SYSTEM AND METHOD FOR INVESTIGATING SUB SURFACE FEATURES OF A ROCK FORMATION

摘要

A method and system for investigating rock formations outside a borehole are provided. The method includes generating a first acoustic wave at a first frequency by a first acoustic source (105); and generating a second acoustic wave at a second frequency by a second acoustic source (115). The first and the second acoustic sources are arranged within a localized area of the borehole (110). The first and the second acoustic waves intersect in an intersection volume (130) outside the borehole. The method further includes receiving a third acoustic wave at a third frequency the third shear acoustic wave returning to the borehole due to a non linear mixing process in a nonlinear mixing zone within the intersection volume at a receiver (135) arranged in the borehole. The third frequency is equal to a difference between the first frequency and the second frequency.