oa Desert Sparse 3D as an Alternative to 2D Exploration

Classically, the first step in exploration corresponds to shooting of 2D seismic, in order to obtain a preliminary image of the subsurface. Through interpretation of these initial data, sub-areas are defined with good exploration potential. Thereof the most prospective areas are then covered with 2D infill layouts. This classical strategy is now challenged by recent acquisition systems with high-channel capacities which, with an adapted sparse design, allow to acquire 3D seismic in a cost effective way compared to 2D. Furthermore, this “Sparse 3D” approach gives a better definition of the prospective areas. A sparse 3D has been acquired by Total E&P Libya on the NC192 concession, with a design optimization derived from decimation test performed on conventional 3D. This sparse 3D has documented a major progress in imagery compared to pre-existing 2D acquired in 1992 by previous operators. Based on the new images, major elements of the structural framework had to be revised, which in term resulted in an optimized definition of new prospects. When surface and subsurface conditions are favourable for sparse 3D acquisition, it has to be considered as a serious alternative to conventional 2D. Then this method may improve significantly the geological understanding of the subsurface under reasonable costs.