Geological Magazine,
Journal Year:
2023,
Volume and Issue:
160(9), P. 1817 - 1831
Published: Sept. 1, 2023
Abstract
The
concept
of
superposed
fracture
networks
consisting
different
generations,
and
often
types,
fractures
that
have
developed
sequentially
is
discussed.
Superposed
can
consist
types
extension
or
shear
fractures,
each
may
abut,
cross
follow
(reactivate)
earlier
fractures.
An
example
a
network
in
Liassic
limestones
Somerset,
UK,
presented,
which
comprises
two
sets
veins
later
joint
network.
develop
as
damage
zones
around
faults,
with
the
set
crossing
trailing
along
set.
joints
either
cross-cut
reactivate
them,
latter
being
common
for
thicker
(more
than
about
5
mm)
veins.
markedly
geometries
topologies.
are
spatially
clustered
typically
dominated
by
I-nodes,
while
more
evenly
distributed
tend
to
be
Y-nodes.
combined
at
Lilstock
X-nodes
because
so
many
Understanding
development
leads
better
understanding
kinematic,
mechanical,
tectonic
fluid
flow
history
rocks.
Marine and Petroleum Geology,
Journal Year:
2023,
Volume and Issue:
152, P. 106238 - 106238
Published: March 24, 2023
Using
image
logs
from
horizontal
wells
in
the
asymmetric
East
Painter
Reservoir
anticline
Wyoming,
scanlines
and
petrographic
observations
nearby
outcrops,
methods
that
allow
statistical
quantification
of
fracture
spatial
arrangement
patterns
(including
clustering),
we
show
early
Jurassic
Nugget
Formation
sandstone
degree
clustering
intensity
fractures
varies
with
structural
position.
In
backlimb,
are
markedly
more
clustered
than
random,
hierarchical
regularly
spaced
clusters
present,
but
is
low.
forelimb,
arrangements
mostly
indistinguishable
high.
Based
on
log
response,
backlimb
contains
a
higher
proportion
open
fractures,
although
forelimb
has
greater
numbers
fractures.
Spatial
similar
outcrop.
Petrography
reveals
quartz
seals
less
0.15
mm
wide.
Wider
rinds
or
lined
sealed
calcite
filled
by
quartzose
cataclasite.
The
depends
deposits
closure
reactivation
(shearing)
pre-existing
quartz-lined
increased
abundance
strike
dispersion,
results
suggest
forelimbs,
high
intensities
reflect
shear
preexisting
possibly
resulting
numerous
spatially
correlated
most
prolific
gas
water
production
suggesting
sparse
effective
fluid
conduits
closely
partly
damaged/sheared
arrays.
Journal of Structural Geology,
Journal Year:
2023,
Volume and Issue:
173, P. 104915 - 104915
Published: July 11, 2023
Arrays
of
natural
opening-mode
fractures
show
systematic
patterns
in
size
and
spatial
arrangement.
The
controls
on
these
factors
are
enigmatic,
but
many
cases
the
depth
formation
appears
to
be
critical.
Physical,
potentially
depth-dependent
that
could
account
for
variations
include
confining
stress,
fluid
pressure,
strain
rate;
common
inputs
existing
fracture
models.
However,
temperature-dependent
chemical
processes
likely
exert
an
equally
important
control
patterns,
such
have
not
yet
been
rigorously
incorporated
into
models
formation.
Here
we
present
a
spring-lattice
model
simulates
fracturing
extending
sedimentary
rock
beds,
while
explicitly
accounting
cementation
during
opening
fractures,
failure
via
both
elastic
time-dependent
criteria.
Results
illustrate
three
distinct
behaviors
having
documented
analogs,
which
here
term
facies.
"Exclusionary
macrofracturing"
occurs
at
shallow
levels
produces
large,
widely
spaced,
uncemented
fractures;
"multi-scale
fracturing"
moderate
partially
cemented
wide
range
sizes
spacings;
"penetrative
microfracturing"
great
myriad
narrow,
sealed
closely
regularly
spaced.
effect
is
primarily
accelerate
dissolution
precipitation
reactions
increased
temperature
porewater
salinity;
specific
each
facies
will
vary
by
host-rock
lithology,
grain
size,
rate,
thermal
history.
Frontiers in Earth Science,
Journal Year:
2025,
Volume and Issue:
13
Published: April 2, 2025
Exceptionally
large,
well-exposed
sandstone
outcrops
in
New
York
provide
insights
into
folds,
deformation
bands,
and
fractures
that
could
influence
permeability,
heat
exchange,
stimulation
outcomes
of
geothermal
reservoir
targets.
Cambrian
Potsdam
Sandstone
with
<5%
porosity
contains
decimeter-scale
open,
angular-limbed
monoclines
<0.5
km
apart
associated
low-porosity
mm-wide
cataclastic
bands.
Crossing
abutting
relationships
among
sub-vertical
opening-mode
show
four
chronological
Sets
A–D,
striking
NNW,
NE,
NW,
ENE,
respectively.
Fracture
lengths
heights
range
from
millimeters
to
tens
meters.
A
C
macro-fractures,
possibly
B
D,
contain
quartz
deposits.
All
sets
have
abundant
cemented
microfractures
also
record
set
orientations
crosscutting
relations.
Quartz
cement
deposits—evidence
diagenesis—are
the
key
identifying
attributes
outcrop
suitable
for
extrapolation
targets
sandstones
because
they
which
formed
subsurface.
Set
fluid
inclusion
homogenization
temperatures
(120°C–129°C)
are
compatible
fracture
at
>3
depth.
Fractures
stiff
those
≥0.05
mm
(Set
C)
≥0.1
A)
open
potentially
conducive
flow.
D
close
spacing—0.18
m
0.68
m,
respectively—and
define
a
rectangular
connectivity
network
dominated
by
crossing
X
Y
nodes.
aperture
distributions
follow
power
law
slope
−0.8
up
0.15
mm;
other
lognormal
distributions.
weakly
clustered,
while
macro-fractures
commonly
1D
anticlustered
(regular
or
periodic)
arrangements
shorter
length
scales
(<0.2
m).
Sub-horizontal
barren
may
near
surface.
heights,
lengths,
spatial
good
trace
but
low
connectivity.
For
applications,
results
predict
initial
well-test
permeabilities
owing
disconnecting
fractures,
closely
spaced
partly
yield
high
surface
area
exchange.
Quantitative
like
abundance,
orientation,
arrangement,
length,
is
possible
fractured
reservoirs
if
differing
thermal
histories
diagenesis
accounted
for.
