This paper presents a new formulation expressing the apparent liquid permeability in shale strata. We introduce an apparent liquid permeability formulation to predict volumetric flux of oil and gas condensate in liquid-rich shale formations. Nanopores (<100 nm) associated with the structure of shale formations introduce molecular slippage on the pore walls, breaking down the traditional no-slip flow condition. Molecular slippage on the pore walls eases flow; hence, Darcy permeability underestimates liquid flow in shale formations. In this paper, we make a correction to the slippage phenomenon by defining a slip length to properly model fluid flow in shale. Slip length is defined as an extrapolated distance relative to the nanopore wall to compensate for the tangential velocity component. The derived formulation in this study shows that the apparent permeability of liquid-rich shales increases with increased slip length. We present a review of different methods to determine slip length. For ease of use in reservoir simulators, we express apparent permeability with the slip-length modification in a form that is compatible with Darcy's equation.
Apparent Liquid Permeability in Shale
Appiah, Francis, Javadpour, Farzam, and Rouzbeh Ghanbarnezhad Moghanloo. "Apparent Liquid Permeability in Shale." Paper presented at the SPE/AAPG/SEG Unconventional Resources Technology Conference, Denver, Colorado, USA, August 2013. doi: https://doi.org/10.1190/urtec2013-260
Download citation file: