Patent Application
20070256865
1. Field of the Invention
The invention relates generally to directional drilling tools. In particular, the invention relates to directional drilling tool that are used to control the direction of drilling of bore holes.
2. Background Art
Increasingly, the drilling of oil and gas wells is no longer a matter of drilling vertically straight boreholes. Changes in the direction of drilling of boreholes are required for a number of reasons. The most frequent reason is to change from vertical drilling to horizontal drilling or drilling at any angle therebetween. Horizontal drilling has been known for many years and there are a number of established methods of changing the direction from vertical drilling to horizontal drilling. Technology and techniques have now been developed to change the angle of the bore's trajectory by up to and sometimes exceeding 90 degrees from the vertical. Directional drilling using coiled tubing rather than jointed pipe can offer numerous advantages compared to conventional drilling including new approaches to oil and gas traps having non-conventional geometries, economic zone enhancement as can occur, for example, if the borehole is deviated to actually follow an oil or gas bearing strata, improved economics particularly in an under-balanced environment (when formation pressure is sufficient to force hydrocarbons to the surface at potentially explosive rates) and reduced environmental degradation.
The most common existing method to change the direction of drilling is to use a bent support (often called a “bent sub”) for the drill bit. Typically a drill bit powered by a motor is used with a bent sub positioned behind the motor. It is also possible for the bent sub to be positioned in front of the motor. The bent sub effectively causes the axis of rotation of the drill be to be at a different angle to that of the drill pipe. Continuous drilling with the bent sub causes continuous changes of direction which results in a curved well hole in the direction of the bend of the bent sub. When the required curvature has been achieved drilling can be stopped and the bent sub changed for a straight sub to resume straight drilling. Alternatively, the entire drill pipe can be rotated at the surface resulting in a small rotation of the bent sub, motor and drill bit assembly. In that case, the bend of the bent sub will be positioned in a different direction and drilling can be resumed in a different direction. Positional sensors such as gyroscopic sensors are often used to check the progress and direction of the drilling to establish what adjustments to the drilling angle are required.
After deviating a borehole from the vertical, it is not typically practical to sustain continuous drilling operations by rotating the drill string in order to also rotate the bit. Preferably only the bit is rotated by a downhole motor attached to the lower end of the drill pipe. The motor typically includes a rotor-stator that generates torque as drilling fluid passes between the rotor and stator. A bent sub may be positioned behind or in front of the motor. As discussed above, the bent sub deviates the hole by the required amount and may surround a drive shaft that transmits the rotor/stator's torque to a bearing assembly.
Electronics supported in the bottomhole assembly and connected to the surface by a wire line passing through the interior of the drill string can transmit information with respect to the amount of curvature in the borehole's trajectory so that it may be plotted. Once the required curvature has been attained so that the axis of the bit's rotation is pointed in the desired direction, the drilling is stopped and the motor is withdrawn from the well. The bent housing is then either removed or straightened (if it is of the adjustable sort) and the motor is tripped back into the hole to resume drilling. Each time the motor requires service, or a change in the hole's direction is required, this process must be repeated. This results in substantial costs and down time largely due to the time required to make and break all of the joints as the drill string is tripped in and out of the hole. For this reason, jointed drill pipe is now being replaced whenever possible with coiled tubing.
To drill a short radius or medium radius wellbore it is desirable to be able to drill with relative precision along desired or predetermined wellbore paths (“wellbore profiles”), and to alter the drilling direction downhole without the need to retrieve the drilling assembly to the surface. Sufficient torque is needed to rotate the bent sub, drill bit, and any downhole tools disposed below the orienting tool. Drilling assemblies for use with coiled tubing to drill wellbores in the manner described above, preferably need a dedicated orienting device. The orienting device may be located near the drill bit for orienting and controlling the drill bit while drilling the wellbore. The device should be operable during drilling of the wellbore to cause the drill bit to alter the drilling direction.
In addition to controlling the bend angle in the coil tubing, it is also necessary to orient the bend point to control and adjust the borehole's bearing or azimuth. Examples of orienting tools for controlling azimuth are disclosed in U.S. Pat. Nos. 6,955,231, 5,894,896, and 5,441,119.
U.S. Pat. No. 6,955,231 describes a tool for changing the direction of drilling during drilling positioned between drill string and a bent sub. The tool includes at least two housing elements connected to one another, a passage for drilling fluid, a valve adapted for choking the passage so that the tool can be activated for rotation, and a piston adapted for forced guiding of the rotation. Twisted splines may be formed in the wall of the passage and in the wall of the opposite piston to guide rotation of the piston. The tool is activated for rotation by increasing the pressure of the fluid passing through the tool. The rotation ends by relief of the pressure of the fluid. The tool rotation is infinitely variable and is only regulated by monitoring magnetic measurements recorded by measurements-while-drilling (MWD) instruments and techniques.
U.S. Pat. No. 5,894,896 describes an apparatus for azimuthal orientation of a tool in a wellbore. The apparatus includes a tubular housing, a mandrel rotatably supported in the tubular housing and extending therefrom for connection to a toll for rotation, a piston mandrel axially aligned with and connected to the mandrel, and a piston longitudinally movable in an annulus between the piston mandrel and the tubular housing that is non-rotatable relative to the tubular housing. At least one pin is longitudinally movable in concert with the piston arranged to track in respective helical grooves in the mandrel. A flow path selectively delivers pressurized hydraulic fluid to either side of the piston for rotating the mandrel or to both sides of the piston equally to maintain a fixed annular orientation. The orienting tool is independently controlled from the mud flow rate.
U.S. Pat. No. 5,441,119 describes a directional drilling system including a directional drilling tool that has two parts moveable relative to each other in the horizontal or vertical planes. Cam surfaces are provided between the two parts for adjustments to the drilling direction in the vertical plane. A slot and groove mechanism is provided between the two as an example of adjustments in the horizontal plane. The cam surfaces are contoured such that, when the piston and inner parts are rotated with respect to each other, an inner part is adjusted to a position which is off line with respect to the original center line and the center of the drill pipe. Thus, the entire orienting device rotates and moves off center of the drill pipe.
Accordingly, there exists a need for an orienting apparatus that provides sufficient torque output to downhole tools disposed below (further downhole) the orienting apparatus. There also exists a need for an orienting apparatus that allows controlled, accurate rotation of the apparatus, and therefore downhole tools located below the orienting apparatus, from the surface.
In one aspect, the present invention relates to an orienting apparatus comprising at least one housing element configured to couple with a drill string; an actuator disposed inside the at least one housing element; a nozzle coupled to the actuator; a torque generator coupled to the actuator and extending axially downward through the at least one housing, wherein the torque generator is configured to rotate in a first direction as it moves downward; a mandrel coupled to the torque generator; and a stroke adjuster at least partially disposed in an upper end of the mandrel, wherein rotation in the first direction is caused by an increase in differential pressure.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
In one aspect, embodiments of the invention relate to an orienting apparatus that provides variable torque output for rotating downhole tools disposed below the orienting apparatus. In another aspect, embodiments of the invention relate to an orienting apparatus for changing the azimuthal orientation of a tool in a wellbore. In another aspect, embodiments of the invention relate to an orienting apparatus that provides controlled incremental rotation of the orienting apparatus, and therefore, of downhole tools disposed below the orienting apparatus. In another embodiment, the apparatus provides adjustable rotation of the tool in the wellbore during operation, while maintaining torque output.
As shown in
In the embodiment shown in
As shown in greater detail in
Below the piston 212, a piston return spring 232 is disposed around torque generator 230. A thrust bearing 240 may be disposed around torque generator 230 between a lower end of the piston return spring 232 and an upper end of upper body 214. Torque generator 230 extends downward through upper body 214 and into spline housing 216.
Spline housing 216 includes a lower end of torque generator 230, a mandrel 260, an upper clutch 234, and an upper clutch spring 240. A compensator spring 242 and a compensator piston 246 are disposed around torque generator 230, below upper body 214. At least one helical spline 218 is formed on an outside diameter of a lower end of torque generator 230. As shown in more detail in a cross-sectional view of
Referring now to
A pre-determined axial length of space 625 is provided between stop 626 and an upper surface 618 of stroke adjuster 250. The axial length of space 625 limits the downward movement of torque generator 230. The downward movement, and therefore degree of rotation, of torque generator 230 may be pre-selected by selecting a corresponding axial length of space 625 between stop 626 and upper surface 618 of stroke adjuster 250. When assembling the orienting apparatus 25 at the surface of the well, the amount of downward movement of the torque generator 230 may be selected by inserting the stroke adjuster 250 a selected distance within mandrel 260, thereby providing a selected axial length of space 625 between stop 626 and upper surface 618 of stroke adjuster 250. The axial length of space 625 corresponds to a degree of rotation of the orienting tool 25, and in particular the mandrel 260. Accordingly, each stroke of the piston 212 corresponds to a pre-determined degree of rotation of mandrel 260.
Referring now to both
Referring back to the embodiment shown in
As shown in
The spacing of the plurality of teeth 802, 804 may be selected in order to set the amount of rotation of the mandrel. A degree of rotation of the mandrel 260 may be pre-selected by selecting the number of teeth on lower clutch 236 and lower body 224. For example, 24 teeth disposed on lower clutch 236 and 24 teeth disposed on lower body 224 may provide 15 degrees of rotation for every tooth. In another example, 18 teeth disposed on lower clutch 236 and lower body 224 may provide 20 degrees of rotation for every tooth. One of ordinary skill in the art with appreciate that the degree of rotation required and the corresponding number of teeth provided on lower clutch 234 and lower body 224 may be selected based on a desired direction of the wellbore being drilled.
Referring back to
Operation
In one embodiment, fluid is flowed through an interchangeable nozzle 211 disposed in a central passage of the orienting apparatus 25, thereby causing a differential pressure. Piston 212 coupled to torque generator 230 moves downward as a result of the differential pressure. As the torque generator 230 moves and rotates downward until a stop 626 disposed in a lower end of the torque generator 230 contacts an upper surface 618 of stroke adjuster 250. Mandrel 260, coupled to torque generator 230, rotates as a result of the coupling.
As piston 212 moves downward, it moves torque generator 230 downward and compresses piston return spring 232 between a lower surface of piston 212 and upper body 214. In the embodiment shown in
Torque generator 230 moves downward until stop 626 contact upper surface 618 of stroke adjuster 250. As piston 212 and torque generator 230 move downward, upper clutch 234 moves downward. Upper clutch spring 244 compresses between a lower surface of upper clutch 234 and an upper surface of lower body 224. Engagement of the plurality of teeth 270 on torque generator 230 and plurality of teeth 272 on upper clutch 234 causes the upper clutch 234 to rotate in a clockwise direction. Straight splines 252 disposed on an outside diameter of upper end of mandrel 260 allow upper clutch 234 to move downward along the mandrel and rotate the mandrel 260 in accordance with the rotation of torque generator 230, thereby rotating bottom sub 222.
As mandrel 260 rotates, lower clutch 236 rotates in a corresponding clockwise direction due to engagement of straight splines 254 disposed on an outside diameter on a lower end of mandrel 260 and corresponding grooves 808 of lower clutch 236. As the lower clutch 236 rotates, the plurality of teeth 804 move past the plurality of teeth 802 disposed on a lower surface of lower body 224.
The degree of rotation of the bottom sub 222 is determined by the stroke of the piston 212 and torque generator 230, in combination with the design of the plurality of teeth 272 of lower clutch 236. The stroke of the piston 212 and torque generator 230 is limited by the stroke adjuster 250. The axial length of space 25 corresponds to a degree of rotation of mandrel 260, such that the plurality of teeth 804 of lower clutch 236 rotates over the plurality of teeth 802 of lower body 224. For example, in one embodiment, the plurality of teeth 804 of lower clutch 236 includes 24 teeth spaced 15 degrees apart. In this example, stroke adjuster 250 is threaded inside mandrel 260 until lower surface 620 of stroke adjuster 250 contacts shoulder 622 of mandrel 260. In this embodiment, the axial length of space 25 corresponds to a rotational displacement of two pitches of the plurality of teeth 804 of the lower clutch 236. Accordingly, the torque generator 230 moves downward an axial length of space 25 until stop 626 contacts upper surface 618 of stroke adjuster 250. Simultaneously rotation of torque generator 230 forces rotation of mandrel 260, thereby rotating lower clutch 236 through two pitches of the plurality of teeth 804.
In another embodiment, the stroke adjuster 250 may be threaded inside mandrel 260 approximately half the distance of the previous example. Thus, the axial length of space 25 is reduced approximately in half. Accordingly, in this embodiment, the axial length of space 25 corresponds to a rotational displacement of one pitch of the plurality of teeth 804 of the lower clutch 236. Thus, as torque generator 230 moves downward an axial length of space 25 until stop 626 contacts upper surface 618 of stroke adjuster 250, simultaneously rotation of torque generator 230 forces rotation of mandrel 260. Rotation of mandrel 260 causes a rotational displacement of one pitch of the plurality of teeth 804 of lower clutch 236.
Thus, the degree of rotation of the bottom sub, and subsequently azimuthal angle of the drill bit, is adjustable by positioning stroke adjuster 250 inside mandrel 260 to provide a pre-determined axial length of space 625 to correspond with a degree of rotation of mandrel 260. One of ordinary skill in the art will appreciate that the location of the stroke adjuster 250, and therefore, the axial length of space 625, may be selected based on the desired direction to be drilled, formation properties, drilling equipment, etc. One of ordinary skill in the art will also appreciate that the number of teeth and degree of separation of the teeth 804 on the lower clutch 236 may vary. For example, the stroke adjuster 250 may inserted in mandrel 260 so that axial length of space 625 corresponds with a rotational displacement of one pitch, two pitches, three pitches, etc. of the plurality of teeth 804 of lower clutch 236. Further, the number of teeth 804 of lower clutch 236 may be selected to correspond with a desired degree of rotation. For example, 36 teeth may correspond to rotational displacements in increments of 10 degrees, 24 teeth may correspond to rotational displacements in increments of 15 degrees, 18 teeth may correspond to rotational displacements in increments of 20 degrees, etc.
One of ordinary skill in the art will appreciate that the stroke of the torque generator 230 may be adjusted by threading or un-threading the stroke adjuster 250 inside mandrel 260. Further, one of ordinary skill in the art will appreciate that the stroke adjuster 250 may be coupled to the mandrel 260 by any method know in the art. In this embodiment, stroke adjuster 250 is threadedly engaged with mandrel 260, however, stroke adjuster 250 may be coupled by bolts, adhesive, or other locking devices known in the art.
To reset the orientation apparatus 25, the fluid flow through the orientation apparatus 25 is reduced or stopped, thereby reducing the pressure differential across nozzle 211. Piston return spring 232 moves piston 212, and therefore, torque generator 230, upward, back to an initial position. Thrust bearings 240 are provided between piston return spring 232 and upper body 214 to help move the piston 212 and torque generator 230 upward. Because of the biasing of the plurality of teeth 270, 272 of torque generator 230 and upper clutch 234, respectively, torque generator 230 is allowed to rotate in a counter-clockwise direction as it moves upward. Upper clutch spring 244 moves upper clutch 252 upward. Engagement of the plurality of teeth 802, 804 of lower body 224 and lower clutch 236 limit counter-clockwise rotation of mandrel 260 and bottom sub 222. Thus, mandrel 260 and bottom sub 222 remain in a rotated position while the orienting tool 25 is reset. Increasing the differential pressure again across nozzle 211 provide further rotation of mandrel 260 and bottom sub 222. The above mentioned cycle may be repeated until the desired turning of a bent sub or other downhole tool has been reached.
Advantageously, the present invention may provide improved directional control when drilling in a lateral or azimuthal direction from the vertical. Embodiments of the present invention may provide adjustable torque output of an orienting apparatus.
Embodiments of the present invention may provide controlled, incremental rotation of an orienting apparatus.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
