Analysis and Integration of Well Logs, Geochemical Data, and Ultrasonic Velocities of Productive Facies in the Upper Viola Formation in Southwestern Kansas

Abstract

The Ordovician-aged Viola Limestone of southwestern Kansas is a developing carbonate resource play with significant accumulations of hydrocarbons. The Viola surface is an unconformity, and production comes from regions of preserved dolomite on paleo-topographic highs. Evaluation of a cored interval of the upper Viola recognized several distinct facies, which were examined in conjunction with detailed well log analysis and major and trace element concentrations to recognize facies control on Viola production. Cross plots of well log and geochemical data were used to discriminate facies and sequences. Ultrasonic P-wave laboratory measurements and comparison with seismic frequency P-wave velocities were conducted on the same core to understand the potential of seismic attenuation effects and velocity variation in reservoir facies identification. Seismic amplitude and attenuation characteristics of each Viola facies were determined, with implications for seismic facies interpretation and hydrocarbon prospect evaluation. Because of the high frequency nature of the ultrasonic measurements, differences in elastic properties were compared with sonic logs of borehole with the well-log facies, where core samples were not available. Correlating facies of the core sample to ultrasonic measurements, elemental composition, and well-log characteristics provides a work-flow to explore potential Viola targets using 3D seismic datasets. Due to the thin-bed nature of the Viola reservoir facies, seismic resolution is a problem when generating prospect models. Coupling core analysis, attenuation results, and well log facies, enabled a well-established interpretation of 3D seismic facies. This study illustrates the advantages of correlating depositional facies with reservoir quality and linking specific reservoir petrofacies with well log signatures and seismic attenuation effects, ultimately to create a greater understanding of the controls on reservoir quality to aid in predicting new areas of exploration.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018