High Sulfur The Wellbore Sulfur Deposition Prediction

The gas reservoirs with high H2S content are exceptional reservoirs, compared to normal natural gas, the gas with high H2S content posseses the characteristics of corrosivity and acute toxicity, besides that, the most difference is sulfur deposition. A great deal of sulfur deposition would result in a decrease in porosity permeability, a jam of wellbore and surface pipeline, even the well would be off priduction. In this thesis, we mainly focused on high sour gas well, established a sulfur deposition prediction model, Which could help gas well to conduct a advisable production rate so as to prevent elemental sulfur deposit in wellbore. The mainly accomplished work is as follows:(1)Compared several methods of calculating Z-factor, viscosity and relevant nonhydrocarbon correction formula, finding that DPR with W-A nonhydrocarbon correction formula is the best method to calculate Z-factor of gas with high H2S content; Dempsey with Stanging nonhydrocarbon correction formula is the best method to calculate viscosity of gas with high H2S content. The physical property of gas with high H2S content is influenced by H2S content, temperature, pressure.(2)According to the gas-liquid thermodynamics equilibrium and thermodynamics model of dissolved sulfur, normally, sulfur gasification and H2S liquefaction don't exist in the condition of well bore except H2S content is high as 50%. Multiphase flowing would appear when the dissolving capacity of some point in wellbore lower than the initial sulfur saturation. Gas-liquid flowing would appear if separated sulfur is liquid, else it would be gas-solid flowing.(3)Established temperature and pressure distribution prediction model. Combined calculated results with real data to justify reliably of the model. The distribution of temperature and pressure are influenced much by H2S content and gas production. The solid and liquid content would also have affection on pressure and temperature distribution if there is sulfur separated. However, it would have less affect if the amount of separated sulfur is low. The affection on temperature almost could be ignored.(4)Comprehensive research on justifying sulfur deposition was completed. The sulfur could bring out the well with gas flowing when gas velocity at the point of sulfur separation is faster than critical floating velocity. Otherwise, the sulfur would deposit. Compared the calculated results and real sulfur deposition, the method is adaptability.(5)Compared the affection of different gas production and initial sulfur saturation on sulfur deposition. It showed that the less gas production was, the easier sulfur deposited and the less initial sulfur saturation was, the closer separated point to the wellhead.