Physical and Numerical Models of Pore-Scale Trapping of CO 2

1. International Conference on Flows and Mechanics in Natural Porous Media from Pore to Field Scale – Pore2Field Rueil-Malmaison, France November 16-18, 2011 Physical and Numerical Models of Pore-Scale Trapping of CO2 Tim Scheibe, Alexandre Tartakovsky, Uditha Bandara, Bruce Palmer, Mart Oostrom, Changyong Zhang, and Alain Bonneville Pacific Northwest National Laboratory tim.scheibe@pnl.gov

2. Carbon Sequestration Initiative A computational platform and a suite of experimental capabilities that facilitates collaboration to rapidly advance scientific understanding and safe deployment of geologic storage. (3 focus areas, 15 projects, 40 researchers, 5 years, ~$15M) • An experimental suite – In Situ Supercritical Suite (IS3): • Probe reactions at molecular scales under supercritical conditions • Processes that impact the integrity of the caprock • Geochemistry when CO2 is the solvating fluid • A modeling suite – Modelling Schemes for Subsurface Sequestration (MS3): • Simulate cosequestration of multiple gases/fluids • Full coupling of geochemistry, hydrology, and geomechanics within simulators • Physical and numerical modeling of pore-scale processes and incorporation into Darcy-scale simulators • A computational platform - Geologic Sequestration Software Suite (GS3): • Accelerate the translation of data into scientific understanding and, in turn, prediction and simulation • Improve accessibility and use of advanced simulators • 3-D visualization & parameter estimation environment Alain Bonneville Kevin Rosso Tim Scheibe Ian Gorton

3. Multiscale Issues in CO2 Sequestration • Effectiveness of carbon sequestration may be strongly impacted by processes occurring at very small scales • Capillary trapping • Reactions • Porosity-permeability changes • Geomechanics • Density instability • Scale of injection (and therefore simulation) is necessarily very large • “Tyranny of scales” • Field-scale models are largely phenomenological

4. Pore-Scale Modeling Methods • “Models” – Both physical and numerical: • Physical microfluidics models: Oostrom and Zhang • Numerical pore-scale models: Tartakovsky, Bandara and Palmer

5. Experimental Micromodel Setup Zhang et al., ES&T, 2011 Grate et al., Water Resour. Res., 2010 Capability for supercritical CO2 injection at in-situ pressure and temperature Etched silicon wafers with micron-scale precision Solvochromatic dyes for flow visualization

6. Implications for Field-Scale Simulators Zhang et al., Energy Fuels, 25:3493-3505, 2011 Ca = Ratio of viscous to capillary forces M = Viscosity ratio

7. Numerical Simulations • Tartakovsky and Meakin, Adv. Water Resour. 2006 – SPH for multiphase flow • Palmer et al., Int. J. High Performance Computing Applications 2010 – parallel implementation • Grid-free lagrangian method well-suited for problems with moving interfaces • Multiphase flow • Precipitation/dissolution reactions • Biofilm dynamics High performance Smoothed Particle Hydrodynamics (SPH) code for multiphase flow and reactive transport

8. Micromodel Simulations Viscous Fingers log M=-1.95log Ca=-3.87 Capillary Fingers: log M=-0.49 log Ca=-5.91 • 2D SPH implementation to simulate immiscible displacement phenomena for a range of capillary numbers and viscosity ratios • Bandara et al., Int. J. Greenhouse Gas Control (in press) and manuscript in preparation

9. Implications for Field-Scale Simulators Experimental studies provide confidence in pore-scale simulator (validation) Constitutive relationships (P/S/K) for specific pore geometries can be defined from experiments and extended to a wider range of configurations using the validated numerical simulator

10. Effect of Pore-Scale Anisotropy Tartakovsky et al., Physics of Fluids, 2007 • Reservoir scale (continuum) models rely of Pressure-Saturation relationships to model CO2 injection in subsurface • Current state of the art is to treat P(S) as direction independent • Our model shows that P(S) function is direction dependent

11. Mixed and Variable Wettability • Contact angle and which fluid is wetting can vary both spatially and temporally • Spatial variability of mineral surfaces and surface/fluid interaction properties • Reactions with CO2 can modify wettability (Chiquet et al. 2007; Evje and Hiorth 2010; Wan et al 2011) • Wettability of physical micromodels can be controlled through silanization of surfaces (Grate et al., submitted) • Contact angle of wetting fluid can be controlled in SPH through specification of particle-particle interaction forces

12. Mixing-Controlled CaCO3 Precipitation Micromodel experiments (Zhang et al., ES&T, 2010).

13. Connect to Larger Scales… (after Kevrekidis et al. 2003) • Multiscale dimension reduction approach (Tartakovsky and Scheibe, Adv. Water Res., 2011) • Reduce degrees of freedom (number of time steps) solved in microscale simulation by iterating between microscale and macroscale • Perform numerical closure on microscale where insufficient general closure exists

14. Connect to Larger Scales… Complete Pore-Scale Solution Dimension Reduction Solution Multiscale dimension reduction approach (Tartakovsky and Scheibe, Adv. Water Resour., 2011)

15. Summary of Highlights PNNL is developing an integrated experimental and numerical models suite of tools for CO2 sequestration Focus on reactivity of water-wet supercritical CO2 at pressure and temperature and integrated modeling from pore- to reservoir-scales using physical micromodels and advanced computational tools Physical and numerical pore-scale models offer opportunities to gain understanding and quantitative descriptions that can support larger-scale modeling Pore-scale models can be efficiently coupled with continuum-scale models using a hybrid multiscale dimension reduction approach