Productivity Analysis of Fractured Horizontal Wells in Tight Gas Reservoirs Using a Gas–Water Two-Phase Flow Model with Consideration of a Threshold Pressure Gradient

Abstract

Tight gas reservoirs are valuable yet challenging unconventional resources as a result of their complex flow mechanisms. Typical challenges are characterized by gas–water two-phase flows with a threshold pressure gradient (TPG). In this work, experimental studies are initially conducted to investigate and quantify the influence of water saturation on the TPG. A gas–water two-phase flow model is then established for a fractured horizontal well considering the influence of water saturation on gas–water permeability and TPG, along with the dynamic changes in the water–gas ratio. Sensitive studies are performed to investigate the impact of various parameters on the productivity of a horizontal well. The results demonstrate that, as water saturation increases, the TPG increases and the relative permeability of the gas phase decreases, resulting in the gas well productivity decrease. As the permeability decreases, the changes in the TPG become more prominent, leading to a greater impact on productivity. In comparison to a constant TPG, the changes with water saturation in the TPG have a more significant effect on productivity. Hence, it is beneficial to regulate the rate of the water cut increase to enhance production in tight gas reservoirs.