Characterization of Pore Structure and Simulation of Pore-Scale Flow in Tight Sandstone Reservoirs
Min Feng*, Long Wang, Lei Sun, Bo Yang, Wei Wang, Jianning Luo, Yan Wang, Ping Liu
Petroleum Exploration and Production Research Institute, PetroChina Changqing Oilfield Company, Xi’an, 710016, China
* Corresponding Author: Min Feng. Email: 
Fluid Dynamics & Materials Processing https://doi.org/10.32604/fdmp.2024.056421
Received 22 July 2024; Accepted 07 November 2024; Published online 02 December 2024
Abstract
This study sheds light on how pore structure characteristics and varying dynamic pressure conditions influence the permeability of tight sandstone reservoirs, with a particular focus on the Paleozoic reservoirs in the Qingshimao Gas Field. Using CT scans of natural core samples, a three-dimensional digital core was constructed. The maximum ball method was applied to extract a related pore network model, and the pore structure characteristics of the core samples, such as pore radius, throat radius, pore volume, and coordination number, were quantitatively evaluated. The analysis revealed a normally distributed pore radius, suggesting a high degree of reservoir homogeneity and favorable conditions for a connected pore system. However, it was found that the majority of throat radii measured less than 1 μm, which severely restricted fluid flow and diminished permeability. Over 50% of the pores measured under 100 μm
3, further constraining fluid movement. Additionally, 30%–50% of the pore network was composed of isolated and blind-end pores, which significantly impaired formation connectivity and reduced permeability. Based on this, the lattice Boltzmann method (LBM) was used for pore-scale flow simulation to investigate the influence mechanism of pore structure characteristics and dynamic-static parameters such as displacement pressure difference on the permeability performance of the considered tight sandstone reservoirs for various pressure gradients (0.1, 1, and 10 MPa). The simulations revealed a strong relationship between pressure differential and both the number of streamlines and flow path tortuosity. When the pressure differential increased to 1 MPa, 30 streamlines were observed, with a tortuosity factor of 1.5, indicating the opening of additional seepage channels and the creation of increasingly winding flow paths.
Keywords
Tight sandstone; digital core; flow simulation; lattice Boltzmann method
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