Basin structuring and hydro-geophysical characterization of Upper Cretaceous and Eocene fractured deep carbonate reservoirs in the Hajeb Layoun-Jelma-Ouled Asker area (Central Tunisia)

Abstract

In the Hajeb Layoun-Jelma-Ouled Asker-Oued El Hajal folded pull a part basin, situated in Central Tunisia, the shallow and deep Miocene groundwaters are often over exploited. The sedimentary basins, in this area, contain important carbonate deep reservoirs not yet exploited. Turonian (Bireno-Douleb Formations), Maastrichtian (Abiod Formation), and Ypresian (El Gueria Formation) limestones constitute the most important fractured reservoirs in this region. The present study combine geological, hydrogeological, and geophysical data, using 2D seismic reflection, to determine the spatial distribution and the deep structuring of these carbonate reservoirs. Isochron and isopach maps, generated for the study area, highlight the effect of tectonics in structuring these carbonate reservoir horizons. This effect is well presented along the folded structures and the major fault directions: NE-SW, NW-SE, N-S, and E-W responsible of the reservoir compartmentation. Indeed, subsurface faults as well as thickness and facies variations of these carbonate reservoirs should play a key role in the hydraulic flows and the distribution of principal aquifers. Knowledge and highlights of this structuring represent a subsurface modeling for future deep hydrogeologic exploration with proposed fictitious wells in the study area.