Pore-Scale Modelling of Three-Phase Capillary Pressure Curves Directly in Uniformly Wet Rock Images

Yingfang Zhou,Dimitrios Georgios Hatzignatiou,Johan Olav Helland,Yulong Zhao,Jianchao Cai,Richeng Liu

doi:10.1155/2021/6622079

Abstract

In this work, we developed a semianalytical model to compute three-phase capillary pressure curves and associated fluid configurations for gas invasion in uniformly wet rock images. The fluid configurations and favorable capillary entry pressures are determined based on free energy minimization by combining all physically allowed three-phase arc menisci. The model was first validated against analytical solutions developed in a star-shaped pore space and subsequently employed on an SEM image of Bentheim sandstone. The simulated fluid configurations show similar oil-layer behavior as previously imaged three-phase fluid configurations. The simulated saturation path indicates that the oil-water capillary pressure can be described as a function of the water saturation only. The gas-oil capillary pressure can be represented as a function of gas saturation in the majority part of the three-phase region, while the three-phase displacements slightly reduce the accuracy of such representation. At small oil saturations, the gas-oil capillary pressure depends strongly on two-phase saturations.

Highlights

Pore-scale modelling has been used extensively to quantify properties related to two-phase flow in porous media, namely, capillary pressure curves and relative permeability curves
The pore network modeling requires first to extract the pore network from 3D images of porous media with the pore space being represented by an interconnected system of pores and throats having an idealized geometry and constant cross-section [20]
We have developed a semianalytical model to overcome the limitations of a simplified capillary tube model that was constructed with analytical cross-sections; we have applied this model directly on 2D rock images to successfully calculate two-phase capillary pressure curves and fluid configurations in porous media [16, 27] and three-phase entry pressure and fluid configurations [13]

Summary

Introduction

Pore-scale modelling has been used extensively to quantify properties related to two-phase flow in porous media, namely, capillary pressure curves and relative permeability curves. Quasistatic displacement is a reasonable approximation of the threephase flow at the pore scale, and pore-network models can be used to simulate the capillary-dominated threephase flow in porous media [10, 12, 15, 17,18,19]. The advantages of pore network models for the three-phase flow compared with the most recently developed direct methods, such as the level set method [11], pore-morphology method [22], and Lattice Boltzmann method [23, 24], are their efficiency and lack of dependence on grid resolution effects used to represent thin oil layers in the idealized geometry

Methods

Results

Conclusion