Thermohaline Flow and Reactive Solute Transport in Fractured Rock Thomas GRAF Institute of Fluid Mechanics in Civil Engineering
Alberta Geological Survey, Edmonton 2008-2009 Basin Hydrogeologist Sasdf sdaf df Sadf Université Laval, Quebec 2002-2005 Ph.D. 2006-2007 PostDoc Fsda Sdaf» sfda Title Leibniz Universität Hannover since 2009 Professor Georg-August Universität Göttingen 2007-2008 Research Fellow Albert-Ludwigs Universität Freiburg 2001 Diploma in Hydrology Flinders University, Adelaide 1999-2000 Exchange Student 2005 Visiting Scientist
Outline Work Area Mathematical Methods Research Group Student Projects My Ongoing Projects Outlook 3 / 50
Work Area Coupled Geo-Processes FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 4 / 50
Work Area 1. Heterogeneity FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 5 / 50
Work Area 2. Open Fractures FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 6 / 50
Work Area 3. Variable Topography / Unsaturated Soil FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 7 / 50
Work Area 4. Heat Source FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 8 / 50
Work Area 5. Saline Brine FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 9 / 50
Work Area 6. Variable-Density Free Convection FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 10 / 50
Work Area 7. Sealevel Variations / Flooding / Surface Flow FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 11 / 50
Work Area 8. Dissolution / Precipitation of Quartz FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 12 / 50
Research Applications Climatic Change - Geothermal Energy - Radioactive Waste CO2 - etc. FLOODING SURFACE FLOW VADOSE ZONE SEALEVEL VARIATIONS SEAWATER ρ sea FRACTURES PHREATIC ZONE HETEROGENEITY Na-Ca-Cl MAGMA (Heat Source) 13 / 50
Work Goal Understand flow dynamics including coupled geo-processes 14 / 50
THMC - Coupled Processes 15 / 50
THMC - Coupled Processes 16 / 50
HydroGeoSphere Attempt to account for relevant geo-processes in a numerical model Therrien and Sudicky (1996, J Cont Hyd) Numerical groundwater model using Control- Volume Finite Element (CVFE) method Developed in Canada (Waterloo, Québec) Co-developer since 2003 OpenGeoSys, TOUGH2 17 / 50
Outline Work Area Mathematical Methods Research Group Student Projects My Ongoing Projects Outlook 18 / 50
HydroGeoSphere Features Multi-dimensional model 3D: rock matrix 2D: rock fractures 1D: wells, channels Irregular mesh 3D: blocks, prisms, tetrahedrons 2D: rectangles, triangles 1D: lines Variable time-stepping (very efficient) t L+ 1 X = max X max L+ 1 i X L i Multi-species solute transport, heat transfer, fluid flow Variably saturated flow (Richards Equation; Newton Iteration) Variable-density variable-viscosity flow (Picard Iteration) t L 19 / 50
HydroGeoSphere Features 2D overland flow (Diffusion-wave equation) Reactive transport with quartz chemistry Dissolution and precipitation Widening and sealing of fracture and matrix Reaction parameters are fully temperature-coupled SiO 2(s) + 2H O 2 (aq) H 4 SiO 4(aq) 20 / 50
HydroGeoSphere Features Upstream and central weighting of velocities Various time weighting schemes (explicit, Crank-Nicolson, implicit) Full fracture-matrix coupling Discrete fracture approach (DF) Dual continuum approach (DC) Equivalent porous medium approach (EPM) DF DC EPM common nodes (1 unknown) exchange term high K 21 / 50
HydroGeoSphere Features Fully integrated numerical solution of complete hydrologic cycle matrix nodes surface nodes fracture nodes 22 / 50
Numerical Coupling Initial C σ, T next time step no threshold exceeded? update material properties yes N iterations = 0 reduce t repeat timestep reactive TRANSPORT N iterations += 1 Picard Iteration no convergence AND N iterations > 1 yes update fluid properties ρ, µ Newton T C σ FLOW Iteration HEAT TRANSPORT P DARCY q 23 / 50
Outline Work Area Mathematical Methods Research Group Student Projects My Ongoing Projects Outlook 24 / 50
My Vision 25 / 50
Emmy Noether Group DFG funded Nov. 2010 present 3+1+1 years 4 research positions (PhD) 2 MSc projects International team http://www.graf-emmy-noether.uni-hannover.de/ 26 / 50
Outline Work Area Mathematical Methods Research Group Student Projects My Ongoing Projects Outlook 27 / 50
Double-Diffusive Convection Katharina Vujević 28 / 50
Double-Diffusive Convection salt Katharina Vujević heat T1, C1 T2, C2 T2, C3 well mixed fluid layers 29 / 50
Double-Diffusive Convection Form of layers geometry of fracture network? Information of fracture network geometry? Katharina Vujević??? 30 / 50
Coastal Flow Dynamics Jie Yang http://www.uwgb.edu/dutchs/earthsc202notes/tides.htm 31 / 50
Coastal Flow Dynamics Jie Yang Changing flow boundary conditions Surface flow Variable-density flow Variably saturated flow Climatic change Freshwater Salt water 32 / 50
Coastal Flow Dynamics Jie Yang Changing flow boundary conditions Surface flow Variable-density flow Variably saturated flow Climatic change Freshwater Salt water 33 / 50
Coastal Flow Dynamics HydroGeoSphere model Preliminary results Jie Yang 34 / 50
3D Fractured Rock Eugenia Hirthe 35 / 50
3D Fractured Rock Eugenia Hirthe Time truncation error control Role of fracture aperture Role of fracture connectivity in 2D / 3D Role of small / large fractures Which degree of complexity is necessary? 36 / 50
OB Assumption Oberbeck-Boussinesq Assumption (OBA=1,2,3) Carlos Guevara OBA reflects mathematical accuracy of density consideration OB1 (lowest accuracy) OB3 (highest accuracy) Many simulations of variable-density flow use OB1 or 2. Impact of OBA is unclear. 37 / 50
OB Assumption OB Flow Eq. Transport Eq. Darcy Eq. Carlos Guevara 1 ( q) = 1 ρ ( ρφ) t ( j) = ( φω) t q = k μ ( p + ρg z) 2 ( ) ( φω ( ) ( ρφ) ) k ρq = j = q = ( p + ρg z) t t μ 3 ( ρq) = ( ρφ) t ( ρj) = ( ρφω) t q = k μ ( p + ρg z) 38 / 50
Viscosity Variation µ varies with T by one order of magnitude. µ is often assumed constant in studies of variable-density flow. µ affects flux because K = kρg / µ. Qiang Sun viscosity [10-3 kg m -1 sec -1 ] 4 3 2 1 0 brine seawater brackish water freshwater 0 50 100 150 200 250 300 temperature [ C] 39 / 50
Density Benchmark Clemens Cremer Physical sand tank experiment Simmons et al. (2002, Transp Porous Media) Numerical simulation (HydroGeoSphere) Identical fingering 40 / 50
Outline Work Area Mathematical Methods Research Group Student Projects My Ongoing Projects Outlook 41 / 50
Gas Mining 42 / 50
Gas Mining Extraction of natural gas Recoverable gas ~ 1500 km 3 Could supply the entire US for 2 years Extraction via (hydraulic fracturing) fracking Injection of frack fluid to crack the rock Gas can then escape to the surface Environmental concern (frack fluid) 43 / 50
Gas Mining Lake Ontario (1640 km 3 ) 44 / 50
Gas Mining Hydraulic fracturing frack fluid? 45 / 50
Frack Fluid Frack fluid contains toxic additives Arsenic Alcohols Benzene Can these chemicals contaminate groundwater? 46 / 50
Gas Mining HydroGeoSphere model Preliminary results 0.25 h 1h 4h 7h 47 / 50
Outline Work Area Mathematical Methods Research Group Student Projects My Ongoing Projects Outlook 48 / 50
Outlook Open to unresolved questions CO2 sequestration Seawater intrusion Estimation of geothermal potential 49 / 50
Thank You Please visit us at: http://www.graf-emmy-noether.uni-hannover.de/ 50 / 50