Strain And Structural
Partitioning In The Delaware
Basin:
Relation To Play And
Trend Development
Dr. Richard J. Erdlac, Jr.
UTPB/CEED
Based upon work conducted by:
Douglas B. Swift
Richard J. Erdlac, Jr.
West Texas Earth Resources Institute
Exploration Premise
Determination of the play or trend type in a given
region requires knowledge of:
 Structural Deformation Styles/Mechanisms
You don’t say that all faults are normal when compressional
tectonics were active.
 Sedimentation Styles/Mechanisms
You don’t look for salt deformation structures
where salt was never deposited.
DEFORMATION
What is meant by the term?
1. Structural changes that take place in
the original location, orientation, shape,
and volume.
2. Physical or chemical processes that
produce the structural change.
3. Geologic structures that form to
accommodate the changes.
1) DEFORMATION: change in original rock body.
location = translation = rigid body motion
(flexural slip folding, plate tectonics)
orientation = rotation = rigid body motion
(monocline, listric normal faulting)
(ORIGINAL ROCK SIZE PRESERVED)
shape = distortion = non-rigid body motion
(deformed fossil)
volume = dilation = non-rigid body motion
(fractures expand rock, stylolites shrink)
(ORIGINAL ROCK SIZE NOT PRESERVED)
(strain occurs)
Structural changes can vary according to scale of observations
or the definition of the structural boundaries.
2) DEFORMATION : physical & chemical processes
that produce structural changes (within minerals).
1) Microfracturing; Cataclasis; Frictional Sliding
(breaking of crystal lattice)
2) Mechanical Twinning; Kinking
(bending of crystal lattice)
3) Diffusion Creep (T activated)
(movement of crystal vacancies and atoms)
4) Dissolution Creep (pressure solution = stylitization)
(dissolution and reprecipitation of material)
5) Dislocation Creep
(intercrystalline slip of lattice structure along a plane)
This is usually what is meant by strain partitioning.
3) DEFORMATION : geologic structures that form to
accommodate the changes.
Joints and Shear Fractures
Faults
Folds
Cleavage, Foliation, and Lineation
Shear Zones
This is what is generally considered within the
exploration and production mode. However
all three definitions are truly applicable.
What is strain partitioning?
The manner of separating different mechanisms of
deformation that lead to overall bulk or average
strain in a rock.
(Ramsay & Huber, 1983)
(This definition tends to focus on physical and chemical changes.)
Strain can also be related to the change in
any linear dimension of a body.
Strain:
e
l f  lo
lo
(e is also called extension.)
Plane Strain
The easiest way to consider deformation is to assume little
to no volume change in a broad sense and that one
strain axis is unchanged.
(One axis of deformation remains unchanged.)
Pure Shear = Coaxial Strain
Plane Strain
The easiest way to consider deformation is to assume little
to no volume change in a broad sense and that one
strain axis is unchanged.
(One axis of deformation remains unchanged.)
Pure Shear = Coaxial Strain
Plane Strain
The easiest way to consider deformation is to assume little
to no volume change in a broad sense and that one
strain axis is unchanged.
(One axis of deformation remains unchanged.)
Simple Shear = Noncoaxial Strain ( = tan)
=0
 = 0.40
 = 0.60
 = 1.00
Plane Strain
The easiest way to consider deformation is to assume little
to no volume change in a broad sense and that one
strain axis is unchanged.
(One axis of deformation remains unchanged.)
Simple Shear = Noncoaxial Strain ( = tan)
=0
 = 0.40
 = 0.60
 = 1.00
STRUCTURAL PARTITIONING
Using the definitions for deformation we
can partition structures in a megascopic
manner according to the geometric styles
that predominate in a given area.
Let us look at examples within the
Delaware-Val Verde Basin region.
Delaware –
Val Verde
Basins
Seismic
Data
Delaware –
Val Verde
Basins
Play Map
of DVVB
(15)
Tectonic Map
of DVVB
STRUCTURAL PARTITIONING
Three Examples
Brown-Bassett Field: pure shear
(Brown-Bassett Play)
 Waha to Coyanosa:
pure shear
(Central Basin Platform Border Region)
 Grisham Fault Zone:
(Grisham Uplifted Region)
simple shear
Brown-Bassett Field
Brown-Bassett Play
Folding/Faulting (?)
Brown-Bassett
> 1.4 B mcf
Play Map of DVVB
Seismic Map
Production Map
JM
> 705 MM mcf
Will-O
> 50 MM mcf
Tectonic Map of DVVB
Folding/
Faulting
(?)
Brown-Bassett
Folding/
Faulting
(?)
Brown-Bassett
Dry Fork Ridge
Anticline,
Wyoming
Folding/
Faulting
(?)
Brown-Bassett
Dry Fork Ridge
Anticline,
Wyoming
Folding/Faulting (?)
Brown-Bassett
Note
footwall
reversal.
Is it real?
STRUCTURAL PARTITIONING
Three Examples
 Brown-Bassett Field:
(Brown-Bassett Play)
pure shear
Waha to Coyanosa:
pure shear
(Central Basin Platform Border Region)
 Grisham Fault Zone:
(Grisham Uplifted Region)
simple shear
Waha To Coyanosa
Waha/Worsham-Bayer-Coyanosa Area
Folding/Faulting
Play Map of
DVVB
Seismic Map
Worsham-Bayer
> 455 MM mcf
Waha
> 319 MM mcf E
> 241 MM mcf M
Waha, W
> 285 MM mcf
Production
Map
Coyanosa
> 491 MM mcf E
> 989 MM mcf D
> 1 B mcf W
Tectonic Map of DVVB
Seismic Map
S
W,W
Folding /
Faulting
W
S
W,W
W
Tectonic Map
of DVVB
Waha, W
Waha
DB Group Shoot 114
Synclinal Area
Seismic Map
C
C
S CBP
Folding /
Faulting
S
CBP
Tectonic Map
of DVVB
Coyanosa
Synclinal Axis
DB Group Shoot 104
CBP Margin
Seismic Map
S CBP
S
Folding /
Faulting
A
CBP
A
Tectonic Map
of DVVB
CBP
Coyanosa
AnticlinalAnticline
Axis
Axis Projection
Synclinal Axis
DB Group Shoot 105
DB Group Shoot 114
DB Group Shoot 105
Folding / Faulting
DB Group Shoot 104
Fault-induced folds at outcrop scale,
Devonian strata, the Appalachian
Mountains (McConnell et al., 1997).
STRUCTURAL PARTITIONING
Three Examples
 Brown-Bassett Field:
(Brown-Bassett Play)
pure shear
 Waha to Coyanosa:
pure shear
(Central Basin Platform Border Region)
Grisham Fault Zone: simple shear
(Grisham Uplifted Region)
Grisham Fault Zone
Grisham Fault Zone / Grisham Uplifted Region
Simple Shear
Riedel Shear Modeling
Tchalenko, 1970
Simple Shear
B
A
10
CM
0
10
CM
0
2o Convergent
Left-Lateral System
2o Convergent
Left-Lateral System
Wilcox et al., 1973
& P.G. Temple (unpublished work)
Faulting/Folding/Shear Zones
Production Map
Greasewood
> 354 MM mcf
Athens
> 24 MM mcf
Play Map of DVVB
Tectonic Map of DVVB
Mi Vida
> 1 B mcf
Toyah
> 7 MM mcf
Faulting/Folding/Shear Zones
A
S
F
A
F
GF
S
D
Seismic Map
GF
Tectonic Map of DVVB
DB Group Shoot 108
Grisham Fault Zone
Anticlines
Fault
Syncline
Syncline
Dunnavant
D
Faulting/Folding/Shear Zones
Seismic Map
A
A
GF
GF
Seismic Map
Tectonic Map of DVVB
DB Group Shoot 117
Grisham Fault Zone
Anticline Axis
Faulting/Folding/Shear Zones
A
A
A
S
S
Seismic Map
Tectonic Map of DVVB
DB Group Shoot 119B
Anticlines
Syncline
IS THE GRISHAM FAULT ZONE
UNIQUE?
NB – North Baylor
VH – Van Horn
L – Lobo
CM – Chispa Mountain
ML – Mount Locke
V – Valentine
C – Candelaria
R – Ruidosa
S – Shafter (Chalk Draw Fault)
P – Presidio (Tascotal Mesa Fault)
T _ Terlingua (Monocline)
SE – Santa Elena
Trans-Pecos E-W Structural Zones
(Dickerson, 1980 – Trans-Pecos Region – NMGS)
Faulting/Folding/Shear Zones
Other Possible Shear Zones
Toro, S
Perry Bass
Grey Ranch
S U M M A R Y
1)
Deformation is documented in a variety of different ways,
from microscopic to megascopic in scale.
physical & chemical processes – will alter porosity & permeability.
rigid body motion – generate permeability (fractures) & structural traps.
2)
In its simplest manner strain can be considered to be
either pure shear or simple shear (plane strain).
3)
Deformed basins can be structurally partitioned into
various strain categories (pure & simple) based upon the
structural geometries or types encountered.
4)
Knowing the partition type will define the play trend and
the approach to exploration and production in that area.