LE VOT, MICHEL, MICHEL ALLANIC, DIDIER DEREGNAUCORT, and MICHEL GUITTARD, Elf Aquitaine Production, Boussens, France

ABSTRACT: Aquitaine Basin: 3-D Seismic, A Reliable Tool For Deep Gas Exploration and Field Development

The Aquitaine basin of southwestern France lies in the foreland of the Pyrenean fold and thrust belt. Since the first gas discovery in 1939 on the St. Marcet anticline, more than 1000 wells have been drilled in the area. They primarily led to two major gas discoveries (Lacq 1951 and Meillon 1965), which have so far produced over 270 billion standard cu m of gas.

The region is characterized by a very complex structural setting and by the great depths of the petroleum targets (3000-4500 m).

The structural evolution of this basin is strongly influenced by early basement tectonics dating from the hercynian orogeny. The later evolution includes block faulting and associated salt movements at the Jurassic-Cretaceous boundary, extensional tectonics related to the opening of the Gulf of Biscay during the Early Cretaceous (Albian-Aptian) and finally compressive episodes during the Upper Cretaceous and the Eocene (Pyrenean orogeny). In this extremely complex structural setting, conventional two-dimensional seismic data revealed poor quality.

From 1987 to 1992, over 1000 sq km of three-dimensional (3-D) seismic were acquired in the area with dual purposes, field development and deep gas exploration. The results definitely confirm the 3-D seismic as the adapted tool in this context because it allows the definition of precise structural geometries and precise location of fractured zones. As a result, it greatly enhanced our knowledge of the area in helping define models of tectonic evolution as well as dynamics of petroleum systems.

AAPG Search and Discovery Article #90990©1993 AAPG International Conference and Exhibition, The Hague, Netherlands, October 17-20, 1993.