ABSTRACT: Upper Morrow Exploration Model, Baca County, Colorado

John R. Caprara, Jack W. Staley

Upper Morrow sandstones exhibit excellent production characteristics along a well-defined fluvial channel system in the southeastern corner of Baca County, Colorado. The system is charged with hydrocarbons as demonstrated by Flank and Midway fields. However, numerous wet penetrations and field studies indicate that structural enhancement is necessary to trap hydrocarbons.

Subtle synclinal shapes make trapping very difficult while subtle nosing can greatly enhance stratigraphic trapping capabilities. An analysis of structuring in southeastern Baca County indicates that the size of nosing features and anticlines can be as small as 1 mi across. These small structures are difficult to predict beyond the areas of dense well control. Furthermore, seismic data are inaccurate for mapping these features because of lateral velocity variations in shallow parts of the section.

In the study area, well control indicates that an interval in the Atoka section thickens from 50 ft in the east to 200 ft in the west. This east to west trend is interrupted by local thinning at Flank field as well as at other clearly defined structures in the area. A mapping technique was devised using a combined well control-seismic isopach in the Atoka section. Local thinning on seismic sections should occur associated with positive structural features. Through the use of this technique, subtle structural geometries can be substantiated. When combined with Upper Morrow sandstone trends, some of the resulting structural features represent excellent exploration objectives.

AAPG Search and Discovery Article #91002©1990 AAPG Rocky Mountain Section Meeting, Denver, Colorado, September 16-19, 1990