ABSTRACT: Speaker Field: An Integrated Exploration Effort for Morrow Sandstones in Southeast Colorado

WALLACE, KEVIN J., and JOHN J. HEINZ, The Anschutz Corporation, Denver, CO

Exploration for Lower Pennsylvanian Morrowan sandstones in southeastern Colorado is an often frustrating effort. However, finding the elusive sandstone targets can be an extremely rewarding exploration and production experience. Outlining and adhering to a concise exploration program, which integrates good geological and geophysical concepts, is critical to success in the Morrow play.

The Anschutz Corporation has been involved in an extensive exploration effort in southeastern Colorado since late 1985. During this time, our exploration and development effort has yielded a success rate of 45% in a play with a historical success rate near 8%.

Speaker field, located in Cheyenne County, Colorado (T12S, R51W), serves as an example of our exploration and development techniques. The field was discovered in late 1990 using regional geologic concepts and unique seismic data acquisition parameters and processing techniques. Speaker field is a combination structural and stratigraphic trap producing from a lower Morrowan sandstone referred to locally as the Pilger sand. Anschutz has adopted the nomenclature developed by Union Pacific Resources Company in identifying specific stratigraphic intervals within the Morrow related to different age valley-fill sequences. The valley-fill sequences have been identified at Speaker field using extensive core information and careful subsurface log correlations. Within the context of the valley-f ll nomenclature, the productive sand at Speaker field is referred to as the V-11 sand. The sandstone body is coarse to very coarse grained at the base and fines upwards to a very fine-grained sandstone with carbonaceous laminations at the top. The sandstone exhibits low-angle cross-stratification, small-scale ripple laminations, an abrupt contact with the underlying marine shale, and is devoid of any burrowing. Horizontal permeability within the productive sand interval ranges from 9.34 to 5000 md. Porosity ranges from 9.5 to 25.6%. Drilling to date has delineated an oil column of 57 ft with no clearly defined water leg nor associated gas cap.

There are currently six wells producing in the field pumping a daily average of 1400 bbl of oil. Cumulative production through January 1992 exceeds 370 MBO.

AAPG Search and Discovery Article #91017©1992 AAPG Rocky Mountain Section Meeting, Casper, Wyoming, September 13-16, 1992 (2009)