Dtem with short spacing for deep, ahead of the drill bit measurements

摘要

A transmitter on a bottomhole assembly (BHA) is used for generating a transient electromagnetic signal in an earth formation. A processor estimates the distance to a resistivity interface using a signal produced by a receiver on the BHA. The transmitter-receiver distance may be less than 1m. The estimation of the distance is done in real time using a thin conductive sheet approximation.