Assessment of CO2 Injectivity and Storage Capacity in a Depleted Pinnacle Reef Oil Field in Northern Michigan

摘要

The Midwest Regional Carbon Sequestration Partnership is conducting a large-scale CO2 injection test in a depleted Niagaran Pinnacle Reef in northern Michigan. The focus of the dynamic modeling task described in this paper is to evaluate the CO2 injectivity and storage capacity of this closed carbonate reef structure. We discuss the history-matching process to characterize the closed reservoir model using primary and secondary recovery data and its validation with the field pressures in the current CO2 injection phase. Two alternative conceptual geologic models of the reef are constructed to evaluate the level of detail necessary to efficiently model dynamic reservoir behavior without compromising geologic accuracy. We find that our initial black oil formulation under-predicts reservoir pressure and hence over-predicts injectivity during the CO2 injection phase. Transition to a compositional model is currently underway to better represent reservoir dynamics by effectively accounting for interphase and intercomponent mass transfer processes. Lessons learned from this exercise can be drawn upon for possible use in injectivity evaluation of other reefs in the region.