Assessing the Cypress Sandstone for Carbon Dioxide-Enhanced Oil Recovery and Carbon Storage: Part I—Reservoir Characterization of Noble Oil Field, Western Richland County, Illinois

Noble Oil Field, located in southwestern Richland County, Illinois, has a cumulative production of 46 million barrels of oil (MMBO; 257.8 million ft3 , or 7.3 million m3). Approximately 50% of this production is derived from a relatively thin oil reservoir that occurs in a thick (up to 165 ft, or 50 m), fluvial valley-fill sandstone within the Mississippian Cypress Sandstone. Attempts at production from such reservoirs are susceptible to early onset of high produced water and low recovery efficiencies (25%, in the case of Noble Field). As such, these reservoirs have the potential for nonconventional carbon dioxide (CO2)-enhanced oil recovery (EOR), meaning EOR that includes geologic storage of CO2 as a significant component of the process. Reservoir characterization of the thick valley-fill sandstone within the Cypress Sandstone has shown that it is multistory and fluvial. Where multiple stories amalgamate (as in Noble Field), they create thick, relatively widespread sandstone bodies that have characteristics favorable for CO2 storage, such as high lateral and vertical permeability, limited compartmentalization, and large pore volumes. More than 75 MMBO (423.8 million ft3, or 12 million m3) is estimated to remain in the reservoir, of which 30.7 to 46.2 MMBO (172.3 to 259.6 million ft3, or 4.88 to 7.35 million m3) is estimated to be moveable. A residual oil zone may also exist in the field, based on a southwesterly tilted oil–water contact and the occurrence of a persistent, parallel calcite-cemented zone beneath the oil–water contact. A better understanding of these rocks is needed, given the economic importance of the remaining oil resource in the Cypress Sandstone at Noble Field and its potential as a sink for anthropogenic CO2.