Potential Geochemical Releases to Groundwater from an In-Situ Oil Shale Retort

Transcription

1 Potential Geochemical Releases to Groundwater from an In-Situ Oil Shale Retort Earl D. Mattson 1, Carl D. Palmer 1, Robert B. Perkins 2 1 Idaho National Laboratory, 2 Portland State University GWPC 2010 Annual Meeting Water/Energy in Changing Climates September 29, 2010

2 Oil Shale an organic-rich fine-grained sedimentary rock, contains significant amounts of kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be extracted.

3 Ex situ Production Technically viable Shallow systems Kirk s retort

4 Conceptual in situ retort source: Shell

5 Example of Physical Barriers Around a Retort Extraction control Politically acceptable Pollution control Buffer width Retort Zone Freeze Wall Plan View source: Shell

6 Objective: To combine the geochemical information we have obtained from laboratory experiments with heat transport modeling to gain insight into the spatial distribution of the geochemistry about in in-situ retort. Approach: Use a one-dimensional finite element code to calculate the spatial and temporal distribution of temperature about a heat source and then map the temperature-dependent laboratory results onto the temperature field to obtain the spatial distribution of the geochemistry.

7 Hydrous Retorts

8 Mineralogical Composition Mineral Description (wt%) Ankerite Ca(Fe,Mg)(CO3) ±1.4 Quartz SiO ±1.2 Analcime NaAlSi2O6 H2O (zeolite) 14.9 ±0.9 Albite NaAlSi3O8 (authigenic) 4.8 ±0.9 K-Feldspar KAlSi3O8 (authigenic) 17.6 ±1.4 Calcite CaCO3 6.5 ±0.7 Aragonite CaCO ±0.8 Illite/musc. K 0.5 (Al,Fe,Mg) 3 (Si,Al) 4 O 10 (OH) ±1.6 Pyrite FeS2 tr Counts b-7-b Powder x-ray diffraction Position [ 2Theta]

9 Mineralogical Changes in Retorted Oil Shale Concentration (% m/m) Analcime Ankerite Aragonite Calcite Smectite Quartz Temperature ( o C)

10 Raw versus Spent Oil Shale 3Ankerite + Analcime + 5 H 2 O Saponite + 3CaCO Na + + 6CO 2 Powder X-ray Diffraction Red Raw Blue/Green - Retorted

11 Concentration (mmol/l) TIC Na - HCO 3 Geochemistry Of the Retort Water Temperature ( o C) F 100 N Total Concentration (mmol/l) PO 4 Cl Br SO 4 Concentration (mmol/l) 10 1 NH 4 N org Temperature ( o C) NO 3 NO Temperature ( o C)

12 Organics Residual Carbon Solutes in water Ketones Cycloketones Phenols 2-propyl 1-heptanol 2,5-dimethyl-aceta cyclohexanethiol pyrazole

13 Heat Capacity of Oil Shale Applied Kopp s law of additivity of heat capacities: Heat capacity is a weighted sum of the heat capacities of the minerals and organic fractions in the formation. C p (oil shale) = f(minerals) C p (minerals) + f(kerogen) C p (kerogen) + f(char)c p (Char) Thermal Conductivity (W m-1 ºC-1) Grade (gallons/ton) Temperature (K) 1 λ = a + bt + cg r 2 = Data from: Wang et al. (1979) Nottenburg et al. (1978) Vosteen and Schellschmidt (2003)

14 Distribution of Temperature

15 Dominant Aqueous Species

16 Fluoride

17 Total Nitrogen

18 Carbonate Minerals

19 Aluminosilicate Minerals

20 Quartz Aqueous Silica

21 The Rest of the Story.. Unconsolidated Expansion during retorting (~20%)

22 Tisot Chip Test Design 45.5 g/ton Source: Tisot and Sohns, 1970

23 Hydrous Fracture Permeability Test Design 3 orders of permeability reduction

24 Anhydrous Fracture Permeability Results Displacment vs Time Displacment (mm) C 100 C 150 C compaction Thermal Thermal Expansion Expansion Permeability (d) Time (hr)

25 Potential Implications Fracture permeability should be reduced outside of retort zone Flux of solutes will be reduced during retorting Outside the retort zone the change in permeability is reversible with temperature Inside the retort zone, permeability changes are more permanent Kerogen removal Calcite precipitation?? Normalized Log Permeability

26 Summary We have obtained data on the concentrations of dissolved and mineral components in retorted oil shale as a function temperature, mapped the temperature-dependent geochemistry laboratory results onto the spatially-dependent simulated temperature distribution to simulate the potential spatial distribution of the geochemistry near an oil shale retort. speculated implication of permeability changes within and adjacent to the retort will reduce the flux of these solutes in the groundwater Next steps are to verify mechanisms effecting permeability near a retort, incorporate these findings into a flow and transport model, and add As and Hg information.