Final Scientific/Technical Report: DE-FC26-04NT15513 Summary of Research through Phase II/Year 2 of initially approved 3 Phase/3 Year Project – Establishing the Relationship between Fracture- Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin DOE Award Number: DE-FC26-04NT15513 Reporting Period Start: October 1, 2004 Reporting Period End: September 30, 2007 Principal Author and Project Manager: G. Michael Grammer, Ph.D. Associate Professor Department of Geosciences Western Michigan University 1903 W. Michigan Ave. Kalamazoo, MI 49008-5241 Final Report Issued: December 21, 2007 1 DISCLAIMER “This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof”. 2 ABSTRACT This final scientific/technical report covers the first 2 years (Phases I and II of an originally planned 3 Year/3 Phase program). The project was focused on evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin. The characterization of select dolomite reservoirs was the major focus of our efforts in Phases I and II of the project. Structural mapping and log analysis in the Dundee (Devonian) and Trenton/Black River (Ordovician) 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 these 2 studied intervals (based upon fluid inclusion homogenization temperatures and stable isotopic analyses,) coupled with persistent association of this dolomite in reservoirs coincident with wrench fault-related features, is strong evidence for these reservoirs being influenced by hydrothermal dolomitization. In the Niagaran (Silurian), there is a general trend of increasing dolomitization shelfward, with limestone predominant in more basinward positions. A major finding is that facies types, when analyzed at a detailed level, are directly related to reservoir porosity and permeability in these dolomites which increases the predictability of reservoir quality in these units. This pattern is consistent with our 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 the results should be exportable throughout the basin. Much of the data synthesis and modeling for the project was scheduled to be part of Year 3/Phase III, but the discontinuation of funding after Year 2 precluded those efforts. Therefore, the results presented in this document are not final, and in many cases represent a report of “progress to date”. 3 TABLE OF CONTENTS Abstract p. 2 Executive Summary p. 6 Introduction p. Rationale and Goals of the Project Background – Mechanisms for Dolomitization Stratigraphy and Dolomite Occurrences in Michigan Basin Paleozoic Carbonate Reservoirs Structural Elements, Thermal Evolution, and Hydrothermal Mineralization in the Michigan Basin Variations in Dolomitization and Reservoir Geometries in the Michigan Basin Petrographic and Analytical Study of Dolomitized Carbonate Reservoirs Reservoir Characterization – Petrophysical Properties of Carbonate Sediments and Rocks Project Approach and Discussion of Results by Task (Phase I and II) p. Summary of Phase I and II – Devonian and Ordovician p. Summary of Phase I and II – Silurian (Niagaran) p. Discussion: Phase I and II- Initial Results from Tasks 2 and 3 p. “Controls on Dolomitization in the Middle Devonian Dundee Formation - Oil Field Scale Structure and the Distribution of Log-Based Dolomite Lithofacies” Silurian (Niagaran) – Petrophysical Facies and Image Analysis p. Summary of Currently Available Geologic Data through Phase II p. Ordovician Trenton/Black River Trend Silurian Niagaran Trend Devonian Trend Report References p. Bibliography – part of Task 2 (Compilation of currently available p. geologic data and literature). 4 Appendix 1: Practical Synergies for Increasing Domestic Oil Production and p. Geological Sequestration of Anthropogenic CO2: An example from the Silurian of the Michigan Basin Appendix 2: Summary of Currently Available Geologic Data (Task 2) p. Production analysis data and graphs. 1. Ordovician Trenton/Black River 2. Silurian Niagaran 3. Devonian Dundee Appendix 3: Project presentations (abstracts) at professional meetings p. (Year 2/Phase II) Appendix 4: Miscellaneous Project Presentations (titles) p. 5 EXECUTIVE SUMMARY This final scientific/technical report covers the first 2 years (Phases I and II of an originally planned 3 Year/3 Phase program). The project was focused on evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin (Ordovician Trenton-Black River Formations; Silurian Niagara Group; and the Devonian Dundee Formation). Much of the data synthesis and modeling for the project was scheduled to be part of Year 3/Phase III, but the discontinuation of funding after Year 2 precluded those efforts. Dolomitization is widespread and generally a critical factor in the origin of these most prolific, hydrocarbon reservoirs in the Michigan Basin: i.e. the Middle Ordovician Trenton/Black River Formations, the Silurian Niagara Group and the Middle Devonian Dundee Limestone. These units are the most economically important reservoirs in the basin. However, they consist of a wide range of dolomite types resulting in complex spatial variability of both geometry and quality of dolomite reservoirs. The characterization of select dolomite reservoirs was the major focus of our efforts in Phases I and II of the project. Fields were 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. Structural mapping and log analysis in the Dundee (Devonian) and Trenton/Black River (Ordovician) 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 these 2 studied intervals (based upon initial fluid inclusion homogenization temperatures and stable isotopic analyses,) coupled with persistent association of this dolomite in reservoirs coincident with wrench fault- related features, is strong evidence for these reservoirs being influenced by hydrothermal dolomitization. For the Niagaran (Silurian), there is a general trend of increasing dolomitization shelfward, with limestone predominant in more basinward positions. Reservoir quality porosity and permeability is characterized by a combination of dissolution-related molds, vugs, and locally cavernous porosity that is enhanced in the dolomite sections by intercrystalline porosity. A comprehensive high resolution sequence stratigraphic framework was developed for a pinnacle reef in the northern reef trend where we had 100% core coverage throughout the reef section. This sequence framework was then compared with major Niagaran fields in the southern reef trend, although comprehensive correlation and 3-D modeling did not occur because these tasks were part of Phase III. 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 our 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 the results should be exportable throughout the basin. 6 Ten reservoir significant lithofacies were described in the northern reef trend, providing significantly more resolution than the standard 4-6 that are used most often in the basin (e.g. Gill, 1977). Initial petrophysical characterization (sonic velocity analysis under confining pressures) showed a clear pattern that is dependent upon facies and resulting pore architecture. Primary facies is a key factor in the ultimate diagenetic modification of the rock and the resulting pore architecture. Facies with good porosity and permeability clearly showed relatively slow velocity values as would be expected, and low porosity and permeability samples exhibit fast sonic velocity values, again as expected. What is significant is that some facies that have