Patent ID: 6597632
Filing Date: 2003-07-22
Classification: G01V

Abstract:
A method for mapping the open fractures in an earth formation from two seismic signals transmitted into said formation: one high-frequency seismic signal transmitted from within one wellbore and received in another wellbore, and the other low-frequency seismic signal transmitted from the surface; both seismic signals synchronized and transmitted at preselected frequencies, the interaction of the two transmitted signals received and recorded by the down hole receivers; the method comprising:spectrally analyzing said received signals; determining the interaction of the low- and high-frequency signals as they propagate through the open fractures; and determining the relative spectral amplitudes of the high-frequency signal that is transmitted from one wellbore and received in the other; specifically measuring the amplitude difference of the fundamental of the higher frequency and its harmonics during rarefaction and compression cycles of the lower-frequency signal.