Patent ID: 8315486
Filing Date: 2012-11-20
Classification: G01V

Abstract:
1. A method for obtaining information about a subsurface formation from acoustic signals that contain information about to the subsurface formation, comprising: a) providing at least one fiber optic cable deployed within acoustic range of the subsurface formation, said fiber optic cable having a proximal end and a remote end, said proximal end being coupled to a light source and to a proximal photodetector, wherein said fiber optic cable includes randomly spaced impurities and a plurality of selectively placed fiber Bragg gratings, wherein said fiber optic cable is acoustically coupled to the subsurface formation so as to allow the acoustic signals to affect the physical status of at least one grating, wherein at least a portion of the cable that includes at least one of the fiber Bragg gratings is affixed to equipment placed in a borehole and the placement of the Bragg gratings is selected using preexisting information about the subsurface formation; b) transmitting into the fiber optic cable at least one light pulse; c) receiving at the photodetector a first light signal indicative of at least two aspects selected from the group consisting of acoustic events within or outside of the borehole, fluid flow into the borehole, deformation or corrosion of tubing or casing in the borehole, pressure changes in the borehole, and/or changes in the strain state of the formation surrounding the borehole at at least one first section of the fiber optic cable, d) optionally, repeating steps a)-c) so as to collect a second light signal indicative of the physical status of a section of the fiber optic cable and further processing the first and second light signals so as to produce derivative information; and e) outputting at least one of a light signal and the derivative information to a display.