Large-scale field test on abandoned deep anhydrite mine-out for reuse as crude oil storage - A case study

The reuse of abandoned anhydrite mine-outs has significant potential to reduce the cost and period of construction of crude oil storage facilities and provides a new option for exploiting underground space. Based on a case study of the Anhui Hengtai anhydrite mine located in East China, this study formulated a comprehensive field test program to investigate its tightness and stability and evaluate its feasibility for reuse as crude oil storage. Combining the field tests with laboratory tests, the underlying mechanism of interaction among anhydrite, water, and crude oil was revealed, and the stability and tightness of anhydrite mine-out during the storage of crude oil was evaluated. The results indicate that the anhydrite mine-out has good stability and tightness, which is not affected by the presence of crude oil. Additionally, the anhydrite has negligible effects on the crude oil quality; however, the presence of water reduces the strength of anhydrite rock, which has the potential to affect the stability and tightness of the mine-out. It is concluded that the anhydrite mine-out has the potential to be used as underground crude oil storage space, but the long-term contact between anhydrite rock and water should be avoided. This work is expected to benefit future underground space exploitation through reuse of mine-out.