Repeatable branch pipe drilling device and method

Abstract

The present invention relates to a branch pipe drilling device and method capable of repeatable operation. The branch pipe drilling device comprises: an outer tube, the first end of the outer tube is an open end facing the wellhead, the second end is a closed end facing the well bottom, and a guide hole obliquely pointing outward is constructed on the tube wall of the closed end; a piston member, the piston member is arranged in the outer tube and sealedly engaged with the inner wall of the outer tube; and a branch pipe, the branch pipe extends in the outer tube, the first end of the branch pipe is connected to the piston member, and the second end extends into the guide hole; wherein the piston member can move in the outer tube along the axial direction of the outer tube, when the piston member moves along the axial direction of the outer tube toward the closed end of the outer tube, the branch pipe extends out of the outer tube through the guide hole, and when the piston member moves along the axial direction of the outer tube toward the open end of the outer tube, the branch pipe is retracted into the outer tube through the guide hole.

Description

Technical Field

[0001] The present invention relates to the technical field of branch pipe drilling, and in particular to a branch pipe drilling device capable of repeated operation. The present invention also relates to a method for performing repeated operation using the device. Background Art

[0002] Branch pipe production enhancement technology is a carbonate open hole well production enhancement technology. Branch pipe production enhancement tools generally pre-set small diameter branch pipes in the completion string. One end (upper end) of the branch pipe is freely placed in the completion string, and the other end (lower end) passes through the lateral hole on the wall of the completion string. A nozzle is set at the other end of the branch pipe passing through the side hole. After the entire tool is lowered to the predetermined position, high-pressure acid is pumped into the completion string. The acid flows through the branch pipe and the nozzle at a high speed and is ejected onto the well wall, and holes are created in the reservoir through the combined action of the jet and the acid-rock reaction. At the same time, due to the throttling effect of the nozzle, the branch pipe is pulled outward and extends into the hole in the reservoir, and continues to extend into the reservoir, so as to achieve the purpose of connecting the reservoir and increasing production.

[0003] However, the existing branch pipe production stimulation tools can only be operated once underground and cannot be operated repeatedly without pulling out the completion string. In other words, after the branch pipe is extended out of the completion string under the action of throttling, it cannot be retracted and reused. If repeated operations are required, the entire operating string must be pulled out of the wellbore, a new branch pipe production stimulation tool must be replaced or the old tool must be repaired, and then it must be lowered to the predetermined position in the wellbore for operation. Re-entering the operating string requires clearing the well again, washing the well, and preparing acid and completion fluid. This not only prolongs the operation time and wastes liquid, resulting in higher costs, but also increases pollution to the environment. Summary of the invention

[0004] In view of the above problems, the present invention proposes a branch pipe drilling device capable of repeated operation. The device can realize branch pipe drilling repeatedly in one operation pipe string. The present invention also proposes a corresponding branch pipe drilling method capable of repeated operation.

[0005] According to a first aspect of the present invention, a branch pipe drilling device is proposed, comprising: an outer cylinder, a first end of the outer cylinder being an open end facing the wellhead, a second end of the outer cylinder being a closed end facing the bottom of the well, and a guide hole obliquely pointing outward is constructed on the cylinder wall of the closed end; a piston member, the piston member is arranged in the outer cylinder and sealingly engaged with the inner wall of the outer cylinder; and a branch pipe, the branch pipe extends in the outer cylinder, the first end of the branch pipe is connected to the piston member, and the second end of the branch pipe extends into the guide hole; wherein the piston member can move in the outer cylinder along the axial direction of the outer cylinder, when the piston member moves along the axial direction of the outer cylinder toward the closed end of the outer cylinder, the branch pipe extends out of the outer cylinder through the guide hole, and when the piston member moves along the axial direction of the outer cylinder toward the open end of the outer cylinder, the branch pipe is retracted into the outer cylinder through the guide hole.

[0006] Through the above device, the branch pipe can be extended or retracted with the movement of the piston member. Thus, the operator can control the extension degree of the branch pipe by controlling the position of the piston member. After a single branch pipe drilling is completed, the branch pipe can be retracted into the outer tube by moving the piston member toward the open end of the outer tube. Then, the entire drilling device can be adjusted to another appropriate position, and the branch pipe can be extended again by moving the piston member toward the closed end. Thus, repeated branch pipe drilling operations can be achieved.

[0007] In one embodiment, a closed cavity is formed between the piston member and the closed end of the outer tube, and at least one selectively opened fluid channel is constructed on the outer tube to allow fluid flow between the closed cavity and the space outside the outer tube, and when the fluid in the closed cavity decreases, the branch pipe extends outward through the guide hole, and when the fluid in the closed cavity increases, the branch pipe is retracted inward through the guide hole.

[0008] In one embodiment, a first one-way valve is disposed in a portion of the at least one selectively opened fluid passage, allowing fluid to flow from the space outside the outer cylinder into the closed cavity.

[0009] In one embodiment, a flow controller allowing fluid to flow from the closed cavity to the space outside the outer tube is provided in a portion of the at least one selectively opened fluid channel, and the flow controller is constructed so that the speed at which the piston moves toward the closed end of the outer tube does not exceed the speed at which the branch tube extends outward.

[0010] In one embodiment, the flow controller is configured to make the flow rate of the fluid in the closed cavity flowing to the space outside the outer cylinder present a monotonically increasing exponential relationship with respect to the pressure difference between the closed cavity and the space outside the outer cylinder.

[0011] In one embodiment, the flow controller is configured to open when the fluid pressure in the closed cavity reaches a predetermined threshold, allowing the fluid in the closed cavity to flow to the space outside the outer cylinder.

[0012] In one embodiment, the piston member includes a piston channel that penetrates the piston member along the axial direction of the outer tube, and the piston channel is connected to the first end of the branch pipe to connect the branch pipe with the upper inner cavity of the outer tube facing the open end, and a second one-way valve allowing fluid to flow from the upper inner cavity into the branch pipe is arranged in the piston channel.

[0013] In one embodiment, the branch pipe drilling device also includes a limit baffle arranged in an outer cylinder above the piston member, a baffle channel extending axially therethrough is constructed at the center of the limit baffle, and a sealing member is arranged on the end face of the second end of the limit baffle; the piston member includes a first piston channel and a second piston channel extending axially therethrough along the outer cylinder, the first piston channel is centered relative to the piston member, the second piston channel is offset relative to the central axis of the piston member, and the first end of the branch pipe is inserted into the second piston channel or is connected to the second piston channel; wherein, when the first end of the piston member is engaged with the end face of the second end of the limit baffle, the sealing member prevents the baffle channel from communicating fluid with the second piston channel and the branch pipe.

[0014] According to a second aspect of the present invention, a method for branch pipe drilling using the above-mentioned branch pipe drilling device is proposed, comprising the following steps: an extension step: moving the piston member connected to the branch pipe toward the closed end of the outer cylinder so that the branch pipe can extend outward through the guide hole; a retraction step: moving the piston member connected to the branch pipe toward the open end of the outer cylinder so that the branch pipe can be retracted inward through the guide hole; repeated drilling operations are achieved by repeatedly executing the above-mentioned extension step and retraction step.

[0015] In one embodiment, in the extending step, fluid is injected into the outer tube at a first pressure so that the fluid in the closed cavity between the piston member and the closed end of the outer tube flows to the space outside the outer tube through a fluid channel provided with a flow controller, thereby achieving the movement of the piston member toward the closed end of the outer tube.

[0016] In one embodiment, in the extending step, before injecting the fluid into the outer tube at a first pressure, the fluid is first injected into the outer tube at a second pressure lower than the first pressure, so that the fluid is ejected through the branch pipe.

[0017] In one embodiment, in the retracting step, fluid is injected into the space outside the outer tube at a third pressure, so that the fluid in the space outside the outer tube can flow to the closed cavity between the piston member and the closed end of the outer tube through the fluid channel provided with a first one-way valve, thereby realizing the movement of the piston toward the open end of the outer tube.

[0018] In one embodiment, in the extending step, fluid is injected into the outer tube so that the fluid in the closed cavity between the piston member and the closed end of the outer tube flows to the outer tube outer space through a fluid channel provided with a flow controller, thereby realizing the movement of the piston member toward the closed end of the outer tube until the pressure increase in the upper inner cavity of the outer tube is detected; in the retracting step, fluid is injected into the outer tube outer space so that the fluid in the outer tube outer space can flow to the closed cavity between the piston member and the closed end of the outer tube through a fluid channel provided with a first one-way valve, thereby realizing the movement of the piston toward the open end of the outer tube, and the fluid in the outer tube outer space can flow to the upper inner cavity of the outer tube through the branch pipe until the pressure increase in the outer tube outer space is detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be described in more detail below with reference to the accompanying drawings, wherein:

[0020] Figure 1 A schematic structural diagram of a branch pipe drilling device according to a first embodiment of the present invention is shown;

[0021] Figure 2 and Figure 3 They are shown separately Figure 1 Different working states of the branch pipe drilling device;

[0022] Figure 4 A schematic structural diagram of a branch pipe drilling device according to a second embodiment of the present invention is shown;

[0023] Figures 5 to 7 They are shown separately Figure 4 Different working conditions of the branch pipe drilling device.

[0024] In the drawings, the same reference numerals are used for the same components. The drawings are not drawn to scale. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings.

[0026] Figures 1 to 3 A lateral drilling apparatus 100 according to one embodiment of the present invention is shown.

[0027] In the present invention, the "first end" refers to the end facing the wellhead during operation, i.e., the upper end, and the "second end" refers to the end facing the well bottom during operation, i.e., the lower end.

[0028] The branch pipe drilling device 100 includes an outer tube. The first end of the outer tube is an open end, and the second end is a closed end. Figure 1 In the illustrated embodiment, the outer cylinder includes a plurality of casings 1 connected in sequence along the axial direction, and adjacent casings 1 are connected together by a coupling 2. The outer cylinder also includes a closed shell 8 disposed at the second end. The upper end of the closed shell 8 having an opening is connected to the casing 1. The lower end of the closed shell 8 is closed, and a guide hole 9 extending outward obliquely is disposed thereon. Each casing 1 and the closed shell 8 together surround an inner space of the outer cylinder, and the inner space is connected to the wellhead.

[0029] Also like Figure 1 As shown, the branch pipe drilling device 100 further includes a piston member 6. Figure 1 As shown, the piston member 6 is disposed in the inner space of the outer cylinder and can be sealed with the inner wall of the outer cylinder. Thus, the piston member 6 divides the inner space of the outer cylinder into a closed space 102 near the closed end and an upper inner cavity 101 near the open end. Figure 1 In the preferred embodiment shown, the first end and the second end of the piston member 6 are respectively configured with flanges 3 and 5 extending radially outward. A sealing member is arranged on the flange to seal with the inner wall of the outer cylinder. The sealing member here is preferably a large gap sealing member, such as a lip seal such as a Yx sealing ring, a Y-ring, a V-ring, etc.

[0030] In addition, a piston passage is provided in the piston member 6, which penetrates the piston member axially. The upper end of the piston passage is connected to the upper inner cavity 101, and the lower end is open to the closed space 102. A second one-way valve 4 is provided on the piston passage. The second one-way valve 4 allows a fluid having a pressure not lower than the second pressure to flow from the upper inner cavity 101 into the piston passage and flow through the piston passage.

[0031] exist Figure 1 In the illustrated embodiment, each sleeve 1 has a substantially consistent inner diameter to ensure a smooth, sealed fit between the inner wall of the piston member 6 and the outer tube when the piston member 6 slides axially in the outer tube. In addition, the closed housing 8 has a smaller inner diameter, thereby limiting the range of movement of the piston member 6.

[0032] In addition, the branch pipe drilling device 100 further includes a branch pipe 7. Figure 1As shown, the first end of the branch pipe 7 is connected to the second end of the piston member 6 and communicates with the second end of the piston channel. As a result, the fluid flowing through the piston channel via the second one-way valve 4 can flow into the branch pipe 7. The second end of the branch pipe 7 is inserted into the guide hole 9 and slidably seals with the guide hole. A nozzle 12 is configured at the second end of the branch pipe 7. The fluid flowing into the branch pipe 7 can be ejected through the nozzle 12.

[0033] In addition, a plurality of fluid channels are provided at the closed end of the outer cylinder (or at the end of the closed shell 8). These fluid channels are selectively opened to allow fluid flow between the closed cavity 102 and the space outside the outer cylinder.

[0034] In such Figure 1 In the illustrated embodiment, a first one-way valve 11 is disposed in at least one fluid channel. The first one-way valve 11 allows fluid having a pressure not lower than the third pressure to flow from the outer space of the outer cylinder to the closed cavity 102 through the corresponding fluid channel.

[0035] In addition, a flow controller 10 is arranged in at least one other fluid channel. The flow controller 10 is configured so that the speed at which the piston member 6 moves toward the closed end of the outer cylinder does not exceed the speed at which the branch pipe 7 extends outward.

[0036] In a preferred embodiment, the flow controller 10 is configured so that the flow rate of the fluid in the closed cavity 102 flowing to the space outside the outer cylinder is in a monotonically increasing exponential relationship with respect to the pressure difference between the closed cavity 102 and the space outside the outer cylinder. The flow controller 10 can be configured as a flow limiting valve or a valve group including a flow limiting valve, thereby achieving control of the flow rate of the fluid.

[0037] In another preferred embodiment, the flow controller 10 is configured to open when the fluid pressure in the closed cavity 102 reaches a predetermined threshold value, allowing the fluid in the closed cavity 102 to flow to the space outside the outer cylinder. After the flow controller 10 is opened, the flow controller 10 can still make the flow rate of the fluid in the closed cavity 102 flowing to the space outside the outer cylinder present a monotonically increasing exponential relationship with respect to the pressure difference between the closed cavity 102 and the space outside the outer cylinder. For example, such a flow controller 10 can be a combination of an overflow valve and a throttle valve, or a combination of a throttle valve and a rupture disk. The overflow valve and the rupture disk can provide the above-mentioned predetermined threshold value. The combination of the overflow valve and the throttle valve is particularly suitable for the situation where multiple branch pipe drillings are repeatedly implemented.

[0038] The following will refer to Figures 1 to 3 A drilling method using the branch pipe drilling device 100 of the present invention will be described in detail.

[0039] First, assemble the branch pipe drilling device 100. Specifically, assemble the piston member 6, branch pipe 7, closed shell 8, flow controller 10, first one-way valve 11 and other components together with a plurality of casings 1 and couplings 2. During the assembly process, fill the closed space 102 between the piston member 6 and the closed shell 8 (or the closed end of the outer tube) with fluid (for example, water or completion fluid). For example, fluid can be injected into the closed space 102 through the fluid channel where the first one-way valve 11 is located. After assembly, the branch pipe drilling device 100 is preferably in a Figure 1 The state shown, in which the second end of the branch pipe 7 is completely accommodated in the guide hole 9.

[0040] Then, the assembled branch pipe drilling device 100 is lowered into a predetermined position in the well. High-pressure fluid is pumped into the upper inner cavity 101 of the outer tube at a second pressure. Thus, the second one-way valve 4 in the piston member 6 can be opened, so that the fluid in the upper inner cavity 101 can enter the branch pipe 7, and be ejected to the outside of the outer tube through the nozzle 12, and ejected to the formation to be drilled, so as to make a hole in the formation. In this process, the pressure in the upper inner cavity 101 and the enclosed space 102 increases together. Under the action of the flow controller 10, the fluid in the enclosed space 102 cannot flow out, or basically cannot flow out. This makes the position of the piston member 6 immobile or basically immobile.

[0041] Thereafter, a high-pressure fluid is pumped into the upper inner cavity of the outer cylinder at a first pressure (higher than the second pressure). The fluid is further ejected toward the formation through the branch pipe 7 and the nozzle 12. At the same time, the flow controller 10 opens or allows a larger flow rate to pass, so as to allow the fluid in the closed space 102 to flow into the outer space of the outer cylinder, thereby enabling the piston member 6 to be pushed toward the closed end of the outer cylinder (see Figure 2 ). As the piston 6 moves, the branch pipe 7 extends outward through the guide hole 9 under the action of throttling and extends into the hole pre-made in the formation. As the branch pipe 7 extends forward and the fluid is sprayed, the hole-making drilling continues. The branch pipe 7 moves forward until the piston 6 reaches the closed end of the outer cylinder ( Figure 3 ).

[0042] After drilling is completed, stop injecting fluid into the outer tube, and inject high-pressure fluid not lower than the third pressure into the outer space of the outer tube. The first one-way valve 11 opens to allow fluid to flow from the outer space of the annulus to the closed space 102. As a result, the piston 6 can be pushed to move toward the first end close to the wellhead, and the branch pipe 7 can be retracted. Figure 2 The intermediate state shown moves to Figure 1 The second end of the branch pipe 7 is shown in a state where it is completely retracted into the guide hole 9 .

[0043] By adjusting the branch pipe drilling device 100 to another expected location for drilling and repeating the above operation, repeated operations can be performed with one pipe string, thereby effectively shortening the operation time, reducing costs, and reducing environmental pollution.

[0044] Figures 4 to 7 Another embodiment of the present invention is a branch pipe drilling device 200. The structure of the branch pipe drilling device 200 is substantially the same as that of the branch pipe drilling device 100, with the main differences being as follows.

[0045] The piston member 6 of the branch pipe drilling device 200 is constructed with two piston channels penetrating in the axial direction, namely the first piston channel and the second piston channel. The first piston channel is arranged in a central position relative to the piston member 6. A second one-way valve 4 is arranged in the first piston channel. The upper end of the first piston channel is connected to the upper cavity 101, and the lower end is connected to the closed space 102. The second piston channel is arranged offset relative to the axis of the piston member 6. In one embodiment, the upper end of the branch pipe 7 is connected to the lower end of the second piston channel. In another embodiment, the upper end of the branch pipe 7 is inserted into the second piston channel and extends to the upper end of the second piston channel. In this way, the branch pipe 7 is connected to the upper cavity 101 above the piston member 6.

[0046] Also like Figure 4 As shown, in the upper cavity 101 above the piston member 6, a limit baffle 13 is provided. The limit baffle 13 can be fixed on the inner wall of the outer cylinder. For example, the limit baffle 13 can be clamped between adjacent sleeves 1 and thus be confined to the inner side of the coupling 2. This installation method is relatively easy to implement and can achieve rapid assembly. At the same time, if the limit baffle 13 needs to be replaced or maintained, this is also very advantageous. A baffle channel is constructed at the center of the limit baffle 13 and runs through it in the axial direction. As shown in FIG. Figure 4 As shown, the baffle channel is opposite to and can communicate with the first piston channel on the piston member 6. That is, due to the existence of the baffle channel, the limiting baffle 13 will not prevent the fluid or object in the upper cavity 101 from contacting the first piston channel.

[0047] In addition, a baffle seal 131, such as a sealing ring, is provided on the lower end surface of the limit baffle 13 (i.e., the end surface facing the piston member 6). The projection position of the seal 131 on the upper end surface of the piston member 6 is between the first piston channel and the second piston channel of the piston member 6. That is, when the piston member 6 contacts the lower end surface of the limit baffle 13 (see Figure 4 ), the first piston channel is located inside the seal 131, and the second piston channel is located outside the seal 131. Figure 4 In the state shown, the fluid in the upper chamber 101 cannot flow to the second piston channel. Figure 4 In the state shown, the fluid in the second piston channel also cannot flow to the upper cavity 101 .

[0048] The following will refer to Figures 4 to 7 A drilling method using the branch pipe drilling device 200 of the present invention will be described in detail.

[0049] First, the branch pipe drilling device 200 is assembled. Specifically, the piston member 6, the branch pipe 7, the closed shell 8, the flow controller 10, the first one-way valve 11 and other components are assembled together with a plurality of casings 1 and a coupling 2. During the assembly process, the closed space 102 between the piston member 6 and the closed shell 8 (or the closed end of the outer tube) is filled with fluid (for example, water or completion fluid). For example, the fluid can be injected into the closed space 102 through the fluid channel where the first one-way valve 11 is located. In a preferred embodiment, the fluid is directly introduced into the first piston channel through a syringe or a similar tool, so that the second one-way valve 4 is opened to inject the fluid into the closed space 102. In this process, it is ensured that the piston member 6 is against the lower end surface of the limit baffle 13. This injection method is particularly suitable for the case where the outer tube surrounding the closed space 102 is long. In other words, this injection method is conducive to extending the outer tube surrounding the closed space 102. It should be understood that the first piston channel can be omitted when it is not necessary to inject fluid into the closed space 102 through the first piston channel.

[0050] After being assembled, the branch pipe drilling device 200 is preferably Figure 4 The state shown, in which the second end of the branch pipe 7 is completely accommodated in the guide hole 9.

[0051] Then, the assembled branch pipe drilling device 200 is lowered into the predetermined position in the well. High-pressure fluid is pumped into the upper inner cavity 101 of the outer tube at a certain pressure higher than the predetermined threshold of the flow controller 10. Since the effective area of ​​the upper end of the piston member 6 is larger than the second end, the pressure in the closed space 102 is slightly higher than the inner cavity 101, so that the second one-way valve 4 can remain closed. In addition, the pressure in the upper inner cavity 101 and the closed space 102 increases together. Under the action of the flow controller 10, the fluid in the closed space 102 slowly flows out. This enables the piston member 6 to be pushed toward the closed end of the outer tube (see Figure 5 ), separated from the limit baffle 13. The fluid in the upper inner cavity 101 can flow into the branch pipe 7, and then eject to the formation outside the outer cylinder, making a hole in the formation. In this process, the piston 6 moves relatively slowly under the action of the flow controller 10, so that the branch pipe 7 extends outward through the guide hole 9 under the action of throttling, and extends into the hole pre-made in the formation. At the same time, the branch pipe 7 continues to spray and make holes, and continues to extend outward until the piston 6 reaches the closed end of the outer cylinder ( Figure 7).

[0052] During the drilling process, the input displacement of the fluid supplied to the upper inner cavity 101 of the outer cylinder from the wellhead is equal to the sum of the displacement through the branch pipe 7 and the volume increase rate of the upper inner cavity 101 caused by the movement of the piston member 6 to the second end. When the piston member 6 reaches the closed end of the outer cylinder, the volume increase rate of the upper inner cavity 101 drops to zero due to the unchanged input displacement, which causes a significant increase in the pressure in the upper inner cavity 101. This pressure change is transmitted to the wellhead. Through this pressure change, the operator can judge that the piston member 6 has reached the closed end of the outer cylinder and thus stop further drilling operations.

[0053] After drilling is completed, stop injecting fluid into the outer tube, and inject high-pressure fluid not lower than the third pressure into the outer space of the outer tube. The first one-way valve 11 opens to allow fluid to flow from the outer space of the annulus to the closed space 102. As a result, the piston 6 can be pushed to move toward the first end close to the wellhead, and the branch pipe 7 can be retracted. Figure 6 and Figure 5 The intermediate state shown moves to Figure 4 The second end of the branch pipe 7 is shown as being completely retracted into the guide hole 9. In the intermediate state, a small amount of high-pressure fluid can flow into the inner cavity 101 through the branch pipe 7 and the second piston passage of the piston member 6. At this time, the operator can observe that the inner cavity 101 has a relatively stable pressure value. Figure 4 In the fully retracted state shown, the upper end of the piston member 6 is in full contact with the lower end surface of the limit baffle 13. Under the action of the seal 131, the fluid cannot continue to flow into the inner cavity 101 through the branch pipe 7, and the input displacement remains unchanged, thereby causing the pressure of the high-pressure fluid in the space outside the outer cylinder to increase. When the operator observes the pressure change, he can judge that the piston member 6 has reached the limit baffle 13 and thus stop further return operation.

[0054] By adjusting the branch pipe drilling device 200 to another expected location for drilling and repeating the above operation, repeated operations can be performed with one pipe string, thereby effectively shortening the operation time, reducing costs, and reducing environmental pollution.

[0055] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A branch pipe drilling device, comprising: An outer cylinder, wherein the first end of the outer cylinder is an open end facing the wellhead, the second end of the outer cylinder is a closed end facing the well bottom, and a guide hole obliquely pointing outward is configured on the cylinder wall of the closed end; A piston member, the piston member is disposed in the outer tube and sealingly engaged with the inner wall of the outer tube; as well as A branch pipe, the branch pipe extends in the outer tube, a first end of the branch pipe is connected to the piston member, and a second end of the branch pipe extends into the guide hole; The piston member can move in the outer tube along the axial direction of the outer tube. When the piston member moves along the axial direction of the outer tube toward the closed end of the outer tube, the branch pipe extends out of the outer tube through the guide hole. When the piston member moves along the axial direction of the outer tube toward the open end of the outer tube, the branch pipe is retracted into the outer tube through the guide hole. A closed cavity is formed between the piston member and the closed end of the outer cylinder. At least one selectively opened fluid channel is configured on the outer cylinder to allow fluid flow between the closed cavity and the space outside the outer cylinder. When the fluid in the closed cavity decreases, the branch pipe extends outward through the guide hole. When the fluid in the closed cavity increases, the branch pipe is retracted inward through the guide hole. The piston member includes a piston channel that penetrates the piston member along the axial direction of the outer tube, and the piston channel is connected to the first end of the branch pipe to connect the branch pipe with the upper inner cavity of the outer tube facing the open end, and a second one-way valve that allows fluid to flow from the upper inner cavity to the branch pipe is arranged in the piston channel.

2. The branch pipe drilling device according to claim 1, characterized in that: A first one-way valve is arranged in a portion of the at least one selectively opened fluid passage to allow fluid to flow from the space outside the outer cylinder into the closed cavity.

3. The branch pipe drilling device according to claim 1, characterized in that: A flow controller is provided in a portion of the at least one selectively opened fluid channel to allow fluid to flow from the closed cavity to the space outside the outer tube, and the flow controller is constructed so that the speed at which the piston moves toward the closed end of the outer tube does not exceed the speed at which the branch pipe extends outward.

4. The branch pipe drilling device according to claim 3, characterized in that: The flow controller is configured to ensure that a flow rate of the fluid in the closed cavity flowing to the space outside the outer cylinder is in a monotonically increasing exponential relationship with respect to a pressure difference between the closed cavity and the space outside the outer cylinder.

5. The branch pipe drilling device according to claim 3, characterized in that: The flow controller is configured to open when the fluid pressure in the closed cavity reaches a predetermined threshold, allowing the fluid in the closed cavity to flow to the space outside the outer cylinder.

6. The branch pipe drilling device according to any one of claims 1 to 5, characterized in that: The branch pipe drilling device further comprises a limit baffle plate arranged in the outer cylinder above the piston member, a baffle plate passage penetrating along the axial direction is configured at the center of the limit baffle plate, and a sealing member is arranged on the end surface of the second end of the limit baffle plate; The piston member comprises a first piston channel and a second piston channel which penetrate the piston member along the axial direction of the outer tube, the first piston channel is centrally arranged relative to the piston member, the second piston channel is offset relative to the central axis of the piston member, and the first end of the branch pipe is inserted into the second piston channel or communicated with the second piston channel; Wherein, when the first end of the piston member is engaged with the end surface of the second end of the limit baffle, the sealing member prevents the baffle channel from communicating with the second piston channel and the branch pipe.

7. A method for performing branch pipe drilling using the branch pipe drilling device according to any one of claims 1 to 6, comprising the following steps: Extending step: moving the piston member connected to the branch pipe toward the closed end of the outer tube so that the branch pipe can extend outward through the guide hole; Retracting step: moving the piston member connected to the branch pipe toward the open end of the outer tube so that the branch pipe can be retracted inwardly through the guide hole; Repeated drilling operation is achieved by repeatedly executing the above-mentioned extending step and retracting step.

8. The method according to claim 7, characterized in that In the extending step, fluid is injected into the outer tube at a first pressure so that the fluid in the closed cavity between the piston member and the closed end of the outer tube flows to the space outside the outer tube through a fluid channel provided with a flow controller, thereby realizing the movement of the piston member toward the closed end of the outer tube.

9. The method according to claim 8, characterized in that In the extending step, before injecting the fluid into the outer tube at a first pressure, the fluid is first injected into the outer tube at a second pressure lower than the first pressure, so that the fluid is ejected through the branch pipe.

10. The method according to claim 7, characterized in that In the retracting step, fluid is injected into the space outside the outer tube at a third pressure, so that the fluid in the space outside the outer tube can flow to the closed cavity between the piston member and the closed end of the outer tube through the fluid channel provided with a first one-way valve, thereby realizing the movement of the piston toward the open end of the outer tube.

11. The method according to claim 7, characterized in that In the extending step, fluid is injected into the outer tube, so that the fluid in the closed cavity between the piston member and the closed end of the outer tube flows to the outer tube outer space through the fluid channel provided with a flow controller, thereby realizing the movement of the piston member toward the closed end of the outer tube, until the pressure in the upper inner cavity of the outer tube is detected to increase; In the retracting step, fluid is injected into the space outside the outer cylinder so that the fluid in the space outside the outer cylinder can flow to the closed cavity between the piston member and the closed end of the outer cylinder through the fluid channel provided with the first one-way valve, thereby realizing the movement of the piston toward the open end of the outer cylinder, and the fluid in the space outside the outer cylinder can flow to the upper inner cavity of the outer cylinder through the branch pipe until the pressure increase in the space outside the outer cylinder is detected.

Images