Assessment of the CO2 Geological Storage Potential of Yanchang Shale Gas Formation (Chang7 Member) Considering the Capillary Sealing Capability of Caprock

Abstract

Reducing net carbon emissions is of great significance for sustainability. Carbon capture, utilization, and storage (CCUS) technology is regarded as one of the most effective approaches to reducing net carbon emissions. A prerequisite for the implementation of the CO2 geological storage project is the assessment of the storage potential of the storage site. In this study, a calculation method of storage potential was proposed to estimate the CO2 storage potential of the Yanchang shale gas reservoir in the Ordos Basin, China. In this method, the CO2 sealing capability of the caprock is taken into account, which determines the maximum CO2 storage pressure of the reservoir. The overall CO2 storage potential consists of four types of storage states (free-state, adsorption, dissolution, and mineralization). The maximum CO2 storage pressure of the Yanchang shale gas reservoir is 13.4 MPa via breakthrough pressure experiments, and the corresponding theoretical storage potential is 7.59 × 1011 t. The potential for free-state, adsorption, dissolution, and mineralization sequestration are 8.42 × 1010 t, 6.88 × 1010 t, 2.45 × 109 t, and 6.05 × 1011 t, respectively. Due to the difficulty in completing mineralization within the engineering time scale, the mineralization potential should not be taken into account when estimating the available CO2 storage potential. The available CO2 potential (including free-state, adsorption, and dissolution) of the Yanchang shale gas reservoir is 1.54 × 1011 t, which is a considerable amount. The Yanchang shale gas formation will be able to accommodate 41.49% of global annual CO2 emissions (according to the data in 2021) if the available CO2 storage potential of the Yanchang shale gas reservoir is fully exploited.