1. 1 David DiCarlo 2, Roy Wung 2, Sid Senthilnathan 2, Chang Da 2, Prasanna Krishnamurthy 2, Keith Johnston 2, Chun Huh 2, Tip Meckel 2, and Hongkyu Yoon 1 1 Sandia National Laboratories 2 University of Texas at Austin March 03, 2016

2. Challenge 1: Sustaining Large Storage Rates Challenge 2: Using pore space with unprecedented efficiency Challenge 3: Controlling undesired or unexpected behavior Theme 3: Buoyancy- Driven Multiphase Flow Multiphase flow and reactive transport at the pore scale --- CT high pressure CO 2 core flood experiments with and without nanoparticles Experimentally tested invasion percolation modeling of buoyancy driven flow Controlling Flow of CO 2 Using Surface-Treated Nanoparticles 2 Senior PersonnelStudents and Post-Docs Chun Huh: nanoparticle chemistry and applications Keith Johnston: nanoparticles chemistry and coatings Tip Meckel: IP flow modeling David DiCarlo: high-pressure flow experiments Hongkyu Yoon: continuum-scale flow modeling Chang Da: nanoparticle chemistry and coatings Sid Senthilnathan: high-pressure flow experiments Prasanna Krishnamurthy: IP flow modeling Roy Wung: high-pressure flow experiments

3. Activity Objectives CO 2 is known to move through fast flow paths bypassing much of the aquifer storage space and potentially leaking faster. Here we inject surface- treated nanoparticles into the brine ahead of the CO 2 to control the CO 2 flow. We discover a) good flow control, and b) a model for the flow physics. Further experiments detail the optimal nanoparticle parameters (coating, concentration, emplacement, etc.) and how buoyancy affects the flow. Storage Efficiency Improve sweep efficiency Predict solubility trapping Predict mineral trapping Controlling Emergence Prevent unwanted fracturing Sustaining Injectivity Control wellbore failure Enhance permeabilty/avoid precipitation during injection Guide injection limits CHALLENGES Enhance capillary (ganglion) trapping Control pathway development Prevent unexpected migration of CO 2

4. Why Nanoparticles? Nanoparticles are much smaller than colloids and can be transported with minimal losses in porous media Nanoparticles can stabilize an emulsion by armoring the interface between the fluids – depends on particle wettability CO 2 Water θ θθ Different nanoparticles Water in CO 2 emulsion CO 2 in water emulsion

5. Nanoparticle Stabilized Emulsions  5 nm silica nanoparticles  5 nm coating PEG  Minimize aggregation & retention  Hydrophilic  Octane in water emulsion formed in test tube by applying high-shear rate 50 μm Will emulsion form with CO 2 in porous media, and if so, how will it affect the flow pattern of CO 2 ?

6. Brine5% Nano10% NanoOctaneCO 2 µ (cP)11.21.30.540.046 ρ (kg/m 3 )101010401080703685 σ(mN/m)N/A 5124 N Ca N/A 4 x 10 -8 1x10 -7 Core Flood Experiments Inject CO 2 analog (octane) or high-pressure CO 2 into a 1’ long, 3” diameter brine-filled core Observe displacement using CT scanning, pressure drops, and effluent measurements Compare with and without nanoparticles in initial brine Do experiments as a function of nanoparticle chemistry, concentration, and emplacement unfavorable mobility capillary dominated

7. n-Octane Displacing Brine w/ and w/o Nanoparticles After 0.1 PV of injection; Images are 1 cm apart color scheme – cold = octane, warm = brine Flow is preferential; expected for unfavorable mobility 7 cm Without nanoparticles With nanoparticles 7 cm

8. Longitudinal View 3 cm Without nanoparticles With nanoparticles 0.1 PV

9. Experiments Using Octane Pressure measurements When nanoparticles are present –Flow is stable –Slower –Higher pressure drop Nanoparticles reduced the mobility of the octane Physical explanation?

10. Pore-Scale Displacement Process No Nanoparticles Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off Initial stage: the core is saturated with Nanoparticle solution Water

11. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off Octane invades the big pores Water Octane Pore-Scale Displacement Process No Nanoparticles

12. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off The interface reaches the minimum radius Water Octane Water Pore-Scale Displacement Process No Nanoparticles

13. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off The interface becomes unstable rapidly jumping forward Water Octane Water Pore-Scale Displacement Process No Nanoparticles

14. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off A droplet of non-wetting phase is “snapped- off” in the pore Water Octane Water Pore-Scale Displacement Process No Nanoparticles

15. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off As the displacement proceeds, subsequent droplets coalesce Water Octane Water Pore-Scale Displacement Process No Nanoparticles

16. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off Flow proceeds to next throat Water Octane Water Pore-Scale Displacement Process No Nanoparticles

17. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off Displacement process begins as before, and octane jumps into pore Water Octane Water Pore-Scale Process With Nanoparticles

18. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off When “snapped-off” nanoparticles armor the surface Water Octane Water Pore-Scale Process With Nanoparticles

19. Non-wetting phase displaces the wetting phase Capillary pressure increases during the displacement Roof- Snap off Droplets do not coalesce, blocking the pore Water Octane Water What about high pressure CO 2 ? Pore-Scale Process With Nanoparticles

20. Without nanoparticles With nanoparticles Early High Pressure CO 2 Displacements After 0.25 PV of injection Only small differences Alter nanoparticle sizes and coatings – Huh & Johnston

21. CO 2 Flood Profiles with New Nanoparticles 21 0 wt% NP 0.5wt% NP 5.0 wt% NP (0.15 PV CO 2 Injected) (0.25 PV CO 2 Injected) (0.50 PV CO 2 Injected) (1.50 PV CO 2 Injected) (0.15 PV CO 2 Injected) (0.25 PV CO 2 Injected) (0.50 PV CO 2 Injected) (1.50 PV CO 2 Injected) (0.15 PV CO 2 Injected) (0.25 PV CO 2 Injected) (0.50 PV CO 2 Injected) (1.50 PV CO 2 Injected)

22. Cross Sections of Invasion and Chase Flood 22 0.15 PV CO 2 0.25 PV CO 2 0.50 PV CO 2 1.50 PV CO 2 0.05 PV Brine 0.10 PV Brine 0.15 PV Brine 0.50 PV Brine 0 wt% NP 0.5wt% NP 5.0 wt% NP

23. Using nanoparticles we can store over 100% more CO 2 Pressure drops look like flow resistance at the front Performed experiments with different emplacements – still optimizing Horizontal Floods 23

24. Can the same mechanism be used to slow or stop vertical leaks? Can we predict movement of CO 2 using models? Perform experiments vertically Vertical Floods 24

25. Have taken a 1 mm resolution scan of cross-bedded sandstone core Perform flow experiments at a low enough velocity so gravity dominates Comparing results to invasion percolation model (capillary dominated migration) – Meckel and Krishnamurthy Comparing results to a full physics flow model (viscous, gravity, and heterogeneity) - Yoon Nanoparticles and Buoyancy Driven Flow 25

26. Activity Impact Presence of nanoparticles in brine slows down CO 2 front propagation in heterogeneous porous media. Nanoparticles in brine are shown to increase amount of capillary trapped CO 2 by over 100%. Experimental and modeling effort taking place to see how nanoparticles alter buoyancy driven flow. Storage Efficiency Improve sweep efficiency Predict solubility trapping Predict mineral trapping Controlling Emergence Prevent unwanted fracturing Sustaining Injectivity Control wellbore failure Enhance permeabilty/avoid precipitation during injection Guide injection limits CHALLENGES Enhance capillary (ganglion) trapping Control pathway development Prevent unexpected migration of CO 2