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A Predictive Model of Dolomitization and Its Control on Reservoir Quality and Seismic Attributes in the Viola Formation, Morrison NE Field, Clark County, Kansas

Abstract

The Viola Limestone is a prominent petroleum reservoir in the Mid-Continent Region, particularly in Oklahoma and Kansas. Coral Coast Petroleum established production from the Viola in 2011 in their Stephens Ranch lease in Clark County, south-central Kansas. Development of this lease has been hindered by the unpredictable production rates encountered in each of the subsequent eleven development wells. Infield drilling locations to date were chosen by favorable structural position as determined by 3D seismic. The best reservoir conditions, however, do not necessarily coincide with structural position. A lithofacies analysis was conducted to characterize which facies is the most productive in the target Viola Limestone using well log analysis, petrographic inspection of well cuttings and thin sections, and the application of the Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS). The wells associated with higher production rates exhibit a diagnostic dolomitized facies in the upper Viola with prominent intercrystalline and fracture porosity, while the non-productive wells remain limestone. We propose a model where paleotopographic highs met the proper water depth conditions for evaporative reflux dolomitization during the initial flooding event after the Viola unconformity, while the associated limestone facies did not. A previous attribute analysis of a 3D seismic survey over Morrison NE Field recognized a “seismic facies” associated with productive wells within the field. These “seismic facies” coincide with the dolomitized facies described in this study. Further exploration of the target Viola Ls. can be enhanced using a detailed predrilling workflow based on our model correlating the favorable dolomitized facies to 3D seismic attributes.