Impedance-matched drilling telemetry system
A downhole telemetry system that uses inductance or capacitance as a mode through which signal is communicated across joints between assembled lengths of pipe wherein efficiency of signal propagation through a drill string, for example, over multiple successive pipe segments is enhanced through matching impedances associated with the various telemetry system components.
1. A drilling telemetry system comprising:
a plurality of communications packages in association with a plurality of drill pipe segments, each pipe segment having an outer surface, and an inner surface, and two ends bearing threads that enable the drill pipe segments to be assembled to form a drill pipe, with each communications package comprising:
i) a first wire coil, having a first impedance, adapted to function as an inductance transmitter,
ii) a second wire coil, having a second impedance, adapted to function as an inductance receiver,
iii) connecting wire, having a length and a third impedance, adapted to electrically adjoin the first wire coil to the second wire coil,
iv) first and second insulating packages, each comprising a magnetic component and an electrically and magnetically insulating component and
v) a polyethylene sleeve
wherein the first wire coil is positioned at one end of a drill pipe segment, the second wire coil is positioned at the other end of the same drill pipe segment, the connecting wire is positioned so that at least a portion of its length lies between the polyethylene sleeve and the inner surface of the pipe segment,
and further wherein first, second and third impedances for a given communications package contribute to a total impedance associated with that communications package that substantially matches total impedance associated with at least one other communications package in the drilling telemetry system.
2. A drill pipe containing an electrical signal transmission line comprising:
a plurality of segments of drill pipe formed of iron or steel tube, each segment having an outer surface and an inner surface and two circular ends that enable the drill pipe segments to be assembled to form a drill pipe with a first end of each segment adjacent and rigidly coupled to a second end of another segment with the inner surfaces of adjoining segments being aligned, each end of each segment additionally comprising:
i) an outer circular groove in said tube end, said outer groove having a groove surface extending into said end from an inner edge adjacent said inner surface to an outer edge adjacent said outer surface;
ii) a coil of electrical conductor in said groove;
iii) a ferrite material within said groove and spacing said coil from said groove surface; and
iv) a nonmagnetic, electrically insulating mate spacing said ferrite material from said groove surface; and
connecting wire electrically insulated from said pipe and electrically connecting the first wire coil to the second wire coil;
wherein when two pipes are assembled into a drill pipe, a coil and ferrite material at each of the connected ends of the pipes are adjacent and facing each other so that an electrical signal carried to one coil along its conductor is coupled to the facing coil for transmission along its conductor to another coil.
3. The drill pipe of claim 2 wherein said ferrite material and said insulator are recessed from the end of said pipe, the recess being covered by an electrically insulating material.
4. The drill pipe of claim 2 wherein said ferrite material and insulator extend to the end of said pipe.
5. The drill pipe of claim 2 wherein said insulator is plastic.
6. The drill pipe of claim 2 wherein said insulator is hard rubber.