CO2 injection is a well-documented method for improving hydrocarbon production rates and increasing oilfield recovery factors. In light of climate concerns, there has been a significant push to utilize CO2 injection for the dual objectives of enhancing oil recovery and carbon storage. Despite the proliferation of CCUS related literature, practical considerations related to reservoir management are rarely discussed. Intelligent reservoir management of a field from primary to tertiary recovery phases yields an understanding of key physical properties and mechanism that govern oil recovery. A well-managed reservoir is also better prepared to benefit from CO2 injection for the synergistic objectives of oil recovery and carbon storage. In this work, we address several underexplored areas in CCUS research:
1.Optimization of primary and tertiary depletionplans to “prepare” a field for carbon storage, takinginto consideration pressure, free gas saturation, andliquid phase saturation distributions. Designparametersinclude appropriate production/injection depths andpattern design/rates.
2.Utilization of primary phase learnings to acceleratethe reservoir into tertiary phase (skippingwaterflooding) to maximize carbon storage.
3.The balance of technical and commercialconsiderations for gas injection design, includinggas supply constraints.
Optimizing oil reservoir development for carbon storage is particularly important in countries with absent or nascent CCUS policies. In our work, we present an integrated carbon storage focused development strategy for a mature Indian oilfield. We leverage multiple analytical and numerical tools to perform an integrated analysis of a depleted stacked pay reservoir. The work uses actual field data from multiple sources with over 30 years of dynamic data. The reservoir has a storage potential of over 5 million metric tonnes, with an incremental oil recovery factor of 11%. Eliminating the waterflooding stage addsapproximately 0.5 million tonnes of storage. Continual production of aquifer water adds an estimated 0.35 million tonnes of storage potential annually. The client has over 50 reservoirs at various developmental stages; this work highlights the tremendous potential of these fields for carbon storage with an integrated reservoir management approach.
Keywords reservoir management, CCUS, carbon storage, EOR, reservoir simulation, reservoir engineering