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 !