Characterization and Hydrocarbon Potential Evaluation of a Shale Gas Reservoir Using Cuttings (SW Algeria)

Abstract

Methods for determining properties of shales from cuttings samples are beneficial as they provide a fast and cost-efficient way for evaluating potential shale reservoirs for which often core sample data and modern wireline logs are missing. A case study is performed on 80 cuttings samples from the radioactive Silurian shales of a Palaeozoic basin in SW Algeria. In this study geochemical (Rock-Eval pyrolysis and LECO carbon analysis), mineralogical (QEMSCAN analysis), structural (CT scanning) and geomechanical (nanoindentation) analyses are performed on cuttings samples to characterize the heterogeneity of the shales and predict shale gas sweet spots. Using these innovative analysis methods reliable values for the properties of the radioactive Silurian shales are obtained. By integrating TOC content values and QEMSCAN data with wireline logs, clear vertical trends/cycles are identified and the strong vertical and lateral heterogeneity of the shales is demonstrated. Using CT scanning different fractural networks are observed and Young’s modulus values obtained from nanoindentation measurements are in the range expected for shales (± 33 GPa) and are appropriate for shale gas production. The shale gas opportunity is confirmed for the radioactive Silurian shales and sweet spots are indicated by high TOC contents and favorable mineralogical compositions and geomechanical properties.