publications

Article

Résumé

In Central –Eastern Tunisia (Kairouan-Sfax area), the Upper Cretaceous interval, includes various hydrocarbon plays as confirmed by the numerous discoveries in this area. Production comes from multiple reservoirs ranging in age from the Upper Cenomanian to the Maastrichtian. The main producing fields are Sidi El Kilani (within the Abiod Formation), Miskar, El Jem (within the Upper Aleg carbonates), Gremda, Rhemmouda, El Aïn, Guebiba, Mahares and El Jem (within the Bireno Member). The main objectives of the present study will be to show, by means of electrofacies analyses the main interesting sectors in terms of reservoirs potential and source rocks availability. On the other hand, surface-subsurface integrated study helps a lot for the reconstitution of palaeoenvironments especially in cases of subsidence, deepening etc. The identification of various electrical expressions, mainly based on Gamma-Ray and Sonic logs, leads to a subdivision of the Upper Cretaceous into numerous units and subunits. In addition, correlatable discontinuities were identified in certain formations, such as in the marly El Haria Formation. In fact, integrated biostratigraphic and wire-line logs studies lead to the identification of the clear shift separating the Paleocene shales from the Maastrichtian marls. This shift expresses an unconformity which is correlatable, at least, at a regional scale. Within the Abiod Formation, four units were identified. The Upper Units (Units 1 and 2) constitutes the Upper Abiod Member, the Unit 3 corresponds to the Middle Abiod, and the Unit 4 corresponds to the Lower Abiod. The Unit 2 which is relatively rich in marl intercalations expresses a progressive transition from the marly Middle Abiod to the carbonatic Upper Abiod. The four units are obvious, especially in Sidi El Kilani-El Jem sector. Laterally, facies changes are very common.