Prediction model of sulfur saturation considering the effects of non-Darcy flow and reservoir compaction

Sulfur deposition in the near wellbore region is generally estimated using Robertsʹ model. However, the model cannot correctly predict sulfur deposition from its assumptions. In the present study, a modified sulfur saturation prediction model is established. The refined model, based on non-Darcy flow, takes into consideration the effects of reservoir compaction, variation in gas properties, and the dependence of sulfur solubility on pressure. In addition, the effect of sulfur deposition on gas well deliverability is also studied. The results showed that the following: (1) the rate of sulfur deposition was underestimated by Robertsʹ Model and that the new and comprehensive model is more accurate and practical in predicting sulfur deposition; (2) reservoir compaction is a common phenomenon, which should be considered in sulfur deposition prediction since it leads to a faster rate of sulfur deposition; (3)the effect of variation in the gas properties on sulfur deposition can be directly attributed to the influence of pressure change; thus, parameters in the model should be calculated according to the corresponding pressures; (4)the radius damage caused by sulfur deposition increases with increasing gas production rate and production time; furthermore, the gas production rate dramatically decreases as sulfur saturation increases.