Evolution of reservoir properties of oil shale rocks under hydro-thermal treatment: Investigations from micro- to macro-scale

Abstract

Treatment with water at sub- and supercritical states which is considered as one of the most promising technologies for oil shale reservoirs development is still understudied. In particular, reliable correlations between most of the reservoir properties and temperature are absent. However, this data may significantly improve the quality of oil recovery predictions applying numerical simulations. This work is devoted to obtaining the dependency between porosity, permeability, organic matter content and temperature through physical modeling of hydrous pyrolysis. A unique experimental program design is proposed to investigate changes in reservoir properties at macro- and micro-scales and connect these changes with composition and pore structure evolution. A set of experiments on hydrous pyrolysis in a closed system was performed at temperatures 110, 250, 300,325, 350, 375, 400, and 450 °C, and the pressure of 23.4 MPa on rock samples of the Bazhenov formation.As a result, the relation between reservoir properties and the temperature was derived, characterized by a few specific temperature zones with particular behaviors of rock porosity and permeability. Effects on reservoir properties were analyzed in a complex way to highlight the mechanisms of void space transformation related both with pore space evolution and reduction. The observed effects include thermal expansion of organic matter with further transformation to synthetic hydrocarbons, formation of new mineral components, mineral matrix swelling and fracturing.