Airborne Gravity Gradiometry in Basin Studies
Abstract:
Over the past decade the Airborne Gravity Gradiometer (AGG) has been applied to a range of hydrocarbon exploration plays in sedimentary basin settings from Australia to the Americas. The AGG was designed and built explicitly for airborne deployment. AGG provides twenty times better spatial resolution [150m versus 3,000m], and ten times less noise [0.10 mGal versus 1.0 mGal] than conventional airborne gravity (Dransfield and Christensen, 2013). Gravity data reflect lateral variations of density in the subsurface and is especially amenable for basement structural mapping of sedimentary basins. Figure 1 (Dransfield, 2007) shows the AGG derived gravity data acquired over the Cliff Head oil field in the Perth Basin in Western Australia. The Cliff Head oil field is located on an anticlinal structure, clearly associated with a corresponding gravity high. Superimposed are the major fault structures in the area, as derived from seismic interpretations. There is a clear correlation between the location of the faults and the edges of the structures in the underlying gravity image.The higher lateral resolution of AGG when compared to conventional airborne gravity results in superior mapping of basement topography in depths less than 6,000m. This information can be used to de-risk further exploration/mapping efforts by optimizing the layout of any subsequent 2D/3D seismic data acquisition programs. This approach has been used recently by Australian petroleum explorer Buru Energy to rapidly and cost-effectively map the basement structures over large areas of the Canning Basin in Western Australia.
Case study examples will illustrate that fixed-wing and helicopter borne AGG, when combined with high-resolution magnetics and available 2D seismic profiles, provide the means to rapidly, efficiently and safely map sedimentary basin architecture.
Dransfield, M. H., 2007, Airborne Gravity Gradiometry in the Search for Mineral Deposits, In Exploration in the New Millennium: Proceedings of Exploration 07, Fifth Decennial International Conference on Mineral Exploration, Ed. B. Milkereit, 341-354
