Antonio Gasos, Ronny Pini , Viola Becattini, Marco Mazzotti

This study evaluates the feasibility of producing carbon neutral oil via CO2 Enhanced Oil Recovery (CO2-EOR) coupled with direct air capture. Existing analyses often provide case-specific insights based on short-term operations that do not encompass the full life cycle of reservoir exploitation. In contrast, we propose a novel, top-down approach based on mass and volume conservation, expanding system boundaries to include emissions from primary, secondary, and tertiary oil recovery phases -- the latter being CO2-EOR. Supported by field data, the analysis demonstrates that CO2-EOR cannot achieve carbon-neutral oil production. Only 30 % of projects produced carbon-neutral oil during EOR, but all of them were significantly carbon-positive when considering the full reservoir life-time. The volume occupied by the emitted CO2 exceeded by at least 3 times the pore space freed by reservoir fluids production, namely oil, water and gas. Considering CO2-EOR in isolation from earlier stages of oil production creates the temporal illusion of carbon-neutral oil, as significant water is co-produced during this phase, freeing storage space without causing direct emissions. The reservoir conditions when CO2-EOR is carried out, however, are the direct consequence of extensive oil extraction and water injection in earlier exploitation phases. Only residual oil zones may offer potential for carbon-neutral oil due to their low oil saturation and lack of legacy emissions. Although CO2-EOR may replace conventional oil production methods, potentially reducing carbon emissions, it risks promoting and perpetuating fossil fuel production, thereby undermining critical climate targets.