The specific goals of this project are to:

• Summarize and critically synthesize all of the publicly available data on the geometrical distribution and reservoir quality of dolomitized reservoirs in the Trenton-Black River, Niagaran, and Dundee formations in the Michigan Basin and how they may be related to fractures.
• Perform a scientifically rigorous characterization of the various structural and stratigraphic controls and modes of dolomite formation in the three intervals. This will include evaluation of the impact dolomitization has on reservoir quality and documentation of the regional and field-scale distribution of these reservoirs by using state-of-the-art methods such as isotopic and trace element analysis, fluid inclusion analysis, determination of pore system architecture, and sonic velocity characterization from six to nine representative fields.
• Develop geological models for the 3-D distribution of reservoir facies for the different types of dolomite reservoirs that will provide operators with a means to high-grade exploration, development, and enhanced recovery efforts in a cost-effective manner.

Western Michigan University
Kalamazoo, MI

The Michigan Basin is a mature hydrocarbon basin that has been recognized by the U.S. Geological Survey as one of the 25 “priority basins” in the United States that contain some 90-95 percent of known and undiscovered domestic hydrocarbon resources (USGS National Assessment of Oil and Gas Resources Program, 2004).

Current activity in the basin is mostly concentrated on step-out development and enhanced production efforts, although moderate exploration efforts continue to be pursued. Over the past >75 years, the basin has produced in excess of 1.3 billion barrels of oil and 5.9 trillion cubic feet (TCF) of natural gas. The most prolific oil producing formations in the basin, with total cumulative production of about 900 million barrels of oil and 4.5 TCF of gas, are the Ordovician Trenton and Black River formations, the Silurian Niagara Group, and the Devonian Dundee Limestone. Each of these units comprises volumetrically significant dolomitized reservoir facies for which several models of formation have been proposed. To maximize the discovery of new reservoirs and for the recovery of bypassed or stranded hydrocarbons in these intervals, it is critically important that the operator have access to scientifically constrained reservoir models that are able to predict the geometrical distribution of the reservoir facies in the subsurface. Utilization of such models will allow the operator to better pursue new exploration efforts, high-grade placement of step-out development wells, and more accurate orientation of directional or horizontal wells.

It is the goal of this project to fully characterize reservoir dolomites in the three units indicated, specifically to determine the relationship of dolomite to fracture trends/fracture density and/or to primary depositional facies and to develop improved models for exploration and development of these reservoirs based upon a better understanding of their 3-D distribution in the subsurface.

Results
The project is expected to result in 1) the development of sequence-stratigraphic-based geological models that will include the 3-D distribution of reservoir facies for each of the different types of dolomite reservoirs that are common in the Michigan Basin; 2) new models that will enable operators to high-grade exploration, development, and enhanced recovery efforts cost-effectively; 3) results that could be exportable to other U.S. regions producing from dolomite reservoirs. Unfortunately, much of the data integration and modeling was terminated due to lack of funding.

Benefits
Results of this project should lead to an increased understanding of regional- and field-scale dolomitized reservoirs in the Michigan Basin and may be exportable to other domestic oil and gas producing basins. Results will likely lead to new, reduced-risk exploration and step-out development play concepts in the Michigan Basin, as well as a better and more complete understanding of the local subsurface distribution of reservoirs to guide enhanced production efforts. Increasing production in the Michigan Basin, and potentially in other domestic basins, has national security implications through the reduction of the amount of foreign oil and gas imports needed to sustain U.S. energy demand. A 10 percent increase in hydrocarbons produced from the three main producing intervals in the Michigan Basin alone would result in added production of about 150 million barrels of oil equivalent for the Nation.

Summary
The characterization of select dolomite reservoirs has been the major focus of researchers’ efforts through Phase II/Year 2. Fields have been prioritized based upon the availability of rock data for interpretation of depositional environments, fracture density, and distribution, as well as thin section, geochemical, and petrophysical analyses. All three of the stratigraphic intervals (Devonian, Silurian, and Ordovician) have been analyzed in detail, and continuing work is focused on the details of the reservoir architecture and the predictability of same.

Structural mapping and log analysis in the Trenton/Black River (Ordovician) and Dundee (Devonian) suggest a close spatial relationship among gross dolomite distribution and regional-scale, wrench fault-related NW-SE and NE-SW structural trends. A high-temperature origin for much of the dolomite in the three studied intervals (based upon a number of fluid inclusion homogenization temperatures and stable isotopic [C/O] analyses that have been completed), coupled with persistent association of this dolomite in reservoirs coincident with wrench fault-related features, is strong evidence in support of these reservoirs being influenced by hydrothermal dolomitization. Ongoing efforts are being focused on determining whether the hydrothermal dolomite represents the only phase of dolomite in these fault-related fields, or whether there is evidence of low-temperature dolomitization as well. In either case, the project’s main concentration is on whether the reservoir quality of the dolomite can be tied to primary facies type and/or an established sequence stratigraphic framework, either of which will enhance the predictability of such reservoirs. At this point, there is strong evidence in the Ordovician and Silurian that dolomite trends (best reservoir quality within dolomite) are following primary facies, but within the sequence stratigraphic framework. More specifically, reservoir quality dolomite is preferentially developed in certain facies, especially within the regressive portions of the sequence framework. The researchers concluded that additional work in this direction may provide a significant predictive tool for both further development work, as well as exploration in these reservoirs.

For the Niagaran (Silurian), a comprehensive, high-resolution sequence stratigraphic framework has been developed for a pinnacle reef in the northern reef trend, where there was 100 percent core coverage throughout the reef section. The researchers currently are testing this sequence framework within a larger reef complex in the southern reef trend (Ray Reef field). A rock-based 3-D model is under construction, utilizing a combination of core data from 18 wells and wireline logs from a total of about 50 wells. The project performers have negotiated an academic license for Petrel (3-D modeling and visualization software) from Schlumberger and continue to work with collaborators at the University of Colorado on the 3-D modeling aspects. Major findings to date are that facies types, when analyzed at a detailed level, have direct links to reservoir porosity and permeability in these dolomites. This pattern is consistent with the project’s original hypothesis of primary facies control on dolomitization and resulting reservoir quality at some level. The identification of distinct and predictable vertical stacking patterns within a hierarchical sequence and cycle framework provides a high degree of confidence at this point that results will be exportable throughout the basin.

The initial stages of data evaluation and synthesis (Task 4) were terminated due to lack of funding at the end of Year 2. Most of the effort on this task necessarily had to follow results of Phase I results from Tasks 2 and Phase II results of Task 3. The project performers have entered into an agreement with Dr. Matthew Pranter, University of Colorado, who has been collaborating with them on the 3-D modeling efforts during Phase II. Jill Haynie, a MS student at CU initiated her research on the petrophysical modeling of the Ray Reef (Silurian).

Technology transfer efforts included formal presentations on the State and national levels as well as ongoing advertisement of the project’s scope, anticipated results and funding agency on the WMU Department of Geosciences website. In Year 2, the researchers presented two papers at the national AAPG Meeting in Houston, TX, three papers at the Midwest Regional Petroleum Technology Transfer Council (PTTC) workshop on carbonate reservoirs, and four papers at the Eastern Section of AAPG (ESAAPG) in Buffalo, NY. Their DOE-sponsored presentations have won the Nelson Best Poster Award at the ESAAPG meeting for the last 2 years. In addition, researchers presented a 1-day short course to 27 professionals from Michigan, Oklahoma, and Texas on carbonate reservoir characterization in November 2006. This workshop included aspects of all work on this project and was subsidized in part by PTTC. Presentations from the project continue to be made by the researchers, with 3 presentations in 2007 at the Eastern Section AAPG meeting in Lexington, KY and one at the Annual GSA meeting in Denver, and at the Annual AAPG meeting in San Antonio (2008).

(February 2008)
Due to lack of available funding, this project did not perform Phase 3 of the proposed work and much of the data synthesis and modeling was terminated. Final report was submitted 12/23/07 and a revised final report is due by March 3, 2008.

Funding
This project was selected in response to DOE’s Oil Exploration and Production solicitation DE-PS26-04NT15450-2B, area of interest 2B: Regional Study and Basin Analysis.

$741,369

$292,106 (39 percent of total)

NETL- Chandra Nautiyal (Chandra.nautiyal@netl.doe.gov or 918-699-2021) 
W. Michigan - Michael Grammer (michael.grammer@wmich.edu or 269-387-3667)

Publications
Barnes, D.A., Parris, T.M., and Grammer, G.M., 2008, Hydrothermal dolomitization of fluid reservoirs in the Michigan Basin, AAPG Ann. Mtg. San Antonio, TX.

Barnes, D.A., Parris, T.M., Harrison, W.B. and Grammer, G.M., 2007, Hydrothermal Dolomite (HTD) in the Michigan Basin, U.S.A., GSA Annual Mtg. Denver, CO.

Barnes, D.A., Parris, T.M., Harrison, W.B. and Grammer, G.M., 2007, Hydrothermal Dolomite (HTD) in the Michigan Basin, U.S.A., Eastern Section AAPG, Lexington, KY.

Harrison, W.B., Barnes, D.A., Grammer, G.M., and Jagucki, P., 2007, Facies and Rock Properties for Reservoir and Caprock Intervals in the Midwest Regional Carbon Sequestration Partnership (MRCSP), State Charlton #4-30 Test Well, Otsego County, Michigan, Eastern Section AAPG, Lexington, KY.

Riley, R.A., Nuttall, B., Harper, J.A., Avary, L., Rupp, J.A., Barnes, D.A., and Grammer, G.M., 2007, Assessing the Potential for C02 – Enhanced Oil Recovery in the MRCSP Region, Eastern Section AAPG, Lexington, KY.

Grammer, G.M., Sandomierski, A.E., Harrison, W.B., Barnes, D.A., and R. Gillespie, 2006, “New insight into the reservoir architecture of Silurian (Niagaran) pinnacle reefs in the Michigan Basin,” ESAAPG, Buffalo, NY.

Grammer, G.M., Barnes, D.A., Harrison, W.B., and R.G. Mannes, 2006, “Combining CO2 sequestration with EOR activities—a synergistic approach for the future: An example from the Michigan Basin,” ESAAPG, Buffalo, NY.

Gillespie, R., Barnes, D.A., Grammer, G.M., and W.B. Harrison, 2006, “Albion/Scipio Field, Michigan: What does a detailed look at cores tell us about the reservoir?,” ESAAPG, Buffalo, NY.

Barnes, D.A., Grammer, G.M., Harrison, W.B., and Gillespie, R., 2006, “Hydrothermal dolomite: Occurrence and mechanisms, Michigan Basin, USA,” ESAAPG, Buffalo, NY.

Grammer, G.M., 2006, “Carbonate Reservoir Characterization—A new look at a Niagaran Pinnacle Reef,” Petroleum Technology Transfer Council, Mt. Pleasant, MI.

Harrison, W.B., 2006, “Michigan Carbonate Reservoirs—Facies and Reservoir Properties,” report, PTTC Workshop, Mt. Pleasant, MI.

Grammer, G.M., 2006, “Enhanced Reservoir Characterization through the Integration of a Sequence Stratigraphic Framework—Examples from Carbonate Reservoirs in the Paradox and Michigan Basins,” report, PTTC Workshop, Mt. Pleasant, MI.

Sandomierski, A.E., Grammer, G.M., and Harrison, W.B., “Evaluating Controls on the Formation and Reservoir Architecture of Niagaran Pinnacle Reefs (Silurian) in the Michigan Basin: A Sequence Stratigraphic Approach,” presented at the 2006 national AAPG Meeting, Houston, TX.

Grammer, G.M., State of Michigan DEQ and DNR, “Recent Advances in Carbonate Sedimentology and Stratigraphy Applied to the Silurian Niagara Group,” Michigan Basin, report, 2005.

Sandomierski, A.E., Grammer, G.M., and Harrison, W.B., “Evaluating Controls on the Formation and Reservoir Architecture of Niagaran Pinnacle Reefs (Silurian) in the Michigan Basin: A Sequence Stratigraphic Approach,” presented at the 2005 ESAAPG Meeting, Morgantown, WV.

Barnes, D.A., Grammer, G.M., Harrison, W.B., Gillespie, R., Stewart, J., Wahr, A., and Kirschner, J., “Oil Field Structural Mapping and the Distribution of Dolomite in the Dundee Formation (Devonian) of Michigan,” presented at the 2005 ESAAPG Meeting, Morgantown, WV.

Masters Theses: 
Continued progress of 5 graduate student (Masters Thesis) projects related to the project was adversely impacted by the loss of funding at the end of the second year. As with much of the project, a number of research initiatives have been started {i.e. 3-D reservoir modeling (Niagaran and Trenton/Black River), basin-scale high resolution sequence stratigraphic framework (Niagaran), variance in regional dolomitization patterns (Devonian and Trenton/Black River), reservoir quality correlated to sonic velocity measurements (Niagaran) and image analysis and 3-D characterization of pore system networks tied to reservoir permeability (Niagaran)} but are not yet completed as alternative funding for these students had to be secured mid-project. The researcher’s plans are to continue presenting the research at regional and national meetings and to publish the research in the peer-reviewed literature (with acknowledgement of DOE support).

Jessica Wold (MS-WMU): Sequence stratigraphy and 3-D reservoir characterization of the Ray Reef (Silurian, Niagaran), Macomb County, Michigan

Amy Noack (MS-WMU): Petrophysical characterization of reservoir facies and related pore architecture, Silurian (Niagaran) Pinnacle reefs, Michigan Basin

Audrey Ritter (MS-WMU): High-resolution sequence stratigraphy and 3-D reservoir characterization of the Belle River Mills Field (Silurian, Niagaran), Michigan

Jennifer Schulz (MS-WMU): Facies control on reservoir quality in hydrothermal dolomite, Albion-Scipio trend, Michigan Basin

Jill Haynie (MS-University of Colorado): Petrophysical modeling of Ray Reef (Silurian), Michigan Basin