Geological exploration bifurcated hole sealing and splitting device and method

Abstract

The invention provides a hole sealing and splitting device and method for a geological exploration bifurcated hole, and belongs to the technical field of hole packers.The hole sealing and splitting device for the geological exploration bifurcated hole comprises a packing pipe, an ejector and a centralizer which are sequentially connected, the end of the packing pipe is sealed, an opening is formed in the end of the centralizer, a plurality of nozzles are evenly arranged in the annular direction of the ejector, the nozzles are detachable, and the nozzles are arranged in the opening. The packer pipe comprises a center pipe, the center pipe is sleeved with an expansion capsule, the problems existing in the prior art are solved, the purposes of one-time well entering and segmented splitting are achieved, the problem of forked hole sealing of new and old well holes of geological prospecting holes in large-depth complex strata is solved, and the packer pipe is suitable for large-depth complex strata geological prospecting. And a powerful technical means is provided for safe and efficient drilling of geological exploration holes.

Description

Technical Field

[0001] The invention belongs to the technical field of hole sealers, and in particular relates to a device and method for sealing and splitting bifurcated holes in geological exploration. Background Art

[0002] In the process of geological exploration, whether in the field of coalfield geological exploration or in other mineral resource exploration activities, bifurcations in the borehole are often encountered. During the construction of the exploration borehole, due to the complexity and uncertainty of the geological structure, the alternation of strata with different hardness and different lithology, or the presence of geological structures such as faults, collapse columns and fissures underground, may cause the direction of the borehole to change, thus forming bifurcated holes. If these bifurcated holes cannot be effectively sealed, a series of serious problems will occur. Taking the coalfield geological exploration hole as an example, if gas leaks from the bifurcated hole, a dangerous environment of gas accumulation will be formed in the exploration area. Once an open flame or high temperature source is encountered, it is very easy to cause an explosion accident, posing a direct threat to the life safety of the explorers. At the same time, in the exploration of other mineral resources, groundwater channeling is also a problem that cannot be ignored. The disordered flow of groundwater may wash away the rock cuttings samples in the borehole, destroy the original structural state of the stratum, and then affect the accuracy of the exploration data, causing subsequent judgments on key information such as mineral reserves and distribution range to deviate. Some affect the safety of subsequent mining operations.

[0003] Traditional sealing methods can still play a certain role when dealing with single boreholes. Usually, a certain sealing material, such as cement slurry or special sealing glue, is injected into the borehole at a certain pressure, and a sealing layer is formed after it solidifies. However, when faced with complex bifurcated hole structures, traditional methods are powerless. The traditional method cannot achieve the ideal sealing effect, which poses a huge safety hazard to exploration operations and subsequent mining operations. At present, the bifurcated hole sealing process in geological exploration has the following shortcomings:

[0004] On the one hand, when bifurcated boreholes occur, conventional sealing techniques are usually used to seal the bifurcated boreholes, that is, by injecting cement slurry into the drill pipe so that the cement slurry flows into the old wellbore and the new wellbore, thereby sealing the old and new wellbores. However, due to the irregular shapes of the bifurcated boreholes, it is difficult to evenly distribute the cement slurry or sealing materials to each bifurcated borehole. As a result, sealing materials often accumulate at some bifurcated locations, while other bifurcated locations are insufficiently sealed or even completely without any material, resulting in poor wellbore sealing.

[0005] On the other hand, the operation of sealing new and old wells by means of orifice pressurization, especially when cement slurry is used as the sealing material, has the characteristics of liquid. Due to the fluidity and incompressibility of liquid, pressure often disperses and loses during the transmission process, making it difficult to transmit evenly and efficiently according to the expected effect, so that some areas cannot obtain enough pressure to drive cement slurry to fill the gaps and spaces in the wellbore. Especially in some complex wellbore structures, such as bends, branches or junctions of different lithology layers, the unevenness of pressure transmission is more prominent. As a result, the sealing effect is greatly reduced, and it is difficult to ensure that the new and old wells can be completely and completely sealed. It is easy to become a leakage channel, which brings great risks and uncertainties to the stability, safety and subsequent mining, construction and other operations of the entire project. It is impossible to effectively meet the high standards and strict requirements required by the sealing operation, which may eventually lead to serious impacts on the quality and benefits of the entire project.

[0006] Thirdly, in the process of sealing old and new wellbores, the sealer currently lacks an accurate measurement formula for formation fracture pressure, and only has a vague qualitative expression, which brings many inconveniences and disadvantages to the sealing construction. It is difficult for construction personnel to accurately determine at what fracture pressure to achieve effective formation fracture. This may lead to loose sealing and leakage, or formation fracture due to excessive pressure, resulting in serious consequences such as formation structure damage and groundwater system disturbance, which greatly affects the quality and safety of the sealing construction and increases engineering risks and costs. Summary of the invention

[0007] The purpose of the present invention is to provide a geological exploration bifurcation hole sealing and splitting device and method, which solves the problems existing in the prior art, achieves the purpose of entering the well once and splitting in sections, solves the problem of bifurcation sealing of new and old wellbores in geological exploration holes with large depths and complex formations, and provides a powerful technical means for the safe and efficient drilling of geological exploration holes.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is as follows: a geological exploration bifurcation hole sealing and splitting device, including a sealing pipe, an injector and a stabilizer connected in sequence, the end of the sealing pipe is sealed, the end of the stabilizer is provided with an opening, a plurality of nozzles are evenly arranged on the ring of the injector, and the nozzles are detachable, the sealing pipe includes a central tube, and an expansion capsule is provided on the outside of the central tube.

[0009] The central tube is provided with an annular groove, a plurality of liquid holes are evenly arranged on the outer side of the annular groove, and a slidable closing sleeve is arranged in the annular groove.

[0010] The closing sleeve is a circular ring structure, and a second through hole is arranged in the closing sleeve.

[0011] The height of the annular groove along the length direction of the isolation pipe is greater than the diameter of the liquid hole, and the height of the closing sleeve along the length direction of the isolation pipe is greater than the diameter of the liquid hole and less than the height of the annular groove.

[0012] A pin is arranged in the annular groove, and the closing sleeve is fixed in the annular groove through the pin.

[0013] An upper joint and a lower joint are respectively arranged at both ends of the isolation pipe, a thread plug is arranged on the lower joint, and the upper joint is detachably connected to the injector.

[0014] A first through hole is provided in the lower joint, and a diameter of the second through hole is smaller than a diameter of the first through hole.

[0015] The outer wall of the central tube is also sleeved with a first floating head and a second floating head, which are respectively located at the two ends of the expansion capsule and connected to the expansion capsule. The first floating head is arranged on the side close to the lower joint, and the second floating head is arranged on the side close to the upper joint. There are gaps between the first floating head and the lower joint, and between the second floating head and the upper joint.

[0016] A method for sealing and splitting a bifurcated hole in geological exploration comprises the following steps:

[0017] Step 1: After the new and old wellbores appear, the intersection position, number, aperture size and other parameters of the new and old wellbores are determined according to the logging trajectory parameters, and then the geological exploration bifurcation hole sealing and splitting device of appropriate specifications is selected and the position of the geological exploration bifurcation hole sealing and splitting device is determined. For deep holes, the lower section of the intersection position of the drill hole can be sealed with a conventional sealing device first, and the intersection position can be split with the geological exploration bifurcation hole sealing and splitting device after the cement solidifies for 48 hours;

[0018] Step 2: Install the nozzle of the ejector. The size of the nozzle is determined according to the thickness of the sandwich wall between the new and old wellbores and the fracture pressure of the formation. Connect the isolation pipe, ejector and centralizer in sequence, and connect them to the ground high-pressure pump. Inject high-pressure liquid through the high-pressure pump to test the performance and construction parameters of the geological exploration bifurcation hole sealing and splitting device. After the test, lower the geological exploration bifurcation hole sealing and splitting device through the pipe string to the intersection of the new and old wellbores.

[0019] Step 3: Continue to pump high-pressure liquid into the pipe string. The high-pressure liquid enters from the opening and penetrates into the expansion capsule through the liquid hole. The expansion capsule absorbs the liquid and expands to contact the hole wall, so as to achieve a stable connection between the isolation pipe and the well wall. A rubber plug or a steel ball matching the closing sleeve is put in through the opening to pressurize. The rubber plug or the steel ball sits on the closing sleeve. The closing sleeve moves downward under the action of high pressure to cut off the pin, and the closing sleeve moves downward in the annular groove to close the liquid hole.

[0020] Step 4: Continue to increase the pressure through the high-pressure pump and inject high-pressure liquid into the pipe string. The high-pressure liquid is ejected through the nozzle of the ejector. The injection depth increases linearly with the increase of pressure, and the aperture also increases with the increase of pressure. When the pressure reaches the critical pressure, the rock can be broken, thereby connecting the new and old wellbores. When the vertical stress on the hole wall reaches the vertical tensile strength of the hole wall rock, the rock will produce brittle fracture in the direction perpendicular to the vertical stress, that is, horizontal cracks will be generated in the direction perpendicular to the vertical stress. The fracture pressure is determined according to the relevant parameters of the formation:

[0021]

[0022] in P F is the fracture pressure of the formation, MPa; P s is the pore fluid pressure, MPa; is the vertical stress, MPa, is the vertical tensile strength, MPa; α is the Biot constant, i.e. the pore elastic constant, which is between 0 and 1 and is usually around 0.5; ν is the Poisson's ratio of the rock, P s Obtained through field testing, ν is obtained through laboratory testing;

[0023] Step 5: After the new and old wellbores are split and connected, a conventional sealing device is used to inject the pre-mixed sealing material through the pipe string into the new and old wellbores to achieve full sealing of the new and old wellbores.

[0024] In step 4, if the intersection position between the new and old wellbores is long, the geological exploration bifurcated hole sealing and splitting device is used according to step 4 to achieve segmented splitting of the intersection position.

[0025] The present invention adopts the above technical scheme and has the following advantages: the geological exploration bifurcation hole sealing and splitting device of the present invention opens one end of the tube body and seals the other end during the process of bifurcation hole sealing, and injects high-pressure liquid into the tube body through the opening. The high-pressure liquid enters the tube body and penetrates into the expansion capsule through the liquid-passing hole provided. After the expansion capsule absorbs the high-pressure liquid, it expands and holds the pressure to closely contact the open hole wall, so that the isolation pipe is sealed. When the expansion capsule absorbs the high-pressure liquid and expands to the maximum, the liquid-passing hole is closed by the sliding closing sleeve, so as to avoid the expansion capsule of the isolation pipe being affected by the high pressure in the later stage. The pressure liquid affects repeated expansion and reduces its lifespan. Then, high-pressure liquid is continuously injected into the pipe body through the opening. The high-pressure liquid is ejected through the set injector nozzle. When the injection pressure of the high-pressure liquid is greater than the fracture pressure of the formation, the pressure penetrates the sandwich wall of different thicknesses between the new and old wellbores, creating an artificial channel for the later cement slurry to flow from the new wellbores to the old wellbores. The present invention solves the problem of difficulty in sealing bifurcated holes in the geological exploration process, and realizes segmented splitting of long bifurcated holes, without causing difficulty in sealing new and old wellbores due to the irregular shape of the bifurcated holes and the difficulty of cement slurry flow. The present invention achieves the purpose of one-time entry into the well and segmented splitting, solves the problem of bifurcated sealing of new and old wellbores in geological exploration holes with large depths and complex formations, and provides a powerful technical means for safe and efficient drilling of geological exploration holes.

[0026] The present invention will be further described below in conjunction with specific implementations and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a geological exploration bifurcated hole sealing and splitting device of the present invention;

[0028] Figure 2 It is a structural schematic diagram of a sealing pipe of a geological exploration bifurcated hole sealing and splitting device according to the present invention;

[0029] Figure 3 It is a schematic diagram of the present invention at the intersection of the new and old wellbores;

[0030] Figure 4 This is the well trajectory data table of the present invention.

[0031] In the figure,

[0032] 1-thread plug, 2-lower joint, 3-expansion capsule, 4-center tube, 5-ring groove, 6-pin, 7-closing sleeve, 8-first floating head, 9-upper joint, 10-nozzle, 11-injector, 12-centralizer, 13-first through hole, 14-second through hole, 15-opening, 16-second floating head. DETAILED DESCRIPTION

[0033] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0034] The directional terms mentioned in this document, such as "lateral", "circumferential", "axial", "horizontal" and "vertical" are consistent with the specific directions on the paper of the drawings in the specification or the corresponding directions in the space shown in the drawings.

[0035] The initial position in this article refers to the working state of the device of this embodiment when entering the intersection of the new and old wellbores, which is consistent with the direction of drilling and is called the front section.

[0036] Example 1

[0037] like Figure 1-2 As shown, a geological exploration bifurcated hole sealing and splitting device includes a sealing pipe, an ejector 11 and a stabilizer 12 connected in sequence. The end of the sealing pipe is sealed, and an opening 15 is provided at the end of the stabilizer 12. A plurality of nozzles 10 are evenly arranged on the ring of the ejector 11 for ejecting high-pressure liquid. The nozzles 10 are detachable, and nozzles 10 of different apertures are adopted for sandwich walls of different thicknesses to obtain different pressures.

[0038] The isolation tube includes a central tube 4, on which is provided an annular groove 5, on the outer side of which are evenly provided a plurality of liquid holes, the height of the annular groove 5 along the length direction of the isolation tube being greater than the diameter of the liquid holes, a slidable closing sleeve 7 is provided in the annular groove 5, and the sliding of the closing sleeve 7 can control the closing and opening of the liquid holes, the height of the closing sleeve 7 along the length direction of the isolation tube being greater than the diameter of the liquid holes and less than the height of the annular groove 5, the closing sleeve 7 is a circular ring structure, and a second through hole 14 is provided in the closing sleeve 7; an expansion capsule 3 is provided on the outer side of the central tube 4, and the expansion capsule 3 expands after absorbing liquid from the liquid holes.

[0039] The liquid-passing hole enables high-pressure liquid to penetrate into the expansion capsule 3. When the expansion capsule 3 expands to the maximum closed state, the expansion capsule 3 is sealed after expansion. At this time, a steel ball or a rubber plug is inserted through the opening 15. The steel ball or the rubber plug matches the closing sleeve 7, driving the closing sleeve 7 to slide laterally along the isolation pipe to close the liquid-passing hole, thereby preventing the expansion capsule 3 from continuing to expand under the influence of high-pressure liquid in the later stage and improving the service life of the isolation pipe.

[0040] A pin 6 is provided in the annular groove 5, and the closing sleeve 7 is fixed in the annular groove 5 by the pin 6, so that the liquid hole is opened in the initial state. At this time, the closing sleeve 7 is in a position where it cannot cover the liquid hole, and the liquid hole in this position is connected to the inside of the second through hole 14.

[0041] An upper joint 9 and a lower joint 2 are respectively provided at both ends of the isolation pipe. A thread plug 1 is provided on the lower joint 2 to seal the end of the isolation pipe. A first through hole 13 is provided in the lower joint 2. The diameter of the second through hole 14 is smaller than that of the first through hole 13. The upper joint 9 and the injector 11 are detachably connected.

[0042] The outer wall of the central tube 4 is also provided with a first floating head 8 and a second floating head 16, which are respectively located at the two ends of the expansion capsule 3 and connected to the expansion capsule 3. The first floating head 8 is arranged on the side close to the lower joint 2, and the second floating head 16 is arranged on the side close to the upper joint 9. There are gaps between the first floating head 8 and the lower joint 2, and between the second floating head 16 and the upper joint 9.

[0043] The first floating head 8 and the second floating head 16 are used to fix the expansion capsule 3 to enhance the stability of the expansion capsule 3 .

[0044] The centralizer 12 is mainly used to stabilize the geological exploration bifurcation hole sealing and splitting device in the hole to prevent deflection.

[0045] The geological exploration bifurcation hole sealing and splitting device of the present invention, in the process of bifurcation hole sealing, high-pressure liquid is injected through the opening 15 by a high-pressure pump, and the high-pressure liquid penetrates into the expansion capsule 3 through the provided liquid-passing hole. After the expansion capsule 3 absorbs the high-pressure liquid, it expands and holds the pressure to be in close contact with the well wall, so that the isolation pipe is sealed. When the expansion capsule 3 absorbs the high-pressure liquid and expands to the maximum, the liquid-passing hole is closed by sliding the closing sleeve 7, so that the expansion capsule of the isolation pipe is prevented from being continuously expanded by the influence of the high-pressure liquid in the later stage, which reduces its service life. Then, the high-pressure liquid is continuously injected through the opening 15, and the high-pressure liquid is ejected through the nozzle 10 of the ejector 11, so that the high-pressure liquid presses the sandwich wall between the new and old wellbores, providing a channel for the flow of cement slurry in the later stage. The present invention can realize the full-section sealing of the new and old wellbores of the geological exploration hole, and can also realize partial sealing.

[0046] Example 2

[0047] Taking a coal mine in Anhui as an example, during the geological exploration process, new and old wellbores diverged. Due to the irregular shape of the bifurcated holes, it is difficult to completely seal them using conventional sealing methods. In order to achieve full hole closure of the new and old wellbores, it is planned to use a bifurcated hole sealing and splitting device to solve the problem of difficult sealing of bifurcated holes.

[0048] Because there are problems with old and new wellbores after 220 meters during the drilling process, the borehole trajectories of the new and old wellbores intersect at 550-600 meters, and the sandwich wall is thick, so the bifurcated hole splitting method is adopted. The first section is sealed from the bottom of the hole to 620 meters, and the hole is sealed while the drill bit is lifted to ensure that the bottom of the drill bit is about 30 meters below the cement slurry surface. The second section of the hole is sealed after the first section of cement is solidified for 72 hours; after the first section of the hole is sealed, 200 meters of J55×Ф127mm casing is lowered into the hole mouth, and the hole is fixed. After 48 hours of fixing, the second section of the hole is sealed. The second section uses the high pressure (8-15MPa) of the bifurcated hole sealing and splitting device to press the sandwich wall of the new and old wellbores to make them conductive, and the cement slurry flows from the new wellbore into the old wellbore, thereby sealing the old wellbore. The specific implementation method is as follows:

[0049] A method for sealing and splitting a bifurcated hole in geological exploration, using the above-mentioned sealing and splitting device, the method comprises the following steps:

[0050] Step 1: After the new and old wellbores appear, the intersection position, quantity, aperture size and other parameters of the new and old wellbores are determined according to the logging trajectory parameters, such as depth, zenith angle and azimuth, and then the geological exploration bifurcation hole sealing and splitting device of appropriate specifications is selected and the position of the geological exploration bifurcation hole sealing and splitting device is determined. For deep holes, the lower section of the intersection position of the borehole can be sealed with a conventional sealing device first, and the intersection position can be split with the geological exploration bifurcation hole sealing and splitting device after the cement solidifies for 48 hours;

[0051] Step 2: The ejector 11 is equipped with a nozzle 10 of a certain size. The size of the nozzle 10 is determined according to the thickness of the sandwich wall between the new and old wellbores and the fracture pressure of the formation. The isolation pipe, the ejector 11 and the centralizer 12 are connected in sequence, and connected to the ground high-pressure pump. The high-pressure liquid is injected through the high-pressure pump to test the performance and construction parameters of the geological exploration bifurcation hole sealing and splitting device. After the test, the geological exploration bifurcation hole sealing and splitting device is lowered into the intersection of the new and old wellbores through the ground pipe string;

[0052] Step 3: Continue to pump high-pressure liquid into the pipe string. The high-pressure liquid enters from the opening 15 and penetrates into the expansion capsule 3 through the liquid hole. The expansion capsule 3 absorbs the liquid and expands to contact the hole wall, so as to achieve a stable connection between the isolation pipe and the well wall. A rubber plug or a steel ball matching the closing sleeve 7 is put in through the opening 15 to pressurize. The rubber plug or the steel ball sits on the closing sleeve 7. The closing sleeve 7 moves downward under the action of high pressure to cut off the pin 6. The closing sleeve 7 moves downward in the annular groove 5 to close the liquid hole.

[0053] Step 4: Continue to increase the pressure through the high-pressure pump and inject high-pressure liquid into the pipe string. The high-pressure liquid is ejected through the nozzle 10 of the ejector 11. The high-pressure liquid is controlled by pressure, displacement and nozzle diameter; the injection depth increases linearly with the increase of pressure, and the aperture also increases with the increase of pressure. When the pressure reaches the critical pressure, the rock can be broken, thereby connecting the new and old wellbores, which is conducive to the later cement slurry flowing from the new wellbore into the old wellbore to seal the old wellbore. When the vertical stress on the hole wall reaches the vertical tensile strength of the hole wall rock, the rock will produce brittle fracture in the direction perpendicular to the vertical stress, that is, horizontal cracks will be generated in the direction perpendicular to the vertical stress. The fracture pressure is determined according to the relevant parameters of the formation:

[0054]

[0055] in P F is the fracture pressure of the formation, MPa; P s is the pore fluid pressure, MPa; is the vertical stress, MPa, is the vertical tensile strength, MPa; α is the Biot constant, i.e. the pore elastic constant, which is between 0 and 1 and is usually around 0.5; ν is the Poisson's ratio of the rock, P s Obtained through field testing, ν is obtained through laboratory testing.

[0056] If the intersection of the new and old wellbores is long, the geological exploration bifurcation hole sealing and splitting device is used according to the above steps to achieve segmented splitting of the intersection.

[0057] Step 5: After the new and old wellbores are split and connected, a conventional sealing device is used to inject pre-mixed sealing materials, such as a mixture of cement slurry and additives, into the new and old wellbores through a pipe string to achieve full sealing of the new and old wellbores.

[0058] In this embodiment, the device and method provided by the present invention can be used to split the sandwich wall between the bifurcation holes of the new and old wellbore, so that the sealing quality of the bifurcation holes is improved by more than 70%. At the same time, the size of the isolation tube can be specifically selected according to different working conditions, such as 20MPa, 35MPa, 70MPa, etc. The isolation tube is sealed after the pressure is held down and sealed, and is not affected by the high-pressure liquid in the later stage, so as to avoid the continuous expansion of the expansion capsule 3 and reduce the service life of the isolation tube. Compared with the prior art, the device and method of this embodiment have a wide range of applications and strong safety performance. It can also be applied to the bifurcation of new and old wellbores in other boreholes, providing safe exploration drilling and disaster prevention channels for geological exploration or geological disaster prevention.

[0059] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The examples of the implementation methods and the parts not described in detail are common knowledge of ordinary technicians in the field. For those skilled in the art, they can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A geological exploration bifurcation hole sealing and splitting device, characterized in that: The invention comprises an isolation pipe, an ejector (11) and a centralizer (12) which are connected in sequence. The end of the isolation pipe is sealed. The end of the centralizer (12) is provided with an opening (15). The ejector (11) is evenly provided with a plurality of nozzles (10) in the annular direction. The nozzles (10) are detachable. The isolation pipe comprises a central pipe (4). The central pipe (4) is provided with an expansion capsule (3) on its outer side.

2. A geological exploration bifurcation hole sealing and splitting device according to claim 1, characterized in that: The central tube (4) is provided with an annular groove (5), a plurality of liquid holes are evenly arranged on the outer side of the annular groove (5), and a slidable closing sleeve (7) is arranged in the annular groove (5).

3. A geological exploration bifurcation hole sealing and splitting device according to claim 2, characterized in that: The closing sleeve (7) is a circular ring structure, and a second through hole (14) is provided in the closing sleeve (7).

4. A geological exploration bifurcation hole sealing and splitting device according to claim 3, characterized in that: The height of the annular groove (5) along the length direction of the isolation pipe is greater than the diameter of the liquid hole, and the height of the closing sleeve (7) along the length direction of the isolation pipe is greater than the diameter of the liquid hole and less than the height of the annular groove (5).

5. A geological exploration bifurcation hole sealing and splitting device according to claim 4, characterized in that: A pin (6) is arranged in the annular groove (5), and the closing sleeve (7) is fixed in the annular groove (5) through the pin (6).

6. A geological exploration bifurcation hole sealing and splitting device according to claim 5, characterized in that: An upper joint (9) and a lower joint (2) are respectively arranged at both ends of the isolation pipe, a thread plug (1) is arranged on the lower joint (2), and the upper joint (9) is detachably connected to the ejector (11).

7. A geological exploration bifurcation hole sealing and splitting device according to claim 6, characterized in that: The lower joint (2) is provided with a first through hole (13), and the diameter of the second through hole (14) is smaller than the diameter of the first through hole (13).

8. A geological exploration bifurcation hole sealing and splitting device according to claim 7, characterized in that: The outer wall of the central tube (4) is also sleeved with a first floating head (8) and a second floating head (16), which are respectively located at the two ends of the expansion capsule (3) and connected to the expansion capsule (3). The first floating head (8) is arranged on a side close to the lower joint (2), and the second floating head (16) is arranged on a side close to the upper joint (9). Gaps are provided between the first floating head (8) and the lower joint (2), and between the second floating head (16) and the upper joint (9).

9. A method for sealing and splitting bifurcated holes in geological exploration, characterized in that: The steps include: Step 1: After the new and old wellbores appear, the intersection position, number, aperture size and other parameters of the new and old wellbores are determined according to the logging trajectory parameters, and then the geological exploration bifurcation hole sealing and splitting device of appropriate specifications is selected and the position of the geological exploration bifurcation hole sealing and splitting device is determined. For deep holes, the lower section of the intersection position of the drill hole can be sealed with a conventional sealing device first, and the intersection position can be split with the geological exploration bifurcation hole sealing and splitting device after the cement solidifies for 48 hours; Step 2: The ejector (11) is equipped with a nozzle (10), the size of which is determined according to the thickness of the sandwich wall between the new and old wellbores and the fracture pressure of the formation. The isolation pipe, the ejector (11) and the centralizer (12) are connected in sequence and connected to a surface high-pressure pump. High-pressure liquid is injected through the high-pressure pump to test the performance and construction parameters of the geological exploration bifurcation hole sealing and splitting device. After the test, the geological exploration bifurcation hole sealing and splitting device is lowered through the pipe string into the intersection of the new and old wellbores. Step 3: continue to pump high-pressure liquid into the pipe column. The high-pressure liquid enters from the opening (15) and penetrates into the expansion capsule (3) through the liquid hole. The expansion capsule (3) absorbs the liquid and expands to contact the hole wall, thereby achieving a stable connection between the isolation pipe and the well wall. A rubber plug or a steel ball matching the closing sleeve (7) is inserted through the opening (15) and pressurized. The rubber plug or the steel ball sits on the closing sleeve (7). The closing sleeve (7) moves downward under the action of high pressure to cut off the pin (6), and the closing sleeve (7) moves downward in the annular groove (5) to close the liquid hole. Step 4: Continue to increase the pressure through the high-pressure pump and inject high-pressure liquid into the pipe string. The high-pressure liquid is ejected through the nozzle (10) of the ejector (11). The injection depth increases linearly with the increase of pressure, and the pore size also increases with the increase of pressure. When the pressure reaches the critical pressure, the rock can be broken, thereby connecting the new and old wellbores. When the vertical stress on the hole wall reaches the vertical tensile strength of the hole wall rock, the rock will produce brittle fracture in the direction perpendicular to the vertical stress, that is, horizontal cracks will be generated in the direction perpendicular to the vertical stress. The fracture pressure is determined according to the relevant parameters of the formation: in P F is the fracture pressure of the formation, MPa; P s is the pore fluid pressure, MPa; is the vertical stress, MPa, is the vertical tensile strength, MPa; α is the Biot constant, i.e. the pore elastic constant, which is between 0 and 1 and is usually around 0.5; ν is the Poisson's ratio of the rock, P s Obtained through field testing, ν is obtained through laboratory testing; Step 5: After the new and old wellbores are split and connected, a conventional sealing device is used to inject the pre-mixed sealing material through the pipe string into the new and old wellbores to achieve full sealing of the new and old wellbores.

10. A method for sealing and splitting bifurcated holes in geological exploration according to claim 9, characterized in that: In step 4, if the intersection position between the new and old wellbores is long, the geological exploration bifurcated hole sealing and splitting device is used according to step 4 to achieve segmented splitting of the intersection position.

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