03 Fracture Origin

8/12/2019 03 Fracture Origin

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1 FRACTUREDSYSTEM ORIGIN


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Fracture System Origin

Based on empirical models of fracture

distribution

Uses underpinning of geologic androck mechanics data

Necessary for effective extrapolation

on interpolation of limited existing

subsurface observations


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Natural Fracture

Classification(A Genetic Classi f ic at ion)

Tectonic Fractures

Fold-related, Fault-related

Regional Fractures Joints, Cleat

Contractional Fractures Chickenwire, Diagenesis-related, Columnar Joints

Surface-related & Induced Unloading, Spall, Weathering


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Assumption:

Fracture orientations faithfully

depict the state of stress at the

time of fracturing

Rocks in the laboratory fracture

in a manner qualitatively similar

to equivalent rocks in nature


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Orders of Magnitude Spanned

Tectonic Fractures 9-10

Regional Fractures 5

Contractional Fractures 2

Surface-Related Fractures 4-5

Pervasiveness of

Natural Fractures


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Tectonic FracturesTectonic fractures are those whose

origin can, on the basis of orientation,distribution, and morphology, be

attributed to or associated with a local

tectonic event.

Fault-Related

Fold-Related


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Fault-Related

Fractures


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Stearns (1972), Courtesy of Cambridge

Air Force Lab

Fractures Associated with Faults

Fractures occur

as a halo or

cloud around the

fault

They may be

unequally

distributed on

the 2 sides ofthe fault


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Fractures Surrounding a Normal Fault

in Miocene Ss

Western

Sinai,

Egypt

10 ft

Footwall

Hangingwall

East West

S 1

S 3


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Fractures & Normal Fault,

Sinai, Egypt


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Fractures Density Around FaultsMiocene Monterrey Fm, Coastal California


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Fractures Around a Normal FaultClastics, Brunei

1 ft


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Nelson et.al.

(2000),

Courtesy of

AAPG


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Fold-Related

Fractures


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Fold-Related Fractures, Pm Ls

Phosphoria Ls, Black Canyon Anti., WY


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From Price

(1966, 1967)Courtesy of

Pergamon Press

Fracture Patterns on Folds


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Schematic of Fractures on Folds

Courtesy of D.W. Stearns


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Tectonic Fold-Related Fractures

Stearns (1982), Courtesy of Cambridge

Air Force Lab


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Fold-Related Fractures

Paleozoic Carbonate, W. Wyoming Thrust Belt


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Tectonic Shear Fractures on a Fold Flank in

Nugget Ss Western Wyoming Thrust Belt

(Lens cap for scale)


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Fold-

Related

Fractures

Back-Limb

Leading-EdgeAnticline

Miss. Ls near

Grand Cache,Alberta

100 ft

1s

2s


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Tectonic Fold-Related FracturesLower Paleozoic Carbonates, Gros Ventres, WY

100 ft


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Tectonic Fractures on Fold Flank inK/T Ss, Rogers Mnt., WY

20 ft

80 deg


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Fold-Related Fractures in Chalk

Tunisia

Courtesy of ETAP


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Multi-Scale Tectonic Fracture

Development in Ss

Sheep Mnt. Anticline, Big Horn Basin,

Wyoming

10 ft

1 ft

Nelson (1985), Courtesy of SPE


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Tectonic Fold-Related Fractures,

Backlimb, Nahanni Ls NWT

100 ft


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Tectonic Fold-Related Fractures,

Backlimb, Nahanni Ls, NWT

T t i F ld R l t d F t T t


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Tectonic Fold-Related Fractures, Teton

Anticline, Montana

Trees are about 30 ft tall


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Fracture Swarms and Fracture Scaling


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Air Photo of Tectonic Fold-Related

Fractures on Teton Anticline,

Sawtooth Mnts, W. Montana


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in an Anticline in Pakistan

Landsat Image (c. 50 mi across)


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Miocene Monterrey Fm, California

A Portion of the FoldFlank is Dominated

by Type 1& Type 2

Extension Fractures


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Type 3 Fold-Related Fractures

K. Chalk, West Coast of Denmark

1 ft


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Various Distributions of Fractures

on Folds in the Middle East

Gholipore (1994),

Courtesy of AAPG


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Regional Fractures

Regional fractures are those which are

developed over large areas of the earths

crust with relatively little change in

orientation, show no evidence of offset

along the plane, and are perpendicular to

major bedding surfaces.

Joints, regional orthogonal fractures


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Regional Fractures, Dev. Antrim Sh

Michigan BasinNelson (1979), Courtesy of AAPG


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Regional FracturesPm Bone Springs Fmnear El Capitan Reef

New Mexico

Photo Courtesy of D. Powley

Ch t i ti f


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Characteristics of

Regional FracturesExtension fractures

Vertical maximum stress

Low stress magnitude

2 directions 90 deg to bedding & 90 deg to oneanother

Systematic set 1st & Non-systematic 2nd

Same as face cleat & butt cleat in coal

Non-pervasive in scale of developmentSubtle control of orientation by rock fabric

Unrelated to local structure

Geometrically aligned with basin shape


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Regional Orthogonal Fractures in Devonian

Antrim Sh, Lake Huron, Michigan

Hammer for scale


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Regional Orthogonal Fractures in

Devonian Antrim Sh, Michigan

3 ft field of view


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Regional Fractures in Tr/Jr Navajo Ss

Lake Powell, Utah

Looking SW NE - SW Trending Fractures

(c. 1 mi Field of View)

Nelson (1979), Courtesy of AAPG


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Systematic Regional Fractures in

Navajo Ss

Colorado River near Page, Arizona

1,800 ft

c. N 10 E

R i l O th l F t i


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Regional Orthogonal Fractures in

K. Kootenai Ss

Near Greatfalls, Montana

Non-Systematic

R i l F t i K


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Regional Fractures in K.

Kootenai Ss

Missouri River

Near Greatfalls,

Montana

5 ft


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Possible Origins for

Regional Fractures

Inherited-upward flaws

Uplift with locked-in pore pressure

Planetary lineationsPlateau uplift

Earth Tides

Subtle regional tectonism

Basin bounding tectonism

Compaction/basin maturation


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Regional Fractures, Chinle Fm, UT

Nelson (1979),

Courtesy of AAPG


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ContractionalFractures


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Contractional Fractures

Are the result of:

Desiccation

Syneresis

Thermal gradients

Mineral phase changes

Chickenwire Perm Reduction


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with Stress, Panoma Field

Chicken ire Perm Red ction


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with Stress, Panoma Field

Production From Chickenwire Fractures


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Production From Chickenwire FracturesGamma Ray Neutron


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Chickenwire Fracture Rocks

Contain Significant Amounts of:

Clay

Silt size quartzGypsum/anhydrite

Amorphous iron oxide grain coatings

Association with carbonate minerals


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Environments most conducive togenerating rocks susceptible to

chickenwire fractures:

Shal low water, low energy,

restr ic ted marine and f luv ial

envi ronments


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Chickenwire fractures involverocks with significant amounts

of:

Poorly sorted , arg i l laceous,

f ine grained clast ics in c lose

prox im i ty to evapo r itecsequences

Sh i k i C t


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Shrinkage in Cement

A Chickenwire Fracture Analog?


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Columnar Joints

Columnar Joints at Devils


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Columnar Joints at Devils

Causeway, Ireland


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Columnar Joints ina Tertiary Volcanic

Neck

Near Salt Lake,

Utah

Nelson (1985)

Vertical Propagation of


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De Graf & Aydin (1986)

Vertical Propagation of

Columnar Joints

Courtesy of GSA

Columnar Jointing in Ss Above a Sill


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Columnar Jointing in Ss Above a Sill

(Hammer for scale) N. Canada, CSPG calander


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Surface-Related Fractures

A diverse group including fractures

developed during unloading, creationof free or unsupported boundaries

(gravity), and weathering processes

in general.

Surface Related Gravitational


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1

23

4

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Surface-Related Gravitational

Fractures, Navajo Ss

Lake Powell, Utah

High water mark is 10-12 ftAfter Nelson (1979),

Courtesy of AAPG

Fresh Unloading Fracture Surface


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400 ft

Fresh Unloading Fracture Surface,

Navajo Ss, Lake Powell, Utah

Th l S lli i T t B lt


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Thermal Spalling in Tert. Basalt

Great Salt Lake Area, Utah

1 ft

Polygonal Fractures in Navajo Ss


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Polygonal Fractures in Navajo Ss

Near Boulder, Utah

10 ft

(Weathering?)After Nelson (1979), Courtesy of AAPG

Natural Tectonic and Exfoliation


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Fractures in Appalachian Outcrop

Tectonic

Exfoliation

8 ft field of view

P ibl P P F t


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Possible Pore Pressure FracturesLower Paleozoic Carbonate Reef, W. Canada

(4 in diameter core)

03 Fracture Origin

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