Patent Application
20190048691
In endeavors such as the exploration or extraction of subterranean resources such as oil, gas, and geothermal energy, it is common to form boreholes in the earth. To form such a borehole 111, a specialized drill bit 112 may be suspended from a derrick 113 by a drill string 114 as shown in
Various electronic devices, such as sensors, receivers, communicators or other tools, may be disposed along the drill string or at the drill bit. To power such devices, it is known to generate electrical power downhole by converting kinetic energy from the 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 and/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.
The turbine described by Inman is known as an axial turbine because the fluid turning the turbine flows parallel to the turbine's axis of rotation. An example of an axial turbine 220 is shown in
It may be typical in downhole applications employing an axial turbine to pass around 800 gallons/minute (3.028 m3/min) of drilling fluid past such a turbine. As the drilling fluid rotates the axial 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 downhole turbine that requires less fluid flow to operate. An additional need exists for a downhole turbine that does not require retrieving a detachable section in order to pass devices through a drill string.
A downhole turbine assembly may comprise a tangential turbine disposed within a section of drill pipe. A portion of a fluid flowing through the drill pipe may be diverted to the tangential turbine generally perpendicular to the turbine's axis of rotation. After rotating the tangential turbine, the diverted portion may be discharged to an exterior of the drill pipe.
As the pressure difference between fluid inside the drill pipe and fluid outside the drill pipe may be substantial, it may be possible to produce a substantially similar amount of energy from a tangential turbine, as compared to an axial turbine, while utilizing substantially less drilling fluid. For example, while it may be typical in downhole applications to pass around 800 gallons/minute (3.028 m3/min) of drilling fluid past an axial turbine of the prior art, as discussed previously, which then may experience a pressure drop of around 5 pounds/square inch (34.47 kPa), diverting around 1-10 gallons/minute (0.003785-0.03785 m3/min) of drilling fluid past a tangential turbine and then discharging it to an annulus surrounding a drill pipe may allow that fluid to experience a pressure drop of around 500-1000 pounds/square inch (3,447-6,895 kPa) capable of producing substantially similar energy.
In the embodiment shown, the tangential turbine 320 is disposed within a sidewall of the drill pipe 315. A rotational axis of the tangential turbine 320 may be parallel to the central axis of the drill pipe while also being offset from the central axis. In this configuration, the primary drilling fluid 323 passing through the drill pipe 315 is not obstructed by the tangential turbine 320, allowing for objects to be passed through the drill pipe 315 generally unhindered.
An outlet 332 for discharging the diverted portion of drilling fluid 333 to an exterior of the drill pipe 315 may be disposed on a sidewall of the drill pipe 315. In the embodiment shown, a check valve 334 is further disposed within the outlet to allow fluid to exit the drill pipe 315 but not enter.
Polycrystalline diamond (PCD) bearings 331 may support the tangential turbine 320 and rotor 321 allowing them to rotate. It is believed that PCD bearings may require less force to overcome friction than traditional mud-lubricated bearing systems described in the prior art. It is further believed that PDC bearings may be shaped to comprise a gap therebetween sufficient to allow an amount of fluid to pass through while blocking particulate. Allowing fluid to pass while blocking particulate may be desirable to transport heat away from a generator or balance fluid pressures.
The tangential turbine 420 may comprise PCD to reduce wear from the fluid entering the chamber 442. In some embodiments, the tangential turbine 420 may be formed entirely of PCD.
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.
This patent application is a continuation of U.S. patent application Ser. No. 15/152,189, filed May 11, 2016 and entitled “Downhole Turbine Assembly,” which claims priority to U.S. Provisional Pat. App. No. 62/164,933 filed on May 21, 2015 and entitled “Downhole Power Generator,” both of which are incorporated herein by reference for all that they contain.
| Number | Date | Country | |
|---|---|---|---|
| 62164933 | May 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15152189 | May 2016 | US |
| Child | 16163627 | US |
