WEBER, L. JAMES, Mobil Exploration and Producing Technical Center, Dallas, TX, and L. P. HARMAN, J. B. VANDERHILL, and E. SHAW, Mobil Exploration and Producing U.S., Inc., Midland, TX

ABSTRACT: Utility of Sequence Stratigraphy in Reservoir Characterization Studies: Case Study Using the McElmo Creek Unit, Greater Aneth Field, SE Utah

Sequence stratigraphic analysis is used to characterize stratified Middle Pennsylvanian carbonate reservoirs of the McElmo Creek Unit in the Greater Aneth field, southeastern Utah. This approach has led to (1) a better understanding of platform-to-basin correlations and associated performance anomalies, (2) a better understanding of interwell heterogeneity related to changes in depositional facies, (3) unit-wide mapping of time-equivalent geologic layers, (4) prediction of reservoir quality by relating deposition and early diagenesis, and (5) a first-pass evaluation of flow zones.

The sequence stratigraphic approach is divided into three aspects: the sequence stratigraphic framework, the stratigraphic layer model, and predictive geology. The sequence stratigraphic framework is established to identify major chronostratigraphic surfaces (e.g., sequence boundaries and flooding surfaces) that constrain correlation of high-frequency depositional cycles. The stratigraphic layer model describes the architecture of high-frequency depositional cyclicity. Nineteen parasequences (i.e., stratigraphic layers or depositional cycles) are described within the Desert Creek and lower Ismay section at McElmo Creek. Time-slice mapping of these synchronous layers and of the facies contained within the layers provides the basis for predicting the distribution and continuity of reser oirs (i.e., predictive geology). A regionally extensive, low-relief tidal flat serves as the stratigraphic datum. Successively younger layers are added to the datum. Each layer top mimics the paleodepositional topography, and the consequent depositional geometry is used to predict facies within each layer. Geologic maps and cross sections illustrate facies distribution and predict reservoir quality and continuity within each depositional layer. Examples relate reservoir performance to facies changes and associated changes in the pore architecture.

AAPG Search and Discovery Article #90993©1993 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah, September 12-15, 1993.