Relevance of Intra-Particle Diffusion in Modelling Hydrocarbon Transport through Dual-Porosity Porous Media in the Absence and Presence of Particles

Transcription

1 Relevance of Intra-Particle Diffusion in Modelling Hydrocarbon Transport through Dual-Porosity Porous Media in the Absence and Presence of Particles Dr. Stephane Ngueleu, Prof. Peter Grathwohl, Prof. Olaf Cirpka Kananaskis, April 22, 2015

2 Outline Introduction Objectives Materials and Methods Results and Discussion Conclusions

3 Introduction (Citizen Journalist Exchange, 2013) (The Canadian Press, 2012)

4 Introduction (Energy Resources Conservation Board, 2013)

5 Introduction (Energy Resources Conservation Board, 2013)

6 Introduction (Energy Resources Conservation Board, 2013)

7 Introduction Oil Flow rate Oil mass Processes Medium type

8 Introduction Sorption Initial state Final state Initial state Advection Diffusion Diffusion Final state Sorption and intra-particle diffusion Pollutant Aquifer Particle particle/grain Inter-pore Intra-pore Inter-particle pore Intra-particle pore Initial state Dispersion Final state

9 Introduction Organic particles (size 10 µm) released from soils and tailings ponds to aquifers. Thin and mature fine tailings (approx. size < 44 µm)! (Figure from en.wikibooks.org) (Figure from

10 Objectives Understand through model-based analysis: Hydrocarbon transport in saturated dual-porosity porous media Organic particle transport and its influence on hydrocarbon transport

11 Materials and Methods Laboratory experiments Porous medium: natural soil with the structure of a clayey sand, grain size up to 2 mm. Organic carbon content Particle density CaCO 3 ( f [weight%] [g cm -3 OC ) ] [weight%]

12 Materials and Methods Organic particles: natural lignite (brown coal) 60.5 weight%. f OC Fine particles d 50 = 0.8 µm Filtered particles d µm Based on the size: dissolved organic carbon (DOC) d 50 : median diameter based on the number of particles

13 Materials and Methods Lindane (gamma-hexachlorocyclohexane): very hydrophobic in water.

14 Materials and Methods Sorption behaviour of lindane through batch sorption experiments Lindane (contaminant) Clayey soil (porous medium) Lignite (Organic particle)

15 Porous medium Materials and Methods Transport simulation through column experiments Length: 15 cm Diameter: 2.4 cm 0.05 ml min -1

16 Materials and Methods Injection phase Lindane alone in 0 to 60 mmol L -1 NaCl Lindane and organic particles in 0 to 60 mmol L -1 NaCl Elution phase 0 to 60 mmol L -1 NaCl 0 to 60 mmol L -1 NaCl! (Figure from en.wikibooks.org)

17 Materials and Methods One-dimensional transport modelling Transport of lindane alone: - Model with kinetic sorption - Model with equilibrium sorption and intra-particle diffusion Transport of lignite particles: Model with straining and attachment Straining Aquifer matrix Attachment Particles Simultaneous transport of lindane and lignite particles

18 Results and Discussion Equilibrium sorption of lindane Clayey soil: - Linear distribution coefficient (K d ): 3.38 ± Low sorption! S K d C Lkg 1 Linear model

19 Results and Discussion Lignite: - Freundlich distribution coefficient (K Fr ): 707 ± 18 - Freundlich exponent (1/n Fr ): 0.72 ± High sorption! S K C 1 Fr n Fr mg 1 1/n Fr L 1/n Fr kg 1 Freundlich model

20 Results and Discussion Column experiments Spatial concentration profile of lindane alone pore volumes Injection stopped X [cm]

21 Results and Discussion Effluent chloride and lindane concentrations Kinetic sorption Porosity n 0.5 Equilibrium sorption and intra-particle diffusion n m n im Dualporosity Ionic strength reduction (60 to 6 mmol L -1 NaCl) did not cause soil particle mobilization.

22 Results and Discussion Effluent lindane and organic particle concentrations d 50 < 0.45 µm Lindane without particles Lindane with fine particles (d 50 = 0.8 µm) Lindane with filtered particles or DOC (d 50 < 0.45 µm) Fine lignite particles were completely retained in the porous medium. Travel time of lindane reduced by 25% with lignite particles < 0.45 µm.

23 Results and Discussion Extension to 2-D transport Hydraulic conductivity (K) and flow field 10 5 K [m s -1 ] 10 7 Hydraulic gradient h 0.005

24 Results and Discussion Separate transport of organic particles and lindane (kinetic sorption) Contamination time [day] Concentration of organic particles [mg L -1 ] 12 Concentration of lindane [mg L -1 ] 5 ½

25 Results and Discussion Particles, 5 days Particles, 1 month Lindane, 5 days Lindane, 1 month C/C in

26 Results and Discussion Particles, 6 months Particles, 1 year Lindane, 6 months Lindane, 1 year C/C in

27 Z [m] Results and Discussion Transport of lindane alone with equilibrium sorption and intra-particle diffusion

28 Z [m] Z [m] Results and Discussion Intra-particle porosity X [m] Inter-particle porosity

29 Results and Discussion Lindane, 5 days Lindane, 1 month Lindane, 6 months Lindane, 1 year

30 Conclusions Lindane transport was represented best when accounting for intra-particle diffusion. Organic particles > 0.45 µm were strongly retained, leading to retarded contaminant transport. Organic particles < 0.45 µm (DOC) enhanced contaminant transport.

31 Conclusions Long term contamination can be an indication of back diffusion from intra-particle pores to inter-particle pores, not an indication of new contamination. Pollutant Aquifer Particle particle/grain Inter-pore Intra-pore Inter-particle pore Intra-particle pore Pollutant Aquifer Particle particle/grain Inter-pore Intra-pore Inter-particle pore Intra-particle pore

32

33 Supplementary Information (Roy and Dzombak, 1997)

34 DISCLAIMER This presentation has been prepared by a representative of WorleyParsons. The presentation contains the professional and personal opinions of the presenter, which are given in good faith. As such, opinions presented herein may not always necessarily reflect the position of WorleyParsons as a whole, its officers or executive. Any forward-looking statements included in this presentation will involve subjective judgment and analysis and are subject to uncertainties, risks and contingencies many of which are outside the control of, and may be unknown to, WorleyParsons. WorleyParsons and all associated entities and representatives make no representation or warranty as to the accuracy, reliability or completeness of information in this document and do not take responsibility for updating any information or correcting any error or omission that may become apparent after this document has been issued. To the extent permitted by law, WorleyParsons and its officers, employees, related bodies and agents disclaim all liability direct, indirect or consequential (and whether or not arising out of the negligence, default or lack of care of WorleyParsons and/or any of its agents) for any loss or damage suffered by a recipient or other persons arising out of, or in connection with, any use or reliance on this presentation or information.