Patent ID: 6747915
Filing Date: 2004-06-08
Classification: G01V

Abstract:
A method of seismic imaging a subsurface formation using a set of seismic sources i and a set of seismic receivers j, wherein there is a complex transmission medium between the two sets, which method comprises the steps of(a) recording with the set of seismic receivers j the signals tij(t) obtained from activating the set of seismic sources i; (b) selecting a seismic receiver m as the location of a virtual source; (c) selecting a seismic receiver k, wherein k is in a predetermined range around the position of seismic receiver m; (d) selecting a seismic source n from the seismic sources i; (e) time-reversing at least a part of the signal tnm(t) to obtain a time-reversed signal tnm(âˆ’t); (f) convolving the time-reversed signal tnm(âˆ’t) with the signal tnk(t) to obtain the convolved signal tconvnmnk(t)=tnm(âˆ’t){circle around (Ã—)}tnk(t); (g) selecting a next source n, repeating steps (e) and (f) until a predetermined number of sources have had their turn; (h) summing the convolved signals over the seismic sources n to obtain a signal tm&it;â€ƒ&it;kv&it;â€ƒ&it;s&it;(t)=&Sum;n&it;tn&it;â€ƒ&it;m&it;â€ƒ&it;n&it;â€ƒ&it;kc&it;â€ƒ&it;o&it;â€ƒ&it;n&it;â€ƒ&it;v,â€ƒWhere tvsmk(t) is the signal received by a receiver at the position k from a virtual source at the position of receiver m; (i) repeating steps (c) through (g) over k; (j) repeating steps (b)-(h) over m to generate a seismic survey with virtual sources m and receivers k; and (k) further processing the virtual source signals to obtain a seismic image.