STATION-CONSISTENT DECONVOLUTION FOR MULTI-SOURCE BOREHOLE SEISMIC DATA

摘要

Receiver coupling variations within a downhole array can occur for a variety of reasons but the effects are most severe when there is an absence of cement behind casing. In such a setting, source-generated body waves couple to the casing and produce axial particle motion which is picked up on the vertical component as high amplitude, narrow band noise. This noise repeats for all shots and has a characteristic spectrum for each receiver. So long as there are more good receivers than bad, robust estimation procedures allow the unwanted residual receiver response to be estimated and removed. Since the vertical component is most severely affected and is also essential for compressional wave imaging it is critical to remove the receiver coupling variations within the array before further processing.rnWe adapt the well-known process of surface-consistent deconvolution to the multi-source VSP geometry where a multi-component downhole array remains stationary. The offset and CMP terms of surface-consistent deconvolution for surface seismic data are replaced by a distance-indexed average term, estimated using a novel re-indexing of shot-receiver pairs. Additionally, a frequency-independent scale factor is optionally included to handle the inevitable rotation of horizontal components. The source and receiver terms are estimated using a median or trimmed mean with Gauss-Seidel iteration. An amplitude-preserving minimum phase operator is then constructed and applied to the data to remove the receiver coupling variations. We illustrate the process on two data sets, one a 40 level Gulf of Mexico walkaway, the other an 8 level HFM (hydraulic fracture monitoring) 34 perforation shot data set.