CN115596352A - Flexible drilling tool system for radial drilling of ultra-deep well and sidetracking process - Google Patents

Abstract

The invention provides a flexible drilling tool system for radial drilling of an ultra-deep well, which comprises: the drill rod is connected with a wellhead turntable arranged on a wellhead; the drilling device is connected to the lower end of the drill rod, and the drilling end of the drilling device is connected with a lower drilling tool; a flexible drilling tool module connected between the drilling apparatus and the lower drilling tool; wherein the flexible drilling tool module has an initial deflection angle, the flexible drilling tool module is configured to enable the flexible drilling tool system to rotate the well track from vertical to horizontal within a preset vertical distance range, the drill rod is driven to rotate through the wellhead turntable, and the flexible drilling tool module can rotate with the wellhead turntable through the drill rod so as to drive the lower drilling tool to perform operation. The invention also provides a sidetracking process for radial drilling of the ultra-deep well.

Description

Flexible drilling tool system for radial drilling of ultra-deep well and sidetracking process

Technical Field

The invention belongs to the technical field of oil exploitation, and particularly relates to a flexible drilling tool system for radial drilling of an ultra-deep well. The invention also relates to a sidetracking process for radial drilling of the ultra-deep well.

Background

A large number of seam holes are formed around a near wellbore of a tower river carbonate reservoir, all-dimensional communication needs to be achieved through a radial hydraulic jet drilling completion technology, and the reserve utilization degree is greatly improved.

At present, the conventional sidetracking process has the problems of high cost, long period and large sag. The cost of single open hole side drilling is estimated at 900 ten thousand yuan, and the cost of single casing side drilling is estimated at 1800 ten thousand yuan. The construction period is 1-2 months. Because the maximum build-up rate is 30 m/30 degrees in the prior art, the vertical distance of the sidetrack drilling is generally more than 90m, and the ultra-short radius radial sidetrack drilling cannot be realized. The main problems are that the conventional short-radius sidetracking tool aims at a small size of a borehole of a Tahe oil field, the mechanical drilling speed is low, the curvature of the oil field is large, the passing capacity of a pipe column is limited, the track control difficulty is large, and the problem of magnetic interference in casing windowing is prominent. This results in a smaller reservoir size that can be communicated with, and a lower probability of the radial drill encountering a fracture hole, thereby making production inefficient.

The existing flexible drilling tool mainly comprises a guide cylinder with a tubular elastic bent shell and a flexible drill rod with a rolling bearing. Although the flexible drilling tool can realize the deflecting and horizontal borehole drilling of a production zone under the condition of high pressure and increase the exposed surface of the production zone to the maximum extent, the conventional flexible drilling tool is easy to leak under the condition of high pressure underground, so that the flexible drilling rod is damaged too early, and the service life of the flexible drilling tool is short. In addition, the conventional flexible drilling tool can achieve a larger vertical distance, and if the drilling of a horizontal borehole with a shorter radius is to be achieved, the conventional flexible drill rod unit is shorter in length and more in number, so that the failure rate of the flexible drilling tool is higher.

Disclosure of Invention

In view of the technical problems, the invention aims to provide a flexible drilling tool system for radial drilling of an ultra-deep well, which can rotate a well track from vertical to horizontal within a vertical distance of 3m and can ensure reliable sealing performance.

The invention also provides a sidetracking process for radial drilling of the ultra-deep well.

To this end, according to a first aspect of the present invention, there is provided a flexible drilling system for radial drilling of ultra-deep wells, comprising: the drill rod is connected with a wellhead turntable arranged on a wellhead; the drilling device is connected to the lower end of the drill rod, and the drilling end of the drilling device is connected with a lower drilling tool; a flexible drilling tool module connected between the drilling apparatus and the lower drilling tool; the flexible drilling tool module has an initial deflection angle, the flexible drilling tool module is configured to enable the flexible drilling tool system to rotate a borehole trajectory from vertical to horizontal within a preset vertical distance range, the drill rod is driven to rotate through the wellhead turntable, and the flexible drilling tool module can rotate with the wellhead turntable through the drill rod so as to drive the lower drilling tool to perform operation.

In one embodiment, the predetermined sag of the flexible drill module is no greater than 3m.

In one embodiment, the initial deflection angle of the flexible drill module is in the range of 1-5 °.

In one embodiment, the flexible drill module comprises: the flexible drill module comprises: a housing; a rotating element connected to a lower end of the housing, the rotating element being rotatable to provide an angle of drilling whiplash; and the limiting element is installed in the shell and is connected with the rotating element through a key slot, the limiting element is used for limiting the rotating range of the rotating element so as to transmit the torque when the wellhead turntable rotates, the first end of the rotating element is constructed into a spherical shape, the second end of the rotating element is constructed into a connecting buckle, a spherical surface is formed in the shell, and the rotating element is matched with the spherical surface through the spherical shape, so that the rotating element and the shell form a hinge structure.

In one embodiment, a connection joint is fixedly connected to the upper end of the housing, the lower end of the connection joint extends into the housing, the position limiting element is fixedly connected to the lower end of the connection joint, and a sealing element is arranged between the position limiting element and the housing.

In one embodiment, a safety reinforcing element for preventing the rotating element from falling off is further provided between the rotating element and the housing.

In one embodiment, the drilling device comprises a safety joint, the flexible drill module is fixedly connected with the safety joint through the connecting joint, the connecting joint is connected with the safety joint in a threaded connection mode, and the connecting thread of the rotating element is connected with the lower drill in a threaded connection mode.

In one embodiment, the lower drill is a drill bit or a milling or fishing male cone.

According to a second aspect of the present invention, there is provided a sidetracking process for radial drilling of ultra-deep wells, comprising the steps of:

providing a flexible drilling tool system as described above;

drift diameter gauges are adopted for drifting;

a whipstock is put into a preset position in the shaft and is hung in a sitting mode;

a drilling tool at the lower part of the flexible drilling tool system adopts a windowing milling cone, and a window is formed by windowing the casing pipe through the flexible drilling tool system;

replacing a drilling tool at the lower part of the flexible drilling tool system with a deflecting drill bit, and lowering the flexible drilling tool system to the window position for deflecting operation;

changing a drilling tool at the lower part of the flexible drilling tool system into a drilling bit, lowering the flexible drilling tool system and carrying out horizontal drilling operation through the window until the radial drilling operation is finished;

and recovering the whipstock.

In one embodiment, the casing is cleaned by a pipe scraper in a position corresponding to the whipstock setting position before running the whipstock, and the wellbore is kept full of drilling fluid after cleaning.

Compared with the prior art, the application has the advantages that:

the flexible drilling tool system can realize that the well track is horizontally changed from vertical to vertical within the range of vertical distance of 3m, compared with the vertical distance of 90m of the existing flexible drilling tool, the size of the lateral drilling vertical distance is greatly reduced, so that the reservoir scale capable of being communicated can be greatly increased, the probability of the radial drilling to meet the fracture hole is obviously improved, the production efficiency is greatly improved, and the operation cost is reduced. Meanwhile, in the drilling construction process, the flexible drilling tool system has certain sealing performance. In addition, the flexible drilling tool system still has reliable sealing performance and working performance under the action of a certain pressure difference between the inside and the outside of the drilling tool. The flexible drilling tool system has no special requirements on operation parameters and supporting equipment, and has good adaptability.

Drawings

The invention will now be described with reference to the accompanying drawings.

Fig. 1 shows the structure of a flexible drilling system for radial drilling of ultra-deep wells according to the present invention.

Fig. 2 shows the structure of a flexible drill module in the flexible drill system according to the present invention.

In the present application, the drawings are all schematic and are used only for illustrating the principles of the invention and are not drawn to scale.

Detailed Description

The invention is described below with reference to the accompanying drawings.

In this application, it is to be noted that the end of the flexible drilling system for radial drilling of ultra-deep wells according to the present invention, which is close to the wellhead when being lowered into the wellbore, is defined as the upper end or the like, and the end away from the wellhead is defined as the lower end or the like.

Fig. 1 shows the structure of a flexible drilling system 100 for radial drilling of ultra-deep wells according to the present invention. As shown in fig. 1, the flexible drilling system 100 comprises a casing 1 arranged in a wellbore, a drill rod 2, a wellhead carousel (not shown) arranged at the wellhead, a drilling device 3, a lower drilling tool 6 arranged at the lower end of the drilling device 3, and a flexible drilling tool module 5 connected between the drilling device 3 and the lower drilling tool 6. The upper end of the drill rod 2 is connected with the wellhead turntable, and the lower end of the drill rod 2 is connected with the upper end of the drilling device 3. The flexible drilling module 5 has an initial deflection angle, and the flexible drilling module 5 is configured to enable the flexible drilling system 100 to turn the borehole trajectory from vertical to horizontal within a predetermined range of vertical. In the actual work progress, drive drilling rod 2 rotatory through the well head carousel, flexible drilling tool module 5 can be rotatory along with the well head carousel through drilling rod 2 to drive lower part drilling tool 6 and carry out corresponding construction operation.

Fig. 2 shows the structure of a flexible drill module 5 according to the present invention. As shown in fig. 2, the flexible drill module 5 includes a housing 9, a connection joint 8 fixedly connected to an upper end of the housing 9, a rotation member 13 connected to a lower end of the housing 9, and a stopper member 11 installed in the housing 9. The lower end portion of the connection joint 8 extends axially inward to the inside of the housing 9 and forms a fixed connection with the housing 9 by means of a thread. The flexible drill modules 5 are connected to upper parts by means of connection joints 8, and when a plurality of flexible drill modules 5 are connected, the connection joints 8 are used to connect connection buckles (see below) of the second section of the rotary element 13 in the upper level of flexible drill modules 5, so as to achieve connection between the plurality of flexible drill modules 5.

As shown in fig. 2, a limiting element 11 is fixedly connected to the lower end of the connecting nipple 8. Limiting element 11 is located at the axial upper end of rotating element 13, and forms the cooperation with rotating element 13 through the keyway contact and be connected, and limiting element 11 is used for limiting rotating element 13's rotation range to the moment of torsion transmission when guaranteeing the wellhead carousel and rotate.

According to the invention, the first end of the rotating element 13 is configured as a ball and the second end as a connecting link. The inner wall of the housing 9 is formed with a spherical surface, and the rotating element 13 can be matched with the spherical surface through a spherical structure, so that the rotating element 13 and the housing 9 form a hinge structure, and the rotating element 13 can rotate within a certain angle range, thereby providing the angle of drilling deflecting.

In order to ensure the tightness of the flexible drill module 5, a sealing element 10 is provided between the limiting element 11 and the housing 9. Preferably, the seal 10 is a high temperature resistant rubber seal. Meanwhile, in the construction process, a sealing element 10 is arranged between the shell 9 and the limiting element 11, a sealing ring 12 is arranged between the shell 9 and the rotating element 13, the sealing performance of the drilling tool in the moving process is guaranteed, and the shell 9 and the rotating element 13 are tightly matched and can bear the pressure difference not exceeding 15 MPa. This provides a seal for the flexible drilling system 100 as a whole. Reliable operation performance can be ensured even if a certain pressure difference exists between the inside and the outside of the flexible drilling tool system 100.

According to the invention, a safety reinforcement element 14 for preventing the rotating element 13 from falling off is also provided between the rotating element 13 and the housing 9, as shown in fig. 2. In one embodiment, the safety reinforcing member 14 is a pin, and a circumferentially extending annular pin groove having an axial width larger than a diameter of the pin is provided on an outer wall surface of the rotating member 13. The safety reinforcement element 14 effectively prevents the flexible drill module 5 from disengaging when the drill is rotated.

As shown in fig. 1, the drilling apparatus 3 includes a jar 31 and a safety joint 32 fixedly coupled to a lower end of the jar 31. The upper end of the jar 31 is connected with the lower end of the drill rod 2, and the flexible drilling tool module 5 is fixedly connected with the safety joint 32 through the connecting joint 8.

According to the invention, in one embodiment the connection sub 8 is screwed into a fixed connection with the safety sub 32, and the connection sub at the second end of the swivel element 13 is screwed into a fixed connection with the lower drilling tool 6. Meanwhile, the upper end of the safety joint 32 is connected with the jar 31 by adopting a thread mode. The adoption of the threaded connection mode enables the flexible drilling tool system 100 to be conveniently and quickly disassembled and assembled, and is beneficial to improving the disassembling and assembling efficiency of tools.

According to the invention, the flexible drill module 5 is itself provided with a certain deflection angle. The initial deflection angle of the flexible drill module 5 is in the range of 1-5 deg.. Thereby, the flexible drill module 5 may achieve a deflection angle of 1-5 °. In practice, the deflection angle that the flexible drilling system 100 can achieve by means of the flexible drilling module 5 is in the range of 30-90 °. In the actual construction process, after a plurality of flexible drilling tool modules 5 are sequentially combined and connected together, the track can be changed from vertical to horizontal under the condition of the vertical distance of 3m. Different initial deflection angles are achieved by adjusting the length (number) of the flexible drill modules 5 and the stop elements 11. Thus, the deflection angle of the flexible drilling tool system 100 is realized by adjusting the number of the components of the flexible drilling tool modules 5.

According to some embodiments of the present invention, the lower drilling tool 6 may be a drilling tool such as a drill bit, mill shoe, milling cone, or fishing cone. For example, when the lower drilling tool 6 is connected as a whipstock drill bit, the flexible drilling tool system 100 is assembled to form a directional whipstock assembly and a corresponding whipstock operation may be performed. When the lower drilling tool 6 is connected as a drilling bit, the flexible drilling tool system 100 is assembled to form a horizontal drilling tool assembly for performing a corresponding horizontal drilling operation. When the lower drilling tool 6 is connected as a windowing milling cone, the flexible drilling tool system 100 is assembled to form a windowing drilling tool assembly, and windowing operation can be performed on the casing 1. When the lower drilling tool 6 is connected as a fishing male cone, the flexible drilling tool system 100 is assembled to form a fishing drilling tool assembly, which can perform fishing operation on the fish falling in the well. In practical applications, the flexible drilling tool system 100 can be adapted to various drilling tool combinations according to different operation mode requirements, thereby satisfying various operation requirements.

According to the present invention, the predetermined sag of the flexible drill module 5 is not more than 3m. The flexible drilling tool system 100 can realize the conversion of the borehole track from vertical to horizontal under the condition that the vertical distance is within 3m through the flexible drilling tool module 5. Compared with the vertical distance of 90m of the existing flexible drilling tool, the vertical distance of the sidetracking drilling tool is greatly reduced, the flexible drilling tool system 100 greatly increases the scale of communicable reservoirs, obviously improves the probability of the radial drilling encountering a seam hole, and is very beneficial to improving the production efficiency and reducing the operation cost.

In use of the flexible drilling tool system 100 according to the present invention, the flexible drilling tool module 5 is connected between the drilling apparatus 3 and the lower drilling tool 6, and is run into the well with the drilling tool. After the drilling tool enters the well, the pump is started to circulate the slurry, and the well mouth turntable drives the drill rod 2 to rotate so as to provide rock breaking power. The flexible drilling tool module 5 synchronously rotates along with the wellhead turntable through the drill rod 2, and then drives the lower drilling tool 6 to perform corresponding construction operation. For example, driving a drill bit to break rock to achieve drilling purposes, driving a shoe mill to open a window to achieve fishing of fish falling downhole, and the like.

The flexible drill system 100 according to the present invention will be further described with the example of the lower drill 6 being a fishing male cone, with the flexible drill system 100 assembled as a fishing drill assembly for fishing fish from downhole drops. First, the fishing male cone is adopted as the lower drilling tool 6, and the fishing male cone is connected to the lower end of the flexible drilling tool module 5 in a threaded connection mode, so that the fishing drilling tool assembly is assembled. And then, the flexible drilling tool system 100 is put into a shaft, the pump is started to circulate slurry, and the drill rod 2 is driven to rotate through the wellhead turntable, so that rock breaking power is provided. The flexible drilling tool module 5 synchronously rotates along with the wellhead turntable through the drill rod 2, so that the fishing male cone is driven to rotate, and then the buckle is made, and therefore fishing operation of fish is achieved.

According to the invention, the sidetracking process for radial drilling of the ultra-deep well is also provided, and by using the flexible drilling tool system 100, the well track can be horizontally changed from vertical within the vertical distance of 3m, the size of the vertical distance of sidetracking can be greatly reduced, and the operation cost is obviously reduced. The specific construction steps of the sidetracking process are described in detail below.

First, a drift diameter gauge drift is used. In one embodiment, the drift is performed using a drift gauge model of phi 162 x 1.8m.

And after the drifting is finished, scraping and cleaning the position, corresponding to the whipstock hanging position, of the casing 1 by a pipe scraper. Specifically, a pipe scraper is adopted to repeatedly scrape pipes for 3 times within the range of 5m from top to bottom of the sitting and hanging position of the whipstock so as to ensure that the sitting and hanging position of the whipstock is regular and clean. And, after cleaning, the wellbore is kept full of drilling fluid to ensure that circulation can be established in the wellbore.

And then, descending the whipstock to a preset position in the shaft and sitting and hanging. The whipstock is oriented by a Measurement While Drilling (MWD) instrument in the sitting and hanging process, and the whipstock is separated from the hand after the orientation is finished, so that the sitting and hanging of the whipstock are finished.

And then, performing windowing and window repairing operation. The lower drilling tool 6 of the flexible drilling tool system 100 adopts a windowing milling cone, and the windowing milling cone, the flexible drilling tool module 5, a float valve joint (not shown), a safety joint 32, a jar 31 and a drill pipe 2 are assembled, so that a windowing drilling tool assembly is formed, and the casing 1 is windowed through the windowing drilling tool assembly. In one embodiment, the lower drill 6 is a window milling cone of type 158mm phi, the flexible drill module 55 is a 133mm flexible drill module, i.e., 310 button type, and the drill rod 2 is a 3-1/2 "drill rod. After the flexible drilling tool system 100 is assembled, when the flexible drilling tool system 100 is drilled down to the position 2m away from the top of the whipstock, the pump is started to circulate the drilling fluid, the drilling fluid is slowly drilled down to the whipstock, the position where the drilling fluid meets the resistance is recorded, and the windowing operation is started. Thereby, the casing 1 is windowed by the flexible drilling tool system 100, thereby forming a window in the sidewall of the casing 1.

In the embodiment, the initial bit pressure of the windowing operation is 1-2t, the bit pressure is gradually increased to 3-3t after the bit pressure is stable, the rotating speed is within the range of 30-60r/min, and the displacement is within the range of 500-600L/min.

And after the windowing operation is finished, performing deflecting operation. The lower drill 6 of the flexible drilling system 100 employs a deflecting drill and assembles the deflecting drill, the flexible drilling module 5, the float valve (not shown), the safety joint 32, the jar 31, and the drill rod 2 to form a deflecting drill assembly through which deflecting work is performed. In one embodiment, the lower drill 6 is a 152mm gauge whipstock drill bit and the flexible drill module 55 is a 120mm size flexible drill module, i.e., 310 button type. After the flexible drilling tool system 100 is assembled, the flexible drilling tool system 100 is lowered to the windowing depth, the drill bit is lowered to a range of 0.5-1m above the whipstock, the pump is started, the displacement is guaranteed to be in a range of 500-600L/min, and in the process, the flexible drilling tool system 100 is slowly lowered to pass through the window. The flexible drilling system 100 does not rotate the drilling tool during passage through the window to avoid damaging the window of the casing. If the window is obstructed, the rotation is really needed and the process should be performed under the guidance of a T-shaped drilling engineer.

And after the deflecting operation is finished, performing horizontal drilling operation. The lower drilling tool 6 of the flexible drilling tool system 100 employs a drilling bit and assembles the drilling bit, the flexible drilling tool module 5, a float valve sub (not shown), the safety sub 32, the jar 31, and the drill pipe 2 to form a horizontal drilling tool assembly through which horizontal drilling operations are performed. In one embodiment, the lower drilling tool 6 is a 152mm drill bit, the flexible drilling module 55 is a 133mm flexible drilling module, i.e., 65m,310 button in length, the jar 31 is a 3-1/2 "jar, and the drill pipe 2 is a 3-1/2" drill pipe. After the flexible drilling tool system 100 is assembled, the flexible drilling tool system 100 is lowered into the wellbore and horizontal drilling operations are performed through the window until radial drilling operations are completed.

And finally, recovering the whipstock to finish sidetracking operation.

The flexible drilling tool system 100 for radial drilling of the ultra-deep well can realize that the track of the well hole is changed from vertical to horizontal within the range of the vertical distance of 3m, and compared with the vertical distance of 90m of the existing flexible drilling tool, the flexible drilling tool system greatly reduces the vertical distance of the side drill, thereby greatly increasing the scale of a communicable reservoir body, obviously improving the probability of the radial drilling in the fracture hole, being very beneficial to improving the production efficiency and reducing the operation cost. Meanwhile, the flexible drilling tool system 100 has a certain sealing property during the drilling construction process. In addition, the flexible drilling tool system 100 still provides reliable sealing and operation performance when a certain pressure differential exists between the interior and exterior of the drilling tool. The flexible drilling tool system 100 has no special requirements on operation parameters and supporting equipment, and has good adaptability. According to the sidetracking process for radial drilling of the ultra-deep well, the flexible drilling tool system 100 is used, the well track can be horizontally changed from vertical within the vertical distance range of 3m, the sidetracking vertical distance can be greatly reduced, the sidetracking process is simple to operate, the operation efficiency can be obviously improved, and the operation cost can be obviously reduced.

It is noted that, as used herein, the terms "comprising," including, "" having, "" containing, "and" containing "as well as variations thereof in language or syntax, and words of assignment and/or homology, mean" including but not limited to.

It is to be understood that all technical and scientific terms, and/or expressions used throughout this disclosure have the same or similar meaning as commonly understood by one of ordinary skill in the art unless specifically defined or stated otherwise herein. The phraseology, terminology, and symbols used throughout this disclosure are for the purpose of description and should not be regarded as limiting.

Finally, it should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and do not limit the present invention in any way. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing examples, or that equivalents may be substituted for elements thereof. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A flexible drilling tool system for radial drilling of ultra-deep wells, comprising:

the drilling rod (2) is connected with a wellhead turntable arranged on a wellhead;

the drilling device (3) is connected to the lower end of the drill rod, and the drilling end of the drilling device is connected with a lower drilling tool (6);

a flexible drilling tool module (5) connected between the drilling apparatus and the lower drilling tool;

wherein the flexible drill module has an initial deflection angle, the flexible drill module being configured to enable the flexible drill system to turn a wellbore trajectory from vertical to horizontal within a predetermined sag range,

the flexible drilling tool module can rotate along with the wellhead turntable through the drill rod, so that the lower drilling tool is driven to operate.

2. The flexible drilling system of claim 1, wherein the predetermined sag of the flexible drilling module is no greater than 3m.

3. The flexible drill system of claim 1 or 2, wherein the initial deflection angle of the flexible drill module is in the range of 1-5 °.

4. The flexible drilling system of claim 1 or 2, wherein the flexible drilling module comprises:

a housing (9);

a rotating element (13) connected to a lower end of the housing, the rotating element being rotatable to provide an angle of drilling whipstock;

a limiting element (11) which is arranged in the shell and is connected with the rotating element through a key slot, the limiting element is used for limiting the rotating range of the rotating element so as to transmit the torque when the wellhead turntable rotates,

the first end of the rotating element is constructed into a sphere, the second end of the rotating element is constructed into a connecting buckle, a spherical surface is formed in the shell, and the rotating element is matched with the spherical surface through the sphere, so that the rotating element and the shell form a hinge structure.

5. The flexible drilling system according to claim 1 or 2, wherein a connection joint (8) is fixedly connected to the upper end of the housing, the lower end of the connection joint extending into the interior of the housing, the stop element being fixedly connected to the lower end of the connection joint, and a sealing element (10) being provided between the stop element and the housing.

6. Flexible drilling system according to claim 5, characterized in that a safety reinforcement element (14) for preventing the rotation element from falling off is further provided between the rotation element and the housing.

7. The flexible drilling system of claim 6, wherein the drilling device comprises a safety joint (32), the flexible drilling module being fixedly connected with the safety joint by the connection joint,

the connecting joint is connected with the safety joint in a threaded connection mode, and the connecting thread of the rotating element is connected with the lower drilling tool in a threaded connection mode.

8. The flexible drilling system of claim 1 or 7, wherein the lower drilling tool is a drill bit or a milling cone or a fishing cone.

9. A sidetracking process for radial drilling of an ultra-deep well comprises the following steps:

providing a flexible drilling tool system according to any one of claims 1 to 8;

drift diameter gauges are adopted for drifting;

a whipstock is put into a preset position in the shaft and is hung by a seat;

a drilling tool at the lower part of the flexible drilling tool system adopts a windowing milling cone, and a window is formed by windowing the casing pipe through the flexible drilling tool system;

replacing a drilling tool at the lower part of the flexible drilling tool system with a deflecting drill bit, and lowering the flexible drilling tool system to the window position for deflecting operation;

replacing a drilling bit on the lower part of the flexible drilling tool system with a drilling bit, lowering the flexible drilling tool system and performing horizontal drilling operation through the window until radial drilling operation is completed;

and recovering the whipstock.

10. The sidetracking process for radial drilling of ultra deep wells according to claim 9, wherein the casing is cleaned by a scraper in the position corresponding to the whipstock setting position before running the whipstock and the wellbore is kept full of drilling fluid after cleaning.

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