Practical aspects of absolute permeability finding for the lattice Boltzmann method and pore network modeling

Abstract

The importance of pore-scale models deals with their ability to estimate macroscopic parameters such as capillary pressure, absolute and relative permeabilities that are important input data of any reservoir model while studying the microscopic structure of the given samples.The current paper aims to discuss practical aspects of two widely applied techniques for absolute permeability estimation, lattice Boltzmann method (LBM) and pore network modeling. Both approaches analyzed three sandstone and one carbonate samples with different pore structures from the open database of Imperial College London. First, a direct pore-scale modeling via LBM approach was built based on the single relaxation time concept. Later on, pore networks were extracted by using the fast and efficient SNOW algorithm which could be considered as an improved version of a well-known watershed segmentation approach. The paper does not only compare the accuracy of two methods, but rather summarize in which cases a direct pore-scale modeling can be substituted by the simplified pore network approach. It also highlights importance of new insights, for instance, consideration of image resolution and representative elementary volume of the samples as a part of their analysis.Results demonstrate that direct pore-scale modeling allowed to reach a reasonable accuracy in absolute permeability estimation for three studied sandstone samples, although this method will not properly work for bigger pore volume while running simulations on CPU. At the same time, pore networks were able to find values of absolute permeability with reasonably low errors for all samples by varying the filtering parameters while preparing images.