Investigating subterranean formations using electromagnetic and seismic measurements obtained simultaneously using an EM receiver for both measurements

摘要

An EM-seismic logging tool for use in a subterranean formation penetrated by a well bore is configured to make electromagnetic and seismic measurements simultaneously using an EM receiver array for both measurements. The electromagnetic receivers R measure an electromagnetic field and perturbations in the electromagnetic field caused by the mechanical energy generated by the activation of a seismic source 10. The perturbations in the measured electromagnetic field are due to motion of the receiver or motion of the formation. The electromagnetic field may be generated by a transmitter T or may be the earth's naturally occurring electromagnetic field. The transmitter T may be in the wellbore, in a second wellbore, or on the surface. The seismic source may be in the wellbore or on the surface. The receivers R may be clamped to the formation or mechanically isolated from the wellbore walls using soft centralizers. The EM transmitter, EM receivers and seismic source may be synchronised through GPS.