Dynamic Approach in Estimating Permeability in Tight Reservoir Rocks

Abstract

The impact of the permeability on ultra-tight porous media influences flow behaviour inside the media. The unconventional reservoir gas permeability significantly impacts rock property estimation crucial to unconventional resource development. The pressure decay approach estimates the permeability of unconventional rocks by evaluating the pressure difference in reservoirs. A representation of a mathematical model containing gas characteristics related to pressure was developed. When the minimum difference between the experimental pressure and the simulated pressure results stabilizes, the permeability estimation occurs. This study's approach estimated permeability from pulse pressure decay, using laboratory data by testing three gases that include Methane, Helium, and carbon dioxide. This new approach measures the slightest variation in the pressure decay response evaluation based on history matching. This method estimated permeability more accurately when compared with the Cui et al. (2009) analytical solution. The improved estimation of gas permeability in this study was due to the applicability of pressure-dependent gas properties and the entire pressure outcome's implementation to represent pressure decay dynamics. The sensitivity analysis shows that implementing the entire pressure outcome to represent the dynamics of pressure decay is significant in estimating permeability. In contrast, variation in porosity, Langmuir pressure, and Langmuir volume is less significant in the permeability estimation, making the pulse pressure decay approach for estimating permeability to be valid.