Northern Algeria, A General Overview of Hydrocarbon Prospectivity

Messaoudi, Mohamed (Sonatrach)


Abstract: Northern Algeria is a foreland fold and thrust belt zone of Alpine deformation. It is located in north Africa within a geologically complex area between a stable autochthonous (Saharan platform in the south) and a neo-formed oceanic domain (west Mediterranean basin in the north). It is an under explored petroleum province, a significant oil and gas shows have been encountered, and oil seeps are well known in most parts of the area. Oil has been collected from surface seeps since 1875 in Cheliff basin. The first commercial oil discovery in Algeria was registered in Oued Gueterini field in the Tellian nappe in 1948. This field is producing until present time from allochtonous formations (Eocene reservoirs). Mitigated exploration success ratio registered so far is mainly due to seismic control of mapped prospects as well as depth of targeted reservoirs. This area exhibits similar geodynamic and structural framework as the Apennines (Italy), the Zagros (Iran), Alberta (Canada) and south America where important hydrocarbon reserves have been discovered. Main plays are related to Miocene, Cretaceous and Jurassic deposits (sandstone and limestone reservoirs). The petroleum system is proved in the shallow plays (Miocene & Cretaceous) and the new concepts consider that the Jurassic could be an important deeper target. The main potential areas are: the western Mediterranean basin in the north, Tellian Atlas in the central part and the Constantine basin in the east part of saharan atlas. INTRODUCTION The northern Algeria is a zone of Alpine deformation, and it is situated in a geologically complex area, encompassing offshore Mediterranean basin, Tellian atlas and Saharan atlas. Northern Algeria is an under explored petroleum province. Significant oil and gas shows have been encountered and a number of small discoveries were made over 50 years ago (Oued Gueterini, Djebel Foua and Djebel Onk). Most recently oil was discovered in the south east part (Constantine basin). Crude oil has been extracted for centuries from dug tunnels and collected from surface seeps. The first commercial oil discovery in Algeria has been made in the Hodna basin (Oued Gueterini Field). The success rate for exploration is relatively poor due to some wells were drilled on surface structure without understanding the shifting nature in the subsurface, and without seismic control, whereas others, were not drilled deep to reach the deepest target. Four main basins are developed, offshore western Mediterranean basin, Cheliff & Hodna basins in the Tellian atlas and Constantine basins in the east part of Saharan atlas. ALGERIAN OFFSHORE Represents the main part of the south side of the western Mediterranean basin. It is a Neocene basin, constituted by Algero-provençal basin on the east (included sub-baleares basin) and Alboran basin on the west. The Algerian Offshore is still a frontier zone related to deep water play where the shelf is much narrower and plunges steeply into the abyssal plain. The coast lies over, 1200 km from east to west and is characterised by several bays where the shelf is relatively larger (35km).

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