Kinetic modelling of kerogen cracking during oil shale ...€¦ · Rock Eval pyrolysis At 650°C :...

F. Behar and P. Allix – Oil shale symposium october 2012

Kinetic modelling of kerogen cracking during oil shale process : influence of organic matter source

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F. Behar and P. Allix

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General outline !   I – Introduction

!   II – Kerogen characterization § Definition of the main organic matter

§ Initial geological deposit § Oil shale potential

!   III – Understanding the main reaction of kerogen cracking § Kinetic schema § Micro pilot reactor § Mass balances § Compositional model

!   IV – Impact on oil shale yield and chemical composition § Primary products § Secondary reaction

!   V – Conclusions F. Behar and P. Allix – Oil shale symposium october 2012

Oil shale pyrolysis : new challenges for unconventional resources

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Total Organic Carbon

Oil shale process T : 200 to 400°C Weeks to months

How does organic matter quality impact yield and chemical composition of the produced oil ?


Solid organic matter (kerogen)

°API > 30

>7-8%

Classification of organic matter in source rocks

4 F. Behar and P. Allix – Oil shale symposium october 2012

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0.80

1.00

1.20

1.40

1.60

1.80

0.00 0.10 0.20 0.30 0.40

Lacustrine deposit High H/C and low O/C

O/C at. ratio

H/C

at.

ratio

Van Krevelen diagram



Aliphatic chains Low aromatic content Ester – Acids – Ether



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1.20

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1.60

1.80

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Marine deposit Lower H/C and higher O/C

H/C

at.

ratio

O/C at. ratio

Van Krevelen diagram

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Chemical structure of marine organic matter (Type II)


Aliphatic chains and cyclanes Significant aromatic content Ester – Acids – Ether

Type II – S High sulfur content Confined marine deposit



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1.80

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Continental deposit (humic coals) Low H/C and high O/C

H/C

at.

ratio

O/C at. ratio

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Chemical structure of continental organic matter (Type III)


Aromatics and phenols Ester – Acids – Ether

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Shale oil potential


time

tem

pera

ture

FID

sig

nal

S2 peak

Tmax

S1 peak

300°C

650°C

25°C/min

Rock Eval pyrolysis

At 650°C : 100% kerogen conversion è S2 = maximum yield

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Shale oil potential


time

tem

pera

ture

FID

sig

nal

S2 peak

Tmax

S1 peak

300°C

650°C

25°C/min

Rock Eval pyrolysis


0

20

40

60

80

1 2 3

Pyrolysis y

ield (%

)

Oil potential Type I

Type II

Type III

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Shale oil potential : f (organic matter type)


time

tem

pera

ture

FID

sig

nal

S2 peak

Tmax

S1 peak

300°C

650°C

25°C/min

Rock Eval pyrolysis


0

20

40

60

80

1 2 3

Pyrolysis y

ield (%

)

Oil potential

Oil shale pyrolysis : Type I and II are good candidates

Type I

Type II

Type III x

Shale oil potential : f (organic matter type)


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20

40

60

80

1 2 3

Pyrolysis y

ield (%

)

Oil potential

Type I Type II-S Type II

time

tem

pera

ture

FID

sig

nal

S2 peak

Tmax

S1 peak

300°C

650°C

25°C/min

Rock Eval pyrolysis


Oil shale pyrolysis : Type I, II and II – S are good candidates

!   I – Introduction

!   II – Kerogen characterization § Definition of the main organic matter source

§ Initial geological deposit § Oil shale potential

!   III – Understanding the main reaction of kerogen cracking § Kinetic schema § Micro pilot reactor § Mass balances § Compositional model

!   IV – Impact on oil shale yield and chemical composition § Primary products § Secondary reaction

!   V – Conclusions 14

General outline


Two types of kinetic schema for kerogen cracking

...

k1

k2

k3

k4

k5

x1 HCx2 HCx3 HCx4 HCx5 HC

Σxi = HC potentialOrganicmatter(kerogen)

I – Parallel reactions : hydrocarbons are primary products (Burnham and Brown 1987; Ungerer, 1991...)

II – Successive reactions : HC are not directly generated from kerogen (Fitzgerald and van Krevelen, 1959,Tissot, 1969, Lewan 1983, Behar et al., 2008…)

Residue

NSOs 1 and 2 = Asp + Resins

Kerogen NSOs 1 NSOs 2

Petroleum : HC + NSOs 3

Residue Residue Residue

H2O + CO2 H2O + CO2 H2O + CO2


Kerogen cracking in laboratory conditions

!   Open system pyrolysis § Generated asphaltenes are cracked and not vaporised § HC potential from asphaltenes cannot be quantified è Only apparent kinetic schema : parallel reactions

!   Closed pyrolysis system § Generated asphaltenes recovered by solvent extraction

è Kinetics of asphaltenes generation and cracking è Discrimate between parallel and successive kinetic schema


17

Micro reactor : analytical workflow

Pyrolysis experiments: Sealed gold tubes 300 – 400°C 1 week to 6 months

7 cm

1 cm

Kerogen amount : 250 mg – 4 g

C14+ Sat Aro NSOs

Gas C1 and C2-C5 CO2, H2S

C6-C14 Sat Aro

Residual kerogen and prechar

Initial kerogen

gas + liquid + solid > 95%


Source rock

Kerogen

HF/HCl

Thermal cracking of kerogen

- Complex molecule of high molecular weight - Functional groups between kerogen moieties



Thermal cracking of kerogen

Thermal cracking of functional groups

Liquid products : asphaltenes and HC

kerogen

Asphaltenes First source of HC (1)


Asphaltenes

Asphaltenes cracking : resins generation

Resins + HC2 Asphaltenes

Asphaltenes Char precursor


HC generation : 3 main reactions


Kerogen è (CO2 + H2S)1 + Asphaltenes + HC1 + residual kerogen

Asphaltenes è (CO2 + H2S)2 + Resins + HC2 + prechar

Resins è (CO2 + H2S)3 + HC3 + prechar

HC generation : 3 main reactions

Kerogen è (CO2 + H2S)1 + Asphaltenes + HC1 + residual kerogen

Asphaltenes è (CO2 + H2S)2 + Resins + HC2 + prechar

Resins è (CO2 + H2S)3 + HC3 + prechar


2 main steps for hydrocarbon production 1 – Cracking of non mobile compounds (kero + asp + res.) 2 – Partial cracking of the mobile compounds (resins and HC)

Oil shale pyrolysis

Results on 3 selected oil shales

Results on 3 selected oil shales

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Type I lacustrine : Green River Shale (USA) Type II marine : Toarcian Shale (France) Type II-S marine : Jordan Shale (Jordanie)

Oil shale potential : 300-600°C at 25°C/min


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1.60

1.80

0.00 0.10 0.20 0.30 0.40

Jordan Shale

Green River Shale

Toarcian Shale

0

20

40

60

80

1 2 3

Pyrolysis y

ield (%

)

Oil potential

Type I Type II-S Type II

S = 0.7% S = 3.1% S = 12.9%

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Experimental simulation in closed micro reactor

T = 325°C time from 1 to 216h

7 cm

1 cm

Initial amount : 250 mg – 4 g

C14+ Sat Aro NSOs

Gas C1 and C2-C5 CO2, H2S

C6-C14 Sat Aro

Residual kerogen and prechar

Initial kerogen

gas + liquid + solid > 95%



resinsasphaltenes

0

100

200

300

400

500

1 2 3 4 5 6

yield (m

g/g)

Green River Shale

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100

200

300

400

500

1 2 3 4 5 6

yield (m

g/g)

Jordan Shale

0

100

200

300

400

500

1 2 3 4 5 6

yield (m

g/g)

Toarcian Shale

72h 1h 3h 9h 24h 216h 72h 1h 3h 9h 24h 216h 72h 1h 3h 9h 24h 216h

T = 325°C 1 to 216h Kerogen conversion > 80% at 216h

Fluid composition during kerogen conversion


resinsasphaltenes

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100

200

300

400

500

1 2 3 4 5 6

yield (m

g/g)

Green River Shale

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100

200

300

400

500

1 2 3 4 5 6

yield (m

g/g)

Jordan Shale

0

100

200

300

400

500

1 2 3 4 5 6

yield (m

g/g)

Toarcian Shale



Asp max : 400 mg/g Res max : 100 mg/g



Total NSOs = 50% Total NSOs = 50% Total NSOs = 23%

Asphaltenes : unstable class Resins : more stable class

T = 325°C


C14+ sat

C14+aro

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120

160

200

1 2 3 4 5 6

yield (m

g/g)

Green River Shale

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40

80

120

160

200

1 2 3 4 5 6

yield (m

g/g)

Jordan Shale

0

40

80

120

160

200

1 2 3 4 5 6

yield (m

g/g)

Toarcian Shale



T = 325°C


C14+ sat

C14+aro

0

40

80

120

160

200

1 2 3 4 5 6

yield (m

g/g)

Green River Shale

0

40

80

120

160

200

1 2 3 4 5 6

yield (m

g/g)

Jordan Shale

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40

80

120

160

200

1 2 3 4 5 6

yield (m

g/g)

Toarcian Shale


C14+ Sat max = 5% C14+ Aro max = 18%

C14+ Sat max = 10% C14+ Aro max = 9%


C14+ Sat max = 4% C14+ Aro max = 6%

Total C14+ HC = 19% Total C14+ HC = 23% Total C14+ HC = 10%

C14+ sat : almost stable C14+ aro : unstable

T = 325°C


C1-‐C4C6-‐C14

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100

1 2 3 4 5 6

yield (m

g/g)

Green River Shale

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80

100

1 2 3 4 5 6

yield (m

g/g)

Jordan Shale

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60

80

100

1 2 3 4 5 6

yield (m

g/g)

Toarcian Shale



T = 325°C


C1-C4 max = 4% C6-C14 max = 5%

C1-‐C4C6-‐C14

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100

1 2 3 4 5 6

yield (m

g/g)

Green River Shale

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60

80

100

1 2 3 4 5 6

yield (m

g/g)

Jordan Shale

0

20

40

60

80

100

1 2 3 4 5 6

yield (m

g/g)

Toarcian Shale


C1-C4 max = 4% C6-C14 max = 8%


Maximum C6-C14 for the Type I kerogen

T = 325°C


0

15

30

45

60

75

1 2 3 4 5 6

yield (m

g/g)

Green River Shale

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15

30

45

60

75

1 2 3 4 5 6

yield (m

g/g)

Jordan Shale

0

15

30

45

60

75

1 2 3 4 5 6

yield (m

g/g)

Toarcian Shale

CO2

H2S



T = 325°C


0

15

30

45

60

75

1 2 3 4 5 6

yield (m

g/g)

Green River Shale

0

15

30

45

60

75

1 2 3 4 5 6

yield (m

g/g)

Jordan Shale

0

15

30

45

60

75

1 2 3 4 5 6

yield (m

g/g)

Toarcian Shale

CO2

H2S

CO2 max : 3% H2S max : 6%


CO2 max : 5% H2S max : 3%


CO2 max : 3% H2S max : 0.5%

Total Acid gas = 3.5% Total Acid gas = 9% Total Acid gas = 8%

Acid gas : very early generation

T = 325°C

34

Summary

!   First step : kerogen cracking § Most of the asphaltenes are degraded § Resins are more stable class § C14+ aromatics start to be cracked at high kerogen conversion § C14+ saturates are almost stable Still high content in NSOs (asp + resins) : production of low °API and low

mobility fluid, è significant secondary cracking reaction

!   Second step : influence of the secondary cracking reaction § Available compositional kinetic schema


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Compositional kinetic schema for NSOs and HC cracking

C15+ sat

C15+ alkyl aro

C15+ methyl aro

NSOs

C5-C14 sat

Pyrobitumen C6-C14 aro

C1-C4

H2S, CO2

C1

C1

F. Behar – Oil shale Raffinage – 3 mai 2012

36

Summary

!   First step : kerogen cracking § Most of the asphaltenes are degraded § Resins are more stable class § C14+ aromatics start to be cracked at high kerogen conversion § C14+ saturates are almost stable Still high content in NSOs (asp + resins) : production of low °API and low

mobility fluid, è significant secondary cracking reaction

!   Second step : influence of the secondary cracking reaction § Available compositional kinetic schema è Application to the fluid composition obtained at 325°C/216h



C1-‐C4C6-‐C14C14+ sat

C14+aro

Step 2 : thermal cracking of the generated products Kerogen conversion > 80%

T : 300 – 380°C at 4°C/day Total duration : 3 months

Green River Shale

0

100

200

300

300 320 340 360 380Temperature (°C)

yield (m

g/g)

C6-C14 max from C14+ sat cracking High ratio C1-C4/C6-C14 C14+ HC = 22%

C14+ sat = 12%


C1-‐C4C6-‐C14C14+ sat

C14+aro



Jordan Shale

0

100

200

300

300 320 340 360 380Temperature (°C)

yield (m

g/g)

Lower C6-C14 yield lower ratio C1-C4/C6-C14 C14+ HC = 17%

C14+ sat = 6%


C1-‐C4C6-‐C14C14+ sat

C14+aro



Toarcian Shale

0

100

200

300

300 320 340 360 380Temperature (°C)

yield (m

g/g)

similar C6-C14 as for the Jordan shale low ratio C1-C4/C6-C14

C14+ HC = 12% C14+ sat = 6%

40

Conclusions : key geochemical parameters for optimizing oil shale process


!   I – Organic matter type §  Best candidate : Lacustrine organic matter source

!   II – Organic carbon richness §  Best candidate : Lacustrine §  Marine –S soure rock

!   III – Good geochemical parameters §  Organic carbon richness : necessary but not sufficient §  Low organic sulfur content §  High asphaltenes and resins yield during pyrolysis §  C14+ sat / C14+ aro >> 1 in the generated hydrocarbons

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Kinetic modelling of kerogen cracking during oil shale ...€¦ · Rock Eval pyrolysis At 650°C :...

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