Print this pageFrontier Onshore Basin Exploration Methodology: Starting from Scratch, Airborne Gravity and Magnetics Onshore Angola
Applications
In frontier, unexplored onshore areas, often nothing is known of the basin structural architecture or basement depth, save that there is a sedimentary basin in the area. Traditional reconnaissance usually begins with airborne magnetic and/or gravity data acquired over large areas to identify the regional structure and direct lease and seismic acquisition more effectively. In areas with complex overburden such as sub-salt plays or with near surface screens such as basaltic flows, the seismic data are often of poor quality and give rise to ambiguous or multiple competing interpretations. In such cases, the use of these complementary geophysical data may assist the interpreter in discriminating between alternative structural models.
Here a qualitative and quantitative methodology for onshore frontier exploration is described through a case study from the onshore Angolan basins, where an airborne gravity and magnetic data were first to cover such an area consistently (100,000 line-km covering 800,000 km2), improving understanding of the basement depth and regional structure in an area devoid of deep wells and regional seismic. The use of advanced techniques in gravity and magnetic data acquisition, notably, high resolution airborne gravity surveying, enabled a more rigorous and quantitative data analysis and interpretation in 3D. Additionally, a multi-technique approach combining magnetic basement depth estimation and 3-D gravity inversion was followed leading to detailed and accurate basement mapping.
Results and Conclusions
An integrated approach creates a solid footing for structural interpretation and understanding of the basins, and leads naturally to integration with other forms of data including topographic, regional surface geology, surface sampling and satellite data. These additional datasets also provide invaluable constraint for the modelling exercise, along with increased understanding of these data in their regional and mega-regional context for neighbouring areas and countries, allowing tectonic fabric and deformational timing issues to be considered, with the latter being important for the eventual prospectivity evaluation for hydrocarbon development.
The end result of this extensive study is a vastly improved geological and geophysical understanding of previously unknown basins in the interior of Angola. All information are maintained in a GIS framework allowing easy interrogation and integration with future datasets and ideas.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil