American Geophysical Union Fall Meeting V21A-2474

1. Surface Modification Methods to Control Wettability in Immiscible Fluid Displacement Experimental Model Systems Relevant to Geological Carbon Sequestration J.W. Grate, C. Zhang, M. Oostrom, T.W. Wietsma, M.G. Warner, J.W. Pittman, and K.J. Dehoff American Geophysical Union Fall Meeting V21A-2474 The legends PROTECTED INFORMATION and PROPRIETARY INFORMATION apply to information describing Subject Inventions as defined in Contract No. DE-AC05-76RLO1830 and any other information which may be properly withheld from public disclosure thereunder.

2. Contact Angle Measurements -Surface wettability has effect on scCO2 behavior. -In our CSI project, we’re investigating pore-scale displacement of brine by scCO2 at different wettabilities. -Fully water-wet clean silica surfaces can be modified with silanes to alter the wettability, with the majority of such efforts to date related to conversions of water-wet to oil-wet systems.   -While a sizable literature exist on contact angles obtained on silanized surfaces, these are by and large air-water contact angle data, not the oil-water contact angles that are relevant to multiphase flow. Silica UV-ozone cleaned 79 97 3 95 140 13 triethoxy 2-thienyl silane HMDS: hexamethyl disilazane Intermediate wet Water wet Oil wet

4. Experimental Results

5. First experimental test of theory (Van Dijke et al, 2002) relating oil-water and air-water contact angles (submitted to Langmuir)

6. Summary and Conclusions • Smooth silica surfaces were modified with a diverse range of silanes to produce oil wet, intermediate wet, and water wet interfaces. • A linear correlation relating air-water and oil-water contact angles was obtained, allowing oil-water contact angles to be estimated from more common air water contact angle data for modified surfaces • We tested the theory derived by van Dijke and Sorbie that relates the cosines of air-water and oil-water contact angles in terms of the fluid interfacial tensions. Our results are in excellent agreement with this previously untested theory. • Silanizationwas implemented inside a silicon/silica/glass miciromodel, and the contact angle was determined in situ, demonstrating water wet, intermediate wet, and oil wet surfaces. In this approach, a single micromodel technology based on precise dry etched silicon pore networks can be used for studies over a range of controlled wettabilities (vs wettability based solely on material). 6