Oil shale, which comprises abundant organic matter called kerogen, is a vast energy source. Pyrolysis of kerogen in oil shales releases recoverable hydrocarbons. Here we describe the pyrolysis of kerogen using an in-situ upgrading process, which is applicable to the majority of oil shales. The pyrolysis is represented by six kinetic reactions resulting in 10 components and four phases. Expanding Texas A&M Flow and Transport Simulator (TAMU FTSim), which is a variant of TOUGH + simulator (Moridis and Freeman 2014), we develop a fully functional capability that describes kerogen pyrolysis and accompanying system changes with a minimum of simplifications and assumptions. The simulator describes coupled process of mass transport and heat flow through porous and fractured media and includes all known physics and chemistry of reservoir systems. The simulator involves a total of 15 thermophysical states and all transitions between them and computes a simultaneous solution of 11 mass and energy balance equations per element. The simulator solves the equations in a fully implicit manner by solving Jacobian matrix equations using Newton-Raphson iteration method. To conduct a realistic simulation, we account for geological structure of oil shale reservoirs and physical properties of bulk oil shale rock. In addition, we consider interaction between fluids and porous media, diverse equations of state for computation of fluid properties, and numerical modeling of fractured media. We intensively validate the simulator by reproducing the field production data from Shell In-situ Conversion Process implemented in Green River Formation. We conduct sensitivity analyses of diverse reservoir parameters, such as presence or absence of a pre-existing fracture system, oil shale grade, permeability of the pre-existing fracture system, and thermal conductivity of a reservoir formation. We analyze the effects of the reservoir parameters on productivity and find a model that shows a similar production rate curve to the field production. The simulator is successfully validated and provides a powerful tool to evaluate effectiveness of in-situ upgrading processes and corresponding amount of recoverable hydrocarbons.

Oil shale, which is composed of abundant organic matter called kerogen, is a vast energy source. Pyrolysis of kerogen in oil shales releases recoverable hydrocarbons. Here, we describe the pyrolysis of kerogen with an in-situ upgrading process, which is applicable to the majority of oil shales. The pyrolysis is represented by six kinetic reactions resulting in 10 components and four phases. Expanding the Texas A&M Flow and Transport Simulator (FTSim), which is a variant of the TOUGH +simulator (Moridis 2014), we develop a fully functional capability that describes kerogen pyrolysis and accompanying system changes. The simulator describes the coupled process of mass transport and heat flow through porous and fractured media and includes physical and chemical phenomena of reservoir systems. The simulator involves a total of 15 thermophysical states and all transitions between them and computes a simultaneous solution of 11 mass- and energy-balance equations per element. The simulator solves the equations in a fully implicit manner by solving Jacobian matrix equations with the Newton-Raphson iteration method. To conduct a realistic simulation, we account for geological structure of oil-shale reservoirs and physical properties of bulk-oil shale rocks by considering phases and components in the pores. In addition, we involve interaction between fluids and porous media, diverse equations of state (EOSs) for computation of fluid properties, and numerical modeling of fractured media. We intensively reproduce the field-production data of Shell Insitu Conversion Process (ICP) implemented in the Green River formation by conducting sensitivity analyses for the diverse reservoir parameters, such as initial effective porosity of the matrix, oil-shale grade, and the spacing of the natural-fracture network. We analyze the effect of each reservoir parameter on the hydrocarbon productivity and product selectivity. The simulator provides a powerful tool to quantitatively evaluate production behavior and dynamic-system changes during in-situ upgrading of oil shales and subsequent fluid production by thoroughly describing a reservoir model, phases and components, phase behavior, phase properties, and evolution of porosity and permeability.