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
 University/industry consortium for data
gathering and research
 Document role of fractures in Michigan
carbonate reservoirs

Project Team
Dr. James R. Wood, Project Manager,
Michigan Technological University
 Dr. William B. Harrison, III, Co-Principal
Investigator, Western Michigan University

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

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

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

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

Stress Created by Plate Collisions
Eastern Continental Margin
From Versical, 1991
M.S. Thesis, W.M.U
Contemporary Maximum Horizontal
Compressive Stress Directions
From Versical, 1991
M.S. Thesis, W.M.U
Bedding Parallel Strain from
Calcite Twin Analyses
From Versical, 1991
M.S. Thesis, W.M.U
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

Fracture Orientations from
Outcrop Measurements
From Versical, 1991
M.S. Thesis, W.M.U
Antrim Shale Fracture
Orientations
From Dellapenna Thesis, 1991
Correlation of Fracture Frequency
to Logs - Antrim Shale
From Dellapenna Thesis, 1991
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

Riedel Shear Model for Left
Simple Shear
From Versical, 1991
M.S. Thesis, W.M.U
Reidel Shear Development
from Basement Fault
Anticlinal Structures created
by Paired Reidel Shear Faults
From Versical, 1991
M.S. Thesis, W.M.U
Clayton Field Structural
Interpretation from Seismic
Structural Contour Map on
Top of Basement
Structural Model of AlbionScipio 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

Structural Axis Trends in a
Portion of Albion-Scipio Field
From Versical, 1991
M.S. Thesis, W.M.U
Fold Orientations and LeftLateral Wrench Fault Model
From Versical, 1991
M.S. Thesis, W.M.U
Albion-Scipio Field, Riedel
Shear Model
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.

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.
