A comprehensive model for dynamic characteristic curves considering sulfur deposition in sour carbonate fractured gas reservoirs

Calculating sulfur deposition is a key issue in developing sour gas reservoirs, where sulfur solubility plays an important role. However, prediction of sulfur solubility is a difficult problem due to the toxic of H2S. In this work, an analytical model for dual porosity media considering the influence of sulfur deposition was proposed. The Douglas-Jones predictor-corrector method is used to calculate a relationship between time and pressure, which can avoid solving the system of nonlinear equations. The effects of sulfur deposition on well performance were analyzed and some dynamic characteristic curves for predicting sulfur deposition were provided. The results show that the fastest pressure drop appears near the wellbore, which is the primary damage zone for elemental sulfur precipitation and deposition. Flow parameters and storage ratio play the significant influences on the sulfur saturation curve shape. In addition, the reduction of flow parameters and storage ratio lead to the increase of sulfur saturation and decrease of permeability, resulting in the damage of sour gas formation. The advantage of this approach is that it can be used to describe a characteristic curve without considering the sulfur solubility issue. This paper provides a novel method to analyze the impacts of sulfur deposition on well performances in sour carbonate fractured gas reservoirs.