METHOD AND APPARATUS FOR DETECTING OVERPRESSURED ZONE AHEAD OF A DRILL BIT USING RESISTIVITY AND SEISMIC MEASUREMENTS

摘要

A resistivity logging tool suitable for downhole use includes a transmitter and two spaced apart receivers. The measured signals are inverted to determi ne the distance to an overpressured zone in the earth formation. The overpressured zone may be a transition zone in resistivity. The direction of drilling may be controlled based on the determined distance. Optionally, seismic-while drilling measurements may be made from which a separate estima te of the distance can be obtained. The SWD~ measurements may also be processed to estimate the pore pressure.