(50h) Fluid Transport in Shale Nanopores

Production of hydrocarbon in a hydraulically fractured shale starts from the desorption and diffusion of gas/oil from the matrix nanopores to the induced fractures and to the well. In shale nanopores, multiple components such as gas, oil, water, and super critical carbon dioxide (scCO₂) can coexist. Studying the interaction of these components with shale is critical to understanding the oil and gas transport in shale nanopores. We employed molecular simulations to investigate the properties of the fluid/shale system under reservoir conditions including gas adsorption, swelling, wettability, and transport. Our results indicate that kerogen preferentially retains CO₂ over CH₄, and that upon the adsorption of gas kerogen swells significantly. In addition, under ambient condition water partially wets the kerogen surface. However, in the scCO₂ atmosphere, water forms a spherical droplet at the kerogen interface. Our results also suggest that scCO₂ significantly enhances the flow of oil and gas in both organic and inorganic nanopores. Our work provides molecular-level insight into the production decline curve, chemo-mechanical properties of porous materials, and suggests a new mechanism and engineering approach to reduce energy consumption of a nanofluidic system.

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This research was funded by a DOE National Energy Technology Laboratory project.