Analytical Solutions of Leakage through the Caprock in Carbon Sequestration in a Closed-Boundary Aquifer System | AIChE

Analytical Solutions of Leakage through the Caprock in Carbon Sequestration in a Closed-Boundary Aquifer System

Authors 

Mu, L. - Presenter, China University of Petroleum - Beijing
Liao, X., China University of Petroleum - Beijing
Zhao, X., China University of Petroleum - Beijing
Zou, J., China University of Petroleum - Beijing
Chu, H., China University of Petroleum - Beijing
Li, R., China University of Petroleum - Beijing
Zhang, J., CNPC Engineering Technology R&D Company Limited

Deep saline aquifer is deemed as an effective and promising site for carbon sequestration. A geological storage site must be operated safely; however, CO2 may leak through several pathways, openings in the caprock being one of them. Many efforts have been made to monitor the leakage.

This study presents a new analytical method obtaining the pressure change in the monitoring well caused by the leakage through the openings in the caprock to detect the leakage and evaluate the leakage rate. The model is based on the assumptions that the leakage is through the opening in the caprock and the outer boundary of the system is closed. The pressure changes are determined with Laplace transform and superposition principle and then the leakage rate is determined.

The comparison shows that the analytical and numerical solutions are in good agreement. Through the analyses, it can be concluded that the height and permeability of the monitoring aquifer, the location of the monitoring well and the location and the permeability of the opening in the caprock do have some impacts on the leakage. When the opening is close to the injection well or the leakage permeability is high, the leakage rate will increase significantly. The influences of the monitoring aquifer above the sequestration aquifer reflect on its height and permeability. With the increase of the height and the permeability leading to a lager pressure difference, the leakage rate will be larger. The leakage rate is unaffected by the location of the monitoring well. However, decreasing the distance between the injection well and the monitoring well causes the increase of the monitoring pressure. The analytical model in this paper provides a quick and accurate evaluation for the leakage through the caprock in a closed-boundary aquifer system.