Nuri M. Fello and Brian R. Turner

The Murzuq Basin, SW Libya, is one of a series of Palaeozoic intracratonic sag basins on the North African Saharan Platform. The structural fabric of the basin was developed during the Late Proterozoic Pan-African orogenic event, which has strongly influenced the stratigraphy and depositional patterns within the predominantly Palaeozoic clastic basin-fill.

The Upper Ordovician (Ashgillian) Mamuniyat Formation is the primary reservoir target in three oilfields A, B and H within Repsol Oil Operations Concession area NC115, on the NW flank of the Murzuq Basin. A major problem with the Mamuniyat is the location of the sediment provenance, due to the lack of adequate subsurface and outcrop data, and the relationship and controls on sediment flux and the depositional systems. Petrographic data derived from sandstone samples from cored intervals through the Mamuniyat Formation show that they are mainly sublitharenites, with some quartz arenites and litharenites. Compositional data for the three oilfields indicates that they were derived from a similar parent rock, but with differences in modal composition, textural attributes and porosity of the lower, middle and upper parts of the Mamuniyat attributed to temporal variations in source area uplift, base level change, sediment flux and accommodation space. These same tectonic events influenced facies patterns, sediment deposition and interaction between a variety of shallow water marine and fluvial depositional systems across a NW-SE oriented storm-influence coastline.