The elastic moduli change after carbon dioxide flooding into limestone: an experimental study

摘要

Carbon geosequestration in deep saline aquifers is an efficient way to mitigate climate change due to greenhouse gas emissions. The carbonate reservoir is the one of the selected storage site, however, such carbonate rock is sensitive to the acidic environment – where the CO2 saturated formation water could be as medium acid in the reservoir condition. Thus, fully understand such CO2-water-rock interaction and the related rock mechanical properties change are very important for the storage security. However, how the elastic moduli change in the different storage areas are still blank. In this paper, we thus injected scCO2 and CO2 saturated (live) brine into Savonnières limestone core plugs at reservoir conditions to simulate the different areas in the real geosequestration sites. The flooding tests were set as a representative reservoir conditions at approximately 1000m depth with 325 K, 15 MPa confining pressure and 10 MPa pore pressure. The X-ray CT scanning and ultrasonic tests were conducted to monitor the change before and after the flooding. The morphology results showed that the CO2 saturated brine injection had larger dissolution effect than scCO2 and consistent with the calculated Young’s moduli change. Moreover, the Poisson’s ratio slightly had slightly dropped after scCO2 flooding but build up by live brine. We thus suggested that Poisson’s ratio could be used to monitor the CO2 underground conditions (supercritical condition or saturated with brine) in such limestone carbon storage which need more future investigations.