Patent ID: 12252986

In the accompanying drawings, the same reference numerals are used to indicate the same components. In the present application, all accompanying drawings are schematic ones, used to illustrate the principle of the present invention merely, and are not necessarily drawn to actual scale.

DETAILED DESCRIPTION OF EMBODIMENTS

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

As shown inFIG.1, a steerable drilling device100includes an outer tube110, and a central shaft170arranged in the outer tube110. Both the outer tube110and the central shaft170are provided along a longitudinal axis, and the central shaft170is centered with respect to the outer tube110.

An upper end of the central shaft is rotatably supported on an inner wall of the outer tube110through an upper connection mechanism120, and a lower end thereof is rotatably supported on the inner wall of the outer tube110through a lower connection mechanism140.

FIG.2schematically shows the specific structure of the upper connection mechanism120in an embodiment. The upper connection mechanism120includes a first cylinder121, which is arranged within the outer tube110and extends along the longitudinal axis. The first cylinder121is fixedly attached to the inner wall of the outer tube110through a second centralizer123provided between the first cylinder121and the outer tube110. A second cylinder122is arranged in the first cylinder121, and has a lower end fixedly connected to the central shaft170. The second cylinder122extends in the longitudinal direction, and is rotatable about the longitudinal axis with respect to the first cylinder121. As shown inFIG.2, a bearing support124is fixedly attached to a lower end of the first cylinder121, and has an extension that extends radially inwardly, on which a lower thrust bearing125, an upper thrust bearing129, and a sliding bearing126are arranged around the second cylinder122. With the lower thrust bearing125, the upper thrust bearing129and the sliding bearing126, the second cylinder122can be held within and rotatable with respect to the first cylinder121.

In the first cylinder121, an upper sensing element127is provided above the second cylinder122and spaced apart therefrom. A lower sensing element128is provided in the second cylinder122. An electromagnetic connection can be generated between the upper sensing element127and the lower sensing element128.

As shown inFIG.1, the lower connection mechanism140includes a cylindrical connection body141, which has an upper end fixedly connected to a lower end of the central shaft170. The connection body141extends along the longitudinal axis, and is supported on the outer tube110by a first centralizer144provided between the connection body141and the outer tube110, in order to keep the connection body141centered with respect to the outer tube110. The connection body141is rotatably connected to the first centralizer144through a bearing assembly. As a result, the connection body141can be held in and rotatable relative to the outer tube110. The connection body141is hollow, and accommodates a circuit system142and an attitude sensor143therein. The circuit system142may be configured as a circuit board, and the attitude sensor143is configured to measure the deflection and orientation of the well. Instructions from the ground may be transmitted to the circuit system142via the upper sensing element127and the lower sensing element128. The circuit system142can command the attitude sensor143to detect the current deflection and orientation of the steerable drilling device100. The data measured by the attitude sensor143may then be transmitted through the circuit system142to the lower sensing element128, and further to the ground through the lower sensing element128and the upper sensing element127.

In the preferred embodiment shown inFIG.1, the connection body141is provided with a recess at its bottom for receiving the attitude sensor143, so that the attitude sensor143can be stably fixed in the recess, which is beneficial to the accuracy of the measurement. It should be understood, however, that the attitude sensor143may be provided at any suitable position in the connection body141according to practical needs.

As shown inFIG.1, a power generation mechanism130is mounted on the central shaft170. The power generation mechanism130includes an upper turbine131, a generator assembly132, a lower turbine133, and an electromagnetic stabilization assembly134, all of which are provided in sequence from top to bottom. The upper turbine131and the lower turbine133are both free to rotate with respect to the central shaft170. Therefore, as fluid flows through the upper turbine131and the lower turbine133, they may rotate under the action of the fluid. The generator assembly can convert the rotation of the upper turbine131and lower turbine133into electrical energy.

In the preferred embodiment as shown inFIG.1, the upper turbine131and the lower turbine133rotate in opposite directions. In other words, the upper turbine131rotates in a first direction of rotation while the lower turbine133rotates in an opposite, second direction of rotation. Both the first direction of rotation and the second direction of rotation are perpendicular to the longitudinal axis.

The electromagnetic stabilization assembly134may be, for example, an existing electromagnetic brake. By means of the electromagnetic stabilization assembly134, the upper turbine131and the lower turbine133as described above, the central shaft170can be kept stationary with respect to the formation, or in a very slowly rotating state at a speed much less than the rotational speed of the outer tube110.

As shown inFIG.1, a joint drive mechanism150and a drill bit joint160are further provided in the outer tube110, located downstream of the lower connection mechanism140.

The drill bit joint160has a lower end, which extends from a lower end of the outer tube110and configured to be fixedly attached to a drill bit200. A first spherical engagement protrusion161is formed in a middle of the drill bit joint160, and correspondingly, a first spherical engagement groove111is formed in the inner wall of the outer tube110at the lower end thereof. The first spherical engagement groove111is configured to receive the first spherical engagement protrusion161, so as to allow the drill bit joint160to swing freely with respect to the outer tube110.

In addition, in the embodiment as shown inFIG.1, a ball suspension163is provided between the first spherical engagement groove111and the first spherical engagement protrusion161. With the ball suspension163, the rotational torque of the outer tube110can be transmitted to the drill bit joint160, in order to drive the drill bit joint160and the drill bit200in rotation together.

As also shown inFIG.1, an upper end of the drill bit joint160is in a fluid channel112which extends throughout the outer tube110for the fluid in the well to pass through. The fluid in the well can flow through this fluid channel into the drill bit joint160, and thereby flow to the drill bit200.

The joint drive mechanism150includes a plurality, at least three, of drive assemblies. These drive assemblies are arranged circumferentially spaced apart from each other around the upper end of the drill bit joint160. An embodiment of one drive assembly is shown in detail inFIG.3.

As shown inFIG.3, the drive assembly comprises a drive housing151extending parallel to the longitudinal axis, which can be connected to the connection body141of the lower connection mechanism140located above through a connecting bar extending obliquely. In the drive housing151, a motor152, a reducer153, an output shaft154and a driving gear155are arranged, which are connected in sequence from top to bottom. The driving gear155has an axis parallel to the longitudinal axis. The motor152can receive electrical energy from the generator assembly132through the circuit system142, and drive the driving gear155to rotate about its own axis. The drive assembly further includes a driven gear156in engagement with the driving gear155, such that the driven gear156can rotate as the driving gear155rotates. The driven gear156has an axis extending in a radial direction perpendicular to the longitudinal axis. Both the driven gear156and the driving gear155may be formed as bevel gears.

Also as shown inFIG.3, the drive assembly further includes a push rod157extending in the radial direction, which has an inner end facing the upper end of the drill bit joint160. Preferably, the inner end of the push rod157is formed with a second spherical engagement groove159, for receiving a second spherical engagement protrusion162formed on an upper side of the drill bit joint160to form a stable engagement with the drill bit joint160. An outer end of the push rod157is inserted into a central hole156A formed at a center of the driven gear156, which extends along the axis of the driven gear156, i.e., along the radial direction. The central hole156A is provided with a first threaded portion therein. Correspondingly, a second threaded portion is formed on the outer end of the push rod157. When the outer end of the push rod157is inserted into the central hole156A, the first threaded portion and the second threaded portion come into engagement with each other. When the motor151drives the driving gear155, and therefore the driven gear156, to rotate, the push rod157is pressed against the drill bit joint160and thus does not rotate along with the driven gear156. As a result of this relative rotation, the push rod157is able to move in the radial direction under the action of the first and second threaded portions which are in engagement with each other, and thereby push the upper end of the drill bit joint160so that the drill bit joint160can swing.

It should be understood that as the push rod157of a drive assembly generates a combined force to push the upper end of the drill bit joint160in one direction, the push rod of another drive assembly will avoid the upper end of the drill bit joint160accordingly. In this procedure, it can be ensured that the push rods in all the drive assemblies are always pressed against the upper end of the drill bit joint160. As a result, the swing motion of the drill bit joint160can be driven by vector synthesis of multiple drive assemblies. This drive allows a direct control on the direction and angle of the swing motion of the drill bit joint160, so that the drill bit joint160and the drill bit connected thereto can be oriented to the desired state accurately.

It should be understood that during drilling, the drill bit joint160is driven by the outer tube110to rotate about its own axis continuously. In the event that the drill bit joint160swings at an angle relative to the outer tube110(i.e., not in a same axis), in order to ensure that the drill bit joint160and the bit200are accurately oriented to a fixed drilling direction, the plurality of drive assemblies should move periodically, thus pushing or avoiding the upper end of the drill bit joint160in real time.

Also as shown inFIG.3, the push rod157and the driven gear156extend at least partially out of the drive housing151in the radial direction from an opening151A of the drive housing151. A retractable sleeve158, such as a bellows, is arranged around the outer side of the driven gear156and the push rod157that extend at least partially out of the drive housing151from the opening151A of the drive housing151. The retractable sleeve158has one end sealingly connected to the opening151A of the drive housing151, and another end sealingly connected to an inner end edge of the push rod157. The retractable sleeve158and the drive housing151are filled therein with hydraulic oil. This ensures that, after the steerable drilling device100is lowered into the well, the pressure inside of the retractable sleeve158is balanced with that outside of the retractable sleeve158, thus guaranteeing smooth operation of the drive assembly. It should be understood that the hydraulic oil in the drive housing151surrounds the driving gear155and the output shaft154only, but not contacts the motor152and other electrically connected structures thereabove.

Preferably, three drive assemblies are provided, which are evenly spaced 120° apart from each other in the circumferential direction.

In the steerable drilling device100as described above, the central shaft170and the joint drive mechanism150do not bear the axial pressure used to drive the drill bit to deflect, so that corresponding bending and damages would not occur. In particular, force transmission between the drill bit joint160and the joint drive mechanism150occurs mainly in the radial direction only, with essentially zero in the axial direction.

With the above arrangement of the drill bit joint160and the joint drive mechanism150, it is possible for the drive shaft of the drill bit200to deflect by an angle so that the drill bit is able to generate a side cutting force. Controlling the drill bit to swing in this way presents higher precision and accuracy. With the rotatable fit of the structures, including the central shaft170and the power generating mechanism130and the joint driving mechanism150connected therewith, with respect to the outer tube110, it ensures that on the one hand, the outer tube110can be rotated during the drilling operation to reduce the backing pressure, and on the other hand, the central shaft170and the structures mounted thereon can be substantially non-rotating.

It should be understood that non-rotatable or substantially non-rotatable central shaft170is mainly used to prevent the attitude sensor143arranged therein from affecting the accuracy of the detection results due to rotation. On this basis, in order to maintain an effective, sealed electrical connection of the attitude sensor143with other structures, the components that should be electrically connected to the attitude sensor143, such as the power generation mechanism130, the circuit system142or the like in the present invention, are also provided on the central shaft170, such that they do not rotate with respect to each other. Also, in order to ensure that the motor152of the drive assembly can be effectively electrically connected to the circuit system142and the power generation mechanism130, the drive housing151of the drive assembly is fixedly connected to the central shaft170and the connection body141of the lower connection mechanism140(e.g., through the above-mentioned connecting bars), and a passage through which a wire can pass is formed between the drive housing151, the connection body141and the central shaft170. The electric connection to the motor152, the circuit system142and the power generation mechanism130is achieved through the wire. Moreover, the electrical connection between the attitude sensor143and the circuit system142can also be achieved through a wire. In order to achieve this fixed connection of the drive housing151, in the present invention the drive housing151of the drive assembly is disposed independently relative to the outer tube110, and as described above, is arranged within the fluid channel112between the outer tube110and the drill bit joint160for the passage of fluid (e.g., drilling fluid) in the well.

In the context, directional terms “up”, “down” or the like are described with reference to the state when the steerable drilling device is in the well, wherein the term “up” refers to a side facing the ground while the term “down” refers to a side facing the bottom of the well.

Finally, it should be noted that the foregoing is only directed to preferred embodiments of the present invention, which does not constitute any limitations to the present invention. Although the present invention is described in detail with reference to the above embodiments, it is still possible for one skilled in the art to modify the technical solutions defined in the above embodiments or to replace some of the technical features with equivalent ones. Any modifications, equivalent substitutions, improvements or the like made within the spirit and principle of the present invention shall fall within the scope of protection of the present invention.