Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
Evaluation and Modeling of Stratigraphic Control on the Distribution of Hydrothermal Dolomite Reservoir Away From Major Fault Planes
Western Michigan University
Polaris Energy Company
Recent interest by several operators associated with extending the Albion-Scipio hydrothermal dolomite trend indicates the continuing viability of Ordovician Trenton/Black River production in southern Michigan, and suggests that a re-evaluation of the trend utilizing modern geological techniques and approaches might be beneficial to new exploration and production programs not only in the Michigan Basin, but in similar plays in the Appalachian Basin and other regions of the United States. Since mid-2006 fifty-one wells have been drilled using 3-D seismic in and around the giant Albion-Scipio Field, resulting in 36 producers and 15 dry holes. There are at least 30 additional permits in various stages of development. Thirty-two of these new wells have reported some level of oil production which has reached an aggregate of nearly 900,000 barrels as of November, 2008. Estimated primary recoveries are between 30 and 35 percent (Buehner and Davis, 1969; Knowles, 1991; Trevail, 1991) for these types of reservoirs in the Michigan Basin. Increasing the current total recovery for this unit by only 1% by applying new methodologies would add 1,350,000 BO and 2.6 BCF to the already recovered reserves in the Michigan Basin.
Reservoir quality and distribution in fractured, hydrothermal dolomite reservoirs has historically been attributed to faulting and fracturing associated with regional wrench tectonics. Exploration and production strategies are typically focused on identifying fault trends and associated seismic sags. A problem the small operator is often faced with, however, is trying to understand lateral variability in reservoir quality away from the major fault zones and the resulting presence of close step-out dry holes. Based upon preliminary research conducted at WMU focused on the Albion-Scipio trend, the lateral variability of reservoir quality hydrothermal dolomites away from the major fault zones is related to both the primary depositional facies and the sequence stratigraphic framework. Further testing of such a relationship, combined with quantification of resulting pore architecture and permeability values, correlation of pore architecture and permeability to laboratory measured sonic velocity values and 3-D seismic, and 3-D reservoir modeling should lead to better predictability of laterally persistent reservoir zones in these systems and provide a means to enhance reservoir modeling at both the exploration and production scales. This project will focus on reservoir characterization of the giant Albion-Scipio trend of southern Michigan because of the availability of extensive well, core and production data and because of access to recent 3-D seismic data from our industrial partner Polaris Energy. Results are expected to help small operators not only in the Michigan Basin, but should be exportable to other hydrothermal dolomite plays in the United States.
The primary goals of this study are threefold: 1) to evaluate the degree of control that primary depositional facies has on current reservoir variability, and to determine how reservoir quality units that developed laterally away from the major fault zones are controlled by these primary facies and their position within a sequence stratigraphic framework; 2) to correlate laboratory measured sonic velocity data from various reservoir and non-reservoir facies to sonic logs and 3-D seismic signatures; and 3) to produce 3-D stratigraphic and reservoir models using Schlumbergerís 3-D Petrel modeling software that will be tested with recently drilled wells.
Results of this integrated project should lead to reduced exploration risk and increased production from similar mature plays by providing small operators with viable models for predicting and interpreting the stratigraphic control of hydrothermal dolomite reservoirs away from main fault trends. The correlation of sonic velocity to pore architecture and reservoir permeability will provide an immediate means to high grade target zones from sonic log data and may provide enhanced exploration capability when combined with 3-D seismic interpretation. New methodologies resulting from the application of this project will extend the life of similar mature fields and increase the ultimate recovery of hydrocarbons. Results of this project will be disseminated at minimal cost to small operators through technology transfer initiatives such as PTTC workshops and short courses, and technical presentations at professional meetings and will be made available to small operators through digital summaries on CD or DVD.
Principal Investigators: G. Michael Grammer, William B. Harrison III