The Shale Spectrum: Interdisciplinary understanding across oil shale, oil-bearing

shale and gas shale plays

Jeremy Boak, J. Frederick Sarg, Steven Sonnenberg

Center for Applied Petroleum Systems Analysis & Research

Department of Geology & Geological Engineering

Colorado School of Mines

The Center for Oil Shale Technology & Research& The Colorado School of Mines

31st Oil Shale Symposium October 17-21, 2011 at the Cecil H. & Ida Green Center, Colorado School of Mines, Golden, Colorado

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Shale and Mudstone Plays

• Steady demand and new technology drive interest in turning source rock formations into reservoirs

• Mudstone or shale, organic richness is key

• Seeking hydrocarbons that have not migrated far from their sources

• Is there oil that is not kerogen oil?

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Petroleum Systems Perspective

Source - USGS, Petroleum Systems and Geologic Assessment of Oil and Gas in the

Uinta-Piceance Province , Utah and Colorado

Gas shale & Shale gas

Oil-bearing shale & shale-hosted oil

Oil shale & shale oil

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Bakken – Green River Comparison

0

500

1000

1500

2000

2500

3000

3500

0 10 20 30 40TOC (wt %)

Green River

Bakken

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Technical Complexity; Geologic Diversity

• Development of oil shale requires artificial heating of immature kerogen, at surface or in situ

• Development of oil-bearing shale and gas shale depends upon more traditional methods

– applied in much more complex ways

– to kerogen that ranges from incipiently mature to overmature

• What can oil shale development add to the conversation?

• Rocks containing these hydrocarbons span same range of compositions and share rock textures and features

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Shale and Mudstone Mineralogy

Carbonate

Quartz +

FeldsparClay Minerals

Average Shale (1975)

Bakken

Barnett

U. Green River

L. Green River

Chinese Oil Shale

Thailand Oil Shale

Polish Gas Shale

Duvernay

Muskwa

Besa R. Lower black shale

Besa R. Upper black shale

Fort Simpson

Q+F=Clay

Carbonate/Clastic

calcareous/ dolomitic mudstone

argillaceous mudstone

siliceousmudstone

argillaceous marlstone siliceous

marlstone

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What Can Oil Shale Add?

• Physical properties of rocks across range of organic richness and mineralogic variety

• Understanding of kinetics of oil generation

• Understanding of geologic environments of organic-rich sediment

– Variation of organic matter type

– Variation of mineralogy

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Physical Properties of Shale Systems

• All are very tight, impermeable mudstone and siltstone

• Production of hydrocarbons, natural or synthetic, depends on fracturing rock to drain the products

• Properties measured across temperature and pressure range needed

– to describe mechanisms of generation, migration and trapping of oil and gas

– to understand fracturing behaviour for field development

• Understanding properties of broad class of rocks informally called shale can be complementary

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Shale Properties Depend on Organic Richness

0

10

20

30

40

50

0 5 10 15 20 25 30

GPa

Oil Yield (wt %)

Young's Modulus

Bulk Modulus

Shear Modulus

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Fracture Properties Determine Producibility

Chart from Core Labs

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Pressure Gradient Map of Altamont-Bluebell Field

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Kinetics of Oil Generation

• Understanding kinetics of generation requires experiments at temperatures in the range of in situ retorts

• These experiments are important to understanding both synthetic and natural systems

• Can these models constrain models for generation in natural systems?

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Experimental Range for Pyrolysis

• Slow heating

– Changes relative reaction rates

– Affects volatilization of fragments

• Wide range of rates

– From ICP

– To surface retorting (e.g. Fischer Assay)

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Heating Rate (oC/d)

Oil A

PI

Oil API Decrease with Heating Rate

0.1 1 10 100 1,000 10k 100k

40

35

30

25

20

Oil API Gravity

Green River

Fischer Assay

ICP

1 year

5 days

1 day

1 hour

??

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Diversity of Oil Shale Kinetic Models

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0

25,000

50,000

75,000

100,000

125,000

Scheme 1 Scheme 2 Scheme 3

BO

E

Gas

Light Oil

Heavy Oil

Scheme 1

Produced

Unproduced

Unreacted

Residue

Scheme 2

ProducedUnproducedUnreactedResidue

Scheme 3

Produced

Unproduced

Unreacted

Residue

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Understanding Environments of Formation

• Behavior depends on organic content

• Also on mineralogic composition and variability

• Properties result in turn from

– Sedimentary history

– Depositional environments under which they formed

– Diagenetic alteration following deposition

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Fischer Assay Oil Gravity

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0.86

0.87

0.88

0.89

0.90

0.91

0.92

0.93

0.94

0.95

R8

A G

roo

ve

Mah

oga

ny

B G

roo

ve R6 L5 R5 L4 R4 L3 R3 L2 R2 L1 R1 L0 R0

Spe

cifi

c G

ravi

ty

Unit

John Savage 24

Colorado 1

Corehole CR-2

Corehole CR-1

Shell 23-X2

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CR-2 Mineralogy (Dean, Howell, Pitman, 1981)

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Top R5

Top R2

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USBM 01A Well:Salinity, Redox, Oil & Mineral Properties

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CAPSAR Research Consortia

• We have developed three separate research consortia on shale systems

– Green River Formation oil shale

– Bakken shale-hosted oil play

– Niobrara mudstone oil play

• Common ground for each of these consortia include:

– characterization of sedimentologic and petrologic features to create an integrated geologic framework

– measurement of critical properties relating to seismic characterization, rock strength and fracturing behavior

– modeling of rock mechanical behaviour under stress

• Understanding shale systems generically can provide synergistic insights across plays

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Conclusions

• Integrated analysis pays general benefits

– Even of unusual basins like the Green River Formation basins

– Connections between lacustrine and marine?

– Some oil shale basins of ambiguous origin

• Stratigraphic, mineralogic, chemical characterization supports engineering property determination

• Kinetic models have yet to capture behavior across T and time scales

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Shale Play Terminology

Source - USGS, Petroleum Systems and Geologic Assessment of Oil and Gas in the Uinta-Piceance Province , Utah and Colorado

Gas shale & Shale gas

Oil-bearing shale & Shale-hosted oil

Oil shale & shale oil

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Shale and Mudstone Mineralogy

Carbonate

Quartz + FeldsparClay Minerals

Average Shale (1975)

Bakken

Barnett

U. Green River

L. Green River

Chinese Oil Shale

Thailand Oil Shale

Polish Gas Shale

Duvernay

Muskwa

Besa R. Lower black shale

Besa R. Upper black shale

Fort Simpson

Q+F=Clay

Carbonate/Clastic

calcareous/ dolomitic mudstone

argillaceous mudstone

siliceousmudstone

argillaceous marlstone

siliceous marlstone

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