Cap Rock CO2 Breakthrough Pressure Measurement Apparatus and Application in Shenhua CCS Project

Abstract

CO2 breakthrough pressure is a very important factor for cap rock integrity evaluation. It is mainly acquired by laboratory experiments. We developed a set of apparatus to measure CO2 breakthrough pressure, which was based on pulse decay method (residual capillary pressure approach). Breakthrough pressure measurement experiments were conducted on the mudstone samples derived from four important seal formations in Shenhua CO2 aquifer storage project located in Ordos basin in China. The main conclusions are listed below based on experiment results and site characterization: 1) the breakthrough pressure of mudstone samples have sufficient capillary pressure to keep the stored CO2 underground. 2) the mudstones at a deeper burial depth, which may be better consolidated and better diagenetic, tend to have a higher breakthrough pressure. However, mudstones that are too diagenetic may be more likely to generate fractures, which will enhance the permeability and reduce the breakthrough pressure. 3) Breakthrough pressure is just a core scale parameter and site characterization about cap rock thickness, integrity is necessary before a specific formation is selected as a cap rock in CO2 geological storage. 4) Intercalated sand layers will greatly influence the sealing ability of mudstone formations.