Water-rock interaction in CO₂ sequestration in a depleted oil reservoir pilot test

A field test of CO₂ sequestration in the Neogene Minghuazhen Formation in the Bohai Bay Basin (BBB-Nm test) is presented, where the first Chinese pilot project of CO₂ storage in a depleted oil reservoir was implemented. A total of 305 t CO₂ was injected into the sandstone reservoir. The process of injection and pre/post-injection monitoring are described, especially for the geochemical monitoring in the field test. Results show that CO₂ flux monitoring successfully tracked the injected CO₂. Chemical analyses of post-injection brine samples indicate brine may have not been affected by CO₂ injection during the monitoring period, which needs to be confirmed with further investigations before extending the results to deep saline aquifers. (authors)