Boring or penetrating the earth – With tool shaft detail – Shaft carried guide or protector
Reexamination Certificate
2000-07-19
2002-08-27
Bagnell, David (Department: 3672)
Boring or penetrating the earth
With tool shaft detail
Shaft carried guide or protector
C175S045000, C175S061000, C175S073000
Reexamination Certificate
active
06439325
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to drilling oil wells. More specifically, the invention relates to directional drilling and the use of downhole steering. Even more specifically, the invention relates to an apparatus for transferring power between a rotating member and a non-rotating member of a bottom hole assembly.
2. Description of the Related Art
To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled by rotating a drill bit attached to the bottom of a drilling assembly (also referred to herein as a “Bottom Hole Assembly” or “BHA”). The drilling assembly is attached to the bottom of a drill tube, which is usually either a jointed rigid pipe (commonly referred to as the drill pipe) or a relatively flexible spoolable tubing (commonly referred to in the art as the “coiled tubing”). The string comprising the tubing and the drilling assembly is usually referred to as the “drill string.” When jointed pipe is utilized as the tubing, the drill bit is rotated by rotating the jointed pipe from the surface and/or by a mud motor contained in the drilling assembly. In the case of a coiled tubing, the drill bit is rotated by the mud motor. During drilling, a drilling fluid (also referred to as the “mud”)is supplied under pressure into the tubing. The drilling fluid passes through the drilling assembly and then discharges at the drill bit bottom. The drilling fluid provides lubrication to the drill bit and carries to the surface rock pieces disintegrated by the drill bit in drilling the borehole. The drilling fluid passing through the drilling assembly rotates the mud motor. A drive shaft connected to the motor and the drill bit rotates the drill bit.
It is well known that formations capable of producing significant amounts of oil and gas (hydrocarbons) are increasingly difficult to find. In addition, economic, political and environmental concerns can make it impossible to place a drilling system directly over a promising formation. As a result, a substantial proportion of the current drilling activity involves drilling of deviated and horizontal borehholes to more fully exploit the hydrocarbon reservoirs. In deviated and horizontal drilling, the wellbore is intentionally drilled at an angle from vertical by special downhole drilling tools to guide the drill assembly in the desired direction. These wellbores are drilled to reach a part of a formation or reservoir, which cannot be drilled by a straight or vertical hole because of the environmental, political, or economic reasons mentioned. Such boreholes can have relatively complex well profiles. To drill such complex boreholes, steerable drilling assemblies are sometimes utilized. A particular drilling assembly includes a plurality of independently operable force application members to apply force on the wellbore wall during drilling of the wellbore to maintain the drill bit along a prescribed path and to alter the drilling direction. Such force application members may be disposed on the outer periphery of the drilling assembly body or on a non-rotating sleeve disposed around a rotating drive shaft. These force application members are moved radially outward from the drilling assembly by electrical devices or electro-hydraulic devices to apply force on the wellbore in order to guide the drill bit and/or to change the drilling direction outward. In such drilling assemblies, there exists a gap between the rotating and the non-rotating sections. To reduce the overall size of the drilling assembly and to provide more power to the ribs, it is desirable to locate the devices (such as motor and pump) required to operate the force application members in the non-rotating section. It is also desirable to locate electronic circuits and certain sensors in the non-rotating section. Thus, power must be transferred between the rotating section and the non-rotating section to operate mechanical devices and the sensors in the non-rotating section.
In drilling assemblies which do not include a non-rotating sleeve as described above, it is desirable to transfer electrical and mechanical power between the rotating drill shaft and the stationary housing surrounding the drill shaft. The power transferred to the rotating shaft may be utilized to operate sensors or mechanical devices in the rotating shaft and/or drill bit. Power transfer between rotating and non-rotating sections having a gap therebetween can also be useful in other downhole tool configurations.
The present invention, which is especially desirable in a space-restrictive application such as the drilling of very small deviated boreholes, provides contactless inductive coupling to convert electrical power in one section to mechanical power in another section where the sections are rotating and non-rotating sections of downhole oilfield tools, including the drilling assemblies containing rotating and non-rotating members. This direct transfer and conversion has the desirable characteristic of requiring fewer components than other tools that transfer electrical power to operate electrically controlled devices to perform mechanical functions such as operating pumps. Direct conversion means fewer parts, thus leading to more economical, reliable and compact tool designs.
SUMMARY OF THE INVENTION
In general, the present invention provides apparatus for power transfer over a nonconductive gap between rotating and non-rotating members of downhole oilfield tools. The gap may contain a non-conductive fluid, such as drilling fluid or oil for operating hydraulic devices in the downhole tool. The downhole tool, in one embodiment, is a drilling assembly wherein a drive shaft is rotated by a downhole motor to rotate the drill bit attached to the bottom end of the drive shaft. A substantially non-rotating sleeve around the drive shaft includes a plurality of independently operated force application members, wherein each such member is adapted to be moved radially between a retracted position and an extended position. The force application members are operated to exert the force required to maintain and/or alter the drilling direction. In the preferred system, one or more mechanically operated devices such as hydraulic units provide energy (power) to the force application members. A transfer device transfers electrical power between the rotating and non-rotating members, and the electric power is converted directly to mechanical power. An electronic control circuit or unit associated with the rotating member controls the transfer of power between the rotating member and the non-rotating member.
In a preferred embodiment, the present invention is particularly suited for a Rotary Closed-Loop System (RCLS) type tool for drilling deviated boreholes with very small hole sizes. A RCLS system is an automated directional drilling system that contains its own programmed controller and steering sub, and drills continuously in the rotary mode. A non-rotating, orienting sleeve controls steering expanding force application members. Precisely controlled force on the force application members produces resultant force vectors that maintain inclination alignment and direction within the program well path. Course corrections are made continuously while drilling, with no trips required for tool adjustments. Real-time surface monitoring permits changes to the wellpath program if desired. This technology increases the rate-of-penetration, improves hole quality, and enables greater extended reach capability. The embodiment may also comprise measurement while drilling (MWD), geosteering and automated rotary drilling capability.
In general, one or more steering ribs are controlled by hydraulic pressure. A motor located on the rotating shaft of a bottom hole assembly driving an axial piston pump in the non-rotating sleeve manages the generation of hydraulic pressure. The motor windings are positioned on the rotating shaft and a magnetically polarized rotor is located on the non-rotating sleeve. There would be one motor for controlling a hydraulic pump for each st
Peters Volker
Ragnitz Detlef
Bagnell David
Baker Hughes Incorporated
Madan Mossman & Sriram P.C.
Walker Zakiya
LandOfFree
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