METHOD FOR IMAGING SUBTERRANEAN FORMATIONS

摘要

A method for using a tool in a wellbore in a formation to predict an anomaly in the formation ahead of the device, the tool comprising a transmitter for transmitting electromagnetic signals through the formation and a receiver for detecting response signals. the method comprises a) bringing the tool to a first position inside the wellbore; b) energizing the transmitter to propagate a transient electromagnetic signal into the formation; c) detecting a response signal that has propagated through the formation as a result of the transient signal in step (b); d) calculating a derived quantity for the formation as a function of time based on the detected response signal for the formation; e) plotting the derived quantity for the formation against time; f) moving the tool to at least one other position within the wellbore and repeating steps (b) to (e); g) predicting an anomaly in the formation.