PS
Let's Make Outcrops Recover Their Value, Understanding the Rock on the Surface for Predicting into the
Subsurface: Woodford Shale Case Study, Ardmore Basin, Oklahoma*
Henry A. Galvis-Portilla1, Daniela Becerra-Rondon1, and Roger Slatt1
Search and Discovery Article #10907 (2017)**
Posted January 30, 2017
*Adapted from poster presentation given at AAPG Annual Convention & Exhibition, Calgary, Alberta, Canada, June 19-22, 2016
**Datapages © 2017 Serial rights given by author. For all other rights contact author directly.
1
School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma ([email protected])
Abstract
Due to the high cost to acquire well cores, along with today's low-oil-price scenarios, sizeable challenges are emerging especially for
unconventional reservoir characterization. Thus, detailed and integrated outcrop data tied to well log responses provide means to understand
shales on the surface and give supporting notions while predicting reservoir properties into the subsurface. In this work, first we present a
multi-scale approach to characterize the vertical and lateral heterogeneities of a fresh Woodford Shale Outcrop in southern Oklahoma, the
exposed succession is about 350 feet thick, comprising the entire Upper-Devonian and Lower Mississippian Woodford Shale and partially the
overlying Sycamore Limestone and underlying Hunton Group. About 14 detailed lithofacies were recognized, which relate direct observations
and/or measurements such as color, texture, lithology, mineral assemblages and composition, bioturbation, presence and frequency of
laminations and organic richness. Secondly, by cross-correlation with nearby well-logs and using clustering analysis a supervised electrolithofacies classification was conducted, in which a statistical model was generated for permitting the prediction and propagation of up-scaled
lithofacies in non-cored wells. In our case for the Ardmore Basin, the propagated model of lithofacies covers an area of about 64,000 acres and
includes well-log information of 22 wells; depths of the Woodford Shale in the subsurface range from 1000 to 3500 feet. The most remarkable
outcrop-to-subsurface finding of this study is a laterally continuous cyclic pattern of two end-member groups of lithofacies: (1) clay-rich, silicapoor, organic-rich, ductile lithofacies, and (2) clay-poor, silica-rich, carbonate-rich, brittle, fractured, organic-poor lithofacies. As if they were
imitating a cyclic source-reservoir system, in which some lithofacies acts as an oil/gas source and others as reservoirs or fracturable rocks.
Thickness and frequency of these cycles varies stratigraphically throughout the Woodford Shale, resulting in better gross intervals for
unconventional resources within the Upper-Middle and Upper Woodford Shale in the Ardmore Basin.
- - The - UNIVERSITY
Let's Make Outcrops Recover Their Value, Understanding the Rock on the Surface for Predicting
Into the Subsurface: Woodford Shale Case Study, Ardmore Basin, Oklahoma
ABSTRACT
OKLAHOMA
AAPGi & Exhibition 2016
•
y
ConocoPhillips
School of Geology and Geophysics
THE OUTCROP IN THE ARDMORE BASIN
SOUTH - CENTRAL OKLAHOMA
Due to the high cost to acquire well cores along with today's low-oil-pice
scenarios, sizeable challenges are emerging especially for urn:onventional
reservoir characterization. Thus, detailed and integrated outcrop data tied to well
log responses provide means to understand shales on the surface and give
- -of- -
Annual Convention
GALVIS-PORTILLA, Henry', BECERRA-RONDON, Daniela' and SLATI, Roger'
, The University of Oklahoma, School of Geology & Geophysics, Norman, OK. ([email protected])
NATURAL FRACTURES lit MECHANICAL STRATIGRAPHY
•
,
LITHOFACIES, VERTICAL STACKING PATTERNS
&. STRATIGRAPHY
.
Qlurtz-rlch Jithof.cks
(Qlmrtz > 80% )
Massive ~nd hi9r.tv 1nd'Uf~ted
MIcro- to cryptO- oystalline
QUartz aggregates
Very well preserved siliceous
reaystallized tasrnaoit es and
radiolaria (biogenic QUartz)
TOC 1,4 - 2,5 wt%
supporting notions while predictlng reservoir properties into the subsurface.
In this work, fi rst we present a multi-scale approach to characterize the vertical
and lateral heterogeneities of a Woodford Shale Outcrop In southern Oklahoma,
the exposed succession is about 90 feet thick, comprising the Upper member of
the late Devonian-Early Mississippian Woodford Shale and partially the over l~'ing
Sycamore limestone. Detailed rock characterization was conducted, relating direct
observations and/or measurements such as color, texture, lithology, mineral
assemblages, elemental composition, organic richness, as well as geomecharical
proxies such as rock hardness, and abundance and distribution of natural
fractures.
a.y-rlchllthof«Jes
(a.jIS '" 2tI%)
Fissile, flaky. finefy OO1inated
Flattened tasmanites spores
High Zr. n. A!;,nd K
(terrigenous Influence)
Scattered traces of angular
detrital quartz
HighTOC8-15wt%
Secondly, by cross-correlation with nearby well-logs and using statistical analyses
a supervised electro-lithofacies classification was conducted, in which a statistical
model was generated for permitting the prediction and propagation of up-scaled
lithofacies in non-cored wells.
•
•
•
". mr---------,
•t ~
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g
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,I: )0,: " '.
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, of beds ,.per foot "
#
._
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...........
mil
m
Q
g-
_s-< .... _
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Fracture density per 3ft
_ L __
u
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•.•
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Brittle ness tnde~
CiJrborM~
/lthofacks
( CiJrlxm.t5 > SO%)
Massive, oystaliine dolomite
Very fine- to coarse-gralned
The most remarkable outcrop-to-subsurface finding of this study is a laterally
continuous cyclic pattern of two end-member groups of lithofacies: i) clay-rich,
silica-poor, organic-rich, ductile lithofacies, and ii) clay-poor, silica-rich, carbonaterich, brittle, fractured, organic-poor lithofacies. As if they were imitating a C)clic
source-reservoir system, in which some lithofacies acts as oil/gas source and
others as reservoirs or frac-able rocks. Thickness and frequency of these cycles
varies stratigraphically throughout the Woodford Shale, resulting in better gross
intervals for unconyentional resources within the Upper-Middle and U~r
Woodford shale in the Ardmore basin.
subIledral dolomite and
ankerite oystals Ironing
equigranular fabrics
Traces of anhydrite, gypsum
TOC 2.3 - 5 wt%
Radio;>ctlvity
(Gamma- Ray)
Lithology
(Weathering profile )
Blocky Pattern
- O>erty. Oay'poot,
Low radioaClMty.
- Recrystallized fossils
- ~r.tv indurated
and compacted.
MULTI-SCALE ROCK CHARACTERIZATION,
METHODS lit TECHNIQUES
GOING BACK TO THE LATE DEVONIAN
- EARLY MISSISSIPPIAN
OUTCROP TO SUBSURFACE REGIONAL CORRELATIONS
& RESERVOIR CONSIDERATIONS
- Nodular bedding.
OUTOOf'
Pontl'.1 Q/" zoos
fl. kv.
decreases """",arel
- More organics
Thin FI.ke.
HI.5mm
Mud,,,d.
\
;
• More detritus. less
biogenic quartz irIpUI
from radiolaria
""
Upward Pattern
- ChertjShale ratio
irw;reases U"",ard
- Less org!INcs
•••
I •
;
I I
~
\
"
"
TOC I" wtl
•
----
...
Fracture Analys is
Perfect bed·bounded. aU
that span Invertically
~ fromt>ed
I~r:::+j:;::~;r~= fr<>ctures
upper to
--~
.. ..,
specific
lower bed
interfaces. Hooker, 2<113.
Infonnatlon re<;<>rded In
of h3 It.
I. ~ 'Kard' <l< 'Soft' (fis5iI)?
Hul'nbtr ot fractures
FracMe~
Zr(ppm)
AI (p pm)
Co (ppm)
KIpI'm)
~
--
~
~
MI (ppm)
"
' - - -'---
V(ppm)
MD(ppm)
-
~
!
,
-
U(ppm)
-
\
=
.
~
lnterbedding of thick chert beds (11--12 on)
willi very tllin lhale beds «2an)
Moder~te to poot <l<g<'Inic cmtent «3%)
Moderate 10 low fr-actures dtnsity
--...
SlIIIle
9
-.,
.
.........
_ ._
....... - . ... _ """'_"Ol
.....,'",
· "-.U, _ _ _
~
.....
-
shale beds, medium t>ed lIIidmess (4 an)
Very org<Inic rich 5h<IIe be<.h ~nd rn:xIer.rte
rtchness In cherts
H~h density of Nltu'al fradJ res
' _
_
very thin and scattered chell t>eds «2an)
Ex~ leot organic roment (8-15%)
Very low dens<ty of natur~1 fractures
~
G._.G.
.
........
- . . . ",---,-"
,,.,,,.T_.
C1. _
.... ..... _
----,""~
... . , . _ .. 0. _ _ • _ _ ..
~ ".
, "".<L'-",," __
""~_
r - _ ...... _ , _ .. _
~ ----_ , .....
.... n.
diffiwlt to penetrate)
High potential as a hydrocarbon SO.lrCe IMelVal
Good cooned:ivity from tile rod< INtrix
through natural fractures a nd hydnulic
fr<>ctures (good compIetioo q lJality)
High potenti~1 as ~ hydrocarbon SOJrce intelVal
High ductility, Low frackabili ty
Por.>r completion quality
__ c. ... ,... _
.
-......"', '-"'''-''''~ ~"'
--..." ..... _ _ _ _ ..
. .
. . . <i-'-.
. _
na!Ur~1 fractures. low reservoir QU<lity
High brittleness. low completloo Q\.IIlity (too
SlIaie »> Cllert
Thid< 5h<IIe beds (>10em) Interbedded with
REFERENCES
.
...
..
Low potential as a hydrocarbon source InteNal
Por.>r primary porosity ~nd low abufldaoce
Cllert
--__--- ---_
_
-.,.,..,--__
_
- "'--"--"-------'- ------_
....- ---,,----------""-,
,
"
,
,>
--_._"'"""'"-._ -_
--,---- --"""---'-
--, ~", ~
· .-.
..... ,.,,,.
•
~
Homogeneous Interbedding of chert and
S hale beds act iI5 a sou rce for oil / gas,
willie chert beds ptOvide potential
storag.e through naturlll fractures a nd
conr>ectivity to the w e llbore
_ "__
__
... ..-..,,.n
.. ..........
· _ ,LC..,,"" _
" __
"
Cllert »> SlIale
OptImum stratlgrllphlc lIorizons for
shale resoUrce5 consist 0' high
fTeque ncy cycI .... or couplets of SlIIIle
and Clle rt beds e venly bedded.
._. . .
•
,
fl'actu'~
Material (veins)
fl'acMesorientillion ( _ dear)
Tllppm)
r
wlnd~ws
..........
.
"
~
•
-- - ~ ~ ,
Semi-restricted to open marine
Global 5eiI level rise. transgression
Near equatorial latitudes and high
organic productMty
~
f
- Siliceous,
radiol~ria rich
- Higher Si/A! ratios
•
•
Hajor condltlons during
Woodfon:I S hale Deposition
"
wo.
,~.
•
•
--
Middle
.N
and/or days
~
.-
-,-
Sycamo'e
,
Decrliling GB
X- Ray Diffraction
(XRD ) Bulk rock
Mineralogy
NIU( lIllll , ·1'
CADDOflHD
~ ~~~ir-----=~~Ir-----:::7t-~rr------r;(:tj
ardIor d ays
~:S~ .;:1i~"'tJ--
":~t
..jh.n61.5
>5OI'of " mi<;,ons
.,n.ln.
JuDurtU ... ,
:.;~~::~3i;::=::=Ti:~~::::=;~~~:=:=:=~~~===:=::;~~:::=~~~~~:=:==11~~~="":''(O~
J ngysjnqG8
Upw;u d Pattern
- O>ertIShale ratio
~~~
'
J
_ fi" il.
GroInSU.
TXO· uESMrTH
THISWOR.
Sp/ilfmg 51,,,
Scheme for
Uthofacies
dassiflQltlon
.--.
,.,,~
....
" ..,...
~
I
y
ConocoPhillips
SC H OOL OF
GEOLOGY &
GEOPHYSICS
The Univero,ry o f Okbhom.