Patent Application
20190292854
When exploring for or extracting subterranean resources such as oil, gas, or geothermal energy, and in similar endeavors, it is common to form boreholes in the earth. To form such a borehole, an embodiment of which is shown in
At times it may be desirable to alter a direction of travel of a drill bit while it drills from a path it might naturally take through the earth. This may be to steer the drill bit toward valuable resources or away from obstacles. This may also be to merely keep the drill bit from veering off course. Either way, a variety of techniques have been developed allowing for steering of a drill bit as drilling progresses.
A steerable downhole tool may alter a direction of travel of a drill bit while drilling into the earth by extending a rod from openings disposed in a side of the tool. The rod may slide within a cavity, spanning a width of the tool, passing from one of the openings to another and extending from various openings at various times.
The rod may degrade material from an internal surface of a borehole in which the drill bit is traveling, by engaging the surface with cutter elements exposed on opposing tips of the rod. A stabilizer, protruding from the side of the tool, may then push off of the borehole wall opposite from the area of degradation to drive the drill bit into the degraded region.
For example, while the tool is rotating within the borehole, the rod may be extended from a first of the openings. With the rod extended, the tool may be rotated about an axis thereof to degrade a portion of the borehole. After a certain amount of rotation, roughly one-half of a full rotation in some embodiments, the rod may be retracted to a neutral position within the tool. The tool may continue to rotate until a second of the openings is adjacent to the area where the rod was initially extended. At this point, the rod may be extended from the second opening and the tool may be rotated another roughly one-half rotation to continue degradation of the same area.
The side 223 may span from the attachment end 220 to the opposing engagement end 221 and comprise an opening 224 therein. A tip 225, comprising additional cutter elements 227 secured thereto, may be extendable from within the opening 224 to degrade a specific section of an adjacent borehole wall (not shown) surrounding the drill bit 212. A stabilizer 228, axially spaced from the opening 224, may protrude from the side 223. This stabilizer 228 may comprise tough gage elements 229 designed to push against and ride along the borehole wall without wearing away. As the cutter elements 227 of the tip 225 degrade the specific wall section, as described previously, the stabilizer 228 may push off of the borehole wall into the degraded section, as will be described below.
A first opening 324 on a side 323 of the drill bit 312 may be connected to a second opening 334, opposite the first opening 324, by an elongate cavity 330 passing through the drill bit 312. Cutter elements 325, 326, extendable from the first opening 324 and second opening 334 respectively, may be attached to a common rod 331 slidable within the cavity 330. As the rod 331 slides within the cavity 330 the cutter elements 325, 326 may extend or retract from their respective openings. Because both cutter elements 325, 326 are secured to opposing tips of the same rod 331, as one extends the other may retract. In the embodiment shown, the rod 331 is positioned between the engagement end 321 of the drill bit 312 and a plenum 340 of the conduit 338 wherein the nozzles 339 separate therefrom.
Extension or retraction of the cutter elements 325, 326 may be caused by the introduction of pressurized fluid that may urge the rod 331 to slide within the cavity 330. In the embodiment shown, pressurized fluid within a first channel 332 may urge the rod 331 to extend from the first opening 324. Subsequently, pressurized fluid within a second channel 333 may urge the rod 331 to return to a neutral position within the cavity 330. In some embodiments, such as the one shown, at least one spring 335 may also urge the rod 331 toward the neutral position. Pressurized fluid within the second channel 333 may then urge the rod 331 to extend from the second opening 334.
One motivation for securing the cutter elements 325, 326 to the single rod 331 may be to maintain a generally consistent borehole width while drilling. Further, it is believed that the specific positioning of the cutter elements 325, 326 relative to a remainder of the drill bit 312 may be important to maintaining a consistent borehole width. In the embodiment shown, cutter elements 325, 326 disposed on opposing tips of the rod 331 are positioned farther apart from each other than opposing stabilizers 328 protruding from the side 323 of the drill bit 312. The stabilizers 328 themselves may be positioned farther apart than a width of the engagement end 321 of the drill bit 312 such that the cutter elements 325, 326 are not required to degrade too much material. In such a configuration, the cutter elements 325, 326 may remain exposed at all times, to some degree, to an adjacent borehole wall (not shown) surrounding the drill bit 312.
The rod 431 may comprise a shaft 442 surrounded by a bearing sleeve 443. The rod 431 may also comprise replaceable caps 444, 445 secured on opposing tips of the shaft 442. In the embodiment shown the replaceable caps 444, 445 are held to the shaft 442 via a threaded bolt; however a variety of other connections are also possible. The caps 444, 445 may be replaceable to allow for quick exchange should they become worn out or damaged.
A stabilizer body 446 may be threadably secured to the first end 420 of the main body 412. This stabilizer body 446 may have a stabilizer 428 protruding radially therefrom. When the stabilizer body 446 is threaded to the main body 412 the stabilizer 428 may sit axially spaced from the opening 424 of the main body 412. In this position, the stabilizer 428 may push against a borehole wall (not shown) when the rod 431 is extended from the opposite opening 434. In this thread-on configuration, the stabilizer body 446 may be interchangeable with other similar bodies to allow for quick modification of stabilizer size, or merely replacement when worn or damaged.
Translation of the latch 551 may be achieved by adjusting fluid pressures in various chambers surrounding the latch 551. These chambers may be filled by the same pressurized fluid used to urge the rod 531 to extend or retract. For example, in the embodiment shown, a first chamber 552 may be pressurized at a generally constant pressure. When no other forces are acting, this generally constant pressure may urge the latch 551 against the rod 531 to lock it in place. When either of a second chamber 553 or third chamber 554 are filled with pressurized fluid however, the generally constant pressure within the first chamber 552 may be overcome to urge the latch 551 away from the rod 531 and release it from lock. Pressurized fluid being channeled to urge the rod 531 to slide axially in one direction may also feed into the second chamber 553 while pressurized fluid being channeled to urge the rod 531 to slide axially in an opposite direction may feed into the third chamber 554. Thus, in such a configuration, the rod 531 may be axially locked until fluid is sent to urge it in either direction, and then it may be unlocked and free to slide.
After rotating about its axis generally 180 degrees (other amounts are also anticipated), as shown in
Whereas the preceding has been described in particular relation to the figures attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.
