Preliminary cap rock integrity analysis for CO2 geological storage in saline aquifers based on geochemical tests in Shenhua CCS demonstration project, CHINA

Abstract

The most important public concern about CO2 geological storage is the long term isolation performance. To prevent the stored CO2 leakage into groundwater sources or the atmosphere, the possible leakage paths, must be examined and identified. Cap rock integrity is the most important factor to evaluate the long-term CO2 isolation performance. Shenhua CCS demonstration project has several reservoir-cap rock combinations from 1300 to 2500 meters in the storage filed. The formation fluids were collected from 6 formations-- 3 storage target formations, 1 buffer formation below the caprock, 1 formation above the caprock, 1 formation closed to ground. Dissolved free carbon dioxide and bicarbonate radical(HCO -) have been test as soon as possible, then the mineralized degrees were determined by gravimetric method in 24 hours. One of the samples was acidized with nitric acid to pH=2 after filtration, then concentration of common ions were determined by ion chromatograph. CO2 solubility measured from normal pressure and temperature to formation temperature and pressure. The caprock integrity is proved good enough for CO2 geological storage based the preliminary chemistry analysis. After preliminary analysis, according to the parameters and data collected from the inject test, production test, the integrity of the caprocks between the storage layers is also good enough according to the parameters and data collected from the injection tests and production tests.