BURIAL AND THERMAL HISTORY MODELLING OF THE GAFSA‐METLAOUI INTRACONTINENTAL BASIN (SOUTHERN TUNISIA): IMPLICATIONS FOR PETROLEUM EXPLORATION

Abstract

This paper is a contribution to the evaluation of the petroleum potential of southern Tunisia. Its purpose is to report on the burial and thermal histories of the Gafsa‐Metlaoui Basin and the surrounding area in the time interval between the Triassic and the Quaternary. We have used a one‐dimensional deterministic model, which enabled us to integrate the burial and thermal influences on potential source rocks with kinetic parameters, in order to define the timing of hydrocarbon generation and expulsion in relation to the main structural episodes in the study area.The Mesozoic burial history of this basin is characterized by two principal phases of rifting, each of which was followed by a brief episode of thermal (post‐rift) subsidence. The first phase occurred during the Triassic and Jurassic, and was related to the breakup of Gondwana; the second phase occurred during the Cretaceous and Early Tertiary, and was related to the opening of the neo‐Tethyan Mediterranean Sea. Geothermal studies of this basin have allowed us to determine an average surface heat flow of 60 m W/sq. m and an average geothermal gradient of about 25.5d̀C/km. Middle Jurassic source rocks expelled oil from the Cenomanian (about 100 million years ago) to the Quaternary.