RU2798542C1 - Method for drilling a sidetrack of a well with unstable rocks - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to the field of drilling oil and gas wells, and in particular to methods for preventing the destruction and collapse of the walls of the well when drilling intervals with unstable rocks. A zone of unstable rocks is preliminarily determined according to adjacent wells and from well logging data. A port is cut out in the production string. Drilling of the lateral wellbore is carried out on a drill string with telemetry and a drill bit with a screw downhole motor with a slide down zone and a subsequent wellbore stabilization zone up to the top of unstable rocks. The assembly with the telesystem and a downhole motor is removed, and the well is drilled to the design bottomhole using a rotary method with a drill string and a casing liner. The casing liner consists of standard casing pipes equipped with a PDC bit, centralizer and valve from below. The casing tail consists of an auto-hook hanger on top, connecting the casing tail to the drill string, transmitting axial load and torque for drilling. To achieve the target bottomhole during drilling, the trajectory is controlled by a centralizer with a variable circumscribed diameter, which increases the circumscribed diameter with an increase in the pressure of flushing fluid pumping due to the exit of the blades, advanced by the pistons, the under-piston cavity of which is connected by a hole with the central channel. To control the trajectory when drilling above the check valve, the drilling liner is equipped with a non-magnetic branch pipe with a retractable inclinometer module. Thanks to the centralizer with a variable circumferential diameter and the inclinometry module, it is possible to control the trajectory while drilling a well section with a casing liner. After removing the inclinometry module while pumping the required volume of cement, the ball is dropped and placed in the central hole of the check valve to increase the pressure of the flushing fluid in order to open holes for washing out excess cement after cementing. After that, the drill string is uncoupled from the casing liner by dropping the ball from the wellhead into the saddle with increasing pressure in the liner and shearing the pin. The bit is provided with a plugged cementing hole, the plug of which opens when the bit holes become clogged during cementing.

EFFECT: control and monitoring of the trajectory during drilling of a well section with a casing liner, elimination of emergency situations due to clogging of the drilling holes of the bit during cementing.

1 cl, 5 dwg

Description

The invention relates to the field of drilling oil and gas wells, and in particular to methods for preventing the destruction and collapse of the walls of the well when drilling intervals with unstable rocks.

A known method of driving unstable rocks when drilling a sidetrack with a horizontal ending (patent RU No. 2714397, IPC E21B 7/04, publ. lateral wellbore with a pipe string with a shoe installed at the lower end, drilling a lateral wellbore to the design bottomhole. The zone of unstable reservoir rocks is preliminarily determined, after cutting a window in the production string, a sidetrack is drilled with a bit with a diameter of 1.3-2.5% less than the diameter of the cut window with the opening of the zone of unstable reservoir rocks, a sleeveless flying string is lowered to the bottom hole on the drill string , equipped with a landing device at the top, and a drillable drilling shoe at the bottom, increase the hydraulic pressure in the drill string, unhook and remove the landing device with the drill pipe string, while the diameter of the sleeveless flying string is 7-8% less than the diameter of the drilled sidetrack, drilling of the sidetrack from a sleeveless flier string to the design bottomhole, a bit is produced with a bit 1.5-3% less than the inner diameter of the sleeveless flier string

The disadvantages of the method are:

- when assembling a flying string at the wellhead, there is a high probability of blocking the drilled wellbore in the zone of unstable rocks, which will lead to overdrilling of the wellbore, since it takes a lot of time to assemble a welded flying string;

- when welding the flying string by manual arc welding, there is a high probability of obtaining a poor-quality weld, which can lead to rupture of the pipes of the flying string when lowering into the well;

- with this method, it is impossible to set the well drilling trajectory, since drilling is carried out without telemetry and without a stabilizing assembly;

- an uncemented flying column can be moved from its place during tripping operations;

- when applying this method, the section of the production string decreases, since after the installation of the flying string, drilling is carried out with a smaller diameter of the bit.

The closest in technical essence and the achieved result is the method of drilling a sidetrack with unstable rocks (patent RU No. 2785164, IPC E21B 7/04, publ. 05.12.2022, Bull. No. 34), including the definition of zones of unstable rocks, cutting out a window in the production string, drilling a sidetrack to the design bottom, fastening the sidetrack with a pipe string, increasing hydraulic pressure in the drill pipe string, unhooking and removing the landing device. From the window, drilling is carried out on a drill string with telemetry and a drill bit with a screw downhole motor with a set angle and a subsequent stabilization zone of the wellbore to the top of unstable rocks. Then the assembly with the telesystem and the bit with the screw downhole motor is removed and the well is drilled to the design bottomhole using a rotary method on a drill string with a casing liner consisting of standard casing pipes. Casing pipes are equipped from below with a bit with PDC cutters, a centralizer to maintain a stable direction during drilling and a valve with a stop ring, and from above - a suspension device. The casing liner is connected to the drill string by a suspension device that transmits axial load and torque for drilling. Squeezing plugs of the suspension device are used when cementing the liner after drilling to the design bottom hole and flushing the wellbore. The drill string is unhooked from the casing liner by dropping the ball from the wellhead into the saddle with increasing pressure in the liner and shearing the pin, while the length of the casing liner is equal to the sum of the length of the lateral wellbore to the bottom and section L of the liner for sealing in production. Then, according to the data of geophysical surveys, the liner is perforated in the interval of the productive formation and the well is put into operation.

The disadvantages of the method are:

- with this method, it is impossible to control the trajectory and control the trajectory during the drilling of the last section of the well on the casing liner, as a result, failure to reach the design bottomhole, which leads to time and material costs for re-drilling the well section;

- the likelihood of an emergency due to clogging of the drilling holes of the bit when cementing through them, as a result, the hardening of cement in the liner and additional material costs for drilling cement.

The technical objectives of the invention are the creation of a method for drilling a lateral wellbore with unstable rocks, providing control and monitoring of the trajectory during the drilling of a well section on a casing liner, eliminating an emergency due to clogging of the drilling holes of the bit during cementing by supplying the bit with a plugged hole for cementing, plug which opens when the bit holes become clogged during cementing.

Technical problems are solved by the method of drilling a sidetrack of a well with unstable rocks, including determining zones of unstable rocks, cutting a window in the production string, drilling a sidetrack on the drill string with telemetry and a bit with a screw downhole motor with a set angle and subsequent stabilization zone of the wellbore to the roof of unstable formations, extraction of the assembly with a telesystem and a bit with a screw downhole motor, drilling a well to the design bottomhole using a rotary method on a drill string with a casing liner consisting of standard casing pipes equipped with a bit with PDC cutters, a centralizer and a valve from below, and from above - a suspension device with an autocoupler connecting the casing liner to the drill string, transmitting axial load and torque for drilling, cementing the casing liner in the sidetrack and uncoupling the drill string from the casing liner by dropping the ball from the wellhead into the saddle with increasing pressure in the liner and shearing the pin,

What is new is that when drilling, the trajectory is controlled by a centralizer with a variable circumscribed diameter, which increases the circumscribed diameter with an increase in the pressure of pumping the flushing fluid due to the exit of the blades extended by the pistons, the under-piston cavity of which is in communication with the central channel, while to control the trajectory above the check valve, the drill shank is equipped with a non-magnetic branch pipe with an inclinometer module installed with the possibility of extraction, after which, when pumping the required volume of cement, the ball is dropped and placed in the central hole of the check valve to increase the pressure of the flushing fluid in order to open holes for washing out excess cement after cementing, while the bit is equipped with a plugged cementing hole, the plug of which is opened when the bit holes are clogged during cementing.

In FIG. 1 schematically shows the implementation of the proposed method.

In FIG. 2 shows a general view of the shank.

In FIG. 3 shows the centralizer enlarged.

In FIG. 4 shows view A.

In FIG. 5 shows a perspective view of the centralizer.

The method is carried out in the following sequence.

A zone of unstable rocks 1 is preliminarily determined from neighboring wells and from well logging data.

In the production string 2, for example, with a diameter of 168 mm, a window 3 is cut out by any known method, for example, with the installation of a whipstock 4 (Fig. 1), using a cutter, for example, with a diameter of 146 mm, to cut a window (not shown).

The drilling of the lateral wellbore 5 is carried out on a drill string 6 with telemetry and a bit with a screw downhole motor, for example, with a diameter of 143 mm (not shown in Fig. 1) with a gain zone 7 and a subsequent stabilization zone 8 of the wellbore 5 to the top of unstable rocks 9 The assembly with a telesystem and a screw downhole motor is removed, and the well 5 is drilled to the design bottomhole 10 in a rotary way on a drill string 6 with a casing liner 11. The casing liner 11 consists of standard casing pipes 12 (Fig. 2), for example, with a diameter of 114 mm, equipped with a bottom bit 13 with PDC cutters, for example, with a diameter of 143 mm, a centralizer 14, and a valve 15. The casing liner 11 is equipped with a hanging device 16 from the top with an auto-release 17 connecting the casing liner 11 with the drill string 6, which transmits axial load and torque for drilling . To achieve the design bottomhole 10 during drilling, the trajectory is controlled by a centralizer 14 with a variable circumscribed diameter, which increases the circumscribed diameter with an increase in the pressure of pumping the flushing fluid due to the exit of the blades 18, advanced by the pistons 19, the sub-piston cavity 20 of which is connected by the hole 21 with the central channel 22. For example, when At a pressure of 6 MPa, the force of the pistons 19 is not enough to bring out the blades 18, while drilling the trajectory falls with an intensity of up to 5° per 100 meters. And at a pressure of 10 MPa, the blades 18 reach the maximum described diameter, for example, 141 mm, while drilling with a casing liner 11 rises the trajectory with an intensity of up to 3 ° per 100 meters. To control the trajectory when drilling above the check valve 15, the drilling liner 11 is equipped with a non-magnetic nozzle with an inclination module 24 installed with the possibility of extraction. Thanks to the centralizer 15 with a variable described diameter and the inclinometer module 24, the trajectory is controlled and controlled during drilling of a well section on the casing liner 11. After removing the inclinometry module 24 while pumping the required volume of cement, the ball 25 is dropped and placed in the central hole 26 of the check valve 15 to increase the pressure of the flushing fluid in order to open holes 27 to flush out excess cement after cementing. Next, the drill string 6 is uncoupled from the casing liner 11 by dropping the ball 28 from the wellhead into the saddle 29 with increasing pressure in the liner 11 and shearing the pin 30.

The bit 13 is provided with a plugged hole 31 for cementing, the plug 32 of which is opened when the holes 33 of the bit 13 become clogged during cementing. Due to the provision of the bit 13 with a plugged hole 31 for cementing, the plug 32 of which opens when the holes 33 of the bit 13 are clogged during cementing, an emergency situation is eliminated when the flushing holes 33 of the bit 13 are clogged during cementing.

The proposed method provides control and monitoring of the trajectory during drilling of a well section on a casing liner, eliminates an emergency situation due to clogging of the drilling holes of the bit during cementing by providing the bit with a plugged hole for cementing, the plug of which opens when the holes of the bit are clogged during cementing.

Claims (1)

A method for drilling a sidetrack of a well with unstable rocks, including determining zones of unstable rocks, cutting a window in the production string, drilling a sidetrack on the drill string with telemetry and a bit with a screw downhole motor with a set angle and subsequent stabilization zone of the wellbore to the top of unstable rocks, extracting assemblies with a telesystem and a bit with a screw downhole motor, drilling a well to the design bottom hole by rotary method on a drill string with a casing liner consisting of standard casing pipes, equipped with a bit with PDC cutters on the bottom, a centralizer and a valve, and on top - a hanging device with an automatic release connecting a casing liner with a drill string that transmits axial load and torque for drilling, cementing the casing liner in the sidetrack and uncoupling the drill string from the casing liner by dropping the ball from the wellhead into the saddle with increasing pressure in the liner and shearing the pin, characterized in that when while drilling, the trajectory is controlled by a centralizer with a variable circumscribed diameter, which increases the circumscribed diameter with an increase in the pressure of pumping the flushing fluid due to the exit of the blades extended by the pistons, the under-piston cavity of which is in communication with the central channel, while to control the trajectory above the check valve, the drilling liner is equipped with a non-magnetic branch pipe with a the possibility of extraction by the inclinometry module, after extraction of which, when pumping the required volume of cement, the ball is dropped and planted in the central hole of the check valve to increase the pressure of the flushing fluid in order to open holes to flush out excess cement after cementing, while the bit is equipped with a plugged hole for cementing, plug which opens when the bit holes become clogged during cementing.

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