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

Tight gas reservoirs are valuableyet challenging unconventionalresources as a result of their complex flow mechanisms. Typical challengesare characterized by gas-water two-phase flows with a thresholdpressure gradient (TPG). In this work, experimental studies are initiallyconducted to investigate and quantify the influence of water saturationon the TPG. A gas-water two-phase flow model is then establishedfor a fractured horizontal well considering the influence of watersaturation on gas-water permeability and TPG, along with thedynamic changes in the water-gas ratio. Sensitive studies areperformed to investigate the impact of various parameters on the productivityof a horizontal well. The results demonstrate that, as water saturationincreases, the TPG increases and the relative permeability of thegas phase decreases, resulting in the gas well productivity decrease.As the permeability decreases, the changes in the TPG become moreprominent, leading to a greater impact on productivity. In comparisonto a constant TPG, the changes with water saturation in the TPG havea more significant effect on productivity. Hence, it is beneficialto regulate the rate of the water cut increase to enhance productionin tight gas reservoirs.