Oil-Oil Correlation and Potential Source Rocks in the Chotts Basin, Tunisia

摘要

The Chotts basin, located in Central Tunisia, constitutes a prolific hydrocarbon province for oil and gas production. In spite of the long history of exploration and production, few geochemical investigations were performed until now. For this study, the geochemical survey, using Rock Eval Pyrolysis, GC and GC/MS techniques, is based on the analysis of a total of 561 cutting samples from middle Ordovician Azzel Formation (Fm), Late Silurian-Early Devonian Fegaguira Fm, Permian Zoumit Fm and Middle Jurassic Nara equiv. Fm as well as 14 oil samples collected from producing wells in the area. Rock Eval results show that the Fegaguira Fm constitutes a mature oil and gas prone source rock exhibiting good to very good petroleum potential. The Azzel Fm displays poor to fair petroleum potential. While the Jurassic and the Permian Formations, although their good source rock characteristics, they are very local. Oil/oil correlation data testified that oils have a common source. They generated from a shaly source rock deposited in a marine environment under suboxic conditions, regardless of their variable maturity or expulsion times. Oil/source rock correlations proved that the Fegaguira Fm is the main source rock that has been charged the Ordovician and Triassic reservoirs in the Chotts basin. The maturation of source rocks and hydrocarbons generation and expulsion histories were evaluated by means of 1D basin modeling. The 1D models constructed for the studied basin indicate maximum burial was reached during Cretaceous times which produced a very important pulse in hydrocarbon generation within the major part of the basin.