Induced Sulfur Deposition During Carbon Dioxide Miscible Flooding in Carbonate Reservoirs

The existence of sulfur compounds in crude oils decreases their economical value and creates many problems of sulfur deposition in the vicinity of a wellbore hole, in well completion and/or production equipment, and in producing reservoir rocks. Laboratory testing of carbonate reservoirs containing sulfur and asphaltene shows that carbon dioxide flooding is likely to be more efficient if these reservoirs have permeabilities near 10 md than higher levels. Furthermore, faster production rates are likely to reduce displacement efficiency as the contaminants deposit in porous medium and increase damage. Likewise, crude oil viscosity increases with increase of sulfur and asphaltene contents for different temperatures.

Eight core flooding experiments were conducted using multiple flow rates, and reservoir rock permeabilities. All runs were conducted at secondary mode (no water flooding) using carbon dioxide slug size of 15 % hydrocarbon pore volume (HCPV). Three other runs using different initial oil saturations were also performed to study the effect of mobile oil saturation. Our results suggest that application of CO₂ flooding to these reservoirs could exacerbate damage to the reservoir porous rocks.