Seismic imaging a subsurface formation
AssigneeShell Oil Company
InventorRodney William Calvert
Life of this patent
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Abstract
A method of seismic imaging a subsurface formation using an array of seismic sources and an array of seismic receivers located subsurface, wherein there is a complex transmission medium between the two sets by creating a virtual source at a selected receiver within the array, time-reversing a portion of the signal related to the selected source and receiver and convolving the time-reversed portion of the signal with the signal at adjoining receivers within the array and repeating the process for signals attributable to various surface sources to create a seismic image of a target formation.
Claims7
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(−t);
- (f) convolving the time-reversed signal tnm(−t) with the signal tnk(t) to obtain the convolved signal tconvnmnk(t)=tnm(−t){circle around (×)}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 t m k v s ( t ) = ∑ n t n m n k c o n v ,
- Where 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.
Dependencies are inferred from the claim text.