Integration of geological and petrophysical data in reservoir characterization of Pennsylvanian Upper Morrow "C-sand" in Wilburton Field, Morton County, Kansas

The Morrow C-sand reservoir at Wilburton Field is an incised-valley-fill fluvial sandstone of Pennsylvanian age. It is compartmentalized into five flow units, each of which possesses particular geological and petrophysical characteristics. Understanding the scale, geometry, and internal complexity of this depositional system is important because these sandstones represent the main hydrocarbon reservoirs in Wilburton Field. Described core, wire-line logs, petrophysical measurements and production data were integrated for Morrow C-sand depositional model and reservoir characterization. Morrow C-sand valley was incised into the underlying marine section during a relative drop in sea level. As relative sea level rose in a series of pulses, the valley was filled with fluvial sediments consisting of thick channel sandstone facies that comprise the Wilburton Field reservoir and floodplain facies. The vertical succession is composed of coarse-grained sandstones which represent amalgamated stacked channels, and point bar sediments separated by thin overbank deposits. Following fluvial sediment deposition, a marine transgression commenced during which some of the channel sands were reworked by marine processes. The relative sea level continued to rise and an overlying section of black marine shales was deposited sealing the Morrow C-sand valley. Five flow units were defined within the Morrow C-sand reservoir based on stratigraphy and petrophysical characteristics. These flow units are genetically related to the original stratigraphy of the valley-fill. Reservoir quality is controlled by the internal heterogeneities of the depositional facies. The performance of wells in the field is determined by the number and quality of the flow units from which they produce. The presence of non-reservoir rocks within the valley-fill, such as floodplain deposits, provides permeability barriers and obstacle to fluid flowGeological Science