Production of mature oil fields emits significant amount of CO₂ related to circulation and handling of large volumes of gas and water. This can be reduced either by (1) using a low-carbon energy source and/or (2) reducing the volumes of the non-hydrocarbon produced/injected fluids. This paper describes how improved oil recovery techniques can be designed to reduce CO₂ intensity (kgCO₂/bbl oil) of oil production by efficient use of the injectants. It is shown that CO₂ emissions associated with injection of chemicals is strongly influenced by water cut at the start of the project, extent of the water cut reduction, and chemical utilization factor defined as the volume of produced oil per mass or volume of the injectant. As an example, for the oil field considered in this study, 3–8% reduction in water cut can result in 50–80% reduction in its CO₂ intensity. In addition to the incremental oil production with lower CO₂ intensity, the earlier implementation of enhanced oil recovery methods can extend the lifetime of the mature fields if carbon emission cut-offs are applied. In case of CO₂ enhanced oil recovery (EOR), the large storage potential for CO₂ can significantly reduce the overall CO₂ emissions of oil, albeit at a large energetic cost. For CO₂ EOR using CO₂ captured from gas power plants, improving the utilization factor from 2 bbl/tCO₂ to 4 bbl/tCO₂ can reduce the CO₂ intensity of the produced oil from 120 kgCO₂/bbl to 80 kgCO₂/bbl (33% reduction).

We suggest alternative objective functions based on the concept of thermoeconomics (or exergoeconomics) that could be used for simultaneous maximization of economics and energy efficiency of oil-production systems. The suggested functions are evaluated for an oil reservoir, where water is injected to improve its recovery factor. We find that life-cycle optimization of water-injection projects in terms of net present value (NPV) and net cumulative exergy (NCE) leads to consistent results. We show that managing reservoirs based on a long-term objective leads to significant reduction in their CO₂ footprint. For oil production by water injection, commitment to reduce CO₂ emission provides an opportunity to maximize the NPV of these projects. The sustainability of water injection into hydrocarbon reservoirs is highly dependent on the volumes of the injected and produced liquids. Above a critical water cut (80% in this study), the energy efficiency of the project decreases dramatically, and its CO₂ footprint increases exponentially.