A workflow for estimating the CO2 injection rate of a vertical well in a notional storage project

A workflow that considers regulatory and technical constraints applicable to subsurface CO₂ injection projects was developed to determine fluid injection rates accurately. The constraints considered include, but are not limited to, maximum injection bottomhole pressure, maximum injection pressure at the surface or wellhead pressure, and threshold vibration velocity. The workflow was developed and tested using a reservoir model developed from site characterization data of an Illinois Basin CarbonSAFE Phase II notional storage project. The Nexus® reservoir simulation software suite and the Peng-Robinson equation-of-state were used to perform compositional dynamic simulations. Reservoir modeling results indicated that (1) the regulated and technically feasible CO₂ injection rate of a vertical well is predetermined by the most stringent parameter amongst maximum bottomhole pressure, maximum wellhead (surface injection) pressure, and threshold vibration velocity constraints; (2) the threshold vibrational velocity constraint predetermines CO₂ injection rate for high-permeability injection zones; and (3) the most stringent constraint for low-permeability injection zones could be either the maximum bottomhole pressure or the maximum wellhead pressure. However, the injection rate may be further reduced if faults or hydraulically conductive fractures are present within the injection zone and adjacent formations because the pressure required to reactivate the faults may be lower than maximum injection bottomhole pressure, maximum wellhead pressure, and vibrational velocity constraints.