OPTICAL FIBER BASED DOWNHOLE SEISMIC SENSOR SYSTEM BASED ON RAYLEIGH BACKSCATTER

摘要

The present invention provides an optical fiber-based seismic monitoring system including a light source that drives an optical fiber positioned within a borehole. At least one light sensor analyzes Rayleigh backscattered light to obtain an acoustic signal for each of multiple points along the borehole. One or more processors operate to determine microseismic event direction, distance, and/or intensity based at least in part on phase information of said acoustic signals. The acoustic signal cross-correlations, semblances, or phase-sensitive similarity measures can be determined as a function of scanning direction to accurately determine the relevant microseismic event information. The optical fiber may be positioned in the cemented annulus of a cased borehole having a shape that extends along more than one dimension (e.g., an L-shaped borehole).