Role of Fractures in Michigan Oil and Gas Reservoirs

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 Team

• Dr. James R. Wood, Project Manager, Michigan
  Technological University
• Dr. William B. Harrison, III, Co-Principal
  Investigator, Western Michigan University

4
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

5
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

6
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

7
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

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Stress Created by Plate Collisions Eastern
Continental Margin
From Versical, 1991 M.S. Thesis, W.M.U
9
Contemporary Maximum Horizontal Compressive
Stress Directions
From Versical, 1991 M.S. Thesis, W.M.U
10
Bedding Parallel Strain from Calcite Twin Analyses
From Versical, 1991 M.S. Thesis, W.M.U
11
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

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Fracture Orientations from Outcrop Measurements
From Versical, 1991 M.S. Thesis, W.M.U
13
(No Transcript)
14
Antrim Shale Fracture Orientations
From Dellapenna Thesis, 1991
15
Correlation of Fracture Frequency to Logs -
Antrim Shale
From Dellapenna Thesis, 1991
16
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

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Riedel Shear Model for Left Simple Shear
From Versical, 1991 M.S. Thesis, W.M.U
18
Reidel Shear Development from Basement Fault
19
Anticlinal Structures created by Paired Reidel
Shear Faults
From Versical, 1991 M.S. Thesis, W.M.U
20
Clayton Field Structural Interpretation from
Seismic
21
Structural Contour Map on Top of Basement
22
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

23
Structural Axis Trends in a Portion of
Albion-Scipio Field
From Versical, 1991 M.S. Thesis, W.M.U
24
Fold Orientations and Left-Lateral Wrench Fault
Model
From Versical, 1991 M.S. Thesis, W.M.U
25
Albion-Scipio Field, Riedel Shear Model
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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.

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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.