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Application of chemostratigraphy to the Mungaroo Formation, NW Shelf
K.T. Ratcliffe and A.M. WrightChemostrat Inc, Houston, USA
P. Montgomery, Chevron Energy Technology Company,
Aberdeen, UK
A. Palfrey, A. Vonk, J. Vermeulen and M. Barrett
Chevron Australia Pty Ltd, Perth WA 6000
Paper Outline
What is chemostratigraphy ?
Sample preparation and analysis
Background to study
Mungaroo Formation in the Gorgon Field
Why use chemostratigraphy on the Mungaroo Formation ?
Chemostratigraphic characterisation
Paleoclimate indicators
Provenance indicators
Chemostratigraphic correlation
What this means for stratigraphy in the Mungaroo Formation
What is Chemostratigraphy ?
The characterization, or ‘fingerprinting’ of sedimentary units using inorganic geochemical data
This characterization enables the identification of chemostratigraphic units on the basis of elemental concentrations, ratios or systematic trends
Inorganic geochemistry of sediments is highly variable and sensitive to subtle changes in source composition, facies, weathering or diagenesis. Therefore apparently uniform successions may show primary differences in the chemistry of constituent minerals, particularly in accessory phases
The keys to a successful chemostratigraphic study is to understand the association of elemental chemistry and geology
Why use Chemostratigraphy in the Mungaroo?
The Mungaroo Formation is a typical fluvial system, so tends to be poor in biostratigraphic and palynological markers
Wireline log correlations can be inaccurate since the tendency is to make simple layer-cake correlations and tie sandstones that occur in similar stratigraphic positions and have similar e-log signatures
Seismic correlations do not provide sufficient resolution and can often be ambiguous
Chemostratigraphy offers the potential to refine biostratigraphic and palynological stratigraphies, can remove ambiguity in seismic interpretations and shows that the Mungaroo is not layercake
Gorgon Field
Location and stratigraphy
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
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Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
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Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
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Mun
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North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
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Lith
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atio
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North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
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North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
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base
Tr6
A
Lith
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Mun
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orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
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Lith
stra
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roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tBa
rrow
Gro
upBr
igad
ier
Form
atio
nM
unga
roo
For
mat
ion
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
nian
Lith
stra
tB
arro
w G
rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
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Tr6
Ato
p C
arni
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stra
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wG
roup
Mun
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o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
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r7A
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p T
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Tr6
A
Lith
stra
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roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
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wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ion
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
nian
Lith
stra
tB
arro
w G
rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
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p T
r6A
base
Tr6
Ato
p C
arni
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stra
tB
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wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
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r7A
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p T
r6A
base
Tr6
A
Lith
stra
tB
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wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ion
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
nian
Lith
stra
tB
arro
w G
rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
Ato
p C
arni
an
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ion
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
nian
Lith
stra
tB
arro
w G
rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
Ato
p C
arni
an
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ion
Stratigraphic correlation
3 Time lines7 chemostratigraphic packages
22 geochemical units
How do we get the data ?
1. Surface contaminationRemoved - washing
2. Cuttings chips selected for analysis - picking
3. Sample powdered -grinding
4. Powder “dissolved” –Li metaborate fusion
5. Concentrations for10 major elements23 trace elements
14 Rare earth elements
All reported in xls format
4. Solution analysed-ICP OES and ICP MS
Client BPProject Haynesville
Well Williams-22-3Date 12/11/2009
# Samples Sample ICP-OES ICP-OES ICP-OES ICP-OES ICP-OES ICP-OES ICP-OES ICP-OES ICP-OES ICP-OESwith data Well Name Depth SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O P2O5 Total
wt% wt% wt% wt% wt% wt% wt% wt% wt% wt% wt%1 Williams-22-3 11541.80 42.68 0.51 11.60 3.02 0.021 1.13 16.29 1.21 2.49 0.467 79.412 Williams-22-3 11543.80 46.74 0.58 13.13 4.04 0.035 2.34 12.22 1.09 2.89 0.202 83.273 Williams-22-3 11545.80 37.78 0.45 10.52 3.62 0.029 1.96 18.40 1.08 2.21 0.356 76.414 Williams-22-3 11547.80 53.89 0.66 15.41 4.00 0.019 1.52 7.13 1.11 3.40 0.098 87.245 Williams-22-3 11549.40 44.71 0.57 13.47 3.77 0.024 1.42 13.81 1.24 2.89 0.407 82.316 Williams-22-3 11551.80 45.05 0.61 14.18 3.95 0.022 1.46 12.70 1.20 3.10 0.229 82.527 Williams-22-3 11553.66 45.23 0.54 13.40 3.73 0.022 1.44 13.41 1.23 2.78 0.267 82.068 Williams-22-3 11555.70 46.41 0.57 14.83 4.01 0.022 1.57 12.27 1.00 3.24 0.542 84.479 Williams-22-3 11557.74 49.23 0.60 16.51 4.71 0.020 1.85 9.01 1.08 3.38 0.281 86.6510 Williams-22-3 11559.84 46.88 0.54 13.69 3.91 0.024 1.52 12.69 1.16 2.93 0.159 83.5011 Williams-22-3 11561.82 46.90 0.52 12.16 4.86 0.048 2.29 12.95 1.24 2.46 0.150 83.5812 Williams-22-3 11563.90 52.01 0.58 13.73 3.96 0.024 1.36 9.70 1.32 2.94 0.241 85.8513 Williams-22-3 11565.58 55.07 0.66 15.87 4.00 0.020 1.40 6.75 1.13 3.55 0.202 88.6514 Williams-22-3 11567.84 53.89 0.63 15.32 3.92 0.019 1.40 7.65 1.10 3.41 0.327 87.6715 Williams-22-3 11569.80 55.22 0.62 14.70 4.49 0.018 1.29 6.27 1.34 3.19 0.267 87.4116 Williams-22-3 11571.76 51.48 0.56 13.54 5.18 0.017 1.18 8.62 1.26 2.95 0.241 85.02
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160.00
10.00
20.00
30.00
40.00
50.00
60.00
SiO2 wt%
SiO2 wt%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 160.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
CaO wt%
CaO wt%
Central Gorgon 1
Depth
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
Gamma API
clay
pa
ckag
es
Pac
ka
ge
10
Pac
kage
5P
acka
ge 4
Pac
kage
3P
acka
ge 2
Pac
kage
1
Nb/Al2O3MgO/Al2O3
North Gorgon-1
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
Gamma API
clay
pa
ckag
es
Pac
ka
ge 1
0P
acka
ge 5
Pac
kage
4P
acka
ge 3
Nb/Al2O3MgO/Al2O3
North Gorgon-2
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
Gamma API
clay
pa
ckag
es
Pac
ka
ge
10
Pac
kage
5P
acka
ge 4
Nb/Al2O3MgO/Al2O3
North Gorgon-3
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
Gamma API
clay
pa
ckag
es
Pac
ka
ge 1
0P
acka
ge 8
Pac
kage
7P
acka
ge 6
aP
acka
ge 6
Pac
kage
5
Nb/Al2O3MgO/Al2O3
0.5 1.0 1.5 2.00.00
0.03
0.06
0.09
0.12
0.15
0.5 1.0 1.5 2.00.00
0.03
0.06
0.09
0.12
0.15
0.5 1.0 1.5 2.00.00
0.03
0.06
0.09
0.12
0.15
Gorgon-1 Gorgon-3
North Gorgon-3
Barrow Group
Barrow Group
Barrow Group
Mungaroo Fm Mungaroo Fm
Mungaroo Fm
Brigadier Fm
Brigadier Fm
(absent)
Brigadier Fm
(absent)
BarrowGroupBrigadierFormationMungarooFormation
Mg
O/A
l 2O
3
Nb/Al2O
3
Mg
O/A
l 2O
3
Mg
O/A
l 2O
3
Nb/Al2O
3
Nb/Al
Chemically recognising lithostrat units
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
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Lith
stra
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arro
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rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
Ato
p C
arni
an
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ion
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
nian
Lith
stra
tB
arro
w G
rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
Ato
p C
arni
an
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ion
First order chemostratigraphic divisions
Gorgon-3
Depth
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
Gamma API
cla
yp
acka
ges
Pac
kage
10P
acka
ge4
Pac
kage
3P
acka
ge2
Pac
kage
1
Tim
elin
e
T1
GA_RB0.12 0.21-
AL_BASES5 0.9-
North Gorgon-6
Depth
3500
3600
3700
3800
3900
4000
4100
4200
4300
Gamma API
cla
yp
acka
ges
Pa
ck
ag
e
10
Pac
kage
5P
acka
ge4
Pac
kage
3
Tim
elin
e
T2
T1
GA_RB0.12 0.21-
AL_BASES5 0.9-
North Gorgon-1
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
Gamma API
cla
yp
acka
ges
Pa
ck
ag
e10
Pac
kage
5P
acka
ge4
Pac
kage
3
Tim
elin
e
T2
T1
GA_RB0.12 0.21-
AL_BASES5 0.9-
North Gorgon-2
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
Gamma API
cla
yp
acka
ges
Pa
ck
ag
e
10
Pac
kage
5P
acka
ge4
Tim
elin
e
T2
GA_RB0.12 0.21-
AL_BASES5 0.9-
North Gorgon-3
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
Gamma API
cla
yp
acka
ges
Pac
kage
10P
acka
ge8
Pac
kage
7P
acka
ge6a
Pac
kage
6P
acka
ge5
Tim
elin
e
T3
GA_RB0.12 0.2-
AL_BASES5 0.9-
Ga/Rb increases through time
Al2O3/bases (CaO+MgO+K2O+Na2O) increases through time
Notable steps that define the solid lines
SO WHAT ????
First order chemostratigraphic divisions
Ga/Rb = kaolinite / illite in claystones – intensely weathered claystones tend to be more kaolinitic
Al/bases = CIA (chemical index of alteration) which is a proxy for the degree of weathering
Gorgon-3
Depth
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
Gamma API
cla
yp
acka
ges
Pac
kage
10P
acka
ge4
Pac
kage
3P
acka
ge2
Pac
kage
1
Tim
elin
e
T1
GA_RB0.12 0.21-
AL_BASES5 0.9-
North Gorgon-6
Depth
3500
3600
3700
3800
3900
4000
4100
4200
4300
Gamma API
cla
yp
acka
ges
Pa
ck
ag
e
10
Pac
kage
5P
acka
ge4
Pac
kage
3
Tim
elin
e
T2
T1
GA_RB0.12 0.21-
AL_BASES5 0.9-
North Gorgon-1
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
Gamma API
cla
yp
acka
ges
Pa
ck
ag
e10
Pac
kage
5P
acka
ge4
Pac
kage
3
Tim
elin
e
T2
T1
GA_RB0.12 0.21-
AL_BASES5 0.9-
North Gorgon-2
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
Gamma API
cla
yp
acka
ges
Pa
ck
ag
e
10
Pac
kage
5P
acka
ge4
Tim
elin
e
T2
GA_RB0.12 0.21-
AL_BASES5 0.9-
North Gorgon-3
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
Gamma API
cla
yp
acka
ges
Pac
kage
10P
acka
ge8
Pac
kage
7P
acka
ge6a
Pac
kage
6P
acka
ge5
Tim
elin
e
T3
GA_RB0.12 0.2-
AL_BASES5 0.9-
Therefore blue = less intense weathering, red = more intense hydrolytic weathering
First order chemostratigraphic divisions
Chemostratigraphic packages
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
nian
Lith
stra
tB
arro
w G
rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
Ato
p C
arni
an
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ion
Packa
ge 2
Package 1
Central Gorgon 1
Depth
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
Gamma API
clay
pac
kage
sP
ac
ka
ge
10
Pac
kage
5P
acka
ge 4
Pac
kage
3P
acka
ge 2
Pac
kage
1
Nb/Al2O3 Cr/Na2O Na2O/Al2O3MgO/Al2O3
North Gorgon-1
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
Gamma API
clay
pac
kage
sP
ac
ka
ge
10
Pac
kage
5P
acka
ge 4
Pac
kage
3
Nb/Al2O3 Cr/Na2O Na2O/Al2O3MgO/Al2O3
North Gorgon-2
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
Gamma API
clay
pac
kage
sP
ac
ka
ge
10
Pac
kage
5P
acka
ge 4
Nb/Al2O3 Cr/Na2O Na2O/Al2O3MgO/Al2O3
North Gorgon-3
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
Gamma API
clay
pac
kage
sP
ac
ka
ge
10
Pac
kage
8P
acka
ge 7
Pac
kage
6a
Pac
kage
6P
acka
ge 5
Nb/Al2O3 Cr/Na2O Na2O/Al2O3MgO/Al2O3
Packages defined using variations in Nb, Cr and Na
SO WHAT ????
Chemostratigraphic packages
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
-0.2 -0.1 0 0.1 0.2
Al
Si
Ti
FeMn
Mg
Ca
NaK
P
Ba
Be
Cr
Ni
Sc
Sr
Zn
Zr
V
Co
CuGa
Rb
Y
Nb
Mo
Sn
Cs
HfTa Th
U
LREEs
MREEs
HREEs
EV1
EV
2
Group 1. Quartz
Group 2. ClayMinerals
Group 3. HeavyMinerals
Illite
Kaolinite
Non Zircon
Zircon
Group 4. Siderite
Group 5. PlagioclaseFeldspar
Chemostratigraphic packages
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
nian
Lith
stra
tB
arro
w G
rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
Ato
p C
arni
an
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ionCentral Gorgon 1
Depth
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
Gamma API
clay
pack
ages
Pa
cka
ge
10
Pac
kage
5P
acka
ge4
Pac
kage
3P
acka
ge2
Pac
kage
1
Nb/Al2O3 Cr/Na2O Na2O/Al2O3Ga/Rb
Al2O3/bases
North Gorgon-1
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
Gamma API
clay
pack
ages
Pa
ck
ag
e10
Pac
kage
5P
acka
ge4
Pac
kage
3
Nb/Al2O3 Cr/Na2O Na2O/Al2O3Ga/Rb
Al2O3/bases
North Gorgon-2
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
Gamma API
clay
pack
ages
Pa
ck
ag
e1
0P
acka
ge5
Pac
kage
4
Nb/Al2O3 Cr/Na2O Na2O/Al2O3Ga/Rb
Al2O3/bases
North Gorgon-3
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
Gamma API
clay
pack
ages
Pa
ck
ag
e10
Pac
kage
8P
acka
ge7
Pac
kage
6aP
acka
ge6
Pac
kage
5
Nb/Al2O3 Cr/Na2O Na2O/Al2O3Ga/Rb
Al2O3/bases
Ga/Rb : Al/bases – change in paleoclimate through time
Na/Al, Cr/Na and Nb/Al in provenance through time
Chemostratigraphic packages
Central Gorgon 1
Depth
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
Gamma API
clay
packa
ges
Pac
ka
ge
10
Pac
kage
5P
acka
ge4
Pac
kage
3P
acka
ge2
Pac
kage
1
Na/Al2O3K2O/Al2O3
Rb/CsGa/Rb
Al2O3/bases
North Gorgon-1
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
Gamma API
clay
packa
ges
Pac
ka
ge
10P
acka
ge5
Pac
kage
4P
acka
ge3
Na/Al2O3K2O/Al2O3
Rb/CsGa/Rb
Al2O3/bases
North Gorgon-2
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
Gamma API
clay
packa
ges
Pac
ka
ge
10
Pac
kage
5P
acka
ge4
Na/Al2O3K2O/Al2O3
Rb/CsGa/Rb
Al2O3/bases
North Gorgon-3
Depth
3400
3500
3600
3700
3800
3900
4000
4100
4200
Gamma API
clay
packa
ges
Pac
ka
ge
10P
acka
ge8
Pac
kage
7P
acka
ge6a
Pac
kage
6P
acka
ge5
Na/Al2O3K2O/Al2O3
Rb/CsGa/Rb
Al2O3/bases
Sandstone data
Gorgon-1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.ba
se T
R6A
top
Car
nian
Lith
stra
tB
arro
w G
rou
pM
unga
roo
For
mat
ion
Gorgon-3
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
Central Gorgon 1
Depth(m)
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
4600
GammaAPI
Pal
ynol
.ba
se T
r6A
top
Car
nian
Lith
stra
tB
arro
w G
roup
Mun
garo
o F
orm
atio
n
North Gorgon-6
Depth(m)
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.ba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-1
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
4500
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
Ato
p C
arni
an
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-2
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
4400
GammaAPI
Pal
ynol
.to
p T
r7Ai
icba
se T
r7A
iiito
p T
r6A
base
Tr6
A
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-4
Depth(m)
3500
3600
3700
3800
3900
4000
4100
GammaAPI
Pal
ynol
.T
r8D
iiiT
r7A
iia
Lith
stra
tB
arro
wG
roup
Mun
garo
o F
orm
atio
n
North Gorgon-3
Depth(m)
3400
3500
3600
3700
3800
3900
4000
4100
4200
4300
GammaAPI
Pal
ynol
.T
r8C
iiiT
r8D
iT
r8D
iii
Lith
stra
tB
arro
wG
roup
Brig
adie
rF
orm
atio
nM
unga
roo
For
mat
ion
Sandstone correlation
Gorgon-1
Depth
3800
3900
4000
4100
4200
4300
4400
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
Pac
kage
2P
acka
ge1
san
du
nits
S a n d 4 e
S a n d 4 b
Sand3a
San
d2
Lith
stra
t
Top z 20
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
Gorgon-3
Depth
3900
4000
4100
4200
4300
4400
4500
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
Pac
kage
2P
acka
ge1
san
du
nits
Sand3a
San
d2
San
d1
Lith
stra
t
Top z 20
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
Central Gorgon 1
Depth
4100
4200
4300
4400
4500
4600
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
Pac
kage
2P
acka
ge1
san
du
nits
S a n d 4 b
S a n d 4 a
Sand3a
San
d2
Lith
stra
t
Top z 20
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
North Gorgon-6
Depth
4000
4100
4200
4300
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
san
du
nits
Sand4b
Sand4a
San
d3a
ii
Sand3a
Lith
stra
t
Top z 20
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
North Gorgon-1
Depth
4100
4200
4300
4400
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
san
du
nits
Sand4b
Sand4a
Sand3aii
San
d3a
iS
and
3a
Lith
stra
t
Top z 20
Q sand
R sand
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
T1Marker
Topzone 20
Top T sand
Top Q sand
Gorgon-1
Depth
3800
3900
4000
4100
4200
4300
4400
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
Pac
kage
2P
acka
ge1
san
du
nits
S a n d 4 e
S a n d 4 b
Sand3a
San
d2
Lith
stra
t
Top z 20
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
Gorgon-3
Depth
3900
4000
4100
4200
4300
4400
4500
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
Pac
kage
2P
acka
ge1
san
du
nits
Sand3a
San
d2
San
d1
Lith
stra
t
Top z 20
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
Central Gorgon 1
Depth
4100
4200
4300
4400
4500
4600
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
Pac
kage
2P
acka
ge1
san
du
nits
S a n d 4 b
S a n d 4 a
Sand3a
San
d2
Lith
stra
t
Top z 20
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
North Gorgon-6
Depth
4000
4100
4200
4300
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
san
du
nits
Sand4b
Sand4a
San
d3a
ii
Sand3a
Lith
stra
t
Top z 20
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
North Gorgon-1
Depth
4100
4200
4300
4400
Gamma API
clay
pack
ages
Pac
kage
4P
acka
ge3
san
du
nits
Sand4b
Sand4a
Sand3aii
San
d3a
iS
and
3a
Lith
stra
t
Top z 20
Q sand
R sand
S Sand
Top z 10
T Sand
Tsu
rfa
ce
T1
T1Marker
Topzone 20
Top T sand
Top Q sand
Each lithostratigraphic unit has a unique geochemical signature The Mungaroo Formation contains three chemostratigraphic surfaces that approximate to chronostratigraphic markers Seven chemostratigraphic packages and 22 units are identified and correlated in the Mungaroo Formation The paleoclimate during deposition of the Mungaroo Formation was becoming increasingly wet, resulting in more intense hydrolytic weathering and increased abundance of kaolinite in the claystone lithologies The older parts of the Mungaroo Formation contain common plagioclase feldspar, implying an intermediate igneous provenance. The intermediate provenance was replaced through time with greater influence of a mafic igneous provenance The Brigadier Formation contains an unknown Nb-rich heavy mineral species, implying that the provenance of this formation is different to that of the Mungaroo Formation
In places, the chemostratigraphic sand unit correlation deviates from the lithostratigraphic sand correlation to an extent that may impact upon gas production. The variation between litho- and chemostratigraphic correlation are potentially vitally important for building reservoir models in the Mungaroo Formation of the Gorgon Field.
ACKNOWLEDGEMENTS Chemostrat would like to thank David Wray and Lorna Dyer of Greenwich University for carrying out
the ICP OES MS analyses and Bill Ellington of Ellington and Associates for carrying out the XRD analyses. We are also grateful to Chemostrat and Chevron Australia for allowing us time and resources
to prepare this manuscript. The authors are grateful to Eric Tenthorey, Andrew Jones and Ben Van Aarssen who reviewed the original manuscript and whose comments were invaluable to the final
document. The authors would like to thank the Gorgon Joint Venture partners, Mobil Australia Resources and Shell Development (Australia) for allowing permission for this paper to be published.
