Ultra-short radius window sidetracking directional tool for multi-branch wellbore and use method thereof

Abstract

The present invention is a multi-branch wellbore ultra-short radius window sidetracking directional tool and a method of use. The window sidetracking tool in the present invention includes an oblique fixture. When the inverted rod of the inverted ...

Description

Technical Field

[0001] The invention relates to an ultra-short radius window opening directional drilling device for multi-branch wells in the petroleum industry and a use method thereof, in particular to an ultra-short radius window opening directional drilling tool for multi-branch wells and a use method thereof. Background Art

[0002] At present, most of my country's old oil fields have entered the middle and late stages of development. The pressure coefficient of the main blocks is getting lower and lower, and the economic efficiency of using traditional drilling methods is getting worse and worse. Opening windows in old wellbores and drilling horizontal wells sideways is one of the most economical means of increasing production in today's oil production. However, conventional side-drilling horizontal wells have long inclined sections and large displacements before the target, and the remaining oil near the old well cannot be effectively mobilized. In response to this development problem, in recent years, ultra-short radius side-drilling horizontal well technology has been developed both at home and abroad. It can quickly drill to the target layer with a curvature radius of 3-5m and drill a horizontal wellbore of a certain length, which greatly saves drilling costs and improves the reservoir utilization. However, for multi-layer reservoirs, single-branch ultra-short radius horizontal wells have a low degree of vertical reserve control, and even in the same oil layer, there is a problem of small planar sweep range. Therefore, it is necessary to develop ultra-short radius multi-branch side-drilling horizontal well technology to improve the economic and effective utilization of "small-scale" residual oil in the plane and between layers. At the same time, in terms of adjusting streamlines in water-drive reservoirs, ultra-short radius multi-branch side-drilling horizontal wells can achieve balanced displacement and utilization according to the planar heterogeneous distribution characteristics of the reservoir by side-drilling horizontal wells in different directions and lengths, thereby expanding the swept volume and improving the recovery rate.

[0003] The existing ultra-short radius side-drilling horizontal well technology is mainly divided into two categories: high-pressure water jet drilling and flexible guide drilling tool rotary drilling. Chinese patent ZL2008101194691 discloses a radial horizontal drilling device, which uses a high-pressure hose to connect a jet drill bit, and the jet drill bit sprays high-pressure water jets to break the rock and form a horizontal wellbore. This technology has the following problems: the horizontal wellbore formed by this jet jet breaking is small in diameter, the channel is irregular, and due to the hose, the hydraulic jet drill bit's forward trajectory is uncontrollable, the formed wellbore trajectory is also irregular, the wellbore trajectory cannot be measured, there is a lack of applicable completion technology, sand-producing reservoirs cannot prevent sand, the wellbore is prone to collapse and closure due to lack of support, and the production decreases rapidly.

[0004] In view of the shortcomings of high-pressure water jet drilling technology, Chinese patents ZL2015104510629, ZL2011201146271, ZL2017109462512, ZL2017105827546, etc. disclose a guided ultra-short radius horizontal well drilling method, and the drilling principle is basically similar: first, the whipstock is set, and the depth is calibrated by magnetic positioning when the whipstock is set, and the normal azimuth of the whipstock is determined by a gyroscope to make it the same as the designed azimuth of the wellbore. After the whipstock is set, the window is opened by a conventional window opening method, and the inclined section is drilled by a guided drilling tool. The guided drilling tool includes a guide tube and a flexible drill rod, wherein the guide tube is a human elbow joint structure, which can only bend unilaterally in a certain direction with a fixed curvature radius, constraining the internal flexible drill rod for inclined drilling. When the guide drill is lowered, a gyroscope is used to adjust the bending direction of the guide tube to make it consistent with the normal direction of the inclined surface of the bevel device, ensuring that the ultra-short radius deflection drilling direction is the same as the wellbore design orientation. The guide drill is mainly used for drilling construction of ultra-short radius deflection well sections. After the deflection section is completed and reaches the target layer, the guide drill is pulled out and the horizontal drill is lowered to complete the horizontal wellbore drilling. This patented technology can complete the deflection section with a curvature radius of 3 to 5m, quickly enter the target layer with a well inclination of 90 degrees, and can drill horizontally for 50 to 100m, which can basically meet the process requirements of ultra-short radius horizontal drilling. However, only single-branch horizontal wells can be drilled inside the same wellbore, and ultra-short radius multi-branch side-drilling horizontal wells cannot be implemented. The technical bottleneck lies in the lack of multi-branch wellbore window side-drilling tools.

[0005] To realize window side drilling in multi-branch wells, multiple whipstocks must be set. The existing technical solution is to use a salvageable whipstock, set it multiple times at different depths in the same wellbore to perform window side drilling, and finally salvage all the whipstocks out of the wellbore for completion operations.

[0006] There are also the following related technical devices disclosed in Chinese patents:

[0007] ZL2014204156245 discloses a variable diameter recyclable whipstock;

[0008] ZL2010105643447 discloses a recyclable track-type deflector;

[0009] ZL972230955 discloses a retractable guide;

[0010] ZL2005101352615 discloses a retrievable whipstock and its salvage tool;

[0011] ZL2010202320321 discloses a salvageable side drilling integrated deflector;

[0012] ZL2010202320321 discloses a suspended positioning type recyclable whipstock;

[0013] ZL2016201515245 discloses a hydraulically sealed recyclable whipstock with a self-closing connecting channel.

[0014] The working principle of the above patented technology is basically similar, and its technical solution is: by sending the tool down to the predetermined position, hydraulically setting the seal, anchoring it in the casing through the slips, and using the inclined iron on the upper part of the tool to guide the window opening tool to grind the casing to open the window. When recovering, a special salvage tool is used to salvage the salvage joint and apply upward force to cut the shear pin, retract the setting piston, release the slips, release the anchor, and recover the whipstock.

[0015] However, if the above technical device is used in the side drilling and window opening construction of multi-branch wells, the following problems will occur:

[0016] The whipstock itself must be equipped with a setting and unsealing mechanism, which increases the complexity of the tool, reduces its reliability, and poses a risk of recovery failure.

[0017] After the whipstock is recovered, a new whipstock must be set at a different depth, and a gyroscope must be lowered each time the whipstock is set to determine the orientation of the whipstock’s slope, which increases the construction period and significantly increases the construction cost.

[0018] After completing the sidetracking of the multi-branch wellbore, the lowest branch wellbore window lacks the whipstock guide, and the completion string cannot be repeatedly run into the branch wellbore.

[0019] Therefore, in order to realize ultra-short radius multi-branch side-drilling horizontal wells and improve the construction efficiency and construction success rate of multi-window side-drilling and reduce operating costs, it is necessary to manufacture window side-drilling directional tools that can be used in conjunction with them to overcome the existing technical bottlenecks and achieve the development effect of reducing costs and increasing efficiency. Summary of the invention

[0020] The purpose of the present invention is to provide a multi-branch wellbore ultra-short radius window side drilling directional tool and a use method, so as to improve the window side drilling construction efficiency and construction success rate, realize multi-window opening, reduce operation costs, and achieve the development effect of reducing costs and increasing efficiency.

[0021] The technical solution of the present invention is achieved in this way:

[0022] The multi-branch wellbore ultra-short radius window sidetracking directional tool comprises an oblique fixture, which is provided with a guide inclination body, a whipstock reverse rod and slips. When the whipstock reverse rod and the whipstock straightening ring in the oblique fixture are lifted out of the well, the guide surface of the guide inclination body can be stacked with the retrievable locator, wherein:

[0023] The recyclable positioner is mainly composed of an upper positioning body, a straightening body and a lower positioning body. Both the upper positioning body and the lower positioning body are provided with guide inclined surfaces. The angle of the guide inclined surface at the lower part of the lower positioning body is the same as the angle of the guide inclined surface of the guide inclined body in the oblique fixer.

[0024] A straightening block is installed in the straightening body, an upper positioning body is connected with the straightening body and a lower positioning body through a fixing pin, and a fishing thread is provided in the upper positioning body;

[0025] The upper positioning body is connected with the positioner undercut rod and the positioner upper joint in sequence.

[0026] The straightening body is provided with a straightening block installation groove in the circumferential direction and at least one group of straightening blocks is installed in the circumferential direction. The straightening block is provided with a spring installation hole and a spring. The two side wing edges of the straightening block are buckled under a pressing plate or a pressing sleeve, and the pressing plate or the pressing sleeve is fixed in the straightening body by a fixing pin.

[0027] The manufacturing length of the centralizing body or the number of the centralizing bodies connected to the recoverable positioner can be adjusted according to the axial distance between the ultra-short radius horizontal branch wellbore 1 and the ultra-short radius horizontal branch wellbore 2.

[0028] The installation orientation between the guide inclined surface of the upper positioning body and the guide inclined surface of the lower positioning body in the recoverable locator is consistent with the azimuth angle of the side-drilling branch wellbore trajectory and can be stacked in the main wellbore. The angle of the guide inclined surface in the upper positioning body in the recoverable locator located below is the same as the angle of the guide inclined surface in the lower positioning body in another recoverable locator stacked thereon; the inclined fixture is retained in the main wellbore below a window window of the ultra-short radius horizontal branch wellbore.

[0029] The upper end of the locator inverted rod is threadedly connected to the locator upper joint, and the lower end of the locator inverted rod is provided with an inverted thread and can be connected with the inverted thread of the inner circle of the lower end of the upper locating body; a salvage thread is provided above the inner circle step in the middle of the upper locating body; the lower outer circle of the locator inverted rod is provided with an inverted thread, and the locator inverted rod is inserted into the inner circle step of the lower part of the upper locating body and connected together through the inverted thread.

[0030] The upper outer circle of the positioner inverted rod is also provided with a straightening ring carrying step. The positioner straightening ring is installed on the outside of the positioner inverted rod above the straightening ring carrying step and is fixed together with the guide inclined surface of the upper positioning body through the positioner straightening screw; the upper part of the positioner inverted rod is threadedly connected with the positioner upper joint, and the upper inner cavity of the positioner upper joint is provided with a drill pipe joint thread or an oil pipe thread.

[0031] The lower positioning body is provided with a center hole and the upper inner circle is provided with an insertion step. Six through holes are evenly opened on the circumference of the insertion step body and one of the through holes is aligned with the normal direction of the lower guide bevel in the circumferential direction. The lower end of the guide bevel in the lower positioning body is a plane.

[0032] The outer circle of the lower end of the straightening body is an inserting outer circle, and 6 countersunk holes are opened in the circumference of the inserting outer circle corresponding to the 6 through holes in the lower positioning body, and the fixing pins can be inserted into the through holes of the lower positioning body and the countersunk holes in the straightening body; when the inserting outer circle of the straightening body is inserted into the inserting step of the lower positioning body, the countersunk holes correspond to the through holes one by one, and the lower positioning body and the straightening body are fixed by the fixing pins; the inner circle of the upper end of the straightening body is also provided with an inserting step, and 6 through holes are also evenly opened in the circumference of the inserting step and correspond to the countersunk holes in the inserting outer circle of the lower part of the upper positioning body one by one and can insert the fixing pins; there is a countersunk hole in the inserting outer circle of the lower part of the upper positioning body, which is aligned with the normal direction of the guide inclined surface of the upper positioning body in the circumferential direction; the inserting outer circle of the lower part of the upper positioning body is arranged below the guide inclined surface.

[0033] The arrangement directions of the slip teeth of the two groups of slip outer walls in the oblique fixer are perpendicular to each other.

[0034] The method of use is used for the multi-branch wellbore ultra-short radius window sidetracking directional tool, and the steps of using the method are as follows:

[0035] A. Set the oblique fixture in the main wellbore, use the window milling cone to mill the casing, form the first window in the casing, and pull out the window drilling tool;

[0036] B. Run the ultra-short radius horizontal drilling assembly drill bit to side-drill an ultra-short radius horizontal branch wellbore 1, and pull out the drill bit after drilling is completed;

[0037] C. According to the azimuth angle of the wellbore between the ultra-short radius horizontal branch wellbore 1 and the ultra-short radius horizontal branch wellbore 2, adjust the normal angle of the guide slope between the lower positioning body and the upper positioning body in the recoverable positioning device;

[0038] D. Lower the recyclable locator so that the lower locator is stacked on the guide bevel of the oblique fixture, and use the window milling cone to mill the casing to form a second window in the casing, or continue to form the next window in a different target layer or the same target layer in the casing according to the steps described in C and D above, and pull out the window drilling tool;

[0039] E. According to the construction design, side-drill the second ultra-short radius horizontal branch wellbore in a different target layer or side-drill the second ultra-short radius horizontal branch wellbore in the same target layer;

[0040] F. A flexible screen is lowered into the main wellbore and the ultra-short radius horizontal branch wellbore located at the lowest layer to implement sand control completion.

[0041] The method for side drilling the ultra-short radius horizontal branch wellbore two in different target layers is that after the window milling of the ultra-short radius horizontal branch wellbore two is completed, the ultra-short radius horizontal drilling combination drilling tool that is lowered starts to drill inclination just after it exits the window, completes the inclination section with a curvature radius of meters, and continues drilling when the well inclination reaches 90° to form the ultra-short radius horizontal branch wellbore two.

[0042] The method for side drilling the ultra-short radius horizontal branch wellbore two in the same target layer is to lower the ultra-short radius horizontal drilling combination drill bit into the side drilling window after the first side drilling window is completed, and start to complete the deflection section with a curvature radius of 3-5 meters as soon as the flexible drill bit exits the window, and continue to drill when the well inclination reaches 90 degrees to form the ultra-short radius horizontal branch wellbore one; when the second side drilling window is completed, continue to drill with the window milling cone and form a stable inclination well section with a longitudinal length equal to the longitudinal distance between the two windows, then remove the window milling cone, lower the ultra-short radius horizontal drilling combination drill bit again, and start to complete the deflection section with a curvature radius of meters after reaching the bottom of the stable inclination well section, and continue to drill when the well inclination reaches 90 degrees to form the ultra-short radius horizontal branch wellbore two.

[0043] Compared with the prior art, the present invention has the following remarkable effects:

[0044] The oblique fixer in the present invention does not need to design a special unsealing mechanism, the tool design is simpler and more reliable, and the occurrence rate of underground accidents can be reduced.

[0045] When using a recyclable locator for window sidetracking, the guide bevel of the lower locator in the recyclable locator can be stacked with the guide bevel of the oblique fixture at the bottom of the window for window sidetracking. Before window sidetracking, the azimuth angle between the guide bevel of the upper locator in the recyclable locator and the guide bevel of the oblique fixture at the bottom can be pre-set according to the design orientation of the branch wellbore track, and the azimuth window directional sidetracking can be directly set. The construction process of measuring gyro is reduced, which is simple and convenient, and can greatly improve the construction efficiency.

[0046] The recoverable locator does not have any sealing mechanisms such as anchor pads, nor does it require an unsealing mechanism. It can be directly salvaged and recovered. The tool structure is simple and reliable, and the construction success rate is greatly improved.

[0047] The inclined fixer is retained at the lower part of the first branch wellbore, which can guide the lowering of the combined drilling tool, ensure the re-entry capability of the first branch wellbore, and provide a large space for the implementation of subsequent operations.

[0048] The multiple branch wellbores formed can exploit a target layer at the same depth in different directions, or can exploit multiple target layers at different depths. The exploitation method is more flexible and the drilling and completion technology is more applicable. The present invention can realize multi-window opening in the main wellbore, reduce operating costs, and achieve a significant development effect of reducing costs and increasing efficiency.

[0049] In summary, the present invention has significant use effects and can generate significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0051] Figure 1 It is a schematic diagram of the working principle of the present invention.

[0052] Figure 2 It is a schematic structural diagram of an oblique fixer in the window opening side drilling directional tool of the present invention.

[0053] Figure 3 It is a structural schematic diagram of a recoverable locator in the window opening side drilling directional tool of the present invention. DETAILED DESCRIPTION

[0054] The accompanying drawings are for reference and illustration only and are not intended to limit the scope of protection of the present invention. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0055] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0056] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0057] See also Figures 1 to 3 The multi-branch wellbore ultra-short radius window sidetracking directional tool comprises an oblique fixture 1, which is provided with an inclined body 1.4, a whipstock reverse rod 1.5 and a slip 1.8. When the whipstock reverse rod 1.5 and the whipstock straightening ring 1.2 in the oblique fixture 1 are lifted out of the well, the inclined surface of the inclined body 1.4 can be stacked with the retrievable positioner 2, wherein:

[0058] The recyclable positioner 2 is mainly composed of an upper positioning body 2.5, a straightening body 2.7 and a lower positioning body 2.11. Both the upper positioning body 2.5 and the lower positioning body 2.11 are provided with guide slopes. The angle of the lower guide slope of the lower positioning body 2.11 is the same as the angle of the guide slope of the guide slope body 1.4 in the oblique fixer 1.

[0059] A straightening block 2.9 is installed in the straightening body 2.7, the upper positioning body 2.5 is connected with the straightening body 2.7 and the lower positioning body 2.11 through a fixing pin 2.6, and a fishing thread is provided in the upper positioning body 2.5;

[0060] The upper positioning body 2.5 is connected with the positioner undercut rod 2.2 and the positioner upper joint 2.1 in sequence.

[0061] The recoverable locator 2 is mainly composed of a lower locating body 2.11, a straightening body 2.7 and an upper locating body 2.5, which are plugged in and fixed into a whole by a fixing pin 2.6. The semi-inclined surface structure at the lower part of the lower locating body 2.11 becomes a guide inclined surface. The angle of the guide inclined surface at the lower part of the lower locating body 2.11 is the same as the angle of the guide inclined body 1.4 in the inclined fixer 1. They can cooperate with each other to realize multi-window opening in the main wellbore, reduce operating costs, and achieve the development effect of reducing costs and increasing efficiency.

[0062] Based on the above embodiment 1, the present invention also has the following embodiments:

[0063] The said straightening body 2.7 is provided with a straightening block installation groove in the circumferential direction and at least one set of straightening blocks 2.9 is installed in the circumferential direction. The straightening block 2.9 is provided with a spring installation hole and is equipped with a spring 2.10. The two side wings of the straightening block 2.9 are buckled under a pressing sheet or a pressing sleeve 2.8. The pressing sheet or the pressing sleeve 2.8 is fixed in the straightening body 2.7 by a fixing pin 2.6. The pressing sheet is a sheet-like body pressed on both sides of the straightening block installation groove by a fixing pin cover. The pressing sleeve 2.8 is an annular sleeve fixed in the circle groove of the straightening body 2.7 on both sides of the straightening block installation groove. Through the above two clamping structures, the straightening block 2.9 can be fixed in the straightening body 2.7. A plurality of groups of straightening blocks 2.9 can be arranged in the straightening body 2.7. At least three longitudinal grooves are opened in the circumferential direction on the middle and upper outer circle of the straightening body 2.7, and at least three longitudinal grooves are opened in the circumferential direction on the middle and lower outer circle. A straightening block 2.9 is installed in each groove. A spring hole is designed at the bottom of the straightening block 2.9. A spring 2.10 is placed in the spring hole and pressed tightly between the straightening block 2.9 and the bottom of the groove. Both ends of the straightening block 2.9 are pressed by a pressing sheet or a pressing sleeve 2.8 and fastened by a fixing pin 2.6. The straightening block 2.9 is higher than the outer surface of the straightening body 2.7 under the support of the spring 2.10, and is supported on the inner wall of the wellbore during the process of going down into the well to play a straightening role. When encountering a jam, the straightening block 2.9 can compress the spring 2.10 to shrink inward and smoothly pass through the jam position.

[0064] The manufacturing length of the centralizing body 2.7 or the number of the centralizing bodies 2.7 connected in the retrievable positioning device 2 can be adjusted according to the axial distance between the ultra-short radius horizontal branch wellbore 1 3 and the ultra-short radius horizontal branch wellbore 2 4. The processing length of the centralizing body 2.7 can be determined according to the axial distance between the ultra-short radius horizontal branch wellbore 1 3 and the ultra-short radius horizontal branch wellbore 2 4, and the length can also be increased by connecting the centralizing bodies 2.7 in series and increasing the number of connections. The lengthened centralizing body 2.7 can be equipped with multiple groups of centralizing blocks 2.9 in the circumferential direction to adjust the distance between the upper positioning body 2.5 and the lower positioning body 2.11 and thereby adjust the longitudinal distance of different sidetracking windows.

[0065] The installation orientation between the guide bevel surface of the upper positioning body 2.5 and the guide bevel surface of the lower positioning body 2.11 in the recoverable positioning device 2 is consistent with the azimuth angle of the side-drilled branch wellbore track and can be stacked in the main wellbore 5. The angle of the guide bevel surface in the upper positioning body 2.5 in the recoverable positioning device 2 located below is the same as the angle of the guide bevel surface in the lower positioning body 2.11 in another recoverable positioning device 2 stacked thereon; the oblique fixture 1 is retained in the main wellbore 5 below the ultra-short radius horizontal branch wellbore-3 window opening. The oblique fixture 1 can be used as a support tool for the subsequent side-drilled ultra-short radius horizontal branch wellbore, and is retained in the main wellbore 5 below the ultra-short radius horizontal branch wellbore-3 window opening.

[0066] The upper end of the positioner inverted rod 2.2 is threadedly connected to the positioner upper joint 2.1, and the lower end of the positioner inverted rod 2.2 is provided with an inverted thread and can be connected with the inverted thread of the inner circle of the lower end of the upper positioning body 2.5; a salvage thread is provided above the inner circle step in the middle of the upper positioning body 2.5, and the salvage thread can be a tubing thread or a drill pipe joint thread, and the recoverable positioner 2 can be salvaged through the tubing string or the drill string connected by the drill pipe; the lower outer circle of the positioner inverted rod 2.2 is provided with an inverted thread, and the positioner inverted rod 2.2 is inserted into the inner circle step at the lower part of the upper positioning body 2.5 and connected together through the inverted thread.

[0067] The upper outer circle of the positioner inverted rod 2.2 is also provided with a straightening ring carrying step, and the positioner straightening ring 2.3 is installed on the outside of the positioner inverted rod 2.2 above the straightening ring carrying step and is fixed to the guide bevel of the upper positioning body 2.5 through the positioner straightening screw 2.4; the upper part of the positioner inverted rod 2.2 is threadedly connected with the positioner upper joint 2.1, and the upper inner cavity of the positioner upper joint 2.1 is provided with a drill pipe joint thread or a tubing thread, which can be connected with the drill pipe or tubing to send the tool into the well. The upper middle part of the positioner inverted rod 2.2 is provided with a straightening ring carrying step, and the outer side of the positioner inverted rod 2.2 above the straightening ring carrying step is provided with a positioner straightening ring 2.3, and the positioner straightening ring 2.3 is fixed to the guide bevel of the upper positioning body 2.5 through the positioner straightening screw 2.4, so that the positioner inverted rod 2.2 remains centered, which is conducive to the smooth implementation of inverting and releasing.

[0068] The lower positioning body 2.11 is provided with a center hole and an insertion step is provided on the upper inner circle. Six through holes are evenly opened on the circumference of the insertion step body and one of the through holes is aligned with the normal direction of the lower guide bevel in the circumferential direction. The lower end of the guide bevel in the lower positioning body 2.11 is a plane. The flat head structure at the lower end of the guide bevel of the lower positioning body 2.11 can prevent self-locking due to the "wedge" effect when cooperating with the guide bevel 1.4 of the oblique fixer 1 or the upper positioning body 2.5 of the recyclable positioner 2.

[0069] The outer circle at the lower end of the centralizing body 2.7 is a plug-in outer circle, and 6 countersunk holes are opened on the circumference of the plug-in outer circle corresponding to the 6 through holes in the lower positioning body 2.11. The fixing pin 2.6 can be inserted into the through holes of the lower positioning body 2.11 and the countersunk holes in the centralizing body 2.7; when the plug-in outer circle of the centralizing body 2.7 is inserted into the plug-in step of the lower positioning body 2.11, the countersunk holes correspond to the through holes one by one, and the lower positioning body 2.11 and the centralizing body are fixed by the fixing pin 2.6. 2.7 is used for fixing; the upper inner circle of the straightening body 2.7 is also provided with a plug-in step, and 6 through holes are evenly opened in the circumferential direction of the plug-in step, which corresponds to the countersunk holes in the plug-in outer circle of the lower part of the upper positioning body 2.5 and can be inserted with the fixing pin 2.6; the plug-in outer circle of the lower part of the upper positioning body 2.5 has a countersunk hole that is aligned with the normal direction of the guide bevel of the upper positioning body 2.5 in the circumferential direction; the plug-in outer circle of the lower part of the upper positioning body 2.5 is arranged below the guide bevel. The upper end of the upper positioning body 2.5 is a guide bevel, and the plug-in outer circle of the lower part also has 6 countersunk holes in the circumferential direction, of which one countersunk hole is aligned with the normal direction of the upper guide bevel in the circumferential direction. When the plug-in outer circle of the lower part of the upper positioning body 2.5 is inserted into the plug-in step of the inner circle of the upper end of the straightening body 2.7, the countersunk holes correspond to the through holes one by one, and can be inserted with the fixing pin 2.6 for fixing. When the upper positioning body 2.5, the straightening body 2.7 and the lower positioning body 2.11 are fixed by the fixing pin 2.6, the upper positioning body 2.5 or the lower positioning body 2.11 can be rotated 60° each time in the circumferential direction so that the through holes and countersunk holes in different orientations are aligned and installed, so that the angle between the normal of the guide inclined surface of the upper positioning body 2.5 and the normal of the guide inclined surface at the lower end of the lower positioning body 2.11 can be selectively adjusted to 0°, 60°, 120°, 180°, 240° or 300° to meet the requirements of casing window opening to different designed azimuths when side drilling different branch wellbores.

[0070] The setting directions of the slip teeth on the outer walls of the two groups of slips 1.8 in the oblique fixture 1 are perpendicular to each other, that is, if the slip teeth in the upper group of slips 1.8 are arranged horizontally, then the slip teeth in the lower group of slips 1.8 are arranged longitudinally, and vice versa. The oblique fixture 1 is mainly formed by the guide bevel 1.4, the cylinder sleeve 1.7 and the cylinder base 1.17 connected by threads. A piston 1.10 and a ball seat 1.15 are arranged between the cylinder sleeve 1.7 and the center tube 1.11. The upper outer circle of the center tube 1.11 is connected to the piston 1.10 by threads, and the ball seat 1.15 is inserted into the center tube 1.11. A limit step is provided on the lower outer circle of the ball seat 1.15, and a stop thread is designed on the lower outer circle of the center tube 1.11. A lock ring 1.14 is installed in the inner cavity at the upper end of the ball seat 1.15, and the lock ring 1.14 is sleeved on the stop thread outside the center tube 1.11. The upper part of the ball seat 1.15 is threadedly connected to the lock ring pressure cap 1.13, and the lock ring pressure cap 1.13 is a limit for the lock ring 1.14 to prevent retreat. The outside of the ball seat 1.15 is an inverted cone structure, and the upper outer circle of the inverted cone structure is provided with a rubber ring groove and a seal 1.6, which can form a seal with the inner wall of the cylinder sleeve 1.7, and the ball seat 1.15 can slide up and down in the cylinder sleeve 1.7. The lower part of the ball seat 1.15 is a hollow step insert structure, which is inserted into the center hole of the cylinder base 1.17 during assembly and can slide freely therein. The upper part of the inner hole of the lower insert of the ball seat 1.15 is a conical seat, which can cooperate with the pressure ball 1.16 and achieve sealing. At this time, the seal 1.6 at the bottom of the piston 1.10 and the seal 1.6 at the top of the ball seat 1.15, as well as the inner wall of the cylinder sleeve 1.7 and the outer wall of the center tube 1.11 form a pressure sealing chamber. A pressure transmission hole 1.12 is provided in the center tube 1.11 below the piston 1.10, which together form the sealing mechanism of the oblique fixer 1. The anchoring mechanism of the oblique fixer 1 is as follows: at least three square holes are opened on the circumference of the corresponding positions of the cylinder sleeve 1.7 and the upper conical surface of the piston 1.10, and the slips 1.8 can be placed. The inner wall of the slip 1.8 is an arc-shaped conical surface structure and cooperates with the conical body of the piston 1.10, and the two are fixed by the slip screw 1.9. At least three square holes are opened on the circumference of the corresponding positions of the cylinder sleeve 1.7 and the lower conical surface of the ball seat 1.15, and the slips 1.8 are also placed therein. The inner wall of the slip 1.8 is an arc-shaped conical surface structure and cooperates with the conical body of the ball seat 1.15, and the two are fixed by the slip screw 1.9. The outer surfaces of the upper and lower groups of slips 1.8 are respectively provided with slip teeth which are perpendicular to each other in the transverse or longitudinal direction. One group of slips 1.8 is anchored to the well wall to ensure the axial fixation of the oblique fixture 1, and the other group of slips 1.8 is anchored to the well wall to ensure the circumferential fixation of the oblique fixture 1, which is beneficial to the support stability during the casing window opening operation.The middle of the bevel guide 1.4 is a through-hole structure, and the lower inner cavity and outer wall are both double-step structures. The small-diameter step of the outer wall can be inserted into the through-hole of the piston 1.10 and sealed by the seal 1.6, which can limit the upward working stroke of the piston 1.10. The bevel reverse rod 1.5 is inserted into the through-hole of the bevel guide 1.4, and the lower outer circle step is designed with reverse threads. The front end of the reverse thread also has an outer circle step and can be inserted into the bevel guide 1.4 equipped with the seal 1.6 and squeezed tightly at the inner circle step of the bevel guide 1.4 to achieve sealing. The inner circle lower part of the bevel guide 1.4 is designed with reverse threads in the inner cavity above the seal 1.6, and the reverse threads can be connected with the reverse threads of the bevel reverse rod 1.5. A straightening ring carrying step is designed in the middle and upper part of the bevel rod 1.5, and a bevel straightening ring 1.2 is mounted on the outer side of the bevel rod 1.5 above the straightening ring carrying step. The bevel straightening ring 1.2 is fixed to the guide surface of the guide bevel body 1.4 by the bevel straightening pin 1.3, so as to ensure that the bevel rod 1.5 maintains a relatively centered state during the lowering process of the bevel fixture 1. The upper part of the bevel rod 1.5 is connected to the bevel upper joint 1.1 by a thread, and the upper inner cavity of the bevel upper joint 1.1 is provided with a drill pipe joint thread or an oil pipe thread, which can be connected to the drill string or the oil pipe string and send the bevel fixture 1 into the well.

[0071] The following takes sidetracking in a vertical wellbore, that is, in a vertical well casing, as an example to illustrate the use of the ultra-short radius window sidetracking directional tool for multi-branch wellbores.

[0072] A method for using a directional tool for opening a window with an ultra-short radius for sidetracking in multi-branch wells. The steps of using the method are as follows:

[0073] A. Set the oblique fixture 1 in the main wellbore 5, use the window milling cone to mill the casing to form the first window in the casing, and pull out the window drilling tool: First, use the drill string to connect the oblique fixture 1 to the designed position in the main wellbore 5, and adjust the normal azimuth of the guide inclined surface 1.4 in the oblique fixture 1 through the gyroscope after reaching the designed depth, so that it is consistent with the designed azimuth of the ultra-short radius wellbore track, and then pull out the gyroscope. Set the oblique fixture 1. Before setting, first put the pressure ball 1.16 from the drill string, and the pressure ball 1.16 falls on the conical seat in the middle and lower part of the ball seat 1.15 to seal the upper space. When hydraulic pressure is applied from the drill string, the pressure is transmitted through the pressure transmission hole 1.12 on the center tube 1.11 to the sealed chamber formed by the cylinder sleeve 1.7 and the seal 1.6 installed on the outer circle of the ball seat 1.15 and the outer circle of the piston 1.10. The pressure acts on the sealed section formed by the ball seat 1.15, the piston 1.10 and the pressure ball 1.16. First, the slip screw 1.9 is cut off, and the ball seat 1.15 drives the lock ring pressure cap 1.13 downward. The lock ring pressure cap 1.13 pushes the lock ring 1.14 downward on the stop thread of the center tube 1.11 and locks the center tube 1.11 to prevent it from retreating. At the same time, the slip screw 1.9 in the ball seat 1.15 is cut off, and the inverted cone structure of the ball seat 1.15 squeezes the slip 1.8 outward and bites into the inner wall of the casing to achieve support. The insert tube structure at the bottom of the ball seat 1.15 passes downward in the center hole of the cylinder base 1.17, which plays a role in straightening and centering on the one hand, and the stop step at the top of the insert tube of the ball seat 1.15 plays a limiting role on the other hand. At the same time, the hydraulic pressure acts on the sealing section formed by the two sets of seals 1.6 inside and outside the piston 1.10. First, the piston 1.10 cuts off the slip screw 1.9 and starts to move upward. The piston 1.10 drives the center tube 1.11 upward. The distance between the piston 1.10 and the ball seat 1.15 is limited by the stop thread and the lock ring 1.14 on the center tube 1.11. At the same time, the inverted cone structure of the piston 1.10 squeezes the slip 1.8 outward to bite into the inner wall of the casing to achieve support. The setting direction of the slip teeth on the outer surface of the upper and lower sets of slips 1.8 is designed to be horizontal or longitudinal respectively. After being anchored on the casing wall, it can ensure the axial fixation of the oblique fixer 1 and the circumferential fixation of the oblique fixer 1, which is beneficial to the support stability during the casing window opening operation. After the seal is fully anchored, the drill string is pressed down to verify the reliability of the seal. After the seal is successfully set, the hydraulic pressure in the drill string is released, the drill string is rotated forward, and the upper drill pipe drives the whipstock reverse rod 1.5 to rotate through the whipstock upper joint 1.1. The whipstock reverse rod 1.5 is released from the guide body 1.4 through the reverse thread at the bottom. The whipstock straightening ring 1.2 can ensure that the whipstock reverse rod 1.5 always rotates in the center, thereby improving the success rate of reverse. After the reverse is successfully reversed, the whipstock upper joint 1.1 and the whipstock reverse rod 1.5 are pulled out of the main wellbore 5, and the straightening ring on the upper part of the whipstock reverse rod 1.5 carries the steps to bring the whipstock straightening ring 1.2 out of the wellbore together.The window milling cone is lowered into the casing under the support and constraint of the guide inclined body 1.4, and the window is opened in the designed direction of the ultra-short radius wellbore, and then the window drilling tool is pulled out.

[0074] B. Lower the ultra-short radius horizontal drilling combination drill tool to side-drill the ultra-short radius horizontal branch wellbore 3, and pull out the drill tool after drilling: lower the ultra-short radius horizontal drilling combination drill tool, which includes a flexible drill bit + a flexible inclination stabilizer + a flexible drill pipe + a conversion joint + a conventional drill pipe from bottom to top, see the patent application number 202011588794.X "A flexible drill string and construction method for ultra-short radius horizontal drilling". When the combination drill tool reaches the window position of the casing, slowly lower the drill tool, and after the flexible drill bit touches the inclined surface of the guide deflector 1.4, lightly apply drilling pressure, and the inclined surface of the guide deflector 1.4 applies a lateral reaction force to the flexible drill bit, which is the same as the design orientation of the ultra-short radius wellbore track, forcing the flexible drill bit to bend laterally, with the bending direction facing the design orientation of the ultra-short radius wellbore track, start drilling and complete the ultra-short radius horizontal branch wellbore 3, and pull out the ultra-short radius horizontal drilling combination drill tool.

[0075] C. According to the azimuth angle of the wellbore between the ultra-short radius horizontal branch wellbore 1 3 and the ultra-short radius horizontal branch wellbore 2 4, adjust the normal angle of the guide slope between the lower positioning body 2.11 and the upper positioning body 2.5 in the recoverable positioner 2;

[0076] D. Lower the recyclable locator 2 so that the lower locator 2.11 is stacked on the guide bevel 1.4 of the oblique fixture 1, and the casing is milled by means of a window milling cone to form a second window in the casing, or the next window in a different target layer or the same target layer is formed in the casing according to the steps described in C and D above, and the window drilling tool is pulled out;

[0077] E. According to the construction design, side-drill the ultra-short radius horizontal branch wellbore 24 in different target layers or side-drill the ultra-short radius horizontal branch wellbore 24 in the same target layer: lower the ultra-short radius horizontal drilling assembly drilling tool, side-drill the ultra-short radius horizontal branch wellbore 24 and the next ultra-short radius horizontal branch wellbore, and pull out the drilling tool after drilling is completed.

[0078] Taking the azimuth angle of 180° of ultra-short radius horizontal branch wellbore 1 and ultra-short radius horizontal branch wellbore 2 as an example, the drilling process of ultra-short radius horizontal branch wellbore 2 4 is described. First, when assembling the recoverable locator 2, adjust the normal direction of the guide bevel surface in the lower positioning body 2.11 and the upper positioning body 2.5 so that the normal direction angle between the two is 0°, and fix them by the fixing pin 2.6. Use the drill pipe to connect the upper joint 2.1 of the locator, lower the recoverable locator 2 into the casing in the well, and fit the guide bevel surface of the lower positioning body 2.11 and the guide bevel surface of the guide bevel body 1.4 in the inclined fixture 1 left in the well together, that is, the normal direction angle of the two bevel surfaces is 180°. At this time, the normal direction of the guide bevel surface of the upper positioning body 2.5 also forms an angle of 180° with the normal direction of the guide bevel surface of the guide bevel body 1.4. The flat head structure at the lower end of the guide bevel surface at the lower part of the lower positioning body 2.11 prevents the self-locking caused by wedging between the guide bevel surface of the guide bevel body 1.4 and the wellbore, which may cause difficulties in the later salvage. The straightening block 2.9 arranged on the straightening body 2.7 is tightened outward by the spring 2.10, and is higher than the outer surface of the straightening body 2.7. Its maximum outer diameter is larger than the inner wall of the casing, and it can be supported on the inner wall of the casing to play a role in straightening and centering. After appropriately pressing down the drill string to bottom out and confirming that the recoverable locator 2 is in place, the drill string is rotated forward, and the upper drill pipe drives the locator reverse rod 2.2 to rotate through the upper joint 2.1 of the locator. The locator reverse rod 2.2 is released from the upper positioning body 2.5 through the reverse thread at the bottom. The locator straightening ring 2.3 can ensure that the locator reverse rod 2.2 always rotates in the center, thereby improving the success rate of reverse threading. After the reverse buckling is successful, the upper joint 2.1 of the positioner and the reverse buckling rod 2.2 of the positioner are pulled out of the wellbore, and the righting ring on the upper part of the reverse buckling rod 2.2 of the positioner carries the step to bring the righting ring 2.3 of the positioner out of the wellbore together.

[0079] The window milling cone is lowered, and the casing is milled and the window is opened under the support and constraint of the upper positioning body 2.5. Since the normal direction of the guide bevel of the upper positioning body 2.5 is opposite to the normal direction of the guide bevel body 1.4, the window opening direction at this time forms an angle of 180° with the direction of the ultra-short radius horizontal branch wellbore 13. After the window opening is completed, the window opening drilling tool is pulled out. The ultra-short radius horizontal drilling assembly drilling tool is lowered to start drilling. After the ultra-short radius horizontal branch wellbore 24 is completed, the ultra-short radius horizontal drilling assembly drilling tool is pulled out. The longitudinal distance between the windows of the ultra-short radius horizontal branch wellbore 13 and the ultra-short radius horizontal branch wellbore 24 can be achieved by adjusting the length of the centralizing body 2.7, or by installing different numbers of centralizing bodies 2.7. The azimuth angle between the ultra-short radius horizontal branch wellbore 13 and the ultra-short radius horizontal branch wellbore 24 can be achieved by adjusting the normal angle of the guide bevel between the upper positioning body 2.5 and the lower positioning body 2.11.

[0080] F. Flexible screens are run into the main wellbore 5 and the ultra-short radius horizontal branch wellbore 3 located at the lowest layer to implement sand control completion.

[0081] The method for side drilling the ultra-short radius horizontal branch wellbore 24 in different target layers is that after the window milling of the ultra-short radius horizontal branch wellbore 24 is completed, the ultra-short radius horizontal drilling combination drilling tool that is lowered starts to drill inclination just after exiting the window, completes the inclination section with a curvature radius of 3-5 meters, and continues to drill when the well inclination reaches 90° to form the ultra-short radius horizontal branch wellbore 24. The specific construction method is as follows: After the casing window milling required for the ultra-short radius horizontal branch wellbore 24 is completed, the ultra-short radius horizontal drilling combination drilling tool is lowered, which includes a flexible drill bit + a flexible inclination stabilizer + a flexible drill pipe + a conversion joint + a conventional drill pipe from bottom to top. When the combination drilling tool reaches the window position, the drilling tool is slowly lowered, and after the flexible drill bit touches the guide inclined surface of the upper positioning body 2.5, the drilling pressure is lightly applied to force the flexible drill bit to bend toward the designed orientation of the ultra-short radius wellbore track, and drilling begins. That is, the inclination section is completed with a curvature radius of 3-5 meters just after the window is opened, and when the well inclination reaches 90°, drilling continues to form a horizontal branch wellbore. The longitudinal distance between the ultra-short radius horizontal branch wellbore 1 3 and the ultra-short radius horizontal branch wellbore 2 4 formed in this way is equal to the longitudinal distance between the two windows, and target layers of different depths can be mined.

[0082] The method for side drilling an ultra-short radius horizontal branch wellbore 24 in the same target layer is as follows: after the first side drilling window is completed, the ultra-short radius horizontal drilling assembly drill bit is lowered, and the flexible drill bit starts to complete the deflection section with a curvature radius of 3-5 meters as soon as it exits the window, and continues to drill when the well inclination reaches 90 degrees to form an ultra-short radius horizontal branch wellbore 24; after the second side drilling window is completed, the window milling cone is continued to be used for drilling and a stable inclination well section with a longitudinal length equal to the longitudinal distance between the two windows is formed, and then the window milling cone is removed, and the ultra-short radius horizontal drilling assembly drill bit is lowered again, and after reaching the bottom of the stable inclination well section, the deflection section is started with a curvature radius of 3-5 meters, and when the well inclination reaches 90 degrees, the drilling is continued to form an ultra-short radius horizontal branch wellbore 24. The ultra-short radius horizontal branch wellbore 1 3 and the ultra-short radius horizontal branch wellbore 2 4 can also exploit the same target layer, as described above: after the first window is completed, the ultra-short radius horizontal drilling combination drilling tool is lowered, and the deflection section is completed with a curvature radius of 3-5 meters as soon as the window is exited. When the well inclination reaches 90°, drilling continues to form the ultra-short radius horizontal branch wellbore 1 3. After the second side drilling window is completed, the window milling cone is continued to be used to drill and form a certain length of stable inclination well section, the longitudinal length of which is equal to the longitudinal distance between the two windows, and then the window milling cone is pulled out, and the ultra-short radius horizontal drilling combination drilling tool is lowered. When the bottom of the stable inclination well section is reached, the deflection section is completed with a curvature radius of 3-5 meters. When the well inclination reaches 90°, drilling continues to form the ultra-short radius horizontal branch wellbore 2 4. The ultra-short radius horizontal branch wellbore 1 3 and the ultra-short radius horizontal branch wellbore 2 4 formed in this way are at the same depth, and the same target layer can be exploited in different directions.

[0083] By analogy, one or more sets of recoverable locators 2 can be lowered again, and the window side drilling can be formed into ultra-short radius horizontal branch wellbores with different azimuths and different depths that can be used for different target layers or the same target layer. After drilling all branch wellbores, the salvage tool is lowered and connected to the salvage thread of the upper positioning body 2.5 in the recoverable locator 2. The recoverable locator 2 can be separated from the oblique fixture 1 by lifting it up and salvaged out of the wellbore. All recoverable locators 2 are salvaged in turn, leaving only the bottom oblique fixture 1 in the main wellbore 5. Then the flexible sand control screen is lowered. Under the guidance of the oblique fixture 1 at the bottom, the flexible sand control screen can be smoothly lowered into the ultra-short radius horizontal branch wellbore 3. The upper sand control screen is suspended in the main wellbore 5 through the tail pipe hanger, and the tail pipe hanger is located above the top branch wellbore, so as to achieve the sand control completion of the main wellbore 5 and the first branch wellbore, that is, the ultra-short radius horizontal branch wellbore 3 in the figure.

[0084] The embodiments described above are only typical embodiments, but the present invention is not limited to these embodiments, and those skilled in the art can make modifications without departing from the spirit and enlightenment of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the creative spirit and creative concept of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope is not limited to the above description.

Claims

1. A multi-branch wellbore ultra-short radius window sidetracking directional tool, comprising an oblique fixture (1), the oblique fixture (1) being provided with an oblique guide body (1.4), an inverted rod (1.5) of the whipstock and a slip (1.8), wherein: The whipstock inverted rod (1.5) is inserted into the through hole of the guide body (1.4); the outer circular step at the lower part is designed with an inverted thread; the front end of the inverted thread also has an outer circular step and can be inserted into the guide body (1.4) equipped with a seal (1.6) and squeezed tightly at the inner circular step of the guide body (1.4) to achieve sealing; the inner circular lower part of the guide body (1.4) is designed with an inverted thread in the inner cavity above the seal (1.6); the inverted thread can be connected with the inverted thread of the whipstock inverted rod (1.5); the upper part of the whipstock inverted rod (1.5) is designed with a straightening ring carrying step; the outer surface of the whipstock inverted rod (1.5) above the straightening ring carrying step is sleeved with a whipstock straightening ring (1.2); when the whipstock inverted rod (1.5) and the whipstock straightening ring (1.2) in the whipstock fixer (1) are lifted to the well, the whipstock inverted rod (1.5) and the whipstock straightening ring (1.2) are inserted into the well; the whipstock inverted rod (1.5) and the whipstock straightening ring (1.2) in the whipstock fixer (1) are lifted to the well; the whipstock inverted rod (1.5) and the whipstock straightening ring (1.2) in the well are lifted to the well; the whipstock inverted rod (1.5) and the whipstock straightening ring (1.2) in the well are sleeved with a straightening ring carrying step; when the whipstock inverted rod (1.5) and the whipstock straightening ring (1.2) in the well are lifted to the well, the whipstock inverted rod (1.5) and the whipstock straightening ring (1.2) in the well are sleeved with a straightening ring carrying step; when the whipstock inverted rod (1.5) and the whipstock straightening ring (1.2) in the well are lifted to After the guide is placed outside the well, the guide bevel surface of the guide bevel body (1.4) can be stacked with the recoverable positioner (2) that is about to enter the well, wherein: the recoverable positioner (2) is mainly composed of an upper positioning body (2.5), a straightening body (2.7) and a lower positioning body (2.11), the upper positioning body (2.5) and the lower positioning body (2.11) are both provided with guide bevel surfaces, and the angle of the lower guide bevel surface of the lower positioning body (2.11) is the same as the angle of the guide bevel surface of the guide bevel body (1.4) in the oblique fixer (1); the straightening body (2.7) is provided with a straightening block (2.9), the upper positioning body (2.5) is connected to the straightening body (2.7) and the lower positioning body (2.11) through a fixing pin (2.6), and the upper positioning body (2.5) is provided with a fishing thread; the upper positioning body (2.5) is connected to the positioner inverted rod (2.2) and the positioner upper joint (2.1) in sequence.

2. The ultra-short radius window sidetracking directional tool for multi-branch wells according to claim 1, characterized in that: The straightening body (2.7) is provided with a straightening block installation groove in the circumferential direction and at least one group of straightening blocks (2.9) is installed in the circumferential direction. The straightening block (2.9) is provided with a spring installation hole in the block body and is equipped with a spring (2.10). The two side wings of the straightening block (2.9) are buckled under a pressing sheet or a pressing sleeve (2.8). The pressing sheet or the pressing sleeve (2.8) is fixed in the straightening body (2.7) by a fixing pin (2.6).

3. The ultra-short radius window sidetracking directional tool for multi-branch wells according to claim 2, characterized in that: The manufacturing length of the centralizing body (2.7) or the number of the centralizing bodies (2.7) connected to the retrievable positioner (2) can be adjusted according to the axial distance between the ultra-short radius horizontal branch wellbore 1 (3) and the ultra-short radius horizontal branch wellbore 2 (4).

4. The ultra-short radius window sidetracking directional tool for multi-branch wells as claimed in claim 3, characterized in that: The installation orientation between the guide bevel surface of the upper positioning body (2.5) and the guide bevel surface of the lower positioning body (2.11) in the recoverable positioning device (2) is consistent with the azimuth angle of the wellbore trajectory of the side-drilling branch well and can be stacked in the main wellbore (5), and the angle of the guide bevel surface in the upper positioning body (2.5) in the recoverable positioning device (2) located below is the same as the angle of the guide bevel surface in the lower positioning body (2.11) in another recoverable positioning device (2) stacked thereon; the oblique fixture (1) is retained in the main wellbore (5) below the window opening window of the ultra-short radius horizontal branch wellbore (3).

5. The ultra-short radius window sidetracking directional tool for multi-branch wells according to claim 1, characterized in that: The upper end of the positioner inverted rod (2.2) is threadedly connected to the positioner upper joint (2.1); the lower end of the positioner inverted rod (2.2) is provided with an inverted thread and can be connected with the inverted thread of the inner circle of the lower end of the upper positioning body (2.5); a salvage thread is provided above the inner circle step in the middle of the upper positioning body (2.5); the lower outer circle of the positioner inverted rod (2.2) is provided with an inverted thread, and the positioner inverted rod (2.2) is inserted into the inner circle step at the lower part of the upper positioning body (2.5) and connected together through the inverted thread.

6. The ultra-short radius window sidetracking directional tool for multi-branch wells as claimed in claim 5, characterized in that: The upper outer circle of the positioner inverted rod (2.2) is also provided with a straightening ring carrying step, and the positioner straightening ring (2.3) is installed on the outside of the positioner inverted rod (2.2) above the straightening ring carrying step and is fixed together with the guide bevel of the upper positioning body (2.5) through the positioner straightening screw (2.4); the upper part of the positioner inverted rod (2.2) is threadedly connected to the positioner upper joint (2.1), and the upper inner cavity of the positioner upper joint (2.1) is provided with a drill pipe joint thread or an oil pipe thread.

7. The ultra-short radius window sidetracking directional tool for multi-branch wells according to claim 4, characterized in that: The lower positioning body (2.11) is provided with a center hole and an upper inner circle is provided with an insertion step, six through holes are evenly opened in the circumference of the insertion step body and one of the through holes is aligned with the normal direction of the lower guide bevel in the circumferential direction, and the lower end of the guide bevel in the lower positioning body (2.11) is a plane.

8. The ultra-short radius window sidetracking directional tool for multi-branch wells according to claim 7, characterized in that: The outer circle of the lower end of the centralizing body (2.7) is a plug-in outer circle, and six countersunk holes are opened on the circumference of the plug-in outer circle corresponding to the six through holes in the lower positioning body (2.11), and the fixing pin (2.6) can be inserted into the through holes of the lower positioning body (2.11) and the countersunk holes in the centralizing body (2.7); when the plug-in outer circle of the centralizing body (2.7) is inserted into the plug-in step of the lower positioning body (2.11), the countersunk holes correspond to the through holes one by one, and the lower positioning body (2.11) and the centralizing body (2.7) are fixedly connected by the fixing pin (2.6). The main body (2.7) is fixed; the upper inner circle of the centralizing body (2.7) is also provided with an insertion step, and 6 through holes are evenly opened in the circumference of the insertion step and correspond one by one to the countersunk holes in the insertion outer circle of the lower part of the upper positioning body (2.5) and can be inserted with a fixing pin (2.6); the insertion outer circle of the lower part of the upper positioning body (2.5) has a countersunk hole that is aligned with the normal direction of the guide inclined surface of the upper positioning body (2.5) in the circumferential direction; the insertion outer circle of the lower part of the upper positioning body (2.5) is arranged below the guide inclined surface.

9. The ultra-short radius window sidetracking directional tool for multi-branch wells according to claim 1, characterized in that: The arrangement directions of the slip teeth on the outer walls of the two groups of slips (1.8) in the oblique fixer (1) are perpendicular to each other.

10. A method for using the ultra-short radius window sidetracking directional tool for multi-branch wells as claimed in any one of claims 1 to 9, characterized in that: The method is used in the following steps: A. setting an inclined fixture (1) in a main wellbore (5), using a window milling cone to mill the casing to form a first window in the casing, and pulling out the window drilling tool; B. lowering an ultra-short radius horizontal drilling assembly drilling tool to side-drill an ultra-short radius horizontal branch wellbore 1 (3), and pulling out the drilling tool after drilling is completed; C. adjusting the normal angle of the guide inclined surface between the lower positioning body (2.11) and the upper positioning body (2.5) of the recoverable positioning device (2) according to the azimuth angle of the wellbore between the ultra-short radius horizontal branch wellbore 1 (3) and the ultra-short radius horizontal branch wellbore 2 (4); D. lowering the recoverable positioning device (2) so that The lower positioning body (2.11) is stacked on the guide body (1.4) of the inclined fixture (1), and the casing is milled by means of a window milling cone to form a second window in the casing, or the next window in a different target layer or the same target layer is continuously formed in the casing according to the steps described in C and D above, and the window drilling tool is removed; E. According to the construction design, the second ultra-short radius horizontal branch wellbore (4) in a different target layer is side-drilled, or the second ultra-short radius horizontal branch wellbore (4) in the same target layer is side-drilled; F. A flexible screen is lowered into the main wellbore (5) and the first ultra-short radius horizontal branch wellbore (3) located in the lowest layer to implement sand control completion.

11. The method for using the ultra-short radius window sidetracking directional tool for multi-branch wells according to claim 10, characterized in that: The method for side drilling the ultra-short radius horizontal branch wellbore 2 (4) in different target layers is as follows: after the window milling of the ultra-short radius horizontal branch wellbore 2 (4) is completed, the ultra-short radius horizontal drilling assembly drill tool that is lowered starts to drill inclination as soon as it exits the window, completes the inclination section with a curvature radius of 3-5 meters, and continues drilling when the well inclination reaches 90° to form the ultra-short radius horizontal branch wellbore 2 (4).

12. The method for using the ultra-short radius window sidetracking directional tool for multi-branch wells according to claim 10, characterized in that: The method for side drilling an ultra-short radius horizontal branch wellbore 2 (4) in the same target layer is as follows: after the first side drilling window is completed, the ultra-short radius horizontal drilling assembly drill bit is lowered, and the flexible drill bit starts to complete the deflection section with a curvature radius of 3-5 meters as soon as it exits the window. When the well inclination reaches 90°, drilling is continued to form an ultra-short radius horizontal branch wellbore 1 (3); after the second side drilling window is completed, the window milling cone is continued to be used for drilling and a stable inclination well section with a longitudinal length equal to the longitudinal distance between the two windows is formed, and then the window milling cone is removed, and the ultra-short radius horizontal drilling assembly drill bit is lowered again. After reaching the bottom of the stable inclination well section, the deflection section is completed with a curvature radius of 3-5 meters. When the well inclination reaches 90°, drilling is continued to form an ultra-short radius horizontal branch wellbore 2 (4).

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