Estimation of Costs and Carbon Offset Credits Associated with Oil Well Plugging Based on Field-verified Natural Gas Emissions from Abandoned Wells of the Kurokawa Oil Field, Japan

We estimated greenhouse gas (GHG) emissions from abandoned oil wells in the Kurokawa oil field in Akita Prefecture, Japan, to explore the potential costs and carbon offset credits associated with reducing GHG emissions. These wells were abandoned, but not capped, following technical failure by the management company, leaving crude oil and natural gas in the field. As no recent gas production records or other data exist for the Kurokawa oil wells, we estimated the amount of methane released by the wells based on old survey data and field optical gas imaging using an infrared camera. Based on these measurements, we estimated methane emissions of 7,300 t-CO2e/year, a substantial amount when compared against the 47,400 t-CO2 estimated methane emissions reported for fiscal 2019 in Akita Prefecture as a whole. We found that plugging the wells would be highly effective in reducing GHG emissions. The cost per t-CO2 reduction was estimated at 3,500 JPY (25 USD), based on a single-well cost of 50 million JPY, which is lower than that associated with reducing other GHGs. The potential GHG reductions from this sequestration project could be authorized as carbon offset credits, which would exceed those accumulated through energy conservation, and at lower cost. Thus, we anticipate that capping abandoned wells will represent an effective approach for securing financial resources.