Method and apparatus for measuring resistivity of an earth formation

摘要

The method and apparatus of the invention determines earth formation resistivity at extended depths into the formation by the use of telemetry transmission signals to measure the formation resistivity. The telemetry transmission signals carry measurement data from downhole sensors (78) through the formation to an uphole receiver (80). The signal transmission is by means of induction telemetry. At the receiver (80), the signal is demodulated to obtain the transmitted measurement data. During the detection of the signal at the receiver, the signal amplitude is also extracted and is used to determine the formation resistivity. In addition, changes in the signal amplitude are also used to indicate formation boundaries for determining well location during directional drilling.