rotate and drill under the drive of the drill string, the flexible core cylinder inside the outer cylinder 300 remains stationary. This avoids the core from being twisted, worn, or stuck due to rotation, ensuring that the core can be collected and preserved completely and smoothly. This improves the stability and success rate of core drilling and further helps to reveal detailed information such as the connectivity of sand bodies in the near-wellbore zone, the distribution of remaining oil, and the characteristics of contamination zones, thereby improving the accuracy of reservoir assessment.

[0214] The embodiments or implementation methods in this application are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0215] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0216] In the description of this application, it should be understood that the terms “comprising” and “having” as used herein, and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, display structure, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are expressly listed, but may include other steps or units that are not expressly listed or that are inherent to such process, method, product, or device.

[0217] The term "and / or" used in this application is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0218] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0219] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A flexible coring device, characterized by, The device includes a flexible core tube, which includes a flexible frame (100). The flexible frame (100) includes multiple joints (110). Each joint (110) has a cavity. The multiple joints (110) are arranged sequentially along a first direction. Adjacent joints (110) are movably connected. The cavities of each joint (110) are interconnected to form a core-taking channel for core movement.

2. The flexible coring device of claim 1, wherein, Along the direction of movement of the core in the core sampling channel, the joint (110) has an upstream end (111) and a downstream end (112), the upstream end (111) has a first connecting arm (1111), and the downstream end (112) has a second connecting arm (1121). The joint (110) is movably connected to the second connecting arm (1121) in the adjacent upstream joint (110) via the first connecting arm (1111), and the joint (110) is movably connected to the first connecting arm (1111) in the adjacent downstream joint (110) via the second connecting arm (1121).

3. The flexible coring device of claim 2, wherein, The first connecting arm (1111) and the second connecting arm (1121) are distributed circumferentially at intervals along the joint (110).

4. The flexible coring device according to claim 1, characterized in that, The two adjacent joint members (110) have a hollow area (120) at the connection position. The flexible skeleton (100) also includes a flexible filler (130), the hollow area (120) is filled with the flexible filler (130), and the flexible filler (130) has a communicating cavity, and the cavities of adjacent joint members (110) are connected through the communicating cavity.

5. The flexible coring device according to claim 1, characterized in that, The flexible core tube also includes a sealing sleeve (140), which is fitted onto the circumferential outer wall of the flexible skeleton (100).

6. The flexible coring device according to any one of claims 1-5, characterized in that, It also includes a core drill bit (200) movably connected to the first joint (110) at the upstream end (111) of the flexible skeleton (100), and the flexible core cylinder is configured to be located inside a rotatable outer cylinder (300) connected to the drill bit; The core drill bit (200) is configured to rotate under the drive of the outer cylinder (300).

7. The flexible coring device according to claim 6, characterized in that, It also includes a core-taking and straightening assembly (400), a first bearing component (500), a second bearing component (600), and a lower connector assembly (700). One end of the core-taking and straightening assembly (400) is movably connected to the first joint (110) at the upstream end (111) of the flexible skeleton (100), and the other end is connected to the first bearing (500), which is mounted on the core drill bit (200). One end of the lower connector assembly (700) is movably connected to the last joint (110) at the downstream end (112) of the flexible skeleton (100), and the other end is configured to be suspended from the drill bit and fixed relative to the drill bit. The second bearing member (600) is sleeved on the outside of the lower connector assembly (700), and the second bearing member (600) is configured to connect with the outer cylinder (300).

8. The flexible coring device according to claim 7, characterized in that, The core-harvesting and straightening assembly (400) includes a blade straightener (410), a core-harvesting claw (420), and a limiting member (430). The blade straightener (410) is connected to the first bearing member (500), and the core-harvesting claw (420) is movably disposed within the blade straightener (410). One end of the limiting member (430) is disposed within the blade straightener (410), and together with the blade straightener (410), they define a space within the blade straightener (410) for the core-harvesting claw (420) to move upward. The blade stabilizer (410) has a blade structure, and the core claw (420) is configured to cooperate with the blade structure when falling in the space to form a snapping structure, which is used to snap the core.

9. The flexible coring device according to claim 8, characterized in that, The inner cavity of the blade stabilizer (410) has a guide mating surface (440), which is configured to engage with the circumferential outer wall of the core claw (420) when the core enters the flexible core tube, so as to push the core claw (420) to move upward in the space.

10. The flexible coring device according to claim 6, characterized in that, The core sampling channel contains a sealed liquid, and the core sampling channel contains a piston (160). The piston (160) can move within the core sampling channel to push the sealed liquid toward the end of the core sampling channel. The end of the core sampling channel has a liquid outlet. The flexible core tube and the outer tube (300) have an annular channel, which is connected to the liquid outlet. The core drill bit (200) has a liquid outlet (250) connected to the annular channel, and the liquid outlet (250) has a sealing element inside.

11. A flexible coring system, characterized in that, include: Drilling tools; The outer cylinder (300) includes a plurality of outer cylinder (300) segments arranged sequentially, and adjacent outer cylinder (300) segments are movably connected; The flexible coring device according to any one of claims 1-10, the flexible coring device includes a flexible coring cylinder and a coring drill bit (200), the flexible coring cylinder is located inside the outer cylinder (300), the flexible coring cylinder includes a flexible frame (100), one end of the flexible frame (100) is suspended from the drill bit and fixed relative to the drill bit, the other end of the flexible frame (100) is movably connected to the coring drill bit (200); the flexible frame (100) has a coring channel inside; The outer cylinder (300) is connected to the drill bit to drive the core drill bit (200) to rotate under the drive of the drill bit.

12. A method for coring in a well, characterized in that, The flexible coring system according to claim 11, the in-well coring method includes the following steps: Control the drill string to rotate the outer cylinder (300) so that the core in the well enters the core sampling channel of the flexible skeleton (100) in the flexible core sampling cylinder and moves toward the end of the core sampling channel.

13. The well coring method according to claim 12, characterized in that, There is an annular channel between the flexible core sampling cylinder and the outer cylinder (300), and a piston (160) is provided in the core sampling channel. There is a sealing liquid in the core sampling channel on the side of the piston (160) facing the end of the core sampling channel. The piston (160) is configured to move within the coring channel under the pressure of the core, thereby pushing the sealing fluid toward the end of the coring channel. The end of the core sampling channel has a liquid outlet hole, which is connected to the annular channel; the core drill bit (200) has a liquid outlet (250) connected to the annular channel, and the liquid outlet (250) has a sealing element inside.

14. The well coring method according to claim 12 or 13, characterized in that, The flexible coring system further includes a blade stabilizer (410), a core-retrieving claw (420), and a limiting member (430). The blade stabilizer (410) is connected to a first bearing member (500), and the core-retrieving claw (420) is movably disposed within the blade stabilizer (410). One end of the limiting member (430) is disposed within the blade stabilizer (410), and together with the blade stabilizer (410), they define a space within the blade stabilizer (410) for the core-retrieving claw (420) to move upward. The blade stabilizer (410) has a blade structure. After obtaining the required core sample, the in-well coring method further includes the following steps: The core-taking claw (420) is controlled to fall within the space and cooperate with the cutting edge structure to form a clamping structure to clamp the rock core.

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