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The key role of hydrocarbon mdistribution in rocks of unconventional reservoirs for thermal processes

Cheremisin Alexey N

Unconventional hydrocarbon reservoirs store an enormous amount of hydrocarbons (HCs). Up to 97 % of these hydrocarbons are inaccessible for conventional recovery methods, including multistage hydraulic fracturing. Thermal enhanced oil recovery (EOR) techniques are focused on the extraction of this unreachable organic matter, including generation of synthetic oil from kerogen (Khakimova, Bondarenko, Cheremisin et. al). Previously thermal EOR for unconventional reservoirs was always studied only in frames of a simplified HC-model. The current study is the first study focused on the precise description of the distribution of different types of hydrocarbons in rocks. The research includes unique laboratory experiments and numerical simulations of thermal EOR. Novel experimental technologies and methods were used in the present work. The results of a unique physical (laboratory) simulation of hot and supercritical water injection to oil shale reservoir proves that up to 30% of organics can be converted to synthetic oil and produced with huff&puff technology. Kerogen and synthetic oil were characterized by stateof-the-art techniques, such as pyrolysis, GCxGC MS, and isotope analysis. It was observed that the correct description of HC distribution within reservoir rocks significantly improves the accuracy of the numerical simulation forecast. Numerical simulation of a field pilot allows optimizing technological parameters of huff&puff process.