Forward and reverse circulation assembly for coring drilling tool and coring operation method using same

Abstract

The invention provides a forward and reverse circulation assembly for a coring drilling tool and a coring operation method using the forward and reverse circulation assembly, the forward and reverse circulation assembly comprises an outer pipe body and an inner containing body arranged in the outer pipe body, and a drilling fluid channel is defined between the outer pipe body and the inner containing body. The core is that at least one longitudinal fluid acceleration groove is formed in the peripheral wall of the inner accommodating body. During operation, drilling fluid is rapidly accelerated when flowing through the acceleration groove, so that a stable negative pressure area is formed at the downstream of the acceleration groove. The negative pressure area upwards sucks fluid and the rock core from the inlet of the rock core through a reverse circulation channel, and protective local reverse circulation is formed. And the mainstream drilling fluid which does not participate in the reverse circulation continuously flows downwards to form a positive circulation for chip removal and cooling. By constructing a positive and negative double-circulation synergistic fluid system, the technical problems that rock cores are broken and the coring rate is extremely low due to mechanical thrust and fluid scouring of a conventional drilling tool in a loose and fragile seabed stratum are solved. The integrity of the rock core sample of the loose and fragile stratum is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of submarine drilling equipment, and in particular to a forward and reverse circulation assembly for a coring drill and a coring operation method using the same. Background Art

[0002] Seabed geological exploration is fundamental to deep-sea resource development and marine science research. One of its core tasks is to obtain rock samples that truly reflect in-situ stratigraphic information through drilling and coring operations. A unique type of engineering geology—loose, fragile strata—is widely distributed across the vast seafloor. Typical examples of this type of strata include, but are not limited to, polymetallic sulfide deposits formed by hydrothermal activity, organic-rich bioclastic sediments, altered basalts, and turbidites. These strata share common geological characteristics: extremely low inter-particle bonding, highly developed porosity, and poor overall structural stability, making them susceptible to fragmentation and collapse when disturbed.

[0003] Existing seafloor coring technologies, such as conventional wireline coring and rotary drilling, rely primarily on mechanical thrust to push or push the core into the core barrel when used in these loose and fragile formations. When this mechanical force acts on the already nearly discrete loose core, it can easily cause structural fragmentation and severe disturbance before the core enters the core barrel.

[0004] Furthermore, the positively circulated drilling fluid required for conventional drilling primarily serves to remove cuttings and cool the drill bit. High-pressure drilling fluid is ejected at high speed from the bottom of the drill bit, directly and violently impacting the hole bottom and the fragile core samples about to enter the core barrel. This hydraulic erosion can dislodge fine-grained material from the loose core, destroying its original bedding and structure, and even completely dispersing the core. This results in extremely low coring yields, sometimes even below 10%, and severely disturbs the samples, rendering them largely worthless for scientific research. Summary of the Invention

[0005] The purpose of the present invention is to provide a forward and reverse circulation assembly for a coring drill and a coring operation method using the same, aiming to solve the problems in the prior art of conventional coring drills due to their single positive circulation mode and mechanical pushing coring method, which lead to severe core breakage and extremely low coring recovery rate due to hydraulic erosion and pipe feed resistance when facing loose and fragile formations.

[0006] The present invention is achieved by the following technical solutions: A forward and reverse circulation assembly for a coring drill, comprising outer tube body; An inner receiving body, used for receiving a core, is disposed inside the outer tube body, and a drilling fluid passage is defined between the inner receiving body and the outer tube body; At least one longitudinal fluid acceleration groove is formed on the outer peripheral wall of the inner receiving body, which is used to form a negative pressure zone by increasing the local flow velocity when the drilling fluid flows through; a reverse circulation channel connecting the vicinity of the core inlet at the lower portion of the inner receiving body with the negative pressure zone, and configured to utilize the suction effect generated by the negative pressure zone to suck part of the drilling fluid and the core upward from the core inlet, thereby forming a local reverse circulation; The mainstream drilling fluid that does not form a local reverse circulation continues to flow along the drilling fluid channel to form a positive circulation.

[0007] As described above, in the forward and reverse circulation assembly for the coring drill, the inner receiving body includes a recovery tube, the lower end of the recovery tube is provided with a docking portion, the docking portion is sleeved with the coring tube, and the fluid acceleration groove is provided on the outer peripheral wall of the docking portion.

[0008] The forward and reverse circulation assembly for the coring drill as described above further includes an annular seal disposed around the docking portion and adjacent to the fluid acceleration groove.

[0009] As described above, in the forward and reverse circulation assembly for the coring drill, the annular seal separates the drilling fluid channel into a first channel located above it and a second channel located below it, a water inlet groove is provided at the upper edge of the docking portion, and the fluid acceleration groove is connected to the bottom of the water inlet groove. The water inlet groove and the fluid acceleration groove together connect the first channel and the second channel.

[0010] As described above, the forward and reverse circulation assembly for the coring drill tool, the reverse circulation channel includes a reflux channel arranged along the axis at the upper end of the coring tube, and the bottom of the reflux channel is connected to a collection chamber for accommodating the core; the part where the upper part of the coring tube and the docking part are connected is provided with an annular groove along the outer circumference, and the annular groove is provided with a drainage port connected to the reflux channel, and the lower side wall of the docking part is provided with a negative pressure channel corresponding to the drainage port, and the negative pressure channel is connected to the negative pressure zone at the opening on the inner wall of the outer tube body.

[0011] In the forward and reverse circulation assembly for the coring drill as described above, the caliber of the negative pressure channel is smaller than the caliber of the drain port.

[0012] In the forward and reverse circulation assembly for the coring drill as described above, the negative pressure channel is arranged to be inclined downward relative to the inner wall of the outer tube.

[0013] In the forward and reverse circulation assembly for the coring drill as described above, a one-way valve is provided in the reflux channel.

[0014] In the forward and reverse circulation assembly for a coring drill as described above, the fluid acceleration groove is asymmetrically arranged along the circumference of the docking portion.

[0015] A coring method, utilizing the forward and reverse circulation assembly for a coring drill as described above, comprises the following steps: S1. System deployment and fluid supply: a forward and reverse circulation assembly including an outer tube and an inner receiving body is placed in the hole, and drilling fluid is pumped into the drilling fluid channel defined between the outer tube and the inner receiving body by a high-pressure pump unit; S2. Forced flow diversion and negative pressure generation: utilizing an annular seal disposed within the drilling fluid channel and surrounding the inner container to separate the drilling fluid channel into an upper first channel and a lower second channel; and forcing the drilling fluid in the first channel, as the sole flow path, to flow through at least one fluid acceleration groove formed on the peripheral wall of the inner container, thereby forming a negative pressure zone within the second channel; S3. The positive and reverse circulation work in coordination, utilizing the negative pressure zone to pump fluid and core upward from the core inlet of the inner containment body through a reverse circulation channel, forming a local reverse circulation to guide and protect the core; at the same time, the mainstream drilling fluid after flowing through the fluid acceleration tank is drawn out from the bottom of the assembly, forming a positive circulation for chip removal, cooling and wall protection.

[0016] Compared with the prior art, the present invention has the following advantages: 1. This invention utilizes fluid dynamics principles to automatically generate a stable negative pressure zone through ingeniously designed fluid acceleration grooves on the outer wall of the inner containment body. This negative pressure zone drives localized reverse circulation, generating a gentle, continuous suction force that "sucks" loose, fragile cores into the inner containment body, rather than the traditional "pushing" or "pushing" method. This "pressure differential-guided" coring method significantly reduces mechanical stress damage to the core and minimizes core disturbance, significantly improving the core recovery rate from loose, fragile formations while maximally preserving the core's original bedding and structural integrity.

[0017] 2. This invention utilizes a sophisticated, coordinated dual-circulation system. A localized reverse circulation system is used for core protection and sampling, while the mainstream drilling fluid continues its conventional forward circulation, performing essential engineering tasks such as chip removal, bit cooling, and hole wall stabilization. This effectively resolves the inherent conflict inherent in conventional single-circulation systems, where high-intensity chip removal fluids inevitably cause severe erosion of fragile cores, achieving both high-quality coring and high-efficiency drilling.

[0018] 3. The negative pressure generation and reverse circulation drive of this invention rely on the fluid energy of the drilling fluid itself, achieving energy conversion through a fixed, component-free fluid acceleration tank, resulting in a passive self-drive system. This design eliminates the need for any additional downhole power sources such as micromotors, turbines, or mechanical pumps, thus avoiding the inherent reliability issues of these complex moving components in the high-pressure, corrosive, and high-vibration environments of the deep sea. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the invention, the following briefly introduces the drawings required for describing the embodiments.

[0020] Figure 1 Schematic diagram of the three-dimensional structure of this embodiment; Figure 2 Schematic diagram of the decomposition structure of this embodiment; Figure 3 Schematic diagram of the three-dimensional structure of the recovery tube in this embodiment; Figure 4 Schematic diagram of the three-dimensional structure of the core tube in this embodiment; Figure 5 is a top view of this embodiment; Figure 6 for Figure 5 Cross-sectional view along AA; Figure 7 for Figure 6 A magnified schematic diagram of point B in the middle; Figure 8 A schematic diagram of a possible structure of the locking and recovery mechanism in Example 1; Figure 9 This is a schematic diagram of the forward and reverse circulation circuits of the drilling fluid during the seabed coring operation in this embodiment. Figure 1 ; Figure 10 This is a schematic diagram of the forward and reverse circulation circuits of the drilling fluid during the seabed coring operation in this embodiment. Figure 2 . DETAILED DESCRIPTION

[0021] To make the purpose, technical solutions and advantages of the present invention clearer, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments described herein are only some preferred embodiments of the present invention, not all embodiments. Based on this embodiment, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] Example 1: This example provides a forward and reverse circulation assembly for coring operations in loose and fragile seabed formations. The forward and reverse circulation assembly serves as a core module of a coring drill tool and works in conjunction with other conventional components of the coring drill tool.

[0023] Please refer to the attached Figures 1 to 10 In one embodiment of the present invention, a forward and reverse circulation assembly for a coring drill comprises an outer tubular body 1 and an inner container 2. The inner container 2 is used to hold core samples obtained from the formation and is removably disposed within the interior of the outer tubular body 1. An annular downward drilling fluid channel 3 is naturally defined between the outer wall of the inner container 2 and the inner wall of the outer tubular body 1, ensuring smooth circulation of the drilling fluid to maintain borehole stability.

[0024] At least one longitudinal fluid acceleration groove 4 is formed on the outer peripheral wall of the inner containing body 2. This fluid acceleration groove 4 is the core feature of this embodiment, and the change of fluid properties is achieved through structural mutation. Specifically, the local flow cross-sectional area of the fluid acceleration groove 4 is designed to be much smaller than the main flow cross-sectional area of the downward drilling fluid channel 3. This differentiated design of the cross-sectional area is based on the continuity equation and Bernoulli's theorem in fluid mechanics. When the drilling fluid is forced into this narrow fluid acceleration groove 4 from the wide main channel, its local flow velocity will be sharply increased several times. According to Bernoulli's principle, the sharp increase in flow velocity will lead to a significant drop in the static pressure of the fluid, thereby forming a stable negative pressure zone 5 in the downstream area of the fluid acceleration groove 4.

[0025] In order to utilize the negative pressure area 5, the forward and reverse circulation assembly of this embodiment is further provided with a reverse circulation channel 6. Figure 3 、 Figure 7 、 Figures 9 and 10 As shown, this channel cleverly connects the vicinity of the core inlet at the bottom of the inner container 2 with the aforementioned negative pressure zone 5. When the negative pressure zone 5 forms a strong low-pressure environment, a suction force is applied to the core inlet through the reverse circulation channel 6. This suction force not only greatly reduces the resistance of the loose seabed core to entering the inner container 2, but also actively draws the core and a small amount of fluid around it into the inner container 2, forming a local reverse circulation from bottom to top. This gentle, guided reverse circulation is the key to ensuring the intact and undisturbed recovery of loose and fragile cores. In the meantime, please refer to Figures 8 to 9The mainstream drilling fluid that does not participate in the formation of local reverse circulation constitutes the main body of the positive circulation. It continues to flow downward along the downward drilling fluid channel 3 and is ejected through the edge of the centering drill bit set at the bottom of the outer tube body 1. The hydraulic impact effect generated by the ejected drilling fluid can effectively assist the drill bit in breaking the rock and cleaning its cutting end face. Subsequently, this fluid carrying energy will suck up the rock cuttings produced by the drill bit cutting, and then return upward along the annular space 200 formed between the outer wall of the outer tube body 1 and the rock hole wall 100. During this return process, the drilling fluid continuously transports the rock cuttings from the bottom of the hole to the hole mouth and finally discharges them to the seabed, completing its most core mission of chip removal as a positive circulation. At the same time, the upward returning fluid also continuously flows through the outer wall of the outer tube body 1, and through heat exchange, it takes away the huge heat generated by friction, playing a key cooling role for the entire coring drill. Moreover, in loose and fragile formations, this stable liquid column filling the annular space 200 can also provide effective support for the fragile hole wall through its hydrostatic pressure, significantly improving the stability of the borehole and providing the necessary guarantee for the smooth progress of the entire coring operation.

[0026] Furthermore, as a preferred embodiment, to achieve structural modularity and recyclability during operation, the inner container 2 can be structurally divided into an upper recovery tube 21 and a lower core tube 23. The lower end of the recovery tube 21 is provided with a precisely machined docking portion 22, which couples to the upper end of the core tube 23 via threads, snaps, interference fits, sleeves, or other conventional connection methods in the art. A fluid acceleration tank 4 is disposed on the outer peripheral wall of the docking portion 22, forming the core foundation of the entire negative pressure generating system.

[0027] Furthermore, to optimize fluid control and enhance the negative pressure effect, the assembly further includes an annular seal 7. The annular seal 7 can be a wear-resistant and corrosion-resistant sealed bearing or a high-performance O-ring combination. The annular seal 7 tightly surrounds the outer circumference of the docking portion 22 and is axially adjacent to the fluid acceleration groove 4.

[0028] Furthermore, the annular seal 7 physically separates the drilling fluid channel 3 into a first channel 31 located above it and a second channel 32 located below it. This separation design creates a differentiated fluid environment. At the upper edge of the docking portion 22, one or more water inlet grooves 8 are provided. The drilling fluid first enters this water inlet groove 8 from the first channel 31, and then the lower part of the water inlet groove 8 directly connects to the fluid acceleration groove 4. In this way, the water inlet groove 8 and the fluid acceleration groove 4 together constitute the only flow path connecting the first channel 31 and the second channel 32. This design forces all downward drilling fluid to pass through the narrow fluid acceleration groove 4, thereby using all the fluid kinetic energy to generate negative pressure, greatly enhancing the suction effect of the reverse circulation.

[0029] Furthermore, as an optional embodiment, the reverse circulation channel 6 can be designed as follows: a return flow channel 61 is provided along the central axis of the upper end of the core tube 23, with its bottom directly connected to the core collection chamber 62. An annular groove 9 is provided on the outer peripheral wall of the upper portion of the core tube 23 where it connects to the docking portion 22. A drain port 63 is provided in the annular groove 9 and penetrates the wall of the core tube 23 to connect to the return flow channel 61. Simultaneously, a negative pressure channel 64 is provided on the lower sidewall of the docking portion 22, corresponding in position to the drain port 63. When the inner tube assembly is assembled, the annular groove 9 forms an intermediate fluid chamber, connecting the drain port 63 and the negative pressure channel 64. Finally, the outlet of the negative pressure channel 64 faces the inner wall of the outer tube body 1 and directly connects to the negative pressure zone 5. Thus, a reverse circulation channel 6 is formed, running from the core collection chamber 62 to the negative pressure zone 5.

[0030] Furthermore, to optimize the fluid dynamics of reverse circulation, the outlet diameter of the negative pressure channel 64 can be designed to be smaller than the inlet diameter of the drain port 63, thereby creating a jet effect and further stabilizing the flow field. Furthermore, the negative pressure channel 64 is tilted downward relative to the inner wall of the outer tube body 1 at an angle of 15-45 degrees, helping to guide the reverse circulation fluid to more smoothly merge into the downward-flowing main fluid.

[0031] Furthermore, to ensure unidirectional reverse circulation, a one-way valve 12 can be provided in the reflux channel 61. This one-way valve 12 can be a simple and reliable gravity-operated ball valve structure, that is, a valve seat is provided in the reflux channel, and a high-density steel ball is placed on the valve seat. Of course, other valve types can also be used, such as spring valves, diaphragm valves, etc.

[0032] As an optional embodiment, the fluid acceleration grooves 4 can be asymmetrically arranged along the circumference of the docking portion 22, for example, only one or two are provided. This asymmetrical design helps to form a more concentrated high-speed jet, thereby generating a stronger negative pressure effect locally.

[0033] It should be emphasized that the forward and reverse circulation assembly for the coring drill tool proposed in this embodiment serves as a core module of the coring drill tool, working in conjunction with other conventional components of the coring drill tool. For example, in actual engineering applications, the forward and reverse circulation assembly for the coring drill tool proposed in this embodiment can be preferably combined with the following conventional components of the prior art to perform deep-sea wireline coring operations after core sample collection.

[0034] In an optional embodiment, in order to match the efficient rope coring operation, the upper end of the recovery tube 21 can also be equipped with a conventional locking and recovery mechanism in the field. This mechanism is used to ensure that the inner container 2 is absolutely stable during the drilling process and can be quickly and reliably recovered when needed. For example, referring to Figure 8 , which can specifically adopt the following structure: Inside the recovery tube 21, a hollow accommodating chamber 211 is machined. The locking and recovery mechanism mainly includes a spearhead assembly 15 that can perform limited axial sliding in the accommodating chamber 211, and a spring-loaded mechanism 16 for achieving locking. The spring-loaded mechanism 16 can specifically include two spring-loaded plates 161 located at the lower part of the accommodating chamber 211. The bottoms of the two spring-loaded plates 161 are hinged to the pin seats at the bottom of the accommodating chamber 211 through pin shafts 162, and can swing inward and outward around the lower fulcrum. The outer side of the middle and upper part of the spring-loaded plate 161 is a locking surface, which can extend outward through a preset through hole on the wall of the recovery tube 21 so as to be engaged with the pressure step or annular groove on the inner wall of the outer tube body 1. A transverse hinge shaft 163 is fixedly provided at the upper part of the accommodating chamber 211. Two connecting plates 164 are coaxially hinged on the hinge shaft 163. The lower ends of the two connecting plates 164 are hinged to the upper ends of the two spring-loaded plates 161 via pins, forming a linkage mechanism. A compression spring 165 is installed between the spearhead assembly 15 and a fixed step within the accommodating chamber 211. This compression spring 165 continuously applies a preload force to the spearhead assembly 15, forcing it to move downward.

[0035] When the inner container 2 is lowered into place via the wire rope and rests on the pressure-bearing step, the tension of the wire rope disappears, and the spearhead assembly 15 no longer bears the upward load. At this point, the stored energy of the compression spring 165 becomes the dominant force, instantly pushing the spearhead assembly 15 downward within the container. This downward displacement, through the connecting plate 164, pushes the upper end of the spring plate 161 outward, effectively extending its outer locking surface and engaging it in the inner wall groove of the outer tube 1, achieving a secure mechanical lock. During recovery, when the dedicated salvage device grasps and pulls the spearhead assembly 15 upward, the powerful upward force first overcomes the reaction force of the compression spring 165 and forces the spearhead assembly 15 to slide upward within the container. It is this forced upward displacement that, through the connecting plate 164, pulls the upper end of the spring plate 161 inward, completely disengaging its locking surface from the groove of the outer tube 1. Once unlocked, the entire inner container 2 can be smoothly recovered to the sea surface by continuing to pull up the wire rope.

[0036] As other feasible alternatives, the above-mentioned locking and recovery functions can also be achieved through other structures. For example, in one possible embodiment, the locking and recovery mechanism can be a magnetic locking mechanism, and the spring-clip mechanism can be replaced by a magnetic locking ring composed of strong permanent magnets. A group of magnets with the N pole facing outward is installed on the outer wall of the docking portion 22 of the inner container 2, and a group of magnets with the S pole facing inward is installed at the corresponding position on the inner wall of the outer tube body 1. When the inner tube assembly is lowered into place, the two groups of magnets are precisely aligned to generate a strong magnetic attraction to achieve locking. During recovery, the lifting mechanical force provided by the salvage device needs to be large enough to overcome the magnetic attraction and achieve unlocking.

[0037] In one possible embodiment, the locking and recovery mechanism can also be a bayonet-type locking mechanism. The snap-on mechanism can be replaced with a mechanical structure similar to a rifle bolt or a light bulb bayonet. One or two radial pins are provided on the outer wall of the docking portion 22, and corresponding "J"-shaped or "L"-shaped guide grooves are machined on the inner wall of the outer tube body 1. During the lowering process of the inner housing 2, the pins are caused to enter the guide grooves by a slight rotation of the wire rope, and the pins fall to the bottom of the grooves to complete the locking. When recovering, first lift it up a short distance, then rotate it in the opposite direction to disengage the pins from the guide grooves.

[0038] In addition, in order to adapt to the complex interlaced formations of loose and hard layers, the outer tube body 1 includes a reamer 13 located at its lower portion, and the reamer 13 is connected to a wedge-shaped centering drill bit 14. The main function of the reamer 13 is to appropriately expand the borehole diameter during the drilling process, creating conditions for the smooth lowering of the core tube 23, and at the same time helping to improve the circulation effect of the drilling fluid. The centering drill bit 14 ensures the accuracy of the drilling direction and prevents the borehole from deviating. These conventional components of the coring drill tool are combined with those proposed in this embodiment to form a set of seabed coring drill tools with excellent performance and capable of coping with extreme working conditions.

[0039] This embodiment achieves a synergistic mechanism of positive and reverse circulation through the carefully designed structural combination described above. During drilling operations, the mainstream drilling fluid forms a positive circulation along the drilling fluid channel 3, responsible for removing drill cuttings and supporting the hole wall. Simultaneously, the negative pressure zone 5 generated by the fluid acceleration groove 4 drives the reverse circulation channel 6 to form a local reverse circulation, specifically responsible for gently sucking and protectively collecting loose core.

[0040] This dual-circulation system's collaborative operation significantly improves coring rates in loose, fragile formations, reduces core breakage, and maintains the formation's in-situ characteristics. The entire system requires no external power and relies entirely on the flow energy of the drilling fluid for automatic control. It offers advantages such as simple structure, reliable operation, and easy maintenance, making it particularly suitable for harsh working environments such as subsea drilling.

[0041] Example 2: This example combines the forward and reverse circulation assembly for coring drill tools described in Example 1 above to propose a coring method suitable for loose and fragile seabed formations. Specifically, it includes the following steps: S1. System Preparation and Deployment Before subsea drilling operations begin, the forward and reverse circulation assembly is assembled as a core module. The inner container 2 is lowered into the outer tubular body 1 of the coring drill via a wireline, using the spearhead assembly 15 at the top of its recovery tube 21. Once the lower end of the inner container 2 is axially aligned with the pressure-bearing step within the outer tubular body 1, its snap-in mechanism 16 automatically engages with the annular groove on the inner wall of the outer tubular body 1, completing deployment. Simultaneously, the surface drilling system's high-pressure pump unit is connected to the drill string, preparing to deliver seawater-based drilling fluid.

[0042] S2. Drilling fluid flow and negative pressure zone formation At the start of the operation, drilling fluid flows from top to bottom into the annular downward drilling fluid channel 3 formed between the outer tube body 1 and the inner containment body 2. Under the diversion and sealing action of the annular seal 7, the entire drilling fluid is forcibly directed into the fluid acceleration groove 4 provided on the outer peripheral wall of the docking portion 22. Due to the sudden decrease in the fluid cross-sectional area, the drilling fluid is rapidly accelerated here, and its static pressure energy is massively converted into kinetic energy, thereby generating a stable, high-intensity negative pressure zone 5 downstream of the fluid acceleration groove 4. This negative pressure zone 5 is connected to the return channel 61 of the core tube 23 via the negative pressure channel 64, providing a continuous pressure differential driving force for the local reverse circulation.

[0043] S3. Forward and reverse circulation coordinated coring When the drilling fluid flows to the bottom of the drill bit, under the action of the negative pressure zone 5, a positive and negative double circulation working in coordination is automatically formed: Local reverse circulation path and function: Under the suction effect of negative pressure zone 5, a portion of drilling fluid, carrying loose core, is drawn from collection chamber 62 at the bottom of core tube 23 through reflux channel 61 (which opens one-way valve 12), drain port 63, annular groove 9, and negative pressure channel 64 into negative pressure zone 5, where it merges with the main fluid. This bottom-up local reverse circulation significantly reduces core entry resistance by replacing mechanical extrusion with pressure differential guidance, ensuring accurate core sampling.

[0044] Forward Circulation Path and Function: The mainstream drilling fluid, not participating in the reverse circulation, continues downward along the downward drilling fluid channel 3 and is ejected at high speed through the pilot drill bit 14, achieving hydraulic impact on the hole bottom and drill bit cooling. Subsequently, this mainstream fluid, entraining rock cuttings, returns upward through the annular space 200 formed between the outer wall of the outer tube 1 and the rock hole wall 100. In this process, it completes three engineering tasks: hydraulic chip removal, forced convection cooling, and static pressure support of the rock hole wall 100 by the liquid column, ultimately being discharged at the seabed orifice.

[0045] S4. Adaptive adjustment of the operation process The drilling process also includes a dynamic optimization step. During drilling, the drilling rig system monitors parameters such as the pump pressure and displacement of the drilling fluid circulation system in real time. Operators can determine the looseness and fragility of the current formation based on geological profile predictions, data from adjacent holes, or real-time feedback on drilling parameters such as torque and drilling pressure changes. Based on this judgment, the output power of the high-pressure pump group can be controlled by frequency conversion to adaptively adjust the displacement and circulation speed of the drilling fluid. Its adjustment strategy aims to achieve an optimal balance between core recovery quality and maintaining 100% stability of the rock hole wall: when encountering extremely loose formations, the displacement is reduced to reduce reverse circulation suction and positive circulation scouring of the hole wall; when entering well-cemented hard interlayers, the displacement can be increased to enhance chip removal efficiency and drill bit cooling.

[0046] S5. Inner tube recovery and recycling operations After each coring cycle, drilling fluid pumping is suspended and a dedicated overshoot is lowered via a wireline. After the overshoot docks with the spearhead assembly 15 at the top of the recovery pipe 21, the wireline is pulled upward to unlock the latch mechanism, allowing the fully loaded inner container 2 to be fully recovered to the surface. After core retrieval and equipment preparation are complete, the inner container can be re-deployed to begin the next coring cycle.

[0047] The above are implementation methods provided in conjunction with specific content, and the specific implementation of this application is not limited to these descriptions. Any method structure that is similar to the method structure of this application, or any technical deduction or replacement based on the concept of this application, should be considered as the scope of protection of this application.

Claims

1. A forward and reverse circulation assembly for a coring drill, characterized in that: Including outer tube (1); An inner receiving body (2) for receiving a rock core and arranged inside the outer tube (1), with a drilling fluid passage (3) defined between the inner receiving body (2) and the outer tube (1); At least one longitudinal fluid acceleration groove (4) is formed on the outer peripheral wall of the inner receiving body (2), which is used to form a negative pressure zone (5) by increasing the local flow velocity when the drilling fluid flows through; a reverse circulation channel (6) communicating with the vicinity of the lower core inlet of the inner receiving body (2) and the negative pressure zone (5), and being used for utilizing the suction effect generated by the negative pressure zone (5) to suck part of the drilling fluid and the core upward from the core inlet, thereby forming a local reverse circulation; The mainstream drilling fluid that has not formed a local reverse circulation continues to flow along the drilling fluid channel (3) to form a positive circulation.

2. The forward and reverse circulation assembly for a coring drill according to claim 1, characterized in that: The inner receiving body (2) comprises a recovery tube (21), a docking portion (22) is provided at the lower end of the recovery tube (21), a core tube (23) is sleeved on the docking portion (22), and the fluid acceleration groove (4) is provided on the outer peripheral wall of the docking portion (22).

3. The forward and reverse circulation assembly for coring drilling tools according to claim 2, characterized in that: It also includes an annular sealing member (7) which is arranged around the docking portion (22) and is adjacent to the fluid acceleration groove (4).

4. The forward and reverse circulation assembly for a coring drill according to claim 3, characterized in that: The annular seal (7) separates the drilling fluid channel (3) into a first channel (31) located above the annular seal and a second channel (32) located below the annular seal. A water inlet groove (8) is provided at the upper edge of the docking portion (22). The fluid acceleration groove (4) is connected to the lower side of the water inlet groove (8). The water inlet groove (8) and the fluid acceleration groove (4) together connect the first channel (31) and the second channel (32).

5. The forward and reverse circulation assembly for a coring drill according to claim 4, characterized in that: The reverse circulation channel (6) includes a reflux channel (61) arranged along the axis of the upper end of the core tube (23), and the bottom of the reflux channel (61) is connected to a collection chamber (62) for accommodating the core; an annular groove (9) is provided along the outer circumference of the portion where the upper part of the core tube (23) is connected to the docking part (22), and a drainage port (63) connected to the reflux channel (61) is provided on the annular groove (9); a negative pressure channel (64) corresponding to the drainage port (63) is opened on the lower side wall of the docking part (22), and the negative pressure channel (64) is connected to the negative pressure zone (5) at the opening on the inner wall of the outer tube body (1).

6. The forward and reverse circulation assembly for a coring drill according to claim 5, characterized in that: The caliber of the negative pressure channel (64) is smaller than the caliber of the drain port (63).

7. The forward and reverse circulation assembly for a coring drill according to claim 5, characterized in that: The negative pressure channel (64) is arranged to be inclined downward relative to the inner wall of the outer tube body (1).

8. The forward and reverse circulation assembly for a coring drill according to claim 5, characterized in that: A one-way valve (12) is provided in the reflux channel (61).

9. The forward and reverse circulation assembly for a coring drill according to any one of claims 5 to 8, characterized in that: The fluid acceleration groove (4) is asymmetrically arranged along the circumference of the docking portion (22).

10. A coring method, using the forward and reverse circulation assembly for a coring drill according to claim 9, characterized in that: The following steps are involved: S1. System deployment and fluid supply: a forward and reverse circulation assembly including an outer tube (1) and an inner container (2) is placed in the hole, and drilling fluid is pumped into a drilling fluid channel (3) defined between the outer tube (1) and the inner container (2) by a high-pressure pump group; S2. Forced flow diversion and negative pressure generation: using an annular seal (7) disposed in the drilling fluid channel (3) and surrounding the inner container (2), the drilling fluid channel (3) is divided into an upper first channel (31) and a lower second channel (32); and the drilling fluid in the first channel (31) is used as the only flow path and forced to flow through at least one fluid acceleration groove (4) formed on the outer peripheral wall of the inner container (2), thereby forming a negative pressure zone (5) in the second channel (32); S3. The positive and reverse circulation work in coordination, utilizing the negative pressure zone (5) to pump fluid and the core upward from the core inlet of the inner receiving body (2) through a reverse circulation channel (6), forming a local reverse circulation to guide and protect the core; at the same time, the mainstream drilling fluid after flowing through the fluid acceleration tank (4) is drawn out from the bottom of the assembly, forming a positive circulation for chip removal, cooling and wall protection.

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