A Pore Network Approach to Study Throat Size Effect on the Permeability of Reconstructed Porous Media

Kai Xu,Sai Xu,Jianchao Cai,Yin Chen,Wei Wei,Haitao Tian

doi:10.3390/w14010077

Kai Xu, Sai Xu + Show 4 more

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https://doi.org/10.3390/w14010077

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Abstract

Permeability is usually considered to be related to porosity. However, rocks with the same porosity may have different permeabilities in some cases, because of the variations in pore and throat size and pore space connectivity. It is vitally important to understand the effect of throat size on the transport property. In this work, five sets of regular pore network models and six core-based models are employed to study the effect of throat size on permeability. Four kinds of random distributions, i.e., uniform, normal, Weibull, and log normal, are utilized to generate random pore size. Pore coordination number is set to be two and six for the verification of the effect of connectivity on permeability. Then, single-phase flow simulation is conducted based on the constructed pore network models. The simulation results show that permeability decreases significantly when only one of the nine throats reduces to half size in terms of diameter. The influence of pore coordination number on permeability is not obvious compared to that of small throat size. This study indicates that small throats play an extremely important role in determining permeability.

Highlights

Micro-structure characterization of reservoir rock is the foundation in both basic flow mechanism studies and industrial applications
60 years, from which we found that pore network model (PNM) is commonly applied to study complex pore structures, e.g., extracting PNM from core samples or constructing stochastic PNM with specific porosity and pore coordination number (PCN)
Single phase flow simulation was performed on the generated PNM

Summary

Introduction

Micro-structure characterization of reservoir rock is the foundation in both basic flow mechanism studies and industrial applications. Lu [1], the purpose of micro-structure characterization is to ascertain what is the essential morphological information, quantify it either theoretically or experimentally, and employ the information to estimate the desired macroscopic properties of the heterogeneous materials. The well-known Kozeny–Carman (KC) equation is such a classical example of predicting permeability by finding the relationship between macroscopic property and microscopic morphological information [2]: iations. Where K is permeability, φ is porosity, Dp is average diameter of sand grains, c is the proportionality and unity factor. The equation holds for fluid flowing through packed beds with particle Reynolds numbers up to approximately 1.0. The KC equation is widely applied in permeability predictions

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