Dawsonite breakdown reactions during pyrolysis in Green River Formation oil shale

Transcription

1 Dawsonite breakdown reactions during pyrolysis in Green River Formation oil shale Jeremy Boak, Colorado School of Mines Justin Birdwell, U. S. Geological Survey

2 Outline Saline Minerals in Green River Formation Dawsonite Breakdown Implications 2 2

3 Nahcolite resource outlines primary saline mineral zone Total in-place nahcolite (NaHCO 3 ) resource in thousands of tons per acre in the Parachute Creek and Garden Gulch Members of the Green River Formation, Piceance Basin, Rio Blanco County, Colorado Inferred extent of nahcolite depocenter outlined in red 3 3

4 Evolutionary Stages Lake Uinta in the Piceance Creek Basin Stage Zone w/mean max (gal/ton) Description 6 Closing lake R8, L7: Mean 18, Avg. Max High lake Mahogany: Mean 29.2, Avg. Max Rising lake R6: Mean 24.7, Avg. Max 56 3 Rapidly fluctuating lake R5: Mean 20.9, Avg. Max 55.7 R4: Mean 31, Avg. Max Transitional lake R3: Mean 19.6, Avg. Max 38 R2: Mean 23.5, Avg. Max 40.8 Progradation of siliciclastic sediments, closing of the lake Thick, laterally extensive rich oil shale beds Thick beds, decrease of evaporites Highly cyclic units, thick evaporite beds High sand input 1 Fresh to brackish lake R1: Mean 22.9, Avg. Max 53.7 Terrestrial organic material 4 4

5 Pyrolysis Reactions of Saline Mineral Nahcolite 2NaHCO 3 = Na 2 CO 3 + H 2 O + CO 2 Nahcolite = Soda Ash + Water + Carbon Dioxide H 2 O:CO 2 = 1:1 Dawsonite* 2 NaAl(OH 2 )CO 3 = Na 2 CO 3 + Al 2 O H 2 O + CO Dioxide Dawsonite = Soda Ash + Alumina + Water + Carbon H 2 O:CO 2 = 2:1 * Reaction cited in Burnham, et al. 1983; patents to Shell, ExxonMobil

6 Well and Mine Locations USGS Colorado 1 USGS CR-2 Savage 24 USBM-01A Shell 23-X2 Horse Draw Mine USGS CR-1 6 6

7 Fischer Assay data reveal saline mineral trend USGS Colorado 1 Well Nahcolite Dawsonite Calcite Gas + Loss Ternary Boundary Minerals Leached Zone Nahcolite Zone Illitic Zone Linear (Nahcolite Zone) 7 Water 7 Oil

8 Fischer Assay data reveal saline mineral trend USGS Colorado 1 Well Dawsonite 2 Nahcolite Ternary Boundary Minerals Leached Zone Nahcolite Zone Illitic Zone Linear (Nahcolite Zone) Dawsonite 8 8 Water Residue

9 Simplified normative components from Fischer Assay Kerogen Nahcolite Nonvolatile Assumes loss part of gas+ loss negligible Defines rich and lean zones Broadly indicates illitic oil shale and nahcolitic oil shale Volatile Carbonate Hydrous Minerals Nahcolite may be overestimated Relatively small fraction of carbonate reacts 9 9

10 CR-2 Mineralogy (Dean, Howell, Pitman, 1981) R6 Top R5 Top R2 10

11 USGS CR-2 Calcite Gas + Loss Minerals Nahcolite Dawsonite 2 Dawsonite 1 Illite Zone Dawsonite Zone Nahcolite Zone Nahcolite Trend Water 1111 Oil

12 USGS CR-2 Dawsonite 2 Nahcolite Dawsonite 1 Ternary Boundary Minerals Upper Leached Lower Leached Illitic Lower Dawsonitic Upper Dawsonitic Nahcolitic Water Residue 1212

13 Additional Dawsonite Reaction Dawsonite breakdown* 2 NaAl(OH 2 )CO 3 = Na 2 CO 3 + Al 2 O H 2 O + CO 2 Dawsonite = Soda ash + Alumina + Water + Carbon dioxide H 2 O:CO 2 = 2:1; occurs above about 350 C Soda Ash breakdown** Na 2 CO 3 + Al 2 O 3 = 2 NaAlO 2 + CO 2 Soda ash + Alumina = Sodium + aluminate Carbon dioxide Cumulative H 2 O:CO 2 = 1:1; above ~400 C (amorphous) * Reaction cited in Burnham, 1983; Shell, ExxonMobil patents ** Reaction cited by Huggins & Greene, 1973; implicit in Dyni patent 13 13

14 Dawsonite breakdown reactions 14 14

15 15 15 Other potential reactions Topology dictated by phase relationships (Zen, 1966) and likely slopes of fluid phase reactions For oil shale, potential additional reactions involving silicates NaAl(OH) 2 CO SiO 2 = NaAlSi 3 O 8 + H 2 O + CO 2 Dawsonite + Silica = Albite + Water + Carbon Dioxide 44.41g g = 80.87g+5.56g g Additional reactions could also involve analcime

16 Dawsonite + quartz breakdown reactions 16 16

17 Do these reactions occur? May be kinetically precluded Appear to be involved in diagenesis in CR

18 CR-2 Mineralogy (Dean, Howell, Pitman, 1981) R6 Top R5 Top R2 18

19 Experiments on Oil Shale Sample from Horse Draw Mine (J. Dyni) Two types of retort: Fischer Assay In-Situ Simulator Characterized raw shale & products XRD mineralogy FTIR phase determination Rock Eval Gas composition 19

20 Experimental Results XRD-Rietveld wt % Raw Shale ISS Spent Fischer Spent All percentages adjusted to an original rock basis 20

21 Mineralogy Normalized to Residue XRD-Rietveld wt % Raw Shale ISS Spent Fischer Spent Mineral fraction only 0 21

22 FTIR Results Normalized absorbance Dawsonitic oil shale After ISS pyrolysis After Fischer Assay pyrolysis Dawsonite & other carbonates (Nacarbonate, ankerite) Dawsonite peaks Aliphatic carbon Silicates Wavenumber (cm -1 )

23 Yield and Rock Eval Data for Dawsonitic Oil Shale In Situ Simulator (ISS) Fischer Assay (FA) Oil (mg/g-rock) Gas (mg/g-rock) Water (mg/g-rock) Residue (mg/g-rock) Oil Specific Gravity Raw Shale ISS Spent FA Spent S 1 (mg-hc/g) S 2 (mg-hc/g) S 3 (mg-co 2 /g) TOC (wt %)

24 ISS Gas Composition Carbon Dioxide Hydrogen Propane Butane Other 1.24 mol % Methane Ethane Hydrogen Sulfide Nitrogen Pentane CO 2 represents 43 mol % (57 wt %) 100 g dawsonitic shale heated in ISS at 360 C for 72 h generates ~1.8 g of CO 2 Assuming all dawsonite degraded (verified by FTIR and XRD) degradation of each dawsonite unit" releases one molecule of CO 2, (based on 100 g sample, 5.5 wt % XRD data) 1.7 g of CO 2 generated by 5.5 g of dawsonite. Rock Eval S 3 indicates 700 mg of CO 2 would be generated by pyrolysis of 100 g of dawsonitic shale S 3 does not represent total CO 2 potential of a sample; it is meant to be the organicderived CO 2, released between C).

25 Conclusions Experimental results in FA and ISS suggest that quartz + dawsonite reaction does not take place Reasonable likelihood that reaction to sodium aluminate does occur Some increase in feldspar component also possible Dawsonite reaction to silicate minerals appears to occur in natural diagenetic systems Unclear under what in situ retorting conditions silicate reaction might occur 25

26 Implications of Alternative Dawsonite Breakdown Reaction Release of most CO 2 from dawsonite would add to carbon footprint of saline zone oil shale production Effect of release of CO 2 and H 2 O near pyrolysis temperature range on pyrolysis products? Kinetic data needed to determine importance of silicate reactions for heat and mass balance Potential of sodium aluminate as a catalyst for organic reactions Does Al resource warrant concern about recovery in feldspars? Dawsonite as a mineral sequestrant for CO 2 26

27 27 BACKUP SLIDES

28 Classification for Mudrocks (75 solid vol % 62 μm) Silica Minerals 90% 10% Chert/Porcelanite/ Diatomite/Spiculite 65% Quartzose Claystone 35% Micrite/Dolomicrite/ Chalk/Wackestone/ Sucrosic Dolomite 28 Carbonate Minerals 10% 25% Marlstone Park Canyon Mahogany Argillaceous Anvil Points shale Carbonate Mahogany shale In situ simulator Dawsonitic shale Argillaceous Claystone Fischer Assay 65% Sialic Claystone Hydrous pyrolysis 90% 75% 35% 10% Garden Gulch Illitic shale 90% Bentonite/Tonstein Aluminosilicate Minerals

29 Classification for Mudrocks (75 solid vol % 62 μm) Silica Minerals 90% 10% Chert/Porcelanite/ Diatomite/Spiculite 65% Quartzose Claystone 35% Argillaceous Claystone 65% Micrite/Dolomicrite/ Chalk/Wackestone/ Sucrosic Dolomite 29 Carbonate Minerals 10% 25% Argillaceous Carbonate Marlstone Sialic Claystone 90% 75% 35% 10% 90% Bentonite/Tonstein Aluminosilicate Minerals

30 Classification for Mudrocks (75 solid vol % 62 μm) Silica Minerals 90% 10% 65% 35% 30 Carbonate Minerals 10% 25% Park Canyon Mahogany shale Anvil Points Mahogany shale In situ simulator Dawsonitic shale Fischer Assay Hydrous pyrolysis 65% 90% 75% 35% 10% Garden Gulch Illitic shale 90% Aluminosilicate Minerals

31 Additional CO 2 release from Nahcolite CO 2 (tons per barrel) Nahcolite 19% Nahcolite 0.8% Production Quality (FA*FA%*Power plant eff.) 31 31

32 Water release from nahcolitic oil shale Water (barrel/barrel oil) Kerogen/Nahcolite ratio 32 32

33 Richness controls CO 2 release 33 33

34 USGS CR-1 Well Ternary Boundary Dawsonite ft ft Nahcolite ft Minerals Dawsonite 1 Water Residue 3434

35 Shale and Mudstone Mineralogy argillaceous mudstone argillaceous marlstone calcareous/ dolomitic mudstone Carbonate siliceous marlstone siliceous mudstone 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 Clay Minerals Quartz + Feldspar 35 35

36 Relationship of Climate and Lake Stratigraphy 36 36

37 Nahcolite breakdown (after Templeton, 1978) Depth (feet) Temperature ( C) Nahcolite Decomp. Top Saline Zone Base Saline Zone Reactions conducted at constant Vg/Vs Calculated for Vg/Vs = 0 U. S. Bureau of Mines/AEC Colorado #1 well used as representative At lithostatic load of saline zone, reaction occurs at ~200 C Substantially below pyrolysis temperature

38 Volume change for kerogen and nahcolite Kerogen Nahcolite Volume (ft 3 ) HC Liquid HC Vapor Coke Kerogen Mineral Volume (ft 3 ) C 150 bar ~2160 feet CO2 Water Natrite Nahcolite Kerogen Mineral 0 before after 0 before after 38 38

39 Will it fracture the rock? 2NaHCO 3 = Na 2 CO 3 + H 2 O + CO 2 2*81.4 g/mol 106 g/mol 18 g/mol 44 g/mol g/cc 2.54 g/cc 2*38.66 cc/mol cc/mol Volume (solids) = cc/mol = 44 % fluid density in void = g/ cc = g/cc Density of CO 2 alone = 44g/35.594cc = g/cc Density of water alone = 18/ = g/cc 39 39

40 Can water alone fracture the rock? Depth (feet) Temperature ( C) Nahcolite/Natrite Water/Steam Top Saline Zone Base Saline Zone Large volume change to steam Occurs at higher T Upper zone generally leached Increased porosity may accommodate volume increase Will activity of water affect pyrolysis?

41 Sodium Carbonate Minerals in Colorado, Utah, and Wyoming World s largest sodium carbonate deposit - Wilkins Peak Member of the GRF, Green River Basin, SW Wyoming as trona (Na 3 (CO 3 )(HCO 3 ) 2H 2 O) Second largest sodium carbonate deposit - Parachute Creek Member of the GRF, Piceance Basin, NW Colorado as Nahcolite (NaHCO 3 ) Minor bedded sodium carbonate deposits in the GRF Uinta Basin contains near Duchesne, Utah Dawsonite is widespread in the lower part of the saline zone of the Piceance Basin, comprising up to ~25% of the rock 41 41