Formation measurements using downhole noise sources

Abstract

A method of performing measurements of an earth formation includes disposing at least a first receiver and a second receiver in one or more monitoring boreholes in a formation, and injecting fluid into the formation from an injection borehole, wherein injecting includes operating a fluid control device to generate seismic and/or acoustic noise having an identifiable characteristic. The method also includes detecting seismic and/or acoustic signals at the first receiver and detecting seismic and/or acoustic signals at a second receiver, the seismic and/or acoustic signals corresponding to the seismic and/or acoustic noise, calculating an estimate of a Green's function between the first receiver and the second receiver by processing seismic and/or acoustic waves detected by the first receiver and the second receiver to at least partially reconstruct the Green's function, and estimating variations in a velocity of a region of the formation by determining variations in the reconstructed Green's function.