Inductive power coupler

This application is a continuation in-part of U.S. application Ser. No. 11/421,387 filed on May 31, 2006, which is a continuation in-part of U.S. application Ser. No. 11/421,357, now U.S. Pat. No. 7,382,273.” U.S. application Ser. No. 11/421,357 is a continuation in-part of U.S. application Ser. No. 11/133,905, now U.S. Pat. No. 7,277,026, filed on May 21, 2005 and entitled, “Downhole Component with Multiple Transmission Elements.” All of these references are herein incorporated by reference for all that they contain.

The present invention relates to downhole drilling, and more particularly, to systems and methods for transmitting power and data to components of a downhole tool string. As downhole instrumentation and tools have become increasingly more complex in their composition and versatile in their functionality, the need to transmit power and/or data through tubular tool string components is becoming ever more significant. Real-time logging tools located at a drill bit and/or throughout a tool string require power to operate. Providing power downhole is challenging, but if accomplished it may greatly increase the efficiency of drilling. Data collected by logging tools are even more valuable when they are received at the surface in real time.

Many attempts have been made to provide high-speed data transfer or usable power transmission through tool string components. One technology developed involves using inductive couplers to transmit an electric signal across a tool joint. U.S. Pat. No. 2,414,719 to Cloud discloses an inductive coupler positioned within a downhole pipe to transmit a signal to an adjacent pipe.

U.S. Pat. No. 4,785,247 to Meador discloses an apparatus and method for measuring formation parameters by transmitting and receiving electromagnetic signals by antennas disposed in recesses in a tubular housing member and including apparatus for reducing the coupling of electrical noise into the system resulting from conducting elements located adjacent the recesses and housing.

U.S. Pat. No. 4,806,928 to Veneruso describes a downhole tool adapted to be coupled in a pipe string and positioned in a well that is provided with one or more electrical devices cooperatively arranged to receive power from surface power sources or to transmit and/or receive control or data signals from surface equipment. Inner and outer coil assemblies arranged on ferrite cores are arranged on the downhole tool and a suspension cable for electromagnetically coupling the electrical devices to the surface equipment is provided.

U.S. Pat. No. 6,670,880 to Hall also discloses the use of inductive couplers in tool joints to transmit data or power through a tool string. The \'880 patent teaches of having the inductive couplers lying in magnetically insulating, electrically conducting troughs. The troughs conduct magnetic flux while preventing resultant eddy currents.

U.S. Pat. No. 7,277,026, also to Hall, discloses a tubular component in a downhole tool string with first and second inductive couplers in a first end and third and fourth inductive couplers in a second end. A first conductive medium connects the first and third couplers and a second conductive medium connects the second and fourth couplers. The first and third couplers are independent of the second and fourth couplers.

All of the above cited references are herein incorporated by reference for all that it discloses.

In one aspect of the present invention, a downhole tool string component has a tubular body with at least one end adapted for threaded connection to an adjacent tool string component. The end has at least one shoulder that abuts an adjacent shoulder of an adjacent end of the adjacent tool string component. At least two electrically conducting coils are disposed within an annular recess formed in the at least one shoulder and an annular trough is disposed in the annular recess. The annular trough houses at least one of the at least two electrically conducting coils and each coil is electrically insulated from each other.

The adjacent shoulder may have at least two adjacent electrically conducting coils and an adjacent annular trough disposed in an adjacent annular recess formed in the adjacent shoulder configured similar to the at least two electrically conducting coils and the annular trough in the downhole tool string component and may couple when the downhole components are connected together at their ends, wherein the at least two coils and the at least two adjacent coils induce magnetic fields in each other when the coils are electrically energized.

The at least two electrically conducting coils and the annular trough may be part of a modular unit that plugs into an electrical circuit disposed in the downhole tool string component. The annular trough may concentrate a magnetic field generated by at least one of the at least two electrically conducting coils.

A first coil of the at least two electrically conducting coils may have at least two annular loops. The first coil may be housed within the annular trough. A magnetic current with a frequency of 35 kHz to 150 kHz may be emitted from the first coil when the first coil is electrically energized. The first coil may have a positive lead and a negative lead that connects the first coil into an electrical circuit disposed in the downhole tool string component.

A second coil of the at least two electrically conducting coils may have a single annular loop. The second coil may be grounded to the at least one shoulder. The second coil may be housed within the annular trough. The second coil may be disposed outside of the annular trough. The second coil may have a lead that connects the first coil into an electrical circuit disposed in the downhole tool string component. A magnetic current with a frequency of 2 MHz to 7 MHz may be emitted from the second coil when the second coil is electrically energized.

The annular trough may comprise segments with a composition alternated between at least two different ferrite alloys. The at least two different ferrite alloys may be manganese zinc ferrite and nickel zinc ferrite. The annular trough may comprise a material comprising a composition selected from the group consisting of ferrite, Ni, Fe, Cu, Mo, Mn, Co, Cr, V, C, Si, Zn alloys and combinations thereof. The annular trough may comprise two side walls and a bottom of uniform thickness.

The downhole tool string component may be a drill pipe, drill collar, a bottom hole assembly, a reamer, a jar, a production pipe, a mandrel, a sleeve, or combinations thereof. An electronic amplifier may be disposed in the downhole tool string component that may amplify an electrical signal of at least one of the at least two electrically conducting coils.

A steel housing may be disposed within the annular recess and houses the annular trough. One of the at least two electrically conducting coils may be disposed intermediate the steel housing and the annular trough.

In another aspect of the present invention, an inductive coupler comprises at least two electrically conducting coils disposed within an annular recess. An annular trough is disposed in the annular recess and houses at least one of the at least two electrically conducting coils. Both of the coils are electrically isolated from one another.