Unravelling the Role of Lithofacies in Controlling Organic Matter Composition in Unconventional Systems Using Ft-Icr-Ms

Abstract

Evolution of organic matter in sedimentary basins over geological times includes formation of kerogen, production of hydrocarbons, expulsion, migration, accumulation and possible transformation within the reservoir. Inorganic components, e.g. mineralogical composition, could play an important role in this evolution of organic matter (Murgich and Jesús Rodríguez, 1998). Jones et al. (1994) emphasized similarities in petroleum generation for shale and carbonate source rocks but stressed possible differences in migration. Carbonate source rocks tend to be more brittle, heterogeneous and tighter than clay rich source rocks, which makes them more prone to fracture and emit hydrocarbons more effectively. As defined by Jarvie (2012), unconventional resource systems include not only organic rich rocks which can generate and store petroleum itself but also juxtaposed organic lean intervals where generated petroleum can migrate into. Those juxtaposed organic lean units also may have different lithofacies than the organic rich units. Improved oil quality could be found in juxtaposed organic lean units, because short distance secondary migration leaves more heavy and polar compounds in the source.