LAUSR

Free oil, rather than adsorbed oil, is potentially the most producible component of tight nanoporous shale reservoirs using existing technologies. To date, a variety of geochemical parameters, mainly related to the retention, migration, and expulsion of generated oil, have been developed to estimate the free oil in shale. However, there is still a lack of theoretical models accounting for the mechanism of oil accumulation in nanoporous shale, which would help evaluate adsorbed and free oil. In this paper, models were developed to estimate the amount of oil confined in nanoporous shale and that is mainly in adsorbed and free states to describe the characteristics of oil accumulation. The models were established for an adsorption saturation situation, and simultaneously considered the multilayer adsorption of an oil mixture and the microstructure of the shale pore system (including pore-throat-fracture). As a case study, adsorbed and free oil in lacustrine shales with different lithofacies, obtained from th...