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UNIQUE MINERALOGY OF OIL UNIQUE MINERALOGY OF OIL SHALE FROM THE PICEANCE SHALE FROM THE PICEANCE
BASIN, COLORADOBASIN, COLORADO
27th Oil Shale Symposium Golden, Colorado
Marcus Wigand (Presenter)Steve Chipera
Giday WoldegabrielJ. William CareyJohn Kaszuba
Doug McCarthy
IntroductionIntroduction
• Recent events have once again made oil shale an attractive potential resource.
• One of the largest deposits, estimated at well over 700 billion barrels, is situated in the western United States in the Piceance Basin of western Colorado.
• The distinct mineralogy of these rocks represents their unique conditions of deposition and subsequent diagenetic alteration.
• Work is again being conducted to determine if oil can be extracted in an economic and environmentally friendly fashion (requires in-situ methods).
Oil Shale Sample CollectionOil Shale Sample CollectionFresh and weathered oil shale samples were collected from the Mahogany Zone and the R-8 zone.
Oil Shale Samples Oil Shale Samples
• Analyzed various Piceance Basin outcrop samples using XRD, SEM and TGA-MS.
• Samples analyzed consist of kerogen-rich materials that are representative of the Mahogany zone of the Green River Formation.
Piceance Basin Oil Shale Mineralogy Piceance Basin Oil Shale Mineralogy • Clays
• Smectite (Expandable Clay) 0 – 25 wt%• Illite / Mica (Non-Expandable) 0 – 20 wt%
• Carbonates• Calcite - CaCO3 0 – 15 wt%• Siderite - FeCO3 0 – 3 wt%• Dolomite / Ankerite – Ca(Fe,Mg)(CO3)2 0 – 45 wt%
• Analcime (Na-Zeolite) 0 – 20 wt%
• Dawsonite - NaAl(CO3)(OH)2 0 – 20 wt%
• Kerogen (amorphous) 0 – 45 wt%
• Pyrite - FeS2 0 – 3 wt%
• Gypsum - CaSO4 • 2H2O 0 – 1 wt%
• Quartz, Feldspar, and other detritus
Interesting Minerals & Interesting Minerals & SodicSodic ConditionsConditions• Buddingtonite, (analogous to an
ammonium version of K-feldspar) is also present and indicates an authigenic origin forming simultaneously with the maturation of the organic materials.
• Dawsonite [NaAl(CO3)(OH)2], is unusual, as it is extremely rare in nature but very abundant in the Piceance Basin.
• Analcime observed in significant quantities in these samples, (especially as nodules and clasts that appear along bedding).
• Nahcolite (NaHCO3), forms economic deposits deeper in the basin.
MordeniteAnalc
ime
Thom-sonite
Chab-azite
Phillip-site
Yuga-waralite
-5 -4 -3 -2-6 -10
-8
-6
-4
-2
0
2
4
6
8
10
Log a(
Na
)+
Log a(SiO )2
Erionite
Natrolite
Scolecite
(From Chipera and Apps, 2001)
35 Co
Qua
rtz
Satu
ratio
n
Expandable Clay in Oil ShaleExpandable Clay in Oil ShaleSample A03Sample A03
• Determine the orientation of clay in the rock.
• Determine expansion of the clay as a solid in the rock.
• Analyzed solid chunk of outcrop sample A03.• 24% Smectite, 20% Illite, 1% Kaolinite
• 20% Kerogen, 20% quartz, 10% Dolomite
• Plus Analcime, Dawsonite, Feldspar, Pyrite, Gypsum
Sample A03 Sample A03
0 water layer 1 water layer 2 water layers
Interlayer CationWater Molecule
SmectiteSmectite Structural States Structural States
A03 Expansion with RH A03 Expansion with RH
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100Hours into Run
%R
H%RHTemperature
Expandable Clay in Sample A03Expandable Clay in Sample A03
• Distinct orientation / foliation of the clay particles• Will produce preferential parting planes
• Fluid and gas flow expected to be facilitated along bedding planes (between layers of cards rather then through them).
• Readily expands/contracts with varying Water Vapor Pressure
• Went from ~11.5 to ~14.5 angstroms.
• Wet – dry cycles may be able to facilitate creation of pathways.
Outcrop Sample (Stop 3)Outcrop Sample (Stop 3)
Nodule
Red Spot
Slice 11 Top
Coating
Slice 01Slice 02
Slice 03Slice 04
Slice 05
Slice 06Slice 07
Slice 08Slice 09
Slice 10Slice 11
Slice 12Slice 13
Outcrop Sample (Stop 3): Sample PreparationOutcrop Sample (Stop 3): Sample Preparation
0 5 10 15 20 25 30 35 40
Analcime
Quartz
K-Feldspar
Plagioclase
Calcite
Ankerite/Dolomite
Mica/Illite
Pyrite
Siderite
Kerogen
Weight Percent
Mineralogy Normalized to nonMineralogy Normalized to non--Kerogen BasisKerogen Basis
0
10
20
30
40
50
60
5 10 15 20 25 30 35 40 45 50Wt. % Kerogen in Sample
AnalcimeQtz-FeldsparCarbonateMica/IllitePyrite
Inorganic RockInorganic Rock--forming Minerals vs. Kerogenforming Minerals vs. Kerogen
0
0.5
1
1.5
2
2.5
3
3.5
4
0 5 10 15 20 25 30 35 40Kerogen Content
Pyrit
e C
onte
nt
A-seriesB-seriesGrabField Trip
Pyrite vs. KerogenPyrite vs. Kerogen
PK
Outcrop Sample (Stop 3)Outcrop Sample (Stop 3)
Nodule
Altered Exterior
Disturbed ZoneMainly:Analcime & Albite
Mainly:Analcime & Albite
Mainly:Ankerite/Dolomite
Ana
lcim
e
Qua
rtz
K-F
elds
par
Plag
iocl
ase
Ker
ogen
Cal
cite
Ank
erite
/D
olom
ite
Mic
a/Ill
ite
Pyrit
e
0
10
20
30
40
50 ShaleExterior Coating
Coating
Slice 4 Slice 4 –– Shale vs. Exterior AlterationShale vs. Exterior Alteration
Alteration ProcessesAlteration Processes
Summary of ResultsSummary of Results
• Mineralogy and kerogen content highly variable between layers.
• No strong trends in kerogen to mineral content.
• Weathered and intrusive zones are:
• Poor in Kerogen content
• Enriched in albite and analcime
• Devoid of pyrite
• Intrusive Zones = reduced carbonate content
• Weathered Exterior = Increased Ankerite content
AcknowledgementsAcknowledgements
Special Thanks to:
Robert LestzMark LooneyKirk HollisMelissa Fittipaldo
Research is funded by Chevron Energy Technology Company
Thank you very much for your attention !