Downhole drive small diameter drill string

Abstract

The application discloses a downhole driving small-diameter drill string, which comprises a side drilling pipe string, a guide structure and a driving pipe string; the side drilling pipe string is a flexible drill string capable of realizing directional drilling, and is a complete drilling pipe string which at least comprises a flexible drill rod, a drill bit or a drilling-while-measuring and control system; the guide structure is connected below the driving pipe string and is run into a well together with the driving pipe string, and the side drilling pipe string enters a stratum by the guide structure and the driving pipe string; and the driving pipe string can provide rotary power for the side drilling pipe string.

Description

Technical Field

[0001] This invention relates to the field of drilling technology, specifically to a downhole drive small-diameter drill string. Background Technology

[0002] In directional drilling, the rotational power of the drill bit is mainly provided by turbine drilling tools and screw drilling tools. The drill string uses sliding drilling, while the drill bit uses rotary drilling; the overall drilling efficiency is generally low.

[0003] Therefore, it is necessary to provide a downhole drive small-diameter drill string to solve the problems mentioned in the background art. Summary of the Invention

[0004] To achieve the above objectives, the present invention provides the following technical solution: a downhole drive small-diameter drill string, comprising a sidetracking string, a guide structure, and a drive string; the sidetracking string is a flexible drill string capable of directional drilling, and is a complete drilling string including at least a flexible drill pipe and a drill bit; the guide structure is connected below the drive string and enters the well together; the sidetracking string enters the formation through the guide structure and the interior of the drive string.

[0005] A power unit is provided at the bottom of the drive string, and a transmission device is provided between the power unit and the side drill string. The power unit can provide rotational power to the side drill string through the transmission device.

[0006] Furthermore, as a preferred embodiment, the guiding structure has a guiding channel inside, and the driving string has a through channel inside. The guiding channel and the through channel are interconnected. The overall outer diameter of the side-drilling string matches the through channel and the guiding channel, so that it can smoothly pass through the guiding structure and the driving string and extend along the main wellbore for drilling.

[0007] Furthermore, as a preferred embodiment, the guiding structure is a directional drilling device, which is inserted into the well along with the drive tubing during operation to guide the sidetracking tubing to achieve sidetracking operations.

[0008] Furthermore, as a preferred embodiment, the power source of the drive string is either hydraulic energy or electrical energy. The drive string includes at least a power end and an output end. The output end is a rigid transmission device or structure, or a combination of several rigid short sections connected by threads, or a combination of several rigid short sections connected by hinges, which can transmit rotational power to the side drill string through a torque transmission mechanism.

[0009] Furthermore, as a preferred embodiment, when the power unit is hydraulically driven, the power unit is a downhole motor, and the drive string also includes a drive channel. The hydraulic fluid can drive the power end to rotate through the drive channel, and the output end outputs torque through the torque transmission mechanism to drive the side-drilling string to rotate and do work.

[0010] Furthermore, as a preferred embodiment, the downhole motor is a turbine motor. The drive string also includes a radial flow channel, which can be located between the power end and the output end, or below the output end, to connect the drive flow channel with the main wellbore annulus. After the fluid completes its driving work at the power end, it can enter the main wellbore annulus along the radial flow channel and return to the surface, forming a drive cycle.

[0011] Furthermore, as a preferred embodiment, the side-drilling string is provided with an internal circulation channel, through which the drilling medium enters directly from the surface into the internal circulation channel of the side-drilling string and continues to the drill bit water hole, and then enters the main wellbore from the side-drilling wellbore and returns to the surface to complete the circulation.

[0012] Furthermore, as a preferred embodiment, at least one torque transmission mechanism is provided between the drive string and the side drill string, the torque transmission mechanism including a drive end torque transmission mechanism and a drill string end torque transmission mechanism; wherein, the drive end torque transmission mechanism extends through the output end, and the distance between the location of the drill string end torque transmission mechanism and the drill bit is greater than the design depth of the branch wellbore and less than the overall length of the output end.

[0013] Furthermore, as a preferred option, the rock breaking method of the side drilling string is either primarily mechanical rock breaking with hydraulic rock breaking as a supplement, or primarily hydraulic rock breaking with mechanical rock breaking as a supplement, and the drilling method is one or more of hydraulic self-drive, mechanical pressurization, and hydraulic pressurization.

[0014] Furthermore, as a preferred embodiment, the flexible drill rod is a highly elastic metal drill rod, a hinged drill rod, or a drill rod composed of multiple torque transmission short sections connected in series.

[0015] Compared with the prior art, the present invention provides a downhole drive small-diameter drill string, which has the following beneficial effects:

[0016] In this embodiment of the invention, the drive string and guide structure can guide the side-drilling string to smoothly enter the formation. The drive string can provide rotational power to the side-drilling string. The torque transmission mechanism can effectively transmit torque, thereby enabling the drive string to provide mechanical energy to the side-drilling string for rock breaking. At the same time, hydraulic energy is used to break rocks or apply drilling pressure, thereby improving the overall drilling efficiency. Attached Figure Description

[0017] Figure 1 A schematic diagram of a downhole drive small-diameter drill string;

[0018] Figure 2 This is a schematic diagram of a torque transmission mechanism in a downhole drive small-diameter drill string. Detailed Implementation

[0019] Please see Figures 1-2 In this embodiment of the invention, a downhole drive small-diameter drill string includes a side-drilling string 1, a guide structure 2, and a drive string 3; the guide structure 2 is connected below the drive string 3 and enters the well together, and the side-drilling string 1 enters the formation through the guide structure 2 and the drive string 3.

[0020] As one of the preferred embodiments of this invention, the side-drilling string 1 includes at least a flexible drill pipe, a drill bit, or a drilling monitoring and control system. Since the flexible drill pipe needs to pass through the guide structure 2, it needs to have sufficient flexibility. Specifically, in this embodiment...

[0021] The flexible drill rod is a highly elastic metal drill rod;

[0022] Furthermore, in addition to sufficient flexibility, the flexible drill pipe also has sufficient rigidity. In this embodiment, the flexible drill pipe rotates under the action of the drive string 3, transmitting torque to the bottom drill bit for mechanical rock breaking.

[0023] Alternatively, as another option, in addition to the drill bit or the measurement and control system while drilling (MWD) below the flexible drill pipe, a downhole motor can be installed to provide drilling power to the drill bit. When a downhole motor is used, the downhole motor is preferably a screw motor. The MWD system can measure the wellbore inclination and azimuth at the bottom of the well and can communicate with the surface control center for directional control. Both the screw motor and the MWD system are currently mature technologies and will not be described again here.

[0024] Preferably, in order to enable the side-drilling string 1 to smoothly enter the formation, the guide structure 2 is provided with a guide channel 4 inside, and the drive string 3 is provided with a through channel 5 inside. The guide channel 4 and the through channel 5 are interconnected to form a channel that allows the side-drilling string 1 to slide forward. The overall outer diameter of the side-drilling string 1 matches the through channel 5 and the guide channel 4, so that it can smoothly pass through the guide structure 2 and the drive string 3 and extend along the main wellbore side-drilling extension.

[0025] During construction, it is usually necessary to lower the guide structure 2 and drive string 3 to the predetermined well depth in advance and complete the orientation and fixing. At this time, the orientation of the guide structure 2 can be fixed and kept consistent with the preset orientation.

[0026] As one of the preferred solutions in this embodiment, the guide structure 2 is a directional guide, which is inserted into the well along with the drive tubing 3, and the two are preferably connected by threads.

[0027] Furthermore, the diameter of the side drill string is in the range of 10-100 mm. Generally speaking, for a smaller side drill string 1, it can easily enter the formation through the guide structure 2, and its rock breaking method and the driving force for extended drilling are mainly hydraulic energy, specifically including hydraulic rock breaking and hydraulic self-propelled forward movement.

[0028] Furthermore, for larger side drill strings 1, relying on hydraulic rock breaking and extended drilling requires overcoming greater forward resistance, and usually requires adopting a rock breaking method mainly based on mechanical energy. Moreover, in the directional deviated well section, hydraulic energy can be used to pressurize in order to better apply drilling pressure to the lower drill string.

[0029] As one of the preferred solutions in this embodiment, the drive string 3 can provide rotational power to the side drill string 1, provide mechanical energy for rock breaking, and at the same time assist in rock breaking or apply drilling pressure with hydraulic energy;

[0030] Preferably, the drive string 3 is a downhole turbine that converts the fluid energy of high-pressure drilling fluid into mechanical energy to output torque. The turbine includes at least a power end 6 and an output end 7. The power end 6 is composed of a turbine blade assembly, and the rotational power output by the turbine blade assembly can drive the internal spindle to rotate. The spindle can be connected to the output end 7 by a threaded or hinged structure.

[0031] Furthermore, the output end 7 may be integrally formed with the mandrel, or include several threaded rigid short sections, or include several hinged rigid short sections.

[0032] Furthermore, the drive column 3 also includes a sealing system and a bearing system to ensure channel sealing and stable torque transmission.

[0033] Furthermore, the torque is transmitted to the side drill string 1 at the output end 7 via the torque transmission mechanism 8.

[0034] As a preferred option, such as Figure 2 The torque transmission mechanism 8 includes a drive-end torque transmission mechanism 801 and a drill string-end torque transmission mechanism 802. The drive-end torque transmission mechanism 801 is preferably a groove, and the drill string-end torque transmission mechanism 802 is preferably a boss. The size of the boss matches the size of the groove, so that the boss can slide inside the groove. To ensure that the boss can smoothly enter the groove, a double helical guide slope is preferably provided at the upper and lower ends of the output end 7. The double helical guide slope can guide the boss to smoothly enter the groove. When the drive-end torque transmission mechanism 801 rotates, the torque can be transmitted to the side drill string 1 through the drill string-end torque transmission mechanism 802.

[0035] Furthermore, as one of the preferred embodiments of this invention, a set of torque transmission mechanisms 8 is provided between the drive string 3 and the sidetracking string 1. The drive-end torque transmission mechanism 801 extends through the entire output end 7 up to the entrance of the guide channel 4 of the guide structure 2. The distance between the drill string end torque transmission mechanism 802 and the drill bit is greater than the design depth of the branch wellbore and less than the overall length of the output end 7. This ensures that when sidetracking begins, the drill string end torque transmission mechanism 802 is located above the drive-end torque transmission mechanism 801. As sidetracking progresses, the drill string end torque transmission mechanism 802 moves forward with the sidetracking string 1 until the predetermined well depth is reached. During this process, the drill string end torque transmission mechanism 802 can ensure that it always slides inside the drive-end torque transmission mechanism 801.

[0036] During drilling, the drive string 3 is driven by high-pressure drilling fluid. The drive string 3 is equipped with a drive flow channel 9 inside. The drive flow channel 9 can connect the fluid flow channel of the upper drill string and the fluid flow channel of the turbine blade assembly. The high-pressure drilling fluid pumped into the well by the surface mud pump can drive the blade assembly to rotate through the drive flow channel 9, thereby driving the power end 6 to rotate. The output end 7 outputs torque through the torque transmission mechanism 8 to drive the side drilling string 1 to rotate and do work.

[0037] Furthermore, after the high-pressure drilling fluid completes its driving work at the power end 6, it needs to enter the wellbore annulus and return to the surface to complete the circulation. As one of the preferred solutions in this embodiment, the drive string 3 is provided with several radial flow channels 10. The radial flow channels 10 are located between the power end 6 and the output end 7. Through the several radial flow channels 10, the drive flow channel 9 can be connected to the wellbore annulus. The high-pressure drilling fluid that has completed its work can enter the main wellbore along the radial flow channels 10 and return to the surface, forming a complete drive circulation loop.

[0038] Preferably, the side-drilling string 1 is provided with a different circulation loop than the drive string 3. The drilling medium of the side-drilling string enters directly from the surface into the internal circulation channel of the side-drilling string 1 until it reaches the drill bit water hole, and then enters the main wellbore from the side-drilling wellbore and returns to the surface to complete the circulation.

[0039] Preferably, the drilling medium circulation loop inside the side-drilling string is filled with high-pressure drilling fluid. The high-pressure drilling fluid can assist in rock breaking, rock carrying, and cooling of the drill bit, and at the same time, it can use its hydraulic energy to provide extended drilling driving force for the side-drilling string 1.

[0040] Preferably, a hydraulic pressurization device 11 can be installed at a local location using the circulation loop of the drive string 3. The hydraulic pressurization device 11 refers to any structure or device that can generate a pressure difference using hydraulic energy. In this embodiment, the hydraulic pressurization device 11 is preferably a piston disc, which is fixedly connected to the side drill string 1. When the circulation loop of the drive string 3 is filled with high-pressure drilling fluid, a portion of the fluid can directly act on the upper end face of the piston disc to provide hydraulic pressurization to the side drill string 1, thus propelling the drill string forward.

[0041] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A downhole drive small-diameter drill string, characterized in that: It includes a side-drilling string (1), a guide structure (2), and a drive string (3); the side-drilling string (1) is a flexible drill string capable of side-drilling, which is a complete drilling string including at least a flexible drill pipe and a drill bit; the guide structure (2) is connected below the drive string (3) and enters the well together; the side-drilling string (1) enters the formation through the guide structure (2) and the drive string (3); The bottom of the drive string (3) is provided with a power device, and a transmission device is provided between the power device and the side drill string (1). The power device can provide rotational power to the side drill string (1) through the transmission device. The guide structure (2) has a guide channel (4) inside, and the drive string (3) has a through channel (5) inside. The guide channel (4) and the through channel (5) are interconnected. The outer diameter of the side drilling string (1) is matched with the through channel (5) and the guide channel (4) so ​​that it can pass smoothly through the guide structure (2) and the drive string (3) and extend along the main wellbore for drilling. The guiding structure (2) is an angled device. The guiding structure (2) is inserted into the well along with the drive string (3) during the operation and is used to guide the side-drilling string (1) to achieve side-drilling operation. When the power unit is driven by hydraulic energy, the power unit is a downhole motor. The drive string (3) also includes a drive channel (9). The hydraulic fluid can drive the power end (6) to rotate through the drive channel (9), and the output end (7) outputs torque through the torque transmission mechanism (8) to drive the side drilling string (1) to rotate and do work. The downhole motor is a turbine motor. The drive string (3) also includes a radial flow channel (10). The radial flow channel (10) is located between the power end (6) and the output end (7), or below the output end (7), for connecting the drive flow channel (9) with the main wellbore annulus. After the fluid completes the driving work through the power end (6), it can enter the main wellbore annulus along the radial flow channel (10) and return to the surface, forming a drive cycle.

2. The downhole drive small-diameter drill string according to claim 1, characterized in that: The power source of the power unit is hydraulic energy or electrical energy. The power unit includes at least a power end (6) and an output end (7). The output end (7) is a combination of several rigid short sections connected by threads or a combination of several rigid short sections connected by hinges. It can transmit rotational power to the side drill string (1) through a torque transmission mechanism (8).

3. The downhole drive small-diameter drill string according to claim 1, characterized in that: The side-drilling string (1) is equipped with an internal circulation channel. The drilling medium of the side-drilling string enters directly from the ground into the internal circulation channel of the side-drilling string (1) until it reaches the drill bit water hole, and then enters the main wellbore from the side-drilling wellbore and returns to the ground to complete the circulation.

4. A downhole drive small-diameter drill string according to claim 2, characterized in that: At least one set of torque transmission mechanism (8) is provided between the drive string (3) and the side drill string (1). The torque transmission mechanism (8) includes a drive end torque transmission mechanism (801) and a drill string end torque transmission mechanism (802). The drive end torque transmission mechanism (801) passes through the output end (7). The distance between the drill string end torque transmission mechanism (802) and the drill bit is greater than the design depth of the branch well and less than the overall length of the output end (7).

5. A downhole drive small-diameter drill string according to claim 1, characterized in that: The rock breaking method of the side drilling string (1) is either mechanical rock breaking as the main method and hydraulic rock breaking as the auxiliary method or hydraulic rock breaking as the main method and mechanical rock breaking as the auxiliary method. The drilling method is one or more of mechanical pressurization and hydraulic pressurization.

6. A downhole drive small-diameter drill string according to claim 1, characterized in that: The flexible drill pipe is a drill pipe composed of multiple torque transmission short sections connected in series.

Images