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AAPG Hedberg Conference, The Evolution of Petroleum Systems Analysis

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Advances in Rock-Eval Method and Source Rock Characterization to Predict In-Situ Liquid Hydrocarbons

Abstract

For the past 40 years, the Rock‐Eval® device has been widely used to estimate the petroleum generation potential of sedimentary organic matter at laboratory scale. However, several questions remain, such as the reliability of the classical S1 parameter (well‐known as the quantity of free hydrocarbons) and their corresponding extrapolation/significance in relation to the geological conditions (e.g. Inan et al., 1998; Jarvie 2012). This paper will review the evolution of the traditional Rock‐Eval® method for source rock characterization and compare traditional applications with new approaches recently developed for characterization of liquid rich rock samples. In 2014, in order to obtain a better assessment of hydrocarbons still present within in‐situ oil rock samples, a specific pyrolysis program for characterization of source‐reservoir rock units was developed and published by IFPEN (France): the Shale PlayTM method (Romero‐Sarmiento et al., 2014; 2016). This method provides new Rock‐Eval parameters (Sh0, Sh1 & Sh2 peaks) that can be used to obtain a better quantification of free and adsorbed hydrocarbons in organic‐rich rock samples. More accurate Rock‐Eval Tmax values can be obtained for in‐situ liquid hydrocarbon samples and correct original oil in place (OOIP) estimations can be calculated in early exploration campaigns of shale oil assessment (Romero‐Sarmiento et al, 2016; 2017). A fundamental improvement of this method is that it separates the conventional S1 peak into two sub‐peaks (Sh0, Sh1), each representing a distinct pool of organic compounds with unique thermal reactivity and chemical composition. Also, a low pyrolysis temperature (100±50°C) is more appropriate to initiate the thermovaporization process, therefore improving the hydrocarbon recovery. Additionally, the two plateaus imposed for 3 minutes at 200 and 350°C allow for a better separation and quantification of the thermovaporized organic compounds still present in liquid‐rich rock samples. It has also been demonstrated that free and sorbed low‐to‐medium molecular weight thermovaporized hydrocarbons (