Print this pagePetroleum Systems of the Ghadames Basin and Illizi Platform
ILLICH, HAROLD, JOHN ZUMBERGE, CRAIG SCHIEFELBEIN, and STEPHEN BROWN
Geochemical analyses of oil and sediment samples from the Ghadames Basin and Illizi Platform of Algeria, Tunisia, and Libya were obtained and interpreted to refine identification of petroleum systems in these basins. Oils possessing a high degree of compositional similarity were identified, classified, and grouped into four major families (Families S1, S2, D1, and D2). Biomarker, isotope, and other geochemical attributes of the oils were compared to extracts from sediments whose stratigraphic ages were known. In this manner, a small group of oils was associated with Silurian shales mainly occurring in the northern part of the Ghadames Basin (Family S2), and another, more widespread family was associated with sediments of Devonian Frasnian age (Family D1). Family D1 oils have considerable compositional heterogeneity and undoubtedly result as a consequence of lateral differences in organic facies. Additional compositional differences in Family D1 can be related to the relative thermal maturity of the oils. Less mature Devonian oils were presumably generated first and apparently migrated farther filling traps on the margins of the productive basins. More mature oils tend to occur in traps located in the interior of the basins. Parts of the Illizi and Ghadames basins have the benefit of multiple hydrocarbon sources with generation and migration mainly occurring during the Cenozoic. Oils derived from both the Silurian and Frasnian occur in the northwest part of the Ghadames Basin.