Analysis of sulfur deposition for high-sulfur gas reservoirs

Abstract

Wellbore sulfur deposition is one of the most common problems during the development of high-sulfur gas reservoirs, which also affects the accuracy of bottomhole pressure(BHP) calculations. However, the existing BHP calculation methods have poor applicability to high-sulfur and water-producing gas wells. In this study, a model for calculating bottomhole pressure suitable for high-sulfur and water-producing gas wells was established. The model was solved by finite difference and iterative methods, and its accuracy was verified by a typical high-sulfur gas well in China. The results show: The pressure prediction errors are mainly distributed within −1%∼5%; As the well depth decreases, the precipitation trend of sulfur gradually increases due to the decrease in solubility; Affected by temperature and pressure distribution, liquid sulfur is often deposited in the lower part of wellbore, while solid sulfur is deposited in the middle-upper section, which will increase the pressure loss and the occurrence of production accidents. Controlling production pressure difference, adopting production system, and injecting sulfur dissolving agents can help prevent sulfur deposits and ensure the safe-efficient production. The findings of this study can help to more clearly reveal the wellbore sulfur deposits characteristics and more accurately calculate the bottom hole pressure of high-sulfur gas wells.