Correction of source-rock permeability measurements owing to slip flow and Knudsen diffusion: a method and its evaluation

Abstract

Source-rock permeability is a key parameter that controls the gas production rate from unconventional reservoirs. Measured source-rock permeability in the laboratory, however, is not an intrinsic property of a rock sample, but depends on pore pressure and temperature as a result of the relative importance of slip flow and diffusion in gas flow in lowpermeability media. To estimate the intrinsic permeability which is required to determine effective permeability values for the reservoir conditions, this study presents a simple approach to correct the laboratory permeability measurements based on the theory of gas flow in a micro/nano-tube that includes effects of viscous flow, slip flow and Knudsen diffusion under different pore pressure and temperature conditions. The approach has been verified using published shale laboratory data. The ''corrected'' (or intrinsic) permeability is considerably smaller than the measured permeability. A larger measured permeability generally corresponds to a smaller relative difference between measured and corrected permeability values. A plot based on our approach is presented to describe the relationships between measured and corrected permeability for typical Gas Research Institute permeability test conditions. The developed approach also allows estimating the effective permeability in reservoir conditions from a laboratory permeability measurement.

Boundary scheme for lattice Boltzmann modeling of micro-scale gas flow in organic-rich pores considering surface diffusion

“…[3,4] Additionally, the experiment-based studies are less accurate due to the extremely low mass transport capability of shale and difficulty in controlling laboratory conditions. [6][7][8][9] As a replacement or supplementary to experiments and theories, numerical simulation has become a promising and effective tool to research and reveal some micro-scale physical mechanisms which fall beyond the scope of experiments and theories. A variety of numerical models, such as molecular dynamics simulation (MD), [10][11][12][13] direct simulation of Monte Carlo (DSMC), [14,15] lattice Boltzmann method (LBM), [16,17] and traditional computational fluid dynamics (CFD), have been widely applied to the studies of micro-gaseous flow.…”

Tight gas production model considering TPG as a function of pore pressure, permeability and water saturation

“…Fitting coefficient a. b Fitting coefficient b TPG versus pore pressure at different water saturation values4 Production model including TPGThis is a well-established fact that under low velocity and low pressure, an effect is always present there, namely gas Klinkenberg effect(Liang et al 2016;Moghaddam and Jamiolahmady 2016;Nakhli et al 2017). To address these effects,Beskok and Karniadakis (1999) offered a rigorous gas flow equation(Deng et al 2014;Liu et al 2018):…”