A Log-based Subsurface Correlation of the D and J Sandstone to Surface Equivalents in Southeastern Colorado

Al-refaei, Yaqoub; Holbrook, John

The D and J sandstone of the Cretaceous Dakota Group are traditionally the main oil and gas producing units within in the Denver Basin. The Dakota Group extends beyond the Denver Basin, which is a sub-basin of the Early Cretaceous Western Interior Basin. The D and J sandstone are well understood within the northern Denver Basin and the linkage between the subsurface units and their equivalents in outcrop in the Front Range is well-established. They have gained less attention in southern parts of the basin and the linkage between the subsurface units and their equivalents in southern outcrop is not yet established. This study investigates the linkage between the subsurface Dakota Group units within the southern Denver Basin and their equivalents in outcrop of southeastern Colorado. This was achieved by correlating sequence stratigraphic surfaces within Dakota Group strata within the Denver Basin using well-log data and then correlating these surfaces with their age-equivalents in outcrop of southeastern Colorado. By proving this linkage, a better understanding for the correlation of Dakota Group strata from subsurface to outcrop is represented in southeastern part of Denver Basin which can be used as a tool in future research in the area and can forward regional paleogeographic reconstruction for this time interval. Subsurface correlations show that the subsurface Huntsman Shale continues in the southern Denver Basin to surface exposure of shoreline equivalent Dry Creek Canyon Formation in southeastern Colorado. The subsurface D reservoir sandstone outcrops in southeastern Colorado as the Romeroville Sandstone, both of which are floored by a correlative sequence boundary. The subsurface J sandstone crops out in the surface as the Mesa Rica Sandstone. This subsurface correlation effort using well-log data confirms prior assertions of these same correlations that were previously proposed based upon sequence similarity, thickness trends, fossil assemblage, and facies similarities.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013