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Dielectric Properties of Oil Shale

Lawrence Livermore National Laboratory

26th Oil Shale Symposium, Golden CO, October 16-18, 2006

Jeffery Roberts. Jerry Sweeney. Philip Harben. Steve Carlson

UCRL-ABS-222487

This work was performed under the auspices of the U.S. Department of Energy by the University ofCalifornia, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.


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Acknowledgements

Anadarko Petroleum Corporation for Wyoming samples

Bureau of Land Management for Anvil Points samples

Paul Daggett


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Can RF energy be effectively util ized for in-situ

heating of oil shales?

Is there a dielectric loss mechanism in the kerogen between 1 MHz and

1 GHz?

Can RF energy significantly penetrate and be deposited within the oilshales?

What is the effect of fluids (and ions) on the dielectric properties of the

oil shales?

What is the effect of temperature on the dielectric properties of the oil

shales?

- measured complex dielectric constant on two sample suites from 1 MHz - 1.8 GHz

- measured complex dielectric constant at various water and brine saturations

- measured complex dielectric constant on dry samples up to ~ 150C


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Measurements Were Conducted Using an HP4291A

Impedance/Material Analyzer and High Temperature

Probe

Anadarko samples (10): SW Wyoming, Green River, 1.994 +/- 0.075 g/cc, 41.53 +/- 5.97 gal/ton*

Anvil Points samples (8): W Colorado, Green River, 1.947 +/- 0.057 g/cc, 45.28 +/- 4.83 gal/ton*

J. Smith, Theoretical Relationship Between Density and Oil Yield for Oil Shales, U.S. Bureau ofMines Pub. 7248, 1969.


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The complex dielectric constant was measured

between 1 MHz and 1.8 GHz on all samples

Teflon (1&3 GHz) 2.1 .0003Water (1 GHz) 77.5 1.2

Water (3 GHz) 76.6 12.0

= -j

is the dielectric constant

is the loss factor

Complex dielectric constant

P ~ f E2

Power dissipated

Dp ~ 1/2/(f)

Skin depth (Penetration depthFor E to fall to 1/e)


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Measurement variabil ity within a sample was tested

4

4.2

4.4

4.6

4.8

5

107 108 109

OS1 P1 dry vs. position of measurement

position aposition bposition cposition d

position eposition fposition gposition h

Realrelativepermittivity

Frequency, Hz

-0.1

-0.05

0

0.05

0.1

107 108 109

OS1 P1 dry vs. position of measurement

position aposition bposition cposition d

position eposition fposition gposition h

Imaginaryrelativ

epermittivity

Frequency, Hz

P- face parallel to bedding

T - face perpendicular to beddingOS1 to OS3 - Anvil Points samples

OS4 to OS7 - Anadarko samples

T (not shown) more variable than P, both relatively small


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Dry, room temperature results for Anadarko

samples

0

2

4

6

8

10

107 108 109

Anadarko shale dry P orientat ion

os4 p2os5 p2os6 p2os7 p1

Realrela

tivepermittivity

Frequency, Hz

-0.4

-0.2

0

0.2

0.4

107 108 109

Anadarko shale dry P orientat ion

os4 p2os5 p2os6 p2os7 p1

Imaginaryrelativepermittivity

Frequency, Hz

No kerogen-related loss mechanism in frequency band


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Complex dielectric constant at different de-ionized

water saturations

0

2

4

6

8

10

12

107 108 109

OS1 P3 vs. DI saturation

Sw = 0%Sw = 36%Sw = 82%Sw = 81%Sw = 86%

Realrelativ

epermittivity

Frequency, Hz

-1

0

1

2

3

4

5

6

107 108 109


Sw = 0%Sw = 36%Sw = 82%Sw = 81%Sw = 86%

Imaginaryrela

tivepermittivity

Frequency, Hz

The loss factor is highly dependent on water saturation


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Large skin depths are measured in dry samples

0

100

200

300

400

500

107 108 109

Anadarko shale dry P or ientation

os4 p2os5 p2os6 p2

os7 p1

Skin

depth,m

Frequency, Hz

0

200

400

600

800

1000

107 108 109

Anvil po ints shale dry P orientat ion

os1 p1os1 p2os1 p3

os1 p4

Skin

depth,m

Frequency, Hz

Heating rates are low in dry samples at lower frequencies.


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Saturation controls skin depth with de-ionized water

0

10

20

30

40

50

107 108 109


Sw 36%

Sw 82%

Sw 81%

Sw 86%

Skindepth,m

Frequency, Hz

0

50

100

150

200

107 108 109

Anadarko shale vs. DI saturation

os5 t1 Sw = 0%os5 t1 Sw = 89%os5 p2 Sw = 0%os5 p2 Sw = 80%

Skindepth,m

Frequency, Hz

For skin depths of 10 meters, f < 20 MHz


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Saline water further reduces the skin depth

0

5

10

15

107 108 109

Anadarko shale brine saturation

os7 t1 Sw = 74%os6 p2 Sw = 91%os7 p1 Sw = 80%

os7 p2 Sw = 81%

Skindep

th,m

Frequency, Hz


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Anadarko dry sample measured at elevated temps

3

4

5

6

7

8

107 108 109

OS4 T4, dry vs. temperature

23 C45 C65 C85 C100 C

Realrelativepermittivity

Frequency, Hz

-0.4

-0.2

0

0.2

0.4

0.6

107 108 109

OS4 T1, dry vs. temperature

23 C45 C

65 C85 C100 C

Imaginaryr

elativepermittivity

Frequency, Hz

No temperature dependent loss mechanism was identified up to 100C


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Anvil Points dry sample measured at elevated temp

4

4.2

4.4

4.6

4.8

5

5.2

5.4

107 108 109

OS1 P1, dry vs. temperature

85 C123 C146 C

Realrelat

ivepermittivity

Frequency, Hz

-0.4

-0.2

0

0.2

0.4

107 108 109

OS1 P1, dry vs. temperature

85 C123 C146 C

Imaginaryrelativepermittivity

Frequency, Hz

No temperature dependent loss mechanism was identified up to 146C


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At higher temperatures there will be a kerogen

related change in the loss factor

Jesch, R.L. and R.H. McLaughlin,Dielectric Measurements of Oil Shale as Functions of Temperature

and Frequency, IEEE Trans. Geoscience and Remote Sensing, Vol. GE-22, No. 2, March 1984

Lower frequencies have a much

larger loss factor above 400 C

During a slow heating process

the loss factor changes will occur

at lower temperatures

Near kerogen decomposition

temperatures, an RF heating

frequency should be utilized

that avoids a runaway loss factor


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In-situ RF heating will be a complex dynamic

process

Below 100C, fluids control dielectric heating

Skin depth is controlled by saturation and brine concentration

Heating rate is controlled by skin depth

Above 100C, fluid migration will dynamically change skin

depth and heating rate

Skin depth will increase

Heating rate will decrease

At kerogen decomposition temperatures, skin depth andheating rate will dynamically change

Skin depth wil l decrease

Heating rate will increase


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In-situ RF heating experiments are essential to

determine the regime of applicability (if any)

Since pore fluids will control the early-phase heating process and limit

RF penetration into the formation, early diffusive heating may be

preferable on an economic basis

If significant drying of the formation near the borehole occurs, RF

heating will penetrate deeper into the formation and preferentially

deposit energy there hence it may be preferable to diffusive heaters

As kerogen breakdown temperatures are reached, previous studies

indicate that the loss factor will significantly increase, reducing RF

penetration. It is not clear if RF heating has any advantage over diffusive

heating in this regime

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