Lake Hope 3D ? a case study

Abstract

In 1992, a 138 km2 3D seismic survey was recorded over the central eastern section of the Lake Hope Block within the South Australian PELs 5 and 6. The 3D data provided a marked increase in data quality and interpretability over the previously recorded 2D seismic data. The survey was recorded over the Sturt/Sturt East, Tantanna, Taloola and Malgoona Fields, and had specific exploration and development objectives. The production history of the Cretaceous and Jurassic reservoirs of the Tantanna Field indicated that the recovery factors for some wells were anomalously high. Potential was recognised both in the Tantanna and Taloola Fields for pool extensions and unswept reserves behind some form of permeability barriers. The 3D dataset has allowed a complex fault pattern to be mapped over these fields. In the Sturt/Sturt East Fields, the objectives were to better define the stratigraphic edges of the Jurassic Poolowanna and Birkhead Formation reservoirs. In the Malgoona Field, the 3D dataset has more clearly defined the trapping geometry, which is a three way dip closure against a basement fault. The highly sampled amplitude data from the 3D may help describe the porosity distribution of the reservoir, a thin sand within the Late Carboniferous Merrimelia Formation. After drilling Hollows 1, an anticline, the remaining exploration potential within the 3D is now confined to stratigraphic, and lowside fault plays. The 3D data will allow these plays to be explored with reasonable risk. The 3D seismic dataset has provided a clearer understanding of the structural style in both the Cretaceous and pre Jurassic sections. This will lead to direct economic benefit through the better definition of reservoir geometries. The depth conversion has been greatly improved through delineation of the high velocity calcite cemented sandstones in the Jurassic section, and the increased stability of the 3D velocity model. The Lake Hope 3D seismic project has demonstrated that land 3D seismic data can be used to revitalise the exploration and development potential of a mature oil province.