Assessment of an Unconventional Shale Resource Play: The Tannezuft “Hot Shales” in Ghadames Basin, South Tunisia

The importance of unconventional shale gas has grown up quickly in the world after evolving into an important resource play for the United States, accounting for more than 14% of produced gas by the end of 2004 (EIA, 2004) and it is expected to become a major source of natural supplies in the United States by 2020. The Ghadames basin, known to be the most important basin in Tunisia, was targeted by the Tunisian Petroleum Exploration to challenge this kind of unconventional resource play. Source rocks potential is primarily determined through geochemical analyses carried out on whole cores, sidewall cores, formation cuttings or outcrop samples. To locate and assess source rocks along the stratigraphic column, exploration organic geochemistry must often do with a limited body of data (oil based mud drilled wells), often discontinuous or poorly located (big gaps between the sampled levels), and therefore not really representative of the information investigated. To overcome this issue, a number of authors have tried to estimate source rocks potential from wireline logging. Laboratory data input will lead to a good calibration process for better geochemical logs results. Some of the wells analyzed during this study are old, time when the quality of geophysical wireline logging was variable these data were excluded from the study. The essential ten keys of shale reservoir assessing are mainly based on geochemical and mineralogical evaluation: (1) A real extent, (2) an appropriate thickness (3) good total organic carbon content (TOC), (4) Kerogen type, (5) convenient thermal maturity degree, (6) suitable mineralogical association (7) Porosity (8) type of hydrocarbon (9) possible production mechanisms and (10) barriers to economic production. In the present study we faced most of the issues cited below, that’s why most of the study was carried on using the wireline logging modeling. The specific goals to achieve using logs analysis are mainly to determine the total organic content, kerogen type, maturity level, created porosity by TOC transformation, mineralogical association and Gas Content.