Triassic Oils and Related Hydrocarbon "Kitchens" in the Adriatic Basin

Luciano Novelli, Gerard Demaison

Without exception, the oils from both the Abruzzi basin and Albanian foredeep are of lower Liassic to Upper Triassic origin. This is demonstrated by biological marker-based correlations between the oils and stratigraphically controlled, carbonate-rich source rocks. The biomarker studies also provided proof to conclude that many of the oils possess low API gravities and high sulfur contents because they are immature rather than biodegraded.

Following the geochemical investigations, a computer-aided, basin-wide maturation simulation of the hydrocarbon kitchens was carried out, with backstripping in geologic time. The simulations, performed with the Tissot-Espitalie kinetic model, used basin-specific kerogen activation energies obtained by the optim method. These simulated values were calibrated with observed values in deep wells. Two characteristics diverge from "normal" petroleum basin situations (e.g., the North Sea basin): sulfur-rich kerogens in the source rocks, featuring relatively low activation energy distributions, and low geothermal gradients in the subsurface.

The geographic outlines of simulated Triassic-lower Liassic hydrocarbon kitchens closely coincide with the zones of petroleum occurrence and production in the Adriatic basin. Furthermore, API gravities of the oils are broadly predicted by the mathematical simulations. This methodology has once again shown its ability to rationally high-grade the petroleum-rich sectors of a sedimentary basin while identifying those areas where chances of success are extremely low regardless of the presence of structures.

AAPG Search and Discovery Article #91032©1988 Mediterranean Basins Conference and Exhibition, Nice, France, 25-28 September 1988.