Harmonising diverse 3D geometries in a hard rock environment for pre-stack imaging

Abstract

Four 3D seismic surveys were acquired by HiSeis Pty Ltd over two years across an existing mining camp. The main objective of these seismic surveys was definition of structures which could assist characterization of mineralised zone that consists mainly of massive sulphides. Initial processing of seismic data started shortly after acquisition in 2011. Preliminary products have shown great promise in resolving complex structural environments and showed potential for direct targeting form seismic data. Our motive for reprocessing the dataset was in integration of all 2011 and 2012 seismic data in an amplitude consistent routine which could bring new value for amplitude based analysis of massive sulphide bodies. Conventional 3D deep-move out corrections (DMO), followed by a post-stack migration algorithm has not been successful in merging diverse datasets. Considerable improvement was achieved through the application of pre-stack time migration (PSTM) algorithm. This allowed us to use unique bin size for all merged seismic surveys. Successful imaging of merged datasets has been challenged. The main reason was that 3D seismic datasets had vastly diverse offset and azimuth distribution. Highly irregular migration fold coverage is an obvious problem which had to be overcome by exclusion of unsuccessful imaged events prior to stacking.