Depositional Environment, Reservoir Properties, and EOR Potential of an Incised-valley-fill Sandstone, Pleasant Prairie Oilfield, Haskell County, Kansas

Abstract

Incised-valley-fill deposits form important hydrocarbon reservoirs and can have internal heterogeneities that affect recovery of hydrocarbon resources. Better understanding of the internal heterogeneity of incised-valley-fill reservoirs will help in more accurate reservoir modeling and more efficient recovery of hydrocarbon resources. Pleasant Prairie oilfield in Haskell County, Kansas, produces oil from an incised-valley-fill reservoir in the Chesterian (Upper Mississippian) Shore Airport Formation. The reservoir is part of a larger paleovalley trend interpreted as a tide-dominated, estuarine depositional system; depositional environments within such systems vary spatially as a result of interactions of tidal and fluvial processes. Core analysis suggests that the reservoir at Pleasant Prairie oilfield is a stacked series of conglomerate-based, fining-upward siliciclastic successions deposited in the river-dominated part of a tide-influenced estuarine system. Core petrophysical data and well-log correlations suggest that reservoir heterogeneity occurs in the form of vertical and lateral compartmentalization. Reservoir modeling indicates a current field-wide recovery factor of 0.30&ndash-&ndash 0.36 of original oil in place. Comparison of modeled original oil in place to production data suggests inaccuracy of reservoir models at the scale of individual well drainage areas. Waterflooding of the reservoir has proven successful for >10 years, and remaining oil in place ranges from 7.8&ndash-&ndash 10.1 mmbo according to Petrel10 years, and remaining oil in place ranges from 7.8&ndash-&ndash 10.1 mmbo according to PetrelTM models, indicating potential for future enhanced oil recovery operations such as CO2 or chemical flooding. Other incised-valley-fill reservoirs, such as Morrowan (Lower Pennsylvanian) oilfields in Colorado and Kansas, originated in similar depositional settings and display similar reservoir properties; such reservoirs may also have potential for future enhanced oil recovery operations.