ABSTRACT: Source Rock Identification and Oil Generation Related to Trap Formation: Southeast Constantine Oil Field

A. Boudjema, A. Rahmani, E. M. Belhadj, M. Hamel, R. Bourmouche

Petroleum exploration began in the Southeast Constantine basin in the late 1940s. Despite the very early discovery of Djebel Onk field (1954), exploration remains very sparse and relatively unsuccessful due mainly to the geological complexity of the region. The Ras-Toumb oil field was discovered only twenty years later. In 1988, a new discovery, the Guerguit-El-Kihal oil field, renewed the interest of explorationists in this region.

The Southeast Constantine Mesozoic-Cenozoic basin has a sedimentary sequence of shales and carbonates with a thickness exceeding 7000 m. Structural traps are related to pyrenean and post-Villafranchian phases. Potential reservoirs with good petrophysical characteristics and seals can be found throughout the section and are mainly Cenomanian-Turonian and Coniacian limestones and dolomites.

The known source rocks are Cenomanian-Turonian and Campanian carbonate shales. Kerogen is a mixture of type II and type III for the Campanian. The kerogen has a fair petroleum potential and is often immature or low mature. The Cenomanian-Turonian kerogen is type II amorphous, with a variable but important petroleum potential. Total organic carbon values range from 1.5% to 7%. Maturity corresponds to the oil window. This source rock is well known throughout the Mediterranean region and is related to the oceanic anoxic event.

Kinetic modeling of this organic matter evolution indicates favorable oil generation timing related to trap formation ages.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990