Alleviation of liquid sulfur blockage by altering sulfur wettability in sour gas reservoirs
In sour gas reservoirs exploitation, liquid sulfur deposited in the formation could block natural gas passage channels, severely reducing gas field production. To address this problem, we successfully regulate the wettability of liquid sulfur on rock surfaces by modifying them with alkoxysilanes. It is found that enhancing the sulfophobicity of the rock surface significantly reduces the difficulty of gas-phase breakthrough of channel blockage caused by liquid sulfur deposition. During the simulated gas flooding process, the liquid sulfur recovery rate in neutral and sulfophobic rocks is increased by 48.3% and 124.4%, respectively, compared with untreated natural sulfophilic rocks, resulting in 29.3% and 50.0% increase in porosity of the rocks after flooding, respectively. These results indicate that the modified rock surface, especially sulfophobic rock surface, could effectively alleviate the blockage of gas production channels caused by liquid sulfur deposition. Mechanisms revealed by visualized experimental results show that in gas flooding in more sulfophobic cores, the swept area of gas phase is larger and the amount of residual sulfur in the swept area is less, so the sulfur recovery rate is higher than untreated sulfophilic rock, and the blockage caused by liquid sulfur in the cores could be effectively reduced.
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