Evaluation of the sealing performance of compressed air energy storage spaces in aquifers: theory and applications

In the context of the rapid development of new energy technologies, energy storage has emerged as a crucial strategic capability. As a new energy storage technology, compressed air energy storage in aquifers (CAESA) is receiving attention due to its advantages of wide distribution and large scale. It has more significant advantages in carrying out compressed air energy storage in aquifers with high exploration and development levels in oil regions. In CAESA, the sealing performance of the caprock system controls the storage capacity and safety. Fully tapping into the sealing potential of the caprock system requires the use of quantitative evaluation indicators. This article proposes a maximum sealing pressure model (Pmax model) to define the sealing capacity of a caprock segment, and provides a method for determining Pmax via mathematical modeling. This model can accommodate various sealing mechanisms, and for the first time, it explains the sealing mechanism of the thickness of the caprock layer from a mathematical and physical perspective. This indicator can be used as a single indicator to measure the sealing performance of the caprock layer during the site selection stage. Based on this indicator and in combination with the short-board principle, we propose the safe sealing pressure index Psafe to quantify the sealing performance of the entire caprock system. We also provide the calculation method and a flowchart, which can be applied during the engineering development and design stage. Finally, using the KD642-7 pilot project planned by Sinopec Shengli Oilfield as an example, the model’s validity has been preliminarily demonstrated.