Structural characteristics of northern Houtman sub-basin, Perth Basin

Abstract

The northern Houtman Sub-basin is an under-explored region of Australia’s western continental margin. It is located at the transition between the non-volcanic margin of the northern Perth Basin and the volcanic province of the Wallaby Plateau and lies adjacent to the Wallaby-Zenith Transform Margin. In 2014, Geoscience Australia acquired new 2D seismic data (GA-349, 3455 km) across the northern Houtman Sub-basin to assess its hydrocarbon prospectivity. Previous studies of the Houtman Sub-basin indicated that en-echelon basin bounding N-NW trending faults are associated with the Permian half graben complex, however, it was not known if this structural style continued into the northern area of the Houtman Sub-basin. This study integrated interpretation of the recently acquired survey, with regional interpretation of the Houtman Sub-basin. This was further supported by well data and geophysical modelling and a regional 2D structural and stratigraphic interpretation developed. Structural mapping was done for the basement, Early Triassic (Woodada Formation) and Early Jurassic (Eneabba Formation). The basement structure of the northern Houtman Sub-basin is controlled by a series of large en-echelon NW-SE trending SW dipping faults, some of which have a throw of more than 10 km. These basement-involved faults control a series of Permian half graben separated by transfer zones and fault ramps. This basement architecture is similar to the inboard part of the southern Houtman Sub-basin, however the structures are larger. The Early Triassic and Early Jurassic faults trend NW-SE similar to the basement-involved faults, however major faults within the Jurassic succession lie about 50 km to the west of the Permian faults. Interpretation of the northern Houtman Sub-basin reveals a structurally complex basin containing a wide range of structural and stratigraphic traps at several stratigraphic levels. Potential plays have been identified in the upper Permian, Triassic and Jurassic successions. They include large stratigraphic plays in the Upper Permian/Lower Triassic, rollover anticlines within the Lower Triassic and Jurassic, and fault propagation folds and fault block plays in the Jurassic.