Patent ID: 8902707
Filing Date: 2014-12-02
Classification: G01V

Abstract:
1. A method of identifying a location of a microseismic event in an earth formation, the method comprising: deploying a first array of near vertically spaced apart acoustic detectors in a borehole in the earth formation; deploying a second array of acoustic detectors at or near a surface of the earth; receiving acoustic signals at the first array of detectors and at the second array of detectors resulting from the microseismic event in the subsurface; using a time of arrival of the received acoustic signals to estimate a vertical location of the microseismic event and a horizontal location of the microseismic event; and determining a statistical measure of uncertainty of the location of the microseismic event using an estimated value of an error in the time of arrival, wherein the statistical measure of uncertainty relates to an error ellipsoid determined using at least (i) a variance factor (s) estimating a picking error of arrivals, (ii) eigenvalues of a parameter covariance matrix, and (iii) a cumulative distribution function (F).