Sub-surface formation boundary detection using an electric-field borehole telemetry apparatus

Abstract

The method of maintaining drill bit advancement in an underground formation that contains shale, including providing an electrical signal from an insulated gap location in a drill string substantially directly behind the bit in the formation, detecting substantial change in a signal as the bit advances, and changing the direction of drilling of the bit as a function of a signal change, to thereby maintain the direction of bit advancement in the formation. A method is disclosed for detecting the existence and direction of adjacent bed boundaries. A short hop transmitter assembly generates a signal that is detected by an associated receiver assembly. The received signal(s) are tied to the azimuthal orientation of the transmitter or receiver and processed to yield the direction and/or the distance of the bed boundary. This information is transmitted to the surface via surface telemetry for real-time control of the drilling assembly to stay within, or to enter, a pay zone.