Mapping subsurface open fractures in a reservoir using a surface impulse and a downhole vibratory source

A method for mapping the open fractures in an earth subsurface formation between two wells, which have been drilled in that subsurface formation, using two seismic signals transmitted into the said formation. One high frequency seismic signal transmitted from within one wellbore and received in another wellbore, and the other a lower frequency seismic impulse generated and transmitted from the surface or near surface. Both seismic signals synchronized in time, the interaction of the two transmitted signals as they propagate through the open fractures, received and recorded by the downhole receivers. The method comprising:

• Recording the time synchronized high frequency ‘carrier’ seismic signal transmitted by a downhole source in one wellbore, and recorded by a receiver array in another wellbore, recording this data set by moving the downhole source vertically at predetermined spacings to provide a complete coverage of the reservoir zone of interest by the source and receiver positions, use this data set as a ‘reference’ to monitor the interaction of the surface generated seismic impulse with the ‘carrier’ signal as both these signals propagate through the fractures;
• Recording a second data set where both the sources, one located at the surface or near surface, which generates a seismic acoustic pulse, and the other a downhole source located in a wellbore that transmits a high frequency ‘carrier’ seismic signal, are activated in synchronism and simultaneously;
• The surface source deployed in a predetermined geometric pattern designed to detect the orientation and location of the open fractures in the reservoir space between the source and receiver wells.