Reservoir Quality and Petrophysical Model of the Tarn Deep-Water … · 2017. 5. 18. · Model of...
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Reservoir Quality and Petrophysical Model of the Tarn Deep-Water Slope-Apron System, North Slope, Alaska
Pacific Section AAPGMay 8, 2006
Alaska Department ofNaturalResources
Kenneth P. Helmold, Alaska Division of Oil & GasWayne J. Campaign, ConocoPhillips Alaska, Inc.William R. Morris, ConocoPhillips Co.Douglas S. Hastings, Brooks Range Petro. Corp.Steven R. Moothart, ConocoPhillips Alaska, Inc.
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Outline
• Regional setting• Petrology of sandstones• Facies and reservoir quality• Regional reservoir quality model• Petrophysical model• Conclusions
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Conclusions• Reservoir quality is initially controlled by
textural parameters related to turbidite elements• Channels are the best reservoirs followed by
lobes, crevasse splays and levees• Mechanical compaction exerts a strong regional
control on reservoir quality• Reservoir quality of Brookian sandstones can
be accurately predicted prior to drilling • Petrophysical model is complicated by
abundance of structural clay and low-density zeolite
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Location of Tarn Field
N
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Stratigraphic Column of North Alaska
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Tarn Slope-Apron Deposits
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• Located at toe-of-slope
• Fed by slope gullies
• Fairly small features
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Outline
• Regional setting• Petrology of sandstones• Facies and reservoir quality• Regional reservoir quality model• Petrophysical model• Conclusions
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Brookian Sandstone CompositionTotal Quartz
Feldspar Lithic Grains
(including chert)
Sedimentary Grains
Volcanic Grains Metamorphic Grains
(including chert)
Paleocene Cenomanian Albian
Cenomanian sands are lithic rich with abundant volcanic rock fragments
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Typical Brookian Sandstones
Albian (Torok)Argillaceous rich RFGenerally lack cement
Paleocene (Flaxman)Chert richMedium-grain sand
Cenomanian (Tarn)Volcanic glass richAnalcime cement
100 µm
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Brookian Sandstone Phi-K Trends
0.001
0.01
0.1
1
10
100
1000
0 5 10 15 20 25 30Porosity (%)
Perm
eabi
lity
(md)
PaleoceneCenomanianAlbian
1 md K cutoff = Phi of 12% Paleocene, 15% Albian, 17% Cenomanian
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Analcime and Microcrystalline Rims
100 μm
100 μm
Silica-rich glass = NaAlSi2O6 • H2O + SiO2Analcime Quartz
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5
10
15
20
25
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2.40 2.50 2.60 2.70 2.80 2.90Grain Density (g/cc)
Ana
lcim
e (b
ulk
%)
ChannelLobesCrev SplayLeveeAban ChanBasin Plain
r = - 0.68
10 μm100 μm
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Outline
• Regional setting• Petrology of sandstones• Facies and reservoir quality• Regional reservoir quality model• Petrophysical model• Conclusions
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Channel Facies
Sedimentary Facies: Amalgamated Ta, some Tb, Tabc, Tc (climbing at margins)
Bed Thickness: Thin to very thickGrain Size: Very fine to fine-grain sandAvg. Porosity: 20 %Avg. Permeability: 33 mdAvg. H2O saturation: 46 %Avg. Dispersed clay: 4 %
Cha
nnel
Leve
e
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Lobe Facies
Sedimentary Facies: Tace, Tabe, Tabce, Tbce, occasional Tae, Tbe
Bed Thickness: Thin to very thick,rare very thin
Grain Size: Very fine- to fine-grain sand, rare mud
Avg. Porosity: 18 %Avg. Permeability: 7 mdAvg. H2O saturation: 61 %Avg. Dispersed clay: 8 %
Lobe
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Crevasse SplayFacies
Sedimentary Facies: Tce (climbing), Tb, Tabe, Tace, rare Tbe, Tbce
Bed Thickness: Very thin to thickGrain Size: Very fine- to lower fine-grain
sand, mud and siltAvg. Porosity: 17 %Avg. Permeability: 3 mdAvg. H2O saturation: 64 %Avg. Dispersed clay: 13 %
Spla
yLe
vee
Leve
e
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Levee Facies
Sedimentary Facies: Tce, TcBed Thickness: Very thin, rare thinGrain Size: Very fine-grain sand,
mud and siltAvg. Porosity: 16 %Avg. Permeability: 2 mdAvg. H2O saturation: 68 %Avg. Dispersed clay: 22 %
Leve
e
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Depositional Control on Reservoir Quality
Best reservoirs in channels; poorest in levees and basin plain
0.01
0.1
1
10
100
1000
10 15 20 25 30Porosity (%)
Perm
eabi
lity
(md)
ChannelLobeCrev SplayLeveeBasin Plain
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Effect of Grain Size on Phi-K
0.01
0.1
1
10
100
1000
0.00 0.05 0.10 0.15 0.20 0.25 0.30Framework Grain Size (mm)
Perm
eabi
lity
(md)
r = 0.63
ChannelLobeCrev SplayLeveeBasin Plain
5
10
15
20
25
30
0.05 0.10 0.15 0.20 0.25 0.30Framework Grain Size (mm)
Poro
sity
(%)
r = 0.61
Facies control on grain size is largely responsible for reservoir quality variability
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Outline
• Regional setting• Petrology of sandstones• Facies and reservoir quality• Regional reservoir quality model• Petrophysical model• Conclusions
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Brookian Erosion Map80 Miles
Tarn Field
Erosion estimates derived from sonic compaction curves
mapped by Matt Burns,from Rowan et. al., 2003;USGS Open-File Report 03-329
Maximum Burial Depth (Dmax) = Present Depth (ft) + Brookian Erosion (ft)
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0.001
0.01
0.1
1
10
100
1000
2000 4000 6000 8000 10000 12000 14000 16000
Dmax (feet)
Perm
eabi
lity
(md)
0
5
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15
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25
30
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40
2000 4000 6000 8000 10000 12000 14000 16000
Dmax (feet)
Poro
sity
(%)
Brookian Phi-K vs. Dmax
Cenomanian
Albian
Model regression
Increasing Burial Depth
Incr
easi
ng G
rain
Siz
e
Increasing Burial Depth
• Locally, reservoir quality is controlled by grain texture related to turbidite elements
• Regionally, reservoir quality is controlled by compaction
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Albian Prospects Cenomanian Prospects
Brookian Reservoir Quality Model
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5
10
15
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0 5 10 15 20 25Predicted Porosity (%)
Mea
sure
d Po
rosi
ty (%
)
0.01
0.1
1
10
100
0.01 0.1 1 10 100Predicted Permeability (md)
Mea
sure
d Pe
rmea
bilit
y (m
d)
Incr
easi
ng B
uria
l Dep
th
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Compaction of Brookian Reservoirs
> 9000’ Dmaxø = 11 %k = 0.1 md
7000-9000’ Dmaxø = 15 %k = 3 md
< 7000’ Dmaxø = 18 %k = 12 md
100 µm
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Outline
• Regional setting• Petrology of sandstones• Facies and reservoir quality• Regional reservoir quality model• Petrophysical model• Conclusions
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Petrophysics: Overview of the Problem
• GR log does not distinguish sand
• RT and RHOB logs do show sand character
• Problem results from presence of analcime and structural clay
• Standard shaly-sand log model is not appropriate
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Effect of Clay on Log Model• Reservoir contains 30-50% argillaceous rock fragments• Lithics are older and more compacted than surrounding shales
• Lithics are “pinpoints” of conductivity that are not connected• Structural clay has little impact on reservoir quality
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Effect of Analcime on Log Model
• Grain densities vary over a wide range from 2.52 – 2.78• A single lithology model would yield poor results• Solve for Φ and grain density allowing for mineralogical variation• Model must use more than one porosity tool
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Resistivity – Mineral Effect Cross PlotEx
cess
Neut
ron
Mine
ralE
ffect
1 10
0.0
3.0
6.0
9.0
12.0
15.0
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24.0
27.0
30.0
RT (OHMM)0 1
Color: XRD.CALCITE_XRD
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RT / XRD.HI_MINRL Crossplot6 Wells
• Neutron correction is developed from the resistivity log• Calculate phi and grain density from standard Neutron/Density cross plot
• Calculate mineral effect on Neutron log from mineral abundances (TS & XRD) and Log Parameter Table• Plot mineral effect against raw logs to determine “best fit”• Deep resistivity has best correlation
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CoreG/C32.4 2.9
Log ModelG/C32.4 2.9
5200
5250
5300
SSTVD
FEETCore Porosity
PCT50 0
Log PorosityV/V0.5 0
Log Sw1 0
Core SwPCT100 0
Grain Density
Model ResultsWell Legend: Well A Well B Well C Well D Well E Well F
0.0
3.0
6.0
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0.000
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0.120
0.150
0.180
0.210
0.240
0.270
0.300
TARN
.PHI
TX
CORE.PHI (PCT)
1 111
1 11 1
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1111
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111 1
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11111 1
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1 11 11
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111
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1111 111 11
111
1111 1111
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1111
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1111
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666666 666666
66 666666666
540540
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• Results are for multiple wells• No log normalization or individual customization
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Conclusions• Reservoir quality is initially controlled by
textural parameters related to turbidite elements• Channels are the best reservoirs followed by
lobes, crevasse splays and levees• Mechanical compaction exerts a strong regional
control on reservoir quality• Reservoir quality of Brookian sandstones can
be accurately predicted prior to drilling • Petrophysical model is complicated by
abundance of structural clay and low-density zeolite
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The End
Reservoir Quality and Petrophysical Model of the Tarn Deep-Water Slope-Apron System, North Slope, AlaskaOutlineConclusionsSlide Number 4Slide Number 5Slide Number 6OutlineBrookian Sandstone CompositionTypical Brookian SandstonesBrookian Sandstone Phi-K TrendsSlide Number 11OutlineSlide Number 13Slide Number 14Slide Number 15Slide Number 16Depositional Control on Reservoir QualitySlide Number 18OutlineBrookian Erosion MapBrookian Phi-K vs. DmaxSlide Number 22Compaction of Brookian ReservoirsOutlineSlide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29ConclusionsSlide Number 31