title: Colorimetric pH Measurement of Pressurized Groundwater Containing CO2.
abstract: A gas-tight pH measurement is needed to monitor water chemistry at a CO2 geological storage site. In the CO2 reservoirs, the temperature and pressure are generally more than the critical point of CO2 (31.2°C and 7.38 MPa). In this study, a colorimetric pH measurement method was examined up to 20 MPa for future application to various CO2 reservoirs. A mixture of two color indicators, bromocresol green (BCG) and metacresol purple (mCP), was considered to be a suitable measurement method between pH 3 and 9. The uncertainty up to 20 MPa was less than 0.12 pH units without any correction of pressure effects. We demonstrated a pH measurement of formation water at the Nagaoka CO2 post-injection site. The pH measurement was successfully accomplished under a high-pressure condition (ca. 11 MPa) and without degassing of CO2.
authors.affiliation: Research Institute of Innovative Technology for the Earth (RITE).
authors.forename: Saeko
authors.initials: S
authors.lastname: Mito
authors.forename: Kei
authors.initials: K
authors.lastname: Okamura
authors.forename: Hideshi
authors.initials: H
authors.lastname: Kimoto