Seismic expression of layer-bound fault systems of the Eromanga and North Sea Basins

Abstract

This paper compares the seismic expression of Lower Tertiary mudstone-dominated sequences of the North Sea basin with Cretaceous siliciclastic sequences of the Eromanga Basin. The paper focuses on the development of layer-bound systems of minor extensional faults that pervasively deform these sequences in both basins. Layer-bound fault systems have only recently been recognised in the North Sea with the availability of high resolution 3D seismic data. The resolution achievable with 3D mapping has revealed that in map-view, these faults are arranged in polygonal networks reminiscent of dessication cracks. This property of polygonality is accounted for in a genetic model based on basin-wide volumetric contraction of muddy sediments during the early stages of compactional dewatering. The recent identification of polygonal organisation to faults in the Lake Hope 3D survey raises the likelihood of a similar genetic mechanism being operative during the formation of layer-bound faults identified throughout the Eromanga Basin. The presence of this system of minor faults has considerable implications for reservoir geometry and seal capacity, for hydrocarbon and water resource exploitation.