Multiattribute analysis for channel element discrimination in the Taranaki Basin, offshore New Zealand

Abstract

A detailed study of Pliocene channel systems within the Taranaki Basin was undertaken from the Parihaka 3D seismic volume to improve our understanding of the Plio-Pleistocene channel elements in terms of structure, channel evolution, and lithology. Seismic picking parameters were chosen based on the lateral resolution for optimal mapping of the channels. Individual and multiattribute studies were performed on single, combined, and complex channel systems with the goal of identifying channel features and discriminating between shale- and sand-rich regions of the channels. For this target and data set, the variance attribute provided key insights into channel features, such as the edge of the channel, meander scrolls, and point bars. Root-mean-square amplitude and sweetness performed equally well in lithology identification, and, combined with variance, it aided in identifying sand-rich channels, as well as small individual channels that could provide sediment pathways into the deepwater Taranaki Basin. Depending on the complexity of the channel system, different attribute analyses had varying success with each system. Therefore, it is important to combine various attributes to discriminate channel elements as fully as possible. The lithologies of individual channels and their elements can be determined using seismic attributes, although it becomes increasingly difficult to discriminate small-scale features within the channel as the complexity of the channel system increases. Chronostratigraphic studies using stratal slicing techniques provided insight into the evolution of the channel system through time, demonstrating an overall sand-rich base of the channel, with a shallower shale-rich lithology at the top of the channel fill.