Patent ID: 7557581

Claim:
A method for imaging a subterranean formation traversed by a wellbore using a tool comprising a transmitter for transmitting electromagnetic signals through the formation and a receiver for detecting response signals, the methods comprising steps: (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) creating an image of the formation within the subterranean formation based on plots from at least two tool positions by plotting the derived quantity for the formation calculated in respect of the tool at the at least two positions in the same plot and fitting at least one curve to at least one series of inflection points in the plots of the derived quantity for said at least two positions.