Organic geochemical characterization of the black shale of Oued Soura, Tamtret region, Southwest Algeria

In recent years, black shale has emerged as a significant unconventional energy resource. The properties of organic matter within shales provide crucial insights into the exploration potential and development prospects of shale hydrocarbons. This study meticulously evaluates the hydrocarbon potential of black shales in the Tamtert region (Djebel-Zereg) by examining their geochemical characteristics. A comprehensive geochemical analysis of five Djebel-Zereg black shale samples was performed using advanced techniques such as Total Organic Carbon (TOC) assessment, Pyrolysis Rock-Eval 6, and elemental analysis. The findings indicated that the TOC content of the samples ranged from 0.51 to 2, with an average of 1.33, suggesting acceptable to very good source rock potential. The S2 values varied between 0.45 and 4 mg/g, averaging 7.3 mg/g, while the Production Index (PI) values ranged from 0.50 to 4.76, with an average of 2.23, further affirming the promising source rock potential. The graphical analysis of Hydrogen Index (HI) versus Oxygen Index (OI) and HI versus Tmax, along with HI values ranging from 51 to 233, indicated the presence of type II and III organic matter, suggesting potential for both gas and oil generation. The correlation between TOC results and the free hydrocarbon ratio (S1) data underscored the presence of indigenous hydrocarbons. Tmax values, spanning from 435 to 465°C with an average of 447°C, and vitrinite reflectance (Ro) values ranging from 0.68 to 1.19%, confirmed that the samples have reached maturity. Given the high TOC content, the identification of type II and III organic matter, and the thermal maturity of these materials, the Djebel-Zereg black shale is classified as a promising oil shale resource.