Kinetic modelling of kerogen cracking during oil shale process : influence of organic matter source F. Behar and P. Allix

Transcription

1 Kinetic modelling of kerogen cracking during oil shale process : influence of organic matter source F. Behar and P. Allix 1

2 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 2

3 Oil shale pyrolysis : new challenges for unconventional resources Solid organic matter (kerogen) Total Organic Carbon >7-8% Oil shale process T : 2 to 4 C Weeks to months API > 3 How does organic matter quality impact yield and chemical composition of the produced oil? 3

4 Classification of organic matter in source rocks 1.8 Lacustrine deposit High H/C and low O/C 1.6 H/C at. ratio Van Krevelen diagram O/C at. ratio 4

5 Classification of organic matter in source rocks Aliphatic chains Low aromatic content Ester Acids Ether 5

6 Classification of organic matter in source rocks Marine deposit Lower H/C and higher O/C H/C at. ratio Van Krevelen diagram O/C at. ratio 6

7 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 7

8 Classification of organic matter in source rocks Continental deposit (humic coals) Low H/C and high O/C H/C at. ratio O/C at. ratio 8

9 Chemical structure of continental organic matter (Type III) Aromatics and phenols Ester Acids Ether 9

10 Shale oil potential Rock Eval pyrolysis Tmax 65 C FID signal 3 C S2 peak 25 C/min temperature S1 peak time At 65 C : 1% kerogen conversion è S2 = maximum yield 1

11 Shale oil potential Rock Eval pyrolysis Tmax 65 C 8 Type I Oil potential FID signal 3 C S2 peak 25 C/min temperature Pyrolysis yield (%) Type II Type III S1 peak time At 65 C : 1% kerogen conversion è S2 = maximum yield 11

12 Shale oil potential : f (organic matter type) Rock Eval pyrolysis Tmax 65 C 8 Type I Oil potential FID signal 3 C S1 peak S2 peak 25 C/min temperature Pyrolysis yield (%) Type II x Type III time At 65 C : 1% kerogen conversion è S2 = maximum yield Oil shale pyrolysis : Type I and II are good candidates 12

13 Shale oil potential : f (organic matter type) Rock Eval pyrolysis Tmax 65 C 8 Oil potential FID signal 3 C S2 peak 25 C/min temperature Pyrolysis yield (%) S1 peak Type I Type II Type II-S time At 65 C : 1% kerogen conversion è S2 = maximum yield Oil shale pyrolysis : Type I, II and II S are good candidates 13

14 ! 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 14 General outline! V Conclusions

15 Two types of kinetic schema for kerogen cracking I Parallel reactions : hydrocarbons are primary products (Burnham and Brown 1987; Ungerer, ) Organic matter (kerogen) k 1 k 2 k 3 k 4 k 5 x 1 HC x 2 HC x 3 HC x 4 HC x 5 HC Σx i = HC potential... II Successive reactions : HC are not directly generated from kerogen (Fitzgerald and van Krevelen, 1959,Tissot, 1969, Lewan 1983, Behar et al., 28 ) H 2 O + CO 2 H 2 O + CO 2 H 2 O + CO 2 Kerogen NSOs 1 NSOs 2 Petroleum : HC + NSOs 3 Residue Residue Residue Residue 15 NSOs 1 and 2 = Asp + Resins

16 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 16

17 Micro reactor : analytical workflow 7 cm Pyrolysis experiments: Sealed gold tubes 3 4 C 1 week to 6 months Kerogen amount : 25 mg 4 g 1 cm Source rock HF/HCl Kerogen Initial kerogen Gas C 1 and C 2 -C 5 CO 2, H 2 S C 6 -C 14 Sat Aro C 14+ Sat Aro NSOs Residual kerogen and prechar gas + liquid + solid > 95% 17

18 Thermal cracking of kerogen - Complex molecule of high molecular weight - Functional groups between kerogen moieties 18

19 Thermal cracking of kerogen Thermal cracking of functional groups 19

20 Liquid products : asphaltenes and HC Asphaltenes kerogen Asphaltenes First source of HC (1) 2

21 Asphaltenes cracking : resins generation Asphaltenes Resins + HC2 Asphaltenes Char precursor 21

22 HC generation : 3 main reactions Kerogen Asphaltenes Resins è (CO 2 + H 2 S) 1 + Asphaltenes + HC1 + residual kerogen è (CO 2 + H 2 S) 2 + Resins + HC2 + prechar è (CO 2 + H 2 S) 3 + HC3 + prechar 22

23 HC generation : 3 main reactions Kerogen Asphaltenes Resins è (CO 2 + H 2 S) 1 + Asphaltenes + HC1 + residual kerogen è (CO 2 + H 2 S) 2 + Resins + HC2 + prechar è (CO 2 + H 2 S) 3 + HC3 + prechar Oil shale pyrolysis 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) Results on 3 selected oil shales 23

24 Results on 3 selected oil shales Green River Shale Jordan Shale Type I lacustrine : Green River Shale (USA) Type II marine : Toarcian Shale (France) Type II-S marine : Jordan Shale (Jordanie) 1. Toarcian Shale Oil shale potential : 3-6 C at 25 C/min Pyrolysis yield (%) Oil potential Type I Type II Type II-S S =.7% S = 3.1% S = 12.9% 24

25 Experimental simulation in closed micro reactor T = 325 C time from 1 to 216h 7 cm 1 cm Initial amount : 25 mg 4 g Initial kerogen Gas C 1 and C 2 -C 5 CO 2, H 2 S C 6 -C 14 Sat Aro C 14+ Sat Aro NSOs Residual kerogen and prechar gas + liquid + solid > 95% 25

26 Fluid composition during kerogen conversion T = 325 C 1 to 216h Kerogen conversion > 8% at 216h Green River Shale Jordan Shale Toarcian Shale resins asphaltenes h 1 3h 2 9h 3 24h 4 72h 5 216h h 5 6 1h 3h 9h 24h 216h 1h 1 3h 2 9h 3 24h 4 72h 5 216h 6 26

27 Fluid composition during kerogen conversion T = 325 C Asp max : 3 mg/g Res max : 2 mg/g Asp max : 4 mg/g Res max : 1 mg/g Asp max : 15 mg/g Res max : 8 mg/g Green River Shale Jordan Shale Toarcian Shale resins asphaltenes h 1 3h 2 9h 3 24h 4 72h 5 216h h 5 6 1h 3h 9h 24h 216h 1h 1 3h 2 9h 3 24h 4 72h 5 216h 6 Total NSOs = 5% Total NSOs = 5% Total NSOs = 23% Asphaltenes : unstable class Resins : more stable class 27

28 Fluid composition during kerogen conversion T = 325 C Green River Shale Jordan Shale Toarcian Shale C 14+ sat C 14+ aro h 1 3h 2 9h 3 24h 4 72h 5 216h h 5 6 1h 3h 9h 24h 216h 1h 1 3h 2 9h 3 24h 4 72h 5 216h 6 28

29 Fluid composition during kerogen conversion T = 325 C C 14+ Sat max = 1% C 14+ Aro max = 9% C 14+ Sat max = 5% C 14+ Aro max = 18% C 14+ Sat max = 4% C 14+ Aro max = 6% Green River Shale Jordan Shale Toarcian Shale C 14+ sat C 14+ aro h 1 3h 2 9h 3 24h 4 72h 5 216h h 5 6 1h 3h 9h 24h 216h 1h 1 3h 2 9h 3 24h 4 72h 5 216h 6 Total C 14+ HC = 19% Total C 14+ HC = 23% Total C 14+ HC = 1% C 14+ sat : almost stable C 14+ aro : unstable 29

30 Fluid composition during kerogen conversion T = 325 C Green River Shale Jordan Shale Toarcian Shale C 1 - C 4 C 6 - C h 1 3h 2 9h 3 24h 4 72h 5 216h h 5 6 1h 3h 9h 24h 216h 1h 1 3h 2 9h 3 24h 4 72h 5 216h 6 3

31 Fluid composition during kerogen conversion T = 325 C C 1 -C 4 max = 4% C 6 -C 14 max = 8% C 1 -C 4 max = 4% C 6 -C 14 max = 5% Green River Shale Jordan Shale Toarcian Shale C 1 - C 4 C 6 - C h 1 3h 2 9h 3 24h 4 72h 5 216h h 5 6 1h 3h 9h 24h 216h 1h 1 3h 2 9h 3 24h 4 72h 5 216h 6 Maximum C 6 -C 14 for the Type I kerogen 31

32 Fluid composition during kerogen conversion T = 325 C 75 Green River Shale 75 Jordan Shale 75 Toarcian Shale CO 2 H 2 S h 1 3h 2 9h 3 24h 4 72h 5 216h h 5 6 1h 3h 9h 24h 216h 1h 1 3h 2 9h 3 24h 4 72h 5 216h 6 32

33 Fluid composition during kerogen conversion T = 325 C CO 2 max : 3% H 2 S max :.5% CO 2 max : 3% H 2 S max : 6% CO 2 max : 5% H 2 S max : 3% 75 Green River Shale 75 Jordan Shale 75 Toarcian Shale CO 2 H 2 S h 1 3h 2 9h 3 24h 4 72h 5 216h h 5 6 1h 3h 9h 24h 216h 1h 1 3h 2 9h 3 24h 4 72h 5 216h 6 Total Acid gas = 3.5% Total Acid gas = 9% Total Acid gas = 8% Acid gas : very early generation 33

34 Summary! First step : kerogen cracking Most of the asphaltenes are degraded Resins are more stable class C 14+ aromatics start to be cracked at high kerogen conversion C 14+ 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 34

35 Compositional kinetic schema for NSOs and HC cracking C 5 -C 14 sat NSOs C 15+ sat H 2 S, CO 2 C 6 -C 14 aro C 15+ alkyl aro Pyrobitumen C 1 -C 4 C 15+ methyl aro C 1 C 1 35 F. Behar Oil shale Raffinage 3 mai 212

36 Summary! First step : kerogen cracking Most of the asphaltenes are degraded Resins are more stable class C 14+ aromatics start to be cracked at high kerogen conversion C 14+ 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 36

37 Step 2 : thermal cracking of the generated products Kerogen conversion > 8% T : 3 38 C at 4 C/day Total duration : 3 months C 14+ HC = 22% C 14+ sat = 12% C 6 -C 14 max from C 14+ sat cracking High ratio C 1 -C 4 /C 6 -C 14 3 Green River Shale 2 1 C 1 - C 4 C 6 - C 14 C 14+ sat C 14+ aro Temperature ( C) 37

38 Step 2 : thermal cracking of the generated products Kerogen conversion > 8% T : 3 38 C at 4 C/day Total duration : 3 months C 14+ HC = 17% C 14+ sat = 6% Lower C 6 -C 14 yield lower ratio C 1 -C 4 /C 6 -C 14 3 Jordan Shale Temperature ( C) C 1 - C 4 C 6 - C 14 C 14+ sat C 14+ aro 38

39 Step 2 : thermal cracking of the generated products Kerogen conversion > 8% T : 3 38 C at 4 C/day Total duration : 3 months C 14+ HC = 12% C 14+ sat = 6% similar C 6 -C 14 as for the Jordan shale low ratio C 1 -C 4 /C 6 -C 14 3 Toarcian Shale Temperature ( C) C 1 - C 4 C 6 - C 14 C 14+ sat C 14+ aro 39

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 C 14+ sat / C 14+ aro >> 1 in the generated hydrocarbons 4