Characterizing Unconventional Hydrocarbon Resources Through Geochemical Analysis

This study presents the use of geochemical analysis in order to improve the evaluation of unconventional recourses. Several parameters were studied including total organic carbon (TOC), free hydrocarbon amount (S1), potential hydrocarbon (S2), hydrogen index (HI), oxygen index (OI), pyrolyzed carbon (PC), and total sulfur content (Total S). The main objective is to understand the relationship between all these parameters and to examine the impact of thermal maturation on the geochemical variables. Organic-rich shale samples were collected and used in this work. The shale samples were maturated at different temperatures and for various durations. The Rock-Eval analysis was carried out before and after each thermal treatment in order to capture the changes in the geochemical properties. The obtained results showed that thermal maturation can significantly change the geochemical properties, reducing the total organic carbon, increasing the S1, and reducing the HI. A reduction in the total organic carbon was observed, the TOC was reduced from around 20 to 15 and 12 wt.% after maturating the shale samples at 250 for one and two days, respectively. While the S1 was increased by three times on average due to the maturation processes. The HI was reduced from around 800 to less than 350 due to the maturation revealing that the kerogen was converted into vaporized hydrocarbon which leaves the shale and leads to the HI reduction. The vaporization of organic matter led to an increase in the rock porosity by around 4 to 8 p.u. Overall, this study confirms the importance of integrating different geochemical properties in order to improve the evaluation of unconventional resources.