BACKGROUND
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 111, an embodiment of which is shown in FIG. 1, a specialized drill bit 112 may be suspended from a derrick 113 by a drill string 114. This drill string 114 may be formed from a plurality of drill pipe sections 115 fastened together end-to-end. As the drill bit 112 is rotated, either at the derrick 113 or by a downhole motor, it may engage and degrade a subterranean formation 116 to form the borehole 111 therethrough. Drilling fluid may be passed along the drill string 114, through each of the drill pipe sections 115, and expelled at the drill bit 112 to cool and lubricate the drill bit 112 as well as carry loose debris to a surface of the borehole 111 through an annulus surrounding the drill string 114.
Various electronic devices, such as sensors, receivers, communicators or other tools, may be disposed along a drill string or at a drill bit. To power such devices, it is known to generate electrical power downhole by converting energy from flowing drilling fluid by means of a generator. One example of such a downhole generator is described in U.S. Pat. No. 8,957,538 to Inman et al. as comprising a turbine located on the axis of a drill pipe, which has outwardly projecting rotor vanes, mounted on a mud-lubricated bearing system to extract energy from the flow. The turbine transmits its mechanical energy via a central shaft to an on-axis electrical generator which houses magnets and coils.
One limitation of this on-axis arrangement, as identified by Inman, is the difficultly of passing devices through the drill string past the generator. Passing devices through the drill string may be desirable when performing surveys, maintenance or fishing operations. To address this problem, Inman provides a detachable section that can be retrieved from the downhole drilling environment to leave an axially-located through bore without removing the entire drill string.
It may be typical in downhole applications employing a turbine similar to the one shown by Inman to pass around 800 gallons/minute (3.028 m3/min) of drilling fluid there past. As the drilling fluid rotates the turbine, it may experience a pressure drop of approximately 5 pounds/square inch (34.47 kPa). Requiring such a large amount of drilling fluid to rotate a downhole turbine may limit a drilling operator's ability to control other drilling operations that may also require a certain amount of drilling fluid.
A need therefore exists for a means of generating electrical energy downhole that requires less fluid flow to operate. An additional need exists for an electrical energy generating device that does not require retrieving a detachable section in order to pass devices through a drill string.
BRIEF DESCRIPTION
A downhole drill pipe may comprise a transducer assembly housed within a lateral sidewall thereof, capable of converting energy from flowing drilling fluid into electrical energy. A portion of a drilling fluid flowing through the drill pipe may be diverted to the transducer assembly and then discharged to an exterior of the drill pipe.
As fluid pressure within the drill pipe may be substantially greater than outside thereof, similar amounts of electricity may be produced as previously possible while using significantly less drilling fluid. For example, while previous technologies may have had around 800 gallons/minute (3.028 m3/min) of drilling fluid experience a pressure drop of around 5 pounds/square inch (34.47 kPa), embodiments of transducer assemblies described herein may divert around 1-10 gallons/minute (0.003785-0.03785 m3/min) of drilling fluid to an annulus surrounding a drill pipe to experience a pressure drop of around 500-1000 pounds/square inch (3,447-6,895 kPa) to produce similar electricity.
In various embodiments, the transducer assembly may comprise a positive displacement motor, such as a progressive cavity motor or rotary vane motor, a Pelton wheel, or one or more turbines.
DRAWINGS
FIG. 1 is an orthogonal view of an embodiment of a drilling operation comprising a drill bit secured to an end of a drill string suspended from a derrick.
FIG. 2 is a partially cutaway, orthogonal view of an embodiment of a downhole transducer assembly, comprising a series of turbines, housed within a lateral sidewall of a section of drill pipe.
FIG. 3 is a partially cutaway, orthogonal view of an embodiment of a downhole transducer assembly comprising a positive displacement motor in the form of a progressive cavity motor.
FIG. 4-1 is a partially cutaway, orthogonal view of another embodiment of a downhole transducer assembly comprising a positive displacement motor, this time, in the form of a rotary vane motor. FIG. 4-2 shows a cross-sectional view of the embodiment of the rotary vane motor.
FIG. 5-1 is a partially cutaway, orthogonal view of an embodiment of a downhole transducer assembly comprising a Pelton wheel. FIG. 5-2 shows a cross-sectional view of the embodiment of the Pelton wheel.
FIG. 6 is a perspective view of a portion of an embodiment of a downhole transducer assembly comprising a turbine and a flow channel.
FIG. 7-1 is a partially cutaway, orthogonal view of an embodiment of a downhole transducer assembly comprising an axially-slidable turbine. FIG. 7-2 is a perspective view of a turbine comprising angled blades. FIG. 7-3 is an orthogonal view of a drill pipe comprising an adjustment mechanism accessible from an exterior thereof.
FIG. 8-1 is a partially cutaway, orthogonal view of an embodiment of a downhole transducer assembly comprising a replaceable turbine. FIG. 8-2 is a perspective view of a turbine comprising a slot disposed therein. FIG. 8-3 is an orthogonal view of a drill pipe comprising a slot disposed in an exterior thereof allowing for replacement of a turbine.
DETAILED DESCRIPTION
FIG. 2 shows one embodiment of a downhole transducer assembly 220, comprising a series of turbines 221 attached to a generator 222, housed within a lateral sidewall of a section of drill pipe 223. In this position, a primary flow 224 of drilling fluid may travel along the drill pipe 223 generally unobstructed by the transducer assembly 220. A portion of this primary flow 224 of drilling fluid may be diverted to create a diverted flow 225 that may be drawn into a course 226 leading to the series of turbines 221.
The diverted flow 225 may impact each of the turbines 221 causing them to rotate. Rotation of the turbines 221 may be transmitted to a rotor 227 of the generator 222 comprising a plurality of magnets of alternating polarity disposed thereon. Rotation of the magnets may induce electrical current in coils of wire wound around poles of a stator 228. By so doing, the transducer assembly 220 may convert energy from the diverted flow 225 into electrical energy that may be used by any of a number of downhole tools. Those of skill in the art will recognize that, in various embodiments, a plurality of magnets, either permanent magnets or electromagnets, and coils of wire may be disposed opposite each other on either a rotor or a stator to produce a similar result.
After rotating the series of turbines 221, the diverted flow 225 may be discharged to an annulus surrounding the drill pipe 223 through an outlet 229 exposed on an exterior thereof. In the embodiment shown, the diverted flow 225 comprises 1-10 gallons/minute (0.003785-0.03785 m3/min) and experiences a pressure drop of 500-1000 pounds/square inch (3,447-6,895 kPa) as it passes the turbines 221.
FIG. 3 shows another embodiment of a downhole transducer assembly 320. In this embodiment, the downhole transducer assembly 320 comprises a positive displacement motor 321 rather than turbines. The positive displacement motor 321 may take the form of a progressive cavity motor comprising a rotor 330, with a helically shaped exterior, eccentrically rotatable within a stator 331, having a likewise helically shaped interior, wherein the helix of the stator 331 comprises more lobes than the helix of the rotor 330.
Similar to the previously discussed embodiment, the downhole transducer assembly 320 comprising the progressive cavity motor may be housed within a lateral sidewall of a section of a drill pipe 323 so as not to obstruct a primary flow 324 of drilling fluid traveling therein. The progressive cavity motor may also be powered by a diverted flow 325 of drilling fluid that may be discharged to an annulus surrounding the drill pipe 323.
Unique manufacturing techniques may be required to form a progressive cavity motor, rotor and stator, of sufficient compactness to fit within a lateral sidewall of a drill pipe as shown. Traditional progressive cavity motor designs typically comprise a steel rotor coated with a hard surface, such as chromium, and a molded elastomer stator secured inside a metal tube housing. At smaller sizes, however, even small amounts of wear on the rotor may become unacceptable and elastomers thin enough to fit may peel away from their tubular housings. Thus, the present embodiment comprises diamond disposed on an exterior of the rotor 330 thereof. This diamond may be deposited on a steel rotor by chemical vapor deposition or other processes. Alternatively, an entire rotor may be formed of polycrystalline diamond in a high-pressure, high-temperature pressing operation. Additionally, it is believed that an elastic interior stator surface may not be necessary when diamond is used.
FIG. 4-1 shows another embodiment of a downhole transducer assembly 420 comprising a positive displacement motor 421. In this embodiment the positive displacement motor 421 takes the form of a rotary vane motor. The rotary vane motor, as also shown in FIG. 4-2, comprises a plurality of vanes 440 mounted to a rotor 430 that may rotate inside a cavity 431 disposed within a lateral sidewall of a drill pipe 423. A rotational center of the rotor 430 may be offset from a center of the cavity 431. Each of the plurality of vanes 440 may be pressed by one of a plurality of springs 441 against an inner wall of the cavity 431 and be allowed to slide into and out of the rotor 430 creating vane chambers 442 where fluid may be contained. At an intake 443 of the motor, the vane chambers 442 may increase in volume while being filled with drilling fluid forced in by a pressure at the inlet 443. At a discharge 444 of the motor, the vane chambers 442 decrease in volume, forcing fluid out of the motor.
FIG. 5-1 shows an embodiment of a downhole transducer assembly 520 comprising a Pelton wheel 521. The Pelton wheel 521, as also shown in FIG. 5-2, comprises a plurality of cups 550 mounted around an exterior of a wheel 551. A portion of drilling fluid 525 traveling along a drill pipe 523 may impinge upon the cups 550 to rotate the wheel 551. Each of the plurality of cups 550 may comprise a geometry capable of redirecting the portion of drilling fluid 525 back in the direction from whence it came. In this manner, a large percentage of the energy of the impinging drilling fluid 525 may be transferred to the wheel 551.
FIG. 6 shows a portion of an embodiment of a downhole transducer assembly 620 comprising a turbine 621. The turbine 621 may comprises a plurality of blades 650 mounted around an exterior of a drum 651. Drilling fluid 625 may be directed toward the turbine 621 through a flow channel 660 that may generate a helical form 661 in the drilling fluid 625. This helical form 661 may allow the drilling fluid 625 to impinge upon the plurality of blades 650 of the turbine 621 at an angle positioned somewhere between parallel and perpendicular to a rotational axis of the turbine 621. It is believed that impinging upon turbine blades at such an angle may allow for a smaller turbine to be used than previously thought possible.
FIG. 7-1 shows a portion of an embodiment of a downhole transducer assembly comprising a turbine 721-1 connected to a generator 722-1 by a shaft 770-1. A course 726-1 leading to the turbine 721-1 may conduct a portion of drilling fluid traveling through a drill pipe to impact the turbine 721-1 tangentially relative to a rotational axis of the turbine 721-1. The turbine 721-1 may be capable of sliding along the shaft 770-1 relative to the course 726-1 (as shown by the dotted lines). By so doing, the turbine 721-1 may move into and out of contact with drilling fluid passing through the course 726-1. Additionally, the turbine 721-1 may comprise an angled geometry such that the turbine 721-1 may be positioned partially within contact with the drilling fluid to varying degrees. For example, FIG. 7-2 shows an embodiment of a turbine 721-2 comprising a plurality of angled blades 771-2 that may catch a passing fluid to varying degrees based on the turbine's 721-2 position relative thereto. p Referring back to FIG. 7-1, the turbine 721-1 may be slid along the shaft 770-1 by a translatable ramp 772-1 that may be accessed from an exterior of a drill pipe holding the downhole transducer assembly. For instance, FIG. 7-3 shows an embodiment of a drill pipe 723-3 comprising a ramp 772-3 accessible from an exterior wall thereof. The ramp 772-3 may be secured in various physical positions along the drill pipe 723-3. While the present embodiment shows a translatable ramp mechanism to slide a turbine, other adjustment mechanisms would also be suitable.
FIG. 8-1 shows a portion of an embodiment of a downhole transducer assembly comprising a turbine 821-1 connected to a generator 822-1 by a shaft 870-1. The turbine 821-1 may be removable from the shaft 870-1 through an opening 880-1 in a side of the drill pipe holding the downhole transducer assembly. For example, FIG. 8-3 shows an embodiment of a drill pipe 823-3 comprising an opening 880-3 on an exterior thereof After one turbine is removed 881-3 through the opening 880-3, a replacement turbine 882-3 may be inserted in its stead. To effectuate such a change, an embodiment of a turbine 821-2, as shown in FIG. 8-2, may comprise a slot 883-2 disposed therein that may fit over a shaft.
Whereas the present invention has been described in particular relation to the drawings 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.
Patent Application
20170241242
