Patent ID: 8749241

Claim:
A method of geophysical prospecting for detecting bodies of fluids in underground formations, comprising the steps of: activating a seismic energy source to transmit seismic energy into the ground, the seismic energy from the activation comprising seismic waves which travel at the speed of sound as attenuated by the materials through which they pass and a slow energy impulse propagating from the energy source to the formations more slowly than the seismic waves; detecting an electromagnetic signal generated by interaction between the slow energy impulse from the activation of the energy source and underground formations including fluids, wherein the detected electromagnetic signal comprises frequencies in the range 0 to 30 Hz; recording data representing a parameter derived from the detected electromagnetic signal against time; and processing the recorded data by correlating it with the depth of fluid-containing underground formations with which the slow energy impulse interacted to generate the electromagnetic signal on the basis that the slow energy impulse travelled from the energy source to the underground formations at an average speed in the range 5 to 30 m/s.