Potential for carbon sequestration in the Hemlock Formation of the Cook Inlet basin, Alaska

Injecting fluids, such as carbon dioxide (CO₂), into hydrocarbon reservoirs has great environmental and oil field development benefits. In this study, the fluid injection and storage potential of the Hemlock Formation was assessed in the whole Cook Inlet basin of southcentral Alaska as well as eight individual oil and gas fields (i.e., Swanson River, North Cook Inlet, Granite Point, Trading Bay, Middle Ground Shoal, Redoubt, Ninilchik, and Cosmopolitan fields) in the basin. The Hemlock Formation, similar to most formations in the Cook Inlet basin, is vertically and horizontally heterogeneous, resulting in compartmentalized reservoirs. Based on core data and petrophysical analysis, the Cook Inlet basin has an estimated CO₂ storage range of 0.91–16.61 gigatonnes (Gt), with a 50% probability (that the quantity will equal or not exceed the calculated estimate) value of 4.33 Gt. The reservoir quality for the Hemlock Formation is assessed and compared among the major oil and gas fields in the whole basin. The eight oil and gas fields from both upper and lower Cook Inlet basin have been selected to better assess the potential of CO₂ storage in the Hemlock Formation. Maps generated for the eight fields show fluid injection sweet spots. Variability among individual fields for fluid storage quantities is caused by changes in porosity, reservoir thickness, and the size of the field.