Numerical Simulation of Gas–Water Two-Phase Flow Patterns in Fracture: Implication for Enhancing Natural Gas Production

Abstract

The main objective of this paper is to investigate the evolution of rock fracture slug structures and decongestion strategies for natural gas extraction processes. For this purpose, the level set method was used to simulate the evolution of the slug structure under the effect of different flow ratios, fracture surface wettability, and fracture tortuosity. The results show that an increase in the water-to-gas flow ratio and fracture tortuosity leads to a significant increase in the proportion of slug structures in the fracture, while an increase in the surface contact angle leads to a decrease in the proportion of slug structures in the fracture. Based on the above slug structure evolution law, a quantitative characterization method for the slug structure of two-phase fluids considering the combined effects of the water–gas flow ratio, average wall contact angle, and flow channel tortuosity was developed. Subsequently, we engage in further discussion on the optimization of the extraction and decongestion process in natural gas extraction.

Keywords

• two-phase flow
• fracture tortuosity
• slug flow
• flow structure