A positive and reverse circulation assembly for a coring drill and a coring operation method using the same

Abstract

The invention provides a positive and reverse circulation assembly for a coring drill and a coring operation method using the same. The positive and reverse circulation assembly comprises an outer pipe body and an inner containing body arranged inside the outer pipe body, and a drilling fluid channel is defined between the outer pipe body and the inner containing body. The core of the invention is that at least one longitudinal fluid acceleration groove is formed on the outer peripheral wall of the inner containing body. During operation, the drilling fluid is sharply accelerated when flowing through the acceleration groove, thereby forming a stable negative pressure zone downstream. The negative pressure zone draws fluid and core upward from the core inlet through a reverse circulation channel, forming a protective local reverse circulation. The main drilling fluid that does not participate in the reverse circulation continues to flow downward, forming a positive circulation for chip removal and cooling. The invention solves the technical problem of core breakage and extremely low core recovery rate in loose and fragile seabed strata caused by mechanical thrust and fluid scouring by constructing a positive and reverse double circulation collaborative fluid system. The core sample integrity of the loose and fragile strata is significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of seabed drilling equipment, and particularly relates to a positive and reverse circulation assembly for a coring drill and a coring operation method using the same. BACKGROUND

[0002] Seabed geological exploration is the basis of deep-sea resource development and marine scientific research, and one of its core tasks is to obtain rock samples that can truly reflect in-situ information of strata through coring operations. In the vast seabed, a special type of engineering geology, loose and fragile strata, is widely distributed. Typical representatives of this type of strata include, but are not limited to, polymetallic sulfide deposits formed by hydrothermal activity, bioclastic sedimentary layers rich in organic matter, and altered basalt and turbidite. The common geological characteristics of these strata are that the cementation between the soil particles is extremely low, the porosity is highly developed, and the overall structural stability is poor, and they are extremely easy to break and collapse when disturbed by external factors.

[0003] Existing seabed coring technologies, such as conventional rope coring and rotary drilling, when faced with the above-mentioned loose and fragile strata, their corresponding conventional coring drills mainly rely on mechanical thrust to "push" or "top" the core into the core tube. When the above-mentioned mechanical force acts on the loose core which is almost dispersed, it is easy to cause the core to be structurally broken and severely disturbed before entering the core tube.

[0004] In addition, the positive circulation drilling fluid necessary for conventional drilling mainly functions to remove cuttings and cool the drill bit. High-pressure drilling fluid is sprayed at high speed from the bottom of the drill bit, directly and violently washing the hole bottom and the fragile core sample about to enter the core tube. This hydraulic erosion will wash away fine particles in the loose core, destroy its original layering and structure, and even completely wash away the core, resulting in a very low final harvest rate of the coring operation, sometimes even less than 10%, and the samples obtained also lose most of their scientific research value due to severe disturbance. SUMMARY

[0005] The purpose of the present application is to provide a positive 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 that the conventional coring drill has a single positive circulation mode and a mechanical pushing and extruding coring method, and when faced with loose and fragile strata, the core is severely broken and the coring harvest rate is extremely low due to hydraulic erosion and pipe entry resistance.

[0006] The present application is realized by the following technical solutions:

[0007] A positive and reverse circulation assembly for a coring drill, comprising

[0008] an outer pipe body;

[0009] a core receiving body for receiving a core, disposed inside the outer tube body, defining a drilling fluid passage therebetween;

[0010] at least one longitudinal fluid accelerating groove formed on the outer peripheral wall of the core receiving body for forming a negative pressure area by increasing local flow velocity when the drilling fluid flows therethrough;

[0011] a reverse circulation passage communicating between the vicinity of a core inlet at a lower portion of the core receiving body and the negative pressure area for using suction generated by the negative pressure area to suck part of the drilling fluid and the core upward from the core inlet to form local reverse circulation;

[0012] wherein the main stream of the drilling fluid not forming local reverse circulation continues to flow along the drilling fluid passage to form positive circulation.

[0013] The positive and reverse circulation assembly for coring drill as described above, wherein the core receiving body comprises a recovery tube, a docking portion is arranged at a lower end of the recovery tube, a coring tube is sleeved on the docking portion, and the fluid accelerating groove is arranged on the outer peripheral wall of the docking portion.

[0014] The positive and reverse circulation assembly for coring drill as described above, further comprising an annular sealing member, which is arranged around the docking portion and adjacent to the fluid accelerating groove.

[0015] The positive and reverse circulation assembly for coring drill as described above, wherein the annular sealing member divides the drilling fluid passage into a first passage above the annular sealing member and a second passage below the annular sealing member, a water inlet groove is arranged at an upper edge of the docking portion, the water inlet groove is connected to the fluid accelerating groove below, and the water inlet groove and the fluid accelerating groove jointly communicate the first passage and the second passage.

[0016] The positive and reverse circulation assembly for coring drill as described above, wherein the reverse circulation passage comprises a reflux passage arranged along the axis at an upper end of the coring tube, a collection cavity for receiving a core is connected to a bottom of the reflux passage; an annular groove is arranged along the outer periphery at a portion where the coring tube is sleeved on the docking portion, a water outlet is arranged on the annular groove and communicates with the reflux passage, a negative pressure passage is arranged in a lower portion of the docking portion and communicates with the water outlet, and the negative pressure passage is connected to the negative pressure area at an orifice of the negative pressure passage facing the inner wall of the outer tube body.

[0017] The positive and reverse circulation assembly for coring drill as described above, wherein the diameter of the negative pressure passage is smaller than the diameter of the water outlet.

[0018] The positive and reverse circulation assembly for coring drill as described above, wherein the negative pressure passage is arranged downwardly inclined relative to the inner wall of the outer tube body.

[0019] The positive and reverse circulation assembly for coring drill as described above, wherein a one-way valve is arranged in the reflux passage.

[0020] The fluid accelerating groove is asymmetrically arranged along the circumference of the interface.

[0021] A coring operation method using the positive and reverse circulation assembly for a coring drill as described above, comprising the following steps:

[0022] S1. System deployment and fluid supply, placing a positive and reverse circulation assembly comprising an outer tube and an inner container in a hole, and pumping drilling fluid into a drilling fluid passage defined between the outer tube and the inner container by a high-pressure pump set;

[0023] S2. Forced flow splitting and negative pressure generation, using an annular seal arranged in the drilling fluid passage and surrounding the inner container to divide the drilling fluid passage into a first passage in the upper part and a second passage in the lower part; and forcing the drilling fluid in the first passage to flow through at least one fluid accelerating groove formed on the outer peripheral wall of the inner container as the only flow path, thereby forming a negative pressure zone in the second passage;

[0024] S3. Positive and reverse circulation cooperative operation, using the negative pressure zone to suck fluid and core upward from the core inlet of the inner container through a reverse circulation passage to form a local reverse circulation to achieve the guidance and protection of the core; at the same time, the main flow of drilling fluid after flowing through the fluid accelerating groove is led out from the bottom of the assembly to form a positive circulation for chip removal, cooling and wall protection.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. The present application automatically generates a stable negative pressure zone by the fluid accelerating groove skillfully arranged on the outer wall of the inner container using the principle of fluid dynamics. The local reverse circulation driven by the negative pressure zone can generate a gentle and continuous suction force to "suck" loose and fragile core into the inner container, rather than the traditional single "push" or "top". This "pressure difference guiding" coring method greatly reduces the mechanical stress damage to the core and minimizes the disturbance to the core, thereby greatly improving the core recovery rate of loose and fragile strata and maximizing the original layering and structural integrity of the core.

[0027] 2. The present application constructs a set of sophisticated positive and reverse circulation cooperative working system. The core local reverse circulation is responsible for core protection and sampling, while the main flow of drilling fluid continues to perform the conventional positive circulation to complete the essential engineering tasks such as chip removal, cooling of the drill bit and stabilization of the hole wall. This effectively solves the inherent contradiction in the conventional single circulation system that high-strength chip removal fluid will inevitably cause severe erosion to fragile core, and realizes the parallelism of high-quality coring and high-efficiency drilling.

[0028] 3、The negative pressure generation and reverse circulation driving of the present application relies on the fluid energy of the drilling fluid, and the energy conversion is realized through a fixed, non-moving part, i.e. fluid acceleration groove, belonging to passive self-driving. The design does not need any additional power source in the well, such as micro motor, turbine or mechanical pump, thereby avoiding the inherent reliability problems of these complex moving parts in the deep sea high pressure, high corrosion and strong vibration environment. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced.

[0030] Figure 1 is a perspective structural schematic diagram of the present embodiment;

[0031] Figure 2 is an exploded structural schematic diagram of the present embodiment;

[0032] Figure 3 is a perspective structural schematic diagram of the recovery pipe in the present embodiment;

[0033] Figure 4 is a perspective structural schematic diagram of the core tube in the present embodiment;

[0034] Figure 5 is a top view of the present embodiment;

[0035] Figure 6 is Figure 5 a sectional view along A-A in the present embodiment;

[0036] Figure 7 is Figure 6 an enlarged schematic diagram at B in the present embodiment;

[0037] Figure 8 is a possible structural schematic diagram of the locking and recovery mechanism in embodiment 1;

[0038] Figure 9 is a positive and reverse circulation line schematic diagram of the drilling fluid when the present embodiment is performing seabed coring operation Figure 1 ;

[0039] Figure 10 is a positive and reverse circulation line schematic diagram of the drilling fluid when the present embodiment is performing seabed coring operation Figure 2 . DETAILED DESCRIPTION

[0040] In order to make the objects, technical solutions and advantages of the present application clearer, the specific embodiments of the present application will be described in detail below with reference to the drawings. It should be explained that the embodiments described herein are only some preferred embodiments of the present application, but not all embodiments. Based on the embodiments, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0041] Embodiment 1: The present embodiment provides a positive and reverse circulation assembly for coring operation in a loose and fragile formation at the seabed, which is a core module of a coring drill tool and works cooperatively with other conventional components of the coring drill tool.

[0042] Please refer to the accompanying drawings Figures 1 to 10 In one specific embodiment of the present application, a positive and reverse circulation assembly for a coring drill tool basically comprises an outer tube body 1 and an inner containing body 2. The inner containing body 2 is used for containing a core sample obtained from a formation and is detachably arranged in an inner region of the outer tube body 1. Between the outer wall of the inner containing body 2 and the inner wall of the outer tube body 1, a ring-shaped downhole fluid passage 3 is naturally defined to ensure that the drilling fluid can circulate smoothly to maintain the stability of the borehole.

[0043] At least one longitudinal fluid accelerating groove 4 is formed on the peripheral wall of the inner containing body 2. The fluid accelerating groove 4 is the core feature of the present embodiment and realizes the change of fluid characteristics through structural mutation. Specifically, the local flow cross-sectional area of the fluid accelerating groove 4 is designed to be much smaller than the main flow cross-sectional area of the downhole fluid passage 3. The differential 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 to be squeezed into the narrow fluid accelerating groove 4 from the wide main passage, its local flow rate will be sharply and several times increased. According to Bernoulli's principle, the sharp increase of flow rate will result in a significant drop of fluid static pressure, thereby forming a stable negative pressure zone 5 in the downstream area of the fluid accelerating groove 4.

[0044] In order to utilize the negative pressure zone 5, the positive and reverse circulation assembly of the present embodiment is also provided with a reverse circulation passage 6. As shown in the drawings Figure 3 、 Figure 7 、 Figures 9 to 10As shown, the channel ingeniously connects the vicinity of the core inlet at the lower part of the content container 2 with the above-mentioned negative pressure zone 5. When the negative pressure zone 5 forms a strong low pressure environment, a suction effect is exerted on the core inlet through the reverse circulation channel 6. This suction force not only greatly reduces the resistance of the loose seabed core into the content container 2, but also actively sucks the core and a small amount of fluid around it into the content container 2, forming a local reverse circulation from bottom to top. This gentle and guiding reverse circulation is the key to ensuring that the loose and fragile core is obtained intact and undisturbed. At the same time, please refer to Figures 8 to 9 , the main drilling fluid that does not participate in the formation of local reverse circulation constitutes the main body of the positive circulation, which continues to flow downward along the above-mentioned drilling fluid channel 3 and is sprayed through the edge of the centering bit provided at the bottom of the outer tube body 1. The hydraulic impact effect of the sprayed drilling fluid can effectively assist the bit in breaking rock and cleaning the cutting end face. Subsequently, this energy-carrying fluid entrains the cuttings generated by the bit cutting and is returned upward along the annular space gap 200 formed between the outer wall of the outer tube body 1 and the borehole wall 100. During this return process, the drilling fluid continuously transports the cuttings from the bottom of the hole to the hole mouth and finally discharges them on the seabed, completing its mission as the core of the positive circulation. At the same time, the upward flowing fluid continuously flows over the outer wall of the outer tube body 1, taking away the huge heat generated by friction through heat exchange, playing a key role in cooling the entire coring drill string. Moreover, in loose and fragile formations, this stable fluid column filled in the annular space gap 200 can also provide effective support for the fragile hole wall through its hydrostatic pressure, significantly improving the stability of the borehole and providing necessary protection for the smooth progress of the entire coring operation.

[0045] Further, as a preferred embodiment, in order to realize structural modularity and recyclability in operation, the content container 2 can be structurally divided into an upper recovery tube 21 and a lower coring tube 23. The lower end of the recovery tube 21 is provided with a precisely machined butt joint 22, which is coupled with the upper end of the coring tube 23 through threads, buckles, interference fit, sleeve joint or other conventional connection methods in the art. The fluid acceleration groove 4 is provided on the outer peripheral wall of the butt joint 22, making it the core base of the entire negative pressure generating system.

[0046] Further, in order to optimize fluid control and enhance negative pressure effect, the assembly also includes an annular seal 7. The annular seal 7 can be a wear-resistant, corrosion-resistant sealing bearing or a combination of high-performance O-rings, which tightly surrounds the outer periphery of the butt joint 22 and is adjacent to the fluid acceleration groove 4 in axial position.

[0047] Further, the annular seal 7 physically separates the drilling fluid channel 3 into a first channel 31 above it and a second channel 32 below it, which creates a differential fluid environment. At the upper end edge of the interface 22, one or more water inlets 8 are provided. The drilling fluid first enters the water inlets 8 from the first channel 31, and then the water inlets 8 directly link to the fluid acceleration groove 4 below. In this way, the water inlets 8 and the fluid acceleration groove 4 together form the only flow path connecting the first channel 31 and the second channel 32. This design forces all the descending 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 reverse circulation.

[0048] Further, as an optional embodiment, the reverse circulation channel 6 can be designed to have a return channel 61 along the central axis at the upper end of the coring tube 23, and the bottom of the channel directly links to the core collection cavity 62. At the part where the coring tube 23 is sleeved with the interface 22, an annular groove 9 is provided on the outer peripheral wall. A drainage port 63 is provided on the annular groove 9 and communicates with the return channel 61 through the wall of the coring tube 23. At the same time, a negative pressure channel 64 corresponding to the drainage port 63 in position is provided on the lower side wall of the interface 22. When the inner tube assembly is assembled, the annular groove 9 becomes an intermediate fluid cavity, so that the drainage port 63 and the negative pressure channel 64 are in communication. Finally, the outlet of the negative pressure channel 64 is directed towards the inner wall side of the outer tube body 1 and directly links to the negative pressure area 5. Thus, the reverse circulation channel 6 from the core collection cavity 62 to the negative pressure area 5 is formed.

[0049] Further, in order to optimize the fluid dynamics effect of reverse circulation, the outlet diameter of the negative pressure channel 64 can be designed to be smaller than the inlet diameter of the drainage port 63 to form a jet effect, further stabilizing the flow field. At the same time, the negative pressure channel 64 is inclined downward relative to the inner wall of the outer tube body 1 at an angle of 15-45 degrees, which helps to guide the reverse circulation fluid to flow more smoothly into the main flow.

[0050] Further, in order to ensure the unidirectionality of reverse circulation, a one-way valve 12 can be provided in the return channel 61. The one-way valve 12 can be a simple and reliable gravity ball valve structure, that is, a valve seat is provided in the return channel, and a steel ball with a larger density is placed on the valve seat. Of course, other forms of valves such as spring valves and diaphragm valves can also be used.

[0051] As an optional embodiment, the fluid acceleration groove 4 can be asymmetrically arranged along the circumference of the interface 22, for example, only one or two. This asymmetric design helps to form a more concentrated high-speed jet, thereby generating a stronger negative pressure effect locally.

[0052] It is emphasized that the positive and reverse circulation assembly for coring drill proposed in the present embodiment is as a core module of a coring drill, which works in cooperation with other conventional components of the coring drill. For example, in actual engineering applications, the positive and reverse circulation assembly for coring drill proposed in the present embodiment can be preferably combined with the following conventional components of the prior art to perform the deep-sea wireline coring operation after the core sample plate collection.

[0053] In an optional embodiment, in order to match the efficient wireline coring operation, the upper end of the recovery pipe 21 can also be configured with a locking and recovery mechanism conventional in the art. The mechanism is used to ensure the absolute stability of the inner containing body 2 during drilling, and can be quickly and reliably recovered when needed. For example, referring to Figure 8 , which can specifically adopt the following structure:

[0054] Inside the recovery pipe 21, a hollow accommodating cavity 211 is processed. The locking and recovery mechanism mainly includes a spearhead assembly 15 which can slide axially in the accommodating cavity 211, and a snap mechanism 16 for locking. The snap mechanism 16 can specifically include two snap plates 161 located at the lower part of the accommodating cavity 211, and the bottom of the two snap plates 161 is hinged to the pin seat on the bottom of the accommodating cavity 211 by a pin shaft 162, which can swing in and out around the lower pivot. The middle and upper part of the outer side of the snap plate 161 is a locking surface, which can extend outward through the through hole preset on the pipe wall of the recovery pipe 21, so as to be clamped with the pressure step or annular clamping groove on the inner wall of the outer pipe body 1. In the upper part of the accommodating cavity 211, a transverse hinge shaft 163 is fixedly arranged. The hinge shaft 163 coaxially hinged has two connecting plates 164. The lower end of the two connecting plates 164 is hinged with the upper end of the two snap plates 161 respectively by a pin, forming a connecting rod linkage mechanism. The spearhead assembly 15 and the fixed step preset in the accommodating cavity 211 are provided with a compression spring 165. The compression spring 165 is used to continuously apply a pre-tightening force to the spearhead assembly 15 to make it have a downward movement trend.

[0055] When the content body 2 is lowered into place by the wire rope and sits on the pressure step, the tension of the wire rope disappears, and the spearhead assembly 15 no longer bears the upward load. At this time, the energy accumulated by the compression spring 165 becomes the dominant force, which instantly pushes the spearhead assembly 15 to slide downward in the accommodating cavity. This downward displacement, through the connecting plate 164, pushes the upper end of the elastic clamping plate 161 outward, so that the locking surface on the outer side effectively extends and clamps into the inner wall clamping groove of the outer pipe body 1, achieving stable mechanical locking. When recovering, after the dedicated fishing tool grabs and pulls the spearhead assembly 15 upward, the strong upward force first overcomes the counterforce of the compression spring 165, and forces the spearhead assembly 15 to slide upward in the accommodating cavity. It is this forced upward displacement that, through the connecting plate 164, pulls the upper end of the elastic clamping plate 161 inward, so that the locking surface completely disengages from the clamping groove of the outer pipe body 1. Once unlocked, continuing to pull the wire rope upward can smoothly recover the entire content body 2 to the sea surface.

[0056] As other possible alternatives, the above-mentioned locking and recovery functions can also be realized by other structures. For example, in one possible embodiment, the locking and recovery mechanism can be a magnetic locking mechanism, and the elastic clamping mechanism can be replaced by a magnetic locking ring composed of strong permanent magnets. A group of N-pole outward-facing magnets are installed on the outer wall of the docking portion 22 of the content body 2, and a group of S-pole inward-facing magnets are installed on the corresponding position of the inner wall of the outer pipe body 1. When the inner pipe assembly is lowered into place, the two groups of magnets are accurately aligned, generating a strong magnetic attraction force to achieve locking. When recovering, the upward mechanical force provided by the fishing tool needs to be large enough to overcome the magnetic attraction force to achieve unlocking.

[0057] In one possible embodiment, the locking and recovery mechanism can also be a bayonet locking mechanism. The elastic clamping mechanism can be replaced by a mechanical structure similar to the bolt of a rifle or the bulb bayonet. One or two radial pins are provided on the outer wall of the docking portion 22, and corresponding "J" or "L" shaped guide grooves are machined on the inner wall of the outer pipe body 1. During the lowering process of the content body 2, the pins enter the guide grooves and fall into the bottom of the grooves to complete the locking. When recovering, first pull up a small distance, then reverse rotation to make the pins disengage from the guide grooves.

[0058] In addition, in order to adapt to complex loose and hard alternating strata, the outer pipe body 1 includes a reamer 13 at its lower part, and the reamer 13 is connected with a wedge-shaped centering bit 14. The main function of the reamer 13 is to appropriately enlarge the diameter of the borehole during drilling, creating conditions for the smooth lowering of the coring pipe 23, and also helping to improve the circulation effect of the drilling fluid. The centering bit 14 ensures the accuracy of the drilling direction and prevents borehole deviation. These conventional components of the coring drilling tool, combined with the embodiment proposed herein, together form a set of seabed coring drilling tools with excellent performance and capable of coping with extreme working conditions.

[0059] The embodiment realizes the synergistic mechanism of positive and reverse circulation through the above-mentioned carefully designed structure combination. In the drilling operation, the main stream of the drilling fluid forms a positive circulation along the drilling fluid channel 3, responsible for the discharge of drill cuttings and the support of the hole wall; at the same time, the negative pressure area 5 generated by the fluid acceleration groove 4 drives the local reverse circulation channel 6 to form a local reverse circulation, which is specially responsible for the gentle suction and protective collection of loose cores.

[0060] The synergistic work of this double circulation system significantly improves the core recovery rate of loose and fragile formations, reduces core breakage, and maintains the in-situ state characteristics of the formation. The entire system does not require external power and relies entirely on the flow energy of the drilling fluid to achieve automatic control, has the advantages of simple structure, reliable work, easy maintenance, etc., and is particularly suitable for harsh working environments such as submarine drilling.

[0061] Embodiment 2: This embodiment combines the positive and reverse circulation assembly for coring drilling tools described in Embodiment 1 above, and proposes a coring operation method suitable for submarine loose and fragile formations. Specifically, it includes the following steps:

[0062] S1. System preparation and deployment

[0063] Before the start of submarine drilling operation, the positive and reverse circulation assembly is assembled as the core module. The content containing body 2 is launched into the outer pipe body 1 of the coring drilling tool through the fishing spear head assembly 15 at the top end of the recovery pipe 21 via the wire rope. When the lower end of the content containing body 2 is axially positioned with the pressure bearing step provided in the outer pipe body 1, the elastic clamping mechanism 16 automatically clamps with the annular clamping groove on the inner wall of the outer pipe body 1, completing the deployment. At the same time, the high-pressure pump set of the sea surface drilling system is connected in series with the drill pipe, ready to deliver seawater-based drilling fluid.

[0064] S2. Drilling fluid flow and negative pressure area formation

[0065] At the beginning of the operation, the drilling fluid flows from top to bottom into the annular downward drilling fluid channel 3 between the outer pipe body 1 and the content containing body 2. Under the guidance and plugging action of the annular seal 7, all the drilling fluid is forcibly introduced into the fluid acceleration groove 4 provided on the outer peripheral wall of the docking portion 22. Due to the sudden reduction of the fluid cross-sectional area, the drilling fluid is sharply accelerated at this point, and its static pressure energy is largely converted into kinetic energy, thereby generating a stable and high-intensity negative pressure area 5 downstream of the fluid acceleration groove 4. The negative pressure area 5 is connected to the return flow channel 61 of the coring pipe 23 through the negative pressure channel 64, providing a continuous pressure difference driving force for local reverse circulation.

[0066] S3. Synergistic coring of positive and reverse circulation

[0067] When the drilling fluid flows to the bottom of the drilling tool, a synergistic positive and reverse double circulation is automatically formed under the action of the negative pressure area 5:

[0068] Local reverse circulation path and function: under the suction of the negative pressure zone 5, a part of the drilling fluid carrying loose core, from the collection cavity 62 at the bottom of the coring tube 23, through the backflow channel 61 (top open the one-way valve 12), the drainage port 63, the annular groove 9 and the negative pressure channel 64, is sucked to the negative pressure zone 5 and is combined with the main flow. This local reverse circulation from bottom to top, through "pressure difference guide" instead of "mechanical pushing", significantly reduces the core into the pipe resistance, and guarantees the core sample.

[0069] Positive circulation path and function: the main flow of drilling fluid that does not participate in reverse circulation continues to flow downward along the downward drilling fluid channel 3, is sprayed at high speed through the centering drill bit 14, completes the hydraulic impact on the hole bottom and the drill bit cooling. Subsequently, the main flow rolls up the cuttings along the annular space gap 200 formed between the outer wall of the outer pipe body 1 and the rock hole wall 100, completes the hydraulic cutting, forced convection heat exchange cooling and the three major engineering tasks of supporting the rock hole wall 100 with the liquid column static pressure in the process, and finally is discharged at the seabed hole.

[0070] S4. Adaptive adjustment of the operation process

[0071] During drilling, a dynamic optimization step is also included. During drilling, the drilling rig system monitors the pump pressure, displacement and other parameters of the drilling fluid circulation system in real time. The operator can judge the loose and fragile degree of the current formation according to the geological profile prediction, adjacent hole data or real-time drilling parameters such as torque and drilling pressure feedback. Based on this judgment, the output power of the high-pressure pump group can be controlled through frequency conversion to adaptively adjust the displacement and circulation speed of the drilling fluid. The adjustment strategy aims to achieve the best balance between core recovery quality and maintaining the stability of the rock hole wall 100: when encountering extremely loose formation, the displacement is reduced to reduce the reverse circulation suction and the flushing of the hole wall by positive circulation; when entering the hard interlayer with better cementation, the displacement can be increased to enhance the cutting efficiency and the cooling effect of the drill bit.

[0072] S5. Inner pipe recovery and circulation operation

[0073] After each coring cycle is completed, the pumping of drilling fluid is suspended, and a dedicated fishing tool is lowered through the wire rope. After the fishing tool is docked with the spear head assembly 15 at the top end of the recovery tube 21, the wire rope is pulled up to unlock the snap mechanism, and the full load core-containing body 2 is completely recovered to the sea surface. After the core is taken out and the equipment is prepared, the core-containing body can be re-launched, and the next coring operation cycle can be started.

[0074] The above is an embodiment provided in combination with specific content, and it is not intended that the specific implementation of the present application is limited to these descriptions. Any similar structure or method as the present application, or any technical deduction or replacement made on the basis of the concept of the present application, should be considered as the protection scope of the present application.

Claims

1. A reverse circulation assembly for a coring drill, characterized by, The application relates to a positive and reverse circulation assembly for drilling a well. The outer tube (1); The content body (2) is arranged inside the outer tube (1) and defines a drilling fluid channel (3) with the outer tube (1); At least one longitudinal fluid accelerating groove (4) is formed on the outer peripheral wall of the content body (2) to form a negative pressure area (5) by increasing the local flow rate when the drilling fluid flows through the groove; A reverse circulation channel (6) is connected between the negative pressure area (5) and the lower part of the content body (2) near a core inlet, and the negative pressure area (5) generates suction to suck part of the drilling fluid and the core from the core inlet upward to form local reverse circulation; The main flow of the drilling fluid which does not form local reverse circulation continues to flow along the drilling fluid channel (3) to form positive circulation; The content body (2) comprises a recovery tube (21), the lower end of the recovery tube (21) is provided with a butt joint part (22), the butt joint part (22) is sleeved with a coring tube (23), and the fluid accelerating groove (4) is arranged on the outer peripheral wall of the butt joint part (22); An annular sealing member (7) is arranged around the butt joint part (22) and is adjacent to the fluid accelerating groove (4); The annular sealing member (7) divides the drilling fluid channel (3) into a first channel (31) above the annular sealing member (7) and a second channel (32) below the annular sealing member (7), the upper edge of the butt joint part (22) is provided with a water inlet groove (8), the water inlet groove (8) is connected with the fluid accelerating groove (4), and the water inlet groove (8) and the fluid accelerating groove (4) jointly connect the first channel (31) and the second channel (32).

2. The positive reverse circulation assembly for a coring drill tool of claim 1, wherein, The reverse circulation channel (6) comprises a reflux channel (61) arranged on the upper end of the coring tube (23) along the axis, the bottom of the reflux channel (61) is connected with a collection cavity (62) for containing the core; an annular groove (9) is arranged on the outer periphery of the part where the coring tube (23) is sleeved with the butt joint part (22), a water outlet (63) is arranged on the annular groove (9) and is connected with the reflux channel (61), a negative pressure channel (64) is arranged in the lower side wall of the butt joint part (22) and is connected with the water outlet (63), and the negative pressure channel (64) is connected with the negative pressure area (5) at the aperture of the side wall of the outer tube (1).

3. The positive reverse circulation assembly for a coring drill tool of claim 2, wherein, The aperture of the negative pressure channel (64) is smaller than that of the water outlet (63).

4. The positive reverse circulation assembly for a coring drill tool of claim 2, wherein, The negative pressure channel (64) is arranged downwardly and obliquely relative to the inner wall of the outer tube (1).

5. The positive reverse circulation assembly for a coring drill tool of claim 2, wherein, A one-way valve (12) is arranged in the reflux channel (61).

6. The positive reverse circulation assembly for a coring drill tool of any one of claims 2-5, wherein, The fluid accelerating groove (4) is asymmetrically arranged along the circumference of the butt joint part (22).

7. A coring method using the positive / negative circulation assembly for a coring drill tool as claimed in claim 6, characterized in that, The application further relates to a drilling method using the positive and reverse circulation assembly. S1. System deployment and fluid supply: a positive and reverse circulation assembly comprising an outer tube (1) and a content body (2) is arranged in a hole, and a high-pressure pump group is used to pump drilling fluid into a drilling fluid channel (3) defined between the outer tube (1) and the content body (2); S2. Forced diversion and negative pressure generation, using an annular seal (7) disposed in the drilling fluid passage (3) around the inner containment body (2), the drilling fluid passage (3) is divided into an upper first passage (31) and a lower second passage (32); and the drilling fluid in the first passage (31) is forced to flow through at least one fluid accelerating groove (4) formed on the outer peripheral wall of the inner containment body (2) as the only flow path, thereby forming a negative pressure zone (5) in the second passage (32); S3. Positive and reverse circulation cooperative operation, using the negative pressure zone (5), the fluid and core are sucked upward from the core inlet of the inner containment body (2) through a reverse circulation passage (6), forming a local reverse circulation to achieve the guidance and protection of the core; at the same time, the main flow of drilling fluid after flowing through the fluid accelerating groove (4) is led out from the bottom of the positive and reverse circulation assembly, forming a positive circulation for chip removal, cooling and wall protection.

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