Patent ID: 9046620
Filing Date: 2015-06-02
Classification: A61P,G01V,G10K

Abstract:
1. A method of generating a three-dimensional image of a rock formation comprising: generating a first acoustic signal by a first acoustic source, wherein the first acoustic signal comprises a first plurality of pulses arranged in a time sequence, the first plurality of pulses being separated in time, each pulse comprising a first modulated signal at a central frequency, wherein central frequencies of two consecutive pulses are different; generating a second acoustic signal by a second acoustic source, wherein the second acoustic signal comprises a second plurality of pulses arranged as a time sequence, the second plurality of pulses being separated in time, wherein a separation in time between centers of two consecutive pulses is the same as a separation in time between centers of two corresponding pulses in the first plurality of pulses, wherein a start time difference is provided between a start time of a broadcast of the second plurality of pulses and a start time of a broadcast of the first plurality of pulses, wherein each pulse comprises a modulated signal and wherein a central frequency of the modulated signal within each pulse in the second plurality of pulses is a selected fraction of the central frequency of the modulated signal within each corresponding pulse in the first plurality of pulses; wherein the first acoustic source and the second acoustic source are arranged within the borehole and are controllable such that trajectories of the first and the second acoustic signals intersect in an intersection volume outside the borehole; receiving, by a receiver arranged within the borehole, a detected signal returning to the borehole, the detected signal including a signal being generated by a non-linear mixing process from the first acoustic signal and the second acoustic signal in a non-linear mixing zone within the intersection volume; performing, by a processor, data processing on the received signal to extract the signal generated by the non-linear mixing process over noise or over signals generated by a linear interaction process, or both; and generating a three dimensional image of a propagation compressional velocity, a propagation of shear velocity, a ratio of compressional velocity and shear velocity, or non-linear properties of a rock formation, or any combination of two or more thereof based on the signal generated by the non-linear mixing process.