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 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

Structural Axis Trends in a

Portion of Albion-Scipio Field

From Versical, 1991

M.S. Thesis, W.M.U

Fold Orientations and Left-

Lateral 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.