Role of Fractures in Role of Fractures in Michigan Oil and Gas Michigan Oil and Gas

ReservoirsReservoirs

Dr. William B. Harrison, IIIDepartment of Geosciences

Western Michigan University

Advanced Characterization of Advanced Characterization of Fractured Reservoirs in Carbonate Fractured Reservoirs in Carbonate

Rocks: The Michigan BasinRocks: 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 TeamProject Team

Dr. James R. Wood, Project Manager, Michigan Technological University

Dr. William B. Harrison, III, Co-Principal Investigator, Western Michigan University

Project Goals and ObjectivesProject 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 ReservoirsTypes 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 FracturesOrigin 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 Regional Analysis of Stress Fields and Fracture Developmentand 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 Stress Created by Plate Collisions Eastern Continental MarginEastern Continental Margin

From Versical, 1991M.S. Thesis, W.M.U

Contemporary Maximum Horizontal Contemporary Maximum Horizontal Compressive Stress DirectionsCompressive Stress Directions

From Versical, 1991M.S. Thesis, W.M.U

Bedding Parallel Strain from Bedding Parallel Strain from Calcite Twin AnalysesCalcite Twin Analyses

From Versical, 1991M.S. Thesis, W.M.U

Sources of Data for Analyses Sources of Data for Analyses of Fracturesof 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, 1991M.S. Thesis, W.M.U

Antrim Shale Fracture Antrim Shale Fracture OrientationsOrientations

From Dellapenna Thesis, 1991

Correlation of Fracture Frequency Correlation of Fracture Frequency to Logs - Antrim Shaleto Logs - Antrim Shale

From Dellapenna Thesis, 1991

Modeling Michigan Structures and Modeling Michigan Structures and Fractures using Riedel ShearsFractures 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 Riedel Shear Model for Left Simple ShearSimple Shear

From Versical, 1991M.S. Thesis, W.M.U

Reidel Shear Development Reidel Shear Development from Basement Faultfrom Basement Fault

Anticlinal Structures created Anticlinal Structures created by Paired Reidel Shear Faultsby Paired Reidel Shear Faults

From Versical, 1991M.S. Thesis, W.M.U

Clayton Field Structural Clayton Field Structural Interpretation from SeismicInterpretation from Seismic

Structural Contour Map on Structural Contour Map on Top of BasementTop of Basement

Structural Model of Albion-Structural Model of Albion-Scipio FieldScipio 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 Structural Axis Trends in a Portion of Albion-Scipio FieldPortion of Albion-Scipio Field

From Versical, 1991M.S. Thesis, W.M.U

Fold Orientations and Left-Fold Orientations and Left-Lateral Wrench Fault ModelLateral Wrench Fault Model

From Versical, 1991M.S. Thesis, W.M.U

Albion-Scipio Field, Riedel Albion-Scipio Field, Riedel Shear ModelShear Model

Summary and ConclusionsSummary 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 ConclusionsSummary 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.