Modeling and Simulation of Transport Phenomena in Organic-Rich Marcellus Shale Rock Matrix

Abstract

Abstract The growing worldwide energy demand has greatly stimulated the exploration and production of unconventional oil and gas resources. Because of the large amount of reserves, shale oil and gas is one of the most promising unconventional energy resources. Therefore, considerable efforts are being undertaken by many research programs to make this resource successfully and economically available. Understanding pore network evolution along with transport phenomena within shale rock matrix is an important issue. The constituents of shale rock matrix include organic matter, nonorganic matter, and pore network. It has been shown for shales that the majority of the pores are isolated from each other, with some evidence for certain pores to form individual systems not necessarily connected with each other. However, hydrocarbons could potentially diffuse through organic matter from one system to another, providing a potentially important production mechanism to supplement the more conventional pressure-driven flow through connected pore systems. Here we present a comprehensive modeling and simulation framework, using digital rock physics (DRP), for diffusion flux analysis in organic-rich Marcellus shale rock matrix. First, three-dimensional (3D) models of the shale rock matrix are reconstructed from nano X-ray microscopy (nano-XRM) and focused ion beam scanning electron microscopy (FIB-SEM) images. Subsequently, the organic-matter-related and nonorganic-matter-related pores are separated from each other, which allow for the integrationof mineralogy and porosity for the most realistic transport phenomenamodeling and simulation in shale reservoir matrix. Second, anewly created 3D representation of the organic matter network is used as an input to model/simulate diffusion flux through the selected region of interest (ROI). Finally, the impact of obtained results on transport phenomena within shale is analyzed. Results indicate that the organic-matter-related pore network strongly dominates over the nonorganic-related pore network within the investigated rock sample. This suggests a strong relationship between porosity and organic content. This creates possible flow pathway channels for the gas and/or liquid to migrate through organic matrix from one pore system to another. The size of the pore-organic matter systems and components, and the connectivity of thesesystems within the shale rock matrix, are key controls on the delivery of fluid from pore to fracture and then towellbore. Results presented in this study are aimed providing new insight into the effects of the matrix composition on transport phenomena in the example from the Marcellus Shale reservoir.