High-resolution Chemostratigraphy in the

Abstract

The �Mississippian Limestone� of the Mid-Continent United States is a complex and highly heterogeneous hydrocarbon play. Its heterogeneity is largely due to the mixed siliciclastic and carbonate nature of the Mid-Continent Mississippian system which yields complex reservoir lithologies and distributions that are laterally discontinuous and difficult to predict. The purpose of this study is to apply chemostratigraphy, a relatively recent method for addressing industry related correlation problems, as an additional reservoir characterization tool that provides insight into chemical attributes of Mississippian-aged sedimentation and how these chemical signatures can be used for potential chronostratigraphic applications. High-resolution sampling (every 0.3m (1ft)) of three subsurface cores for carbon and oxygen stable isotopes has revealed predictable patterns related to facies and vertical stacking patterns as well as to globally recognized secular changes in ocean chemistry. The chemostratigraphic approach applied herein suggests more frequent 3rd order cyclicity than recently defined in other subsurface data sets in the basin which is more consistent with global ties to the individual North American stages and within the Mississippian overall. In addition, ?18O values suggest a level of predictability at the 4th order scale related to shallowing upward packages and mixed meteoric input at cycle tops. Overall, stable isotope curves closely match those of well-established Mississippian global carbon cycling and have been used to suggest time boundaries in this area of the depositional system.