Impacts of salinity on CO 2 spatial distribution and storage amount in the formation with different dip angles
2019
Jing, Jing | Yang, Yanlin | Tang, Zhonghua | Wang, Fugang
Formation dip angle and the distortion of salinity affect the spatial distribution and storage capacity of carbon dioxide (CO₂). In this numerical study, based on an actual CO₂ injection demonstration project (Shiqianfeng group in the Ordos Basin) in China, CO₂ was injected for a period of 20 years at four different formation dip angles (0°, 5°, 10°, 15°). In conjunction, some salinity values were chosen, ranging from saturation salinity to no salinity. A three-dimensional (3D) model was established to systematically explore the influence of different formation dip angles and salinities on the CO₂ spatial distribution and storage amount. The simulation results showed that larger salinity and higher pressure near the injection well will lead the CO₂ gas-phase saturation and mass fraction to be smaller for a given formation dip angle. When salinity is held constant at the saturation value, a larger dip angle will cause a smaller CO₂ gas saturation in the upper right units of the injection well, and a larger gas saturation in the lower left units at the 20th year of CO₂ injection. For large salinity values (full, half, and quarter saturation salinity), the larger the formation dip angle is, the greater the CO₂ total storage amount. For smaller salinity values (0.00 and 0.03), a transition point existed (at 8 and 18.2 years) during the 20-year injection period. Before the transition point, the CO₂ total storage amount also increases with the dip angle. After the transition point, however, the larger the formation dip angle is, the smaller the CO₂ total storage amount becomes. In addition, a lower salinity may lead to the earlier appearance of the transition point.
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