Evaluation of reservoir systems in Paleozoic sedimentary formations of Ghadames and Jefarah basins

Abstract

The paper aims to study the general characteristics of the reservoirs of different reservoirs system in Paleozoic formations in Ghadames and Jefarah basins, located in Libya and in Tunisia. For that, more than twenty six wells were used to illustrate how reservoir properties such as porosity and permeability changes through time from a proximal to a distal sedimentary environments. Reservoirs systems are analysed at two different scales: i) reservoirs scale using data analysed from geological and petrophysical software for reservoir property analysis and constructing of five stratigraphic cross sections through the area have been reconstructed between twenty six wells; ii) core scale using different laboratory petrophysical analysis.The Paleozoic reservoirs are characterized by a large range of siliciclastic reservoirs extending from Cambrian to Permian. Nine main Paleozoic reservoir systems are identified in these two basins these are; the Hasawnah, Hawaz and Mamouniyat Formations (Lower Paleozoic), Akakus, Tadrart, Ouan Kaza and Tahara Formations (Middle Paleozoic) and M'rar and Asadjefar Formations (Upper Paleozoic). These reservoir systems are connected with two major hydrocarbon source rocks known as; the Lower Silurian Tanezuft Formation and Middle-Upper Devonian Awaynat Wanin Formation. The study shows that depositional facies and position within the paleogeographical setting influenced the evolution and the heterogeneity of reservoirs properties.