Patent ID: 8239172

Claim:
A method of evaluating an earth formation using a tool conveyed within a borehole in the earth formation, the tool having a body with a finite, non-zero conductivity, the method comprising: using a transmitter on the tool for producing a transient electromagnetic signal in the earth formation; using at least one receiver for-producing a signal responsive to an interaction of the transient electromagnetic signal with the earth formation, the produced signal comprising a first time interval including a first component responsive to a property of the earth formation and a second component responsive to the conductivity of the tool, and a second time interval subsequent to the first time interval and responsive substantially to the conductivity of the tool; and estimating the first component of the produced signal in the first time interval by performing a least-squares fit only to the produced signal in the second time interval, extrapolating the least-squares fit to define a non-constant extrapolated signal in the first time interval, and subtracting the non-constant extrapolated signal from the produced signal.