METHODS AND APPARATUS FOR GEOPHYSICAL PROSPECTING TO DETECT BODIES OF FLUIDS IN UNDERGROUND FORMATIONS

摘要

A method of geophysical prospecting for detecting bodies of fluids in underground formations comprises the steps of activating a seismic energy source (2) to transmit seismic energy into the ground, detecting an electromagnetic signal (14) generated by interaction between the seismic energy and underground formations (12) including fluids, and recording properties of the detected electromagnetic signal against time, so as to record an electromagnetic signal generated by interaction between a secondary energy impulse (10) from the activation of the energy source and underground formations including fluids. The secondary energy impulse propagates to the formations more slowly than the primary seismic waves from the same activation of the energy source travelling at the speed of sound as attenuated by the materials through which they pass. The detected electromagnetic signal comprises frequencies in the range 0 to 30 Hz. Recorded signals may then be processed to correlate them with the depth and thickness of fluid-containing underground formations with which the secondary energy impulse interacts to generate the electromagnetic waves.