Progress of CO2 injection and monitoring of the Tomakomai CCS Demonstration Project

The Tomakomai CCS Demonstration Project is an offshore CCS project being conducted in the busy port area of Tomakomai City, Hokkaido Prefecture, Japan. The Tomakomai Project has been conducted over nine years from JFY 2012*, comprised of four years of construction, three years and eight months of CO2 injection and ongoing post injection monitoring. The CO2 source is offgas from an HPU of an oil refinery located in the coastal area of the Tomakomai Port. Gaseous CO2 captured by an activated amine process is compressed and injected by two highly deviated injection wells drilled from an onshore site targeting two offshore reservoirs, namely, the sandstone layer of the Lower Quaternary Moebetsu formation and the volcanic and volcaniclastic layers of the Miocene Takinoue formation. CO2 injection into the Moebetsu formation began in April 2016 and was terminated with the cumulative amount at 300,012 tonnes on November 22, 2019. The cumulative CO2 injection into the Takinoue formation ended in 98 tons due to low injectivity. Comprehensive offshore and onshore monitoring facilities comprised of three observation wells, an OBC, four OBSs and an onshore seismic station were deployed, and the monitoring for seismicity and pressure & temperature of the reservoirs started in February 2015, thirteen months before the start of CO2 injection. Since the start of monitoring, no seismicity has been detected at and around the reservoirs. By August 2020, five monitor seismic surveys had been conducted. In the 2nd, 3rd and 4th monitor surveys from JFY 2017 to 2019, a growth of the amplitude anomalies corresponding to the depth interval of CO2 injection into the Moebetsu formation was detected, indicating the evolution of the CO2 plume between 65,000 tonnes and 300,000 tonnes cumulative injection. The data of the 5th monitor survey of August 2020 are under processing. Seasonal marine environmental surveys in line with a domestic law reflecting the London Protocol 1996 have been conducted before, during and after the CO2 injection. To date, indications of seepage of injected CO2 into the ocean have not been detected. The 2018 Hokkaido Eastern Iburi Earthquake of moment magnitude (Mw) 6.6 occurring during the injection period had no effect on the stored CO2, and there was no data suggesting a connection between the CO2 storage and the earthquake. (*JFY denotes April of calendar year to March of following year)