Optimizing CO2 Injection in an Offshore Field Considering Operational Constraints

摘要

The continued increase in oil demand associated with the growing concern about the greenhouse gases has been an additional driver for CO2 injection into oil reservoirs. The application of this EOR method usually occurs at a later stage in the development of a field in which the operating surface facilities were normally not specified to manage high levels of CO2. Therefore, the aim of this work is to evaluate, by proper fluid characterization and compositional reservoir simulation, the benefits and risks of CO2 injection in a particular sector of an offshore reservoir, surrounded by production units not fully specified to deal with elevated concentrations of CO2. The presented workflow, combining reservoir engineering analysis with production equipment aspects, can be applied to any target field for a CO2 injection project. However, it is even more relevant for mature offshore fields, where a CO2 production growth leading to the necessity of replacing all production facilities would probably make the project fail economically. For the particular field analyzed in this article, the deployment of a production unit able to inject CO2 from an external source in an undrained region of the reservoir, hydraulically connected to an area already in production, would bring benefits not only to the region where the injection would occur but also to the adjacent area. The CO2 migration to the neighboring area decreases the levels of CO2 to be processed in the new platform plant, allowing its technical and economic feasibility, as well as increases the recovery factor of the adjoining area, without reaching levels of CO2 and gas flow rates beyond the limits of the plant already in operation. Furthermore, the reservoir’s capacity to retain CO2, acting as a carbon sink, is also evaluated. This study thus presents an integrated workflow for an optimal CO2 injection project design, considering not only the benefits in terms of recovery in the target area of the project, but analyzing the impacts and risks to surrounding areas.