Abstract
Diagenesis encompasses many processes after deposition that are responsible for the dynamic evolution of the pore system. Understanding the role of diagenetic events on the connectivity and distribution of pores and migration pathways is vital for proper characterization of the rock. In this study, we critically examine diagenetic signatures in the Woodford Shale focusing on rock-fluid interactions that cause precipitation and dissolution and assess their impact on reservoir quality via multi-physics models.
Evidence of diagenesis in shales have been extensively investigated by some of the authors in active and previous research. In this study, we focused on capturing the distribution of diagenetic features in the Woodford Shale using multiphysics models. Our methodology establishes a multi-disciplinary framework to incorporate multi-scale multi-physics data from various sources to investigate the impact of diagenesis on the alteration of petrophysical properties. Data incorporated include thin sections, scanning electron microscopy, and mineralogy. We first analyze and quantify the diagenetic signatures in the Woodford Shale. Examining the depositional history of the basin, mineralogy, the different pore types and the associated minerals. We then construct representative 3D pore-scale models and employ multi-component coupled fluid-flow and reactive-transport models to critically investigate these processes. Numerically, this entails concurrent solution of fluid-flow equations for pressures and fluxes, changes in fluid and mineral composition and conservation of solute mass for each component in the pore-network. We analyze porosity occlusion and the changes in migration pathways.
This framework allowed us to determine the influence of chemical diagenesis (precipitation and dissolution) processes on the pore structure, connectivity, and fluid flow, in order to quantify the reservoir quality. Our initial pore-scale simulation effort yields promising results and is able to reproduce major diagenetic features. Future research efforts will include incorporating complex reactive kinetics and geomechanical stress-strain modules in the pore scale simulator that will enable us to examine more complex scenarios.
