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Role of Fractures in Michigan Oil and Gas Reservoirs

Role of Fractures in Michigan Oil and Gas Reservoirs. Dr. William B. Harrison, III Department of Geosciences Western Michigan University. Advanced Characterization of Fractured Reservoirs in Carbonate Rocks: The Michigan Basin. U.S.DOE-funded, 3-year research project - 1998 to 2001

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Role of Fractures in Michigan Oil and Gas Reservoirs

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  1. Role of Fractures in Michigan Oil and Gas Reservoirs Dr. William B. Harrison, III Department of Geosciences Western Michigan University

  2. Advanced Characterization of Fractured Reservoirs in Carbonate Rocks: The Michigan Basin • U.S.DOE-funded, 3-year research project - 1998 to 2001 • University/industry consortium for data gathering and research • Document role of fractures in Michigan carbonate reservoirs

  3. Project Goals and Objectives • Characterization of Fractures in Michigan Reservoirs • Quantifying Fracture Patterns at a Variety of Scales • Developing a Basin Model for Fracture Development • Determine role of Fractures in Hydrocarbon Emplacement or Production

  4. Types of Fractured Reservoirs • Type 1 - Fractures provide all reservoir storage, matrix tight. Fractures provide porosity and permeability. Ex. Antrim Shale • Type 2 - Fractures connect porous and permeable matrix zones. Most reservoir storage and porosity in matrix. Permeability enhanced by fractures. Ex. Niagaran Reef • Type 3 - Fractures initiate porosity/permeability in tight rock. Later solution enhancement creates reservoir quality. Ex. Albion-Scipio Field Trenton

  5. Origin of Fractures • External stress on some portion of rock mass exceeds the breaking strength of the rock. • Three dimensional stress field is designated Sigma-1, Sigma-2, and Sigma-3. Usually one vertical and two horizontal directions, all at right angles to each other. • Most fractures are sub-vertical to vertical

  6. Regional Analysis of Stress Fields and Fracture Development • Intraplate stresses develop throughout the crust, mostly originating at plate boundaries • Contemporary stress fields reflect modern Plate movements • Paleostress fields are recorded in the rocks and reflect ancient plate movements • Contemporary and paleo-stress fields may have different orientations

  7. Sources of Data for Analyses of Fractures • Outcrop measurements • Oriented cores • Borehole imaging logs • Borehole breakout and induced fracture orientations • Structural trend mapping • Remote sensing and stream drainage mapping

  8. Fracture Orientations from Outcrop Measurements From Versical, 1991 M.S. Thesis, W.M.U

  9. Antrim Shale Fracture Orientations From Dellapenna Thesis, 1991

  10. Correlation of Fracture Frequency to Logs - Antrim Shale From Dellapenna Thesis, 1991

  11. Modeling Michigan Structures and Fractures using Riedel Shears • Assumes effective stress is horizontal • Shear is the primary mechanism for development of structures • Fractures will develop at predictable angles to shear direction • Reactivation of structures from basement and throughout the sedimentary column

  12. Riedel Shear Model for Left Simple Shear From Versical, 1991 M.S. Thesis, W.M.U

  13. Reidel Shear Development from Basement Fault

  14. Anticlinal Structures created by Paired Reidel Shear Faults From Versical, 1991 M.S. Thesis, W.M.U

  15. Clayton Field Structural Interpretation from Seismic

  16. Structural Contour Map on Top of Basement

  17. Structural Model of Albion-Scipio Field • Riedel Shear model with left-lateral shear • Localized small-scale folds within field fit shear model • Reactivated basement fault or “zone of weakness” is probable Principle Displacement Zone

  18. Structural Axis Trends in a Portion of Albion-Scipio Field From Versical, 1991 M.S. Thesis, W.M.U

  19. Fold Orientations and Left-Lateral Wrench Fault Model From Versical, 1991 M.S. Thesis, W.M.U

  20. Albion-Scipio Field, Riedel Shear Model

  21. Summary and Conclusions • New 3-Year DOE Project on fractures in Michigan reservoirs in underway. • Research consortium between Michigan Tech. and Western Michigan Universities. • Initial phase is to classify types of fractured reservoirs and determine origin of fractures.

  22. Summary and Conclusions • Fractures are present in most reservoirs, but play vastly different roles depending on lithology and fabric of the matrix. • Fractures enhance permeability and porosity and may be very significant in diagenetic changes. • Stresses that control fractures mostly arise outside the Michigan basin at plate margins.

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