Chemostratigraphic and Depositional Characterization of the Niobrara Formation, CEMEX Quarry, Lyons, CO

Abstract

The Late Cretaceous (89–82 Ma) Niobrara Formation is one of the primary targets for unconventional horizontal well activity in several Rocky Mountain basins. With such an abundance of horizontal activity, the question of lateral heterogeneity within the target formation becomes paramount in determining individual wells' productivity. This study incorporates detailed core description, high resolution chemostratigraphy, and petrophysical analyses from four near-surface cores taken at the Cemex Lyons Cement Quarry in order to assess lateral heterogeneity. The cores were originally intended to determine the geochemistry and extent of the Fort Hays Limestone Member of the Niobrara Formation, the primary target for cement production. However, due to the cores' proximity to one another (<200 m apart) and the presence of not only the Fort Hays Limestone but also the petroliferous chalks and marls of the Smoky Hill Member, the dataset can also be used as a proxy to model hypothetical changes along a pseudo-horizontal well. Initial findings suggest lateral bentonite discontinuity and distinct changes in sedimentary structures along the pseudo horizontal well length, implying small-scale depositional heterogeneity. These lateral depositional variations may have implications for horizontal well completion design and may improve understanding of the depositional environment during Niobrara time.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015