Seismic stratigraphy and hydrocarbon prospectivity of the Aptian–Albian succession along the Oued Bahloul Basin, Central Ouest Tunisia

Abstract

The Aptian–Albian sediments deposited along the Tunisian Atlas and, overlain by the Vraconian seals constitute an attractive hydrocarbon play in the Oued Bahloul Basin of the Central Tunisia. Albian organic-rich shale unconformably underlies the Aptian dolomites and plays as a major source rock proven by oil and gas discovered so far with the Aptian reservoir layers. In central Tunisia, many wells have proven the Aptian–Albian play in structural traps, with an oil discovery in central onshore and offshore Tunisia. In order to document and map the reservoir distribution and stratigraphic-trap fairway, the Aptian–Albian sedimentary package is divided into a number of depositional sequences and systems tracts using key regional seismic lines calibrated with boreholes. Tracing of the key surfaces bounding the Aptian–Albian has been carried out using all the seismic lines provided from Tunisian Company of Petroleum Activities (ETAP). The interpretation of 2D seismic lines can allow for the reconstruction of 3D structural elements to reduce potential risk prior to exploratory drilling. Relative sea-level fluctuations and rejuvenation of major faults significantly influenced the Aptian–Albian depositional system creating regional unconformities and influencing the evolution of accommodation space. Although the development of the seismic sequences is partially influenced by local tectonics, the overall stacking pattern of the Aptian–Albian sedimentary strata displays seven third-order cycles and two second-order cycle, which is in harmony with the eustatic sea level chart. In this work, the facies analysis using sequence stratigraphy and seismic sedimentology offer useful insight to Aptian hydrocarbon exploration in Oued Bahloul Basin and other analogous basins and can contribute in the exploration and reservoir development.