High-pressure visual experimental studies of oil-in-water dispersion droplet size Zachary M. Aman a,n , Claire B. Paris b , Eric F. May a , Michael L. Johns a , David Lindo-Atichati b a Centre for Energy, School of Mechanicaland Chemical Engineering, The University of Western Australia, 35 Stirling Highway, Crawley 6009, WA, Australia b University of Miami, Rosenstiel School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Miami, FL 33149, United States HIGHLIGHTS  High-pressure autoclave used to study oil-in-water dispersion.  Droplet sizes captured visually with sapphire cell and high-speed camera.  An inertial model was used to predict the mean droplet size with Re.  Deepwater blowout may sequester small oil droplets in water column. GRAPHICAL ABSTRACT Mean diameter of crude oil droplets in water, as a function of mixing speed in a high-pressure sapphire cell. Droplet size distributions were captured visually, to improve estimation of the mean droplet size generated during deepwater blowout. article info Article history: Received 24 September 2014 Received in revised form 20 January 2015 Accepted 24 January 2015 Available online 4 February 2015 Keywords: Droplet size Mixing Deepwater blowout Multiphase flow abstract The formation of oil-in-water dispersions is a critical step during the blowout of coastal and deepwater oil and gas production systems, and is a determining factor in the vertical and lateral migration of oil through the associated adjacent water column. In this study a high-pressure sapphire visual autoclave apparatus was used to measure the size of crude oil droplets that were saturated with gas and dispersed in an aqueous phase as a function of mixing speed. Oil-in-water droplet size distributions were measured at pressures of 11 MPa, for autoclave stirring rates of 200–1000 RPM (1076 rRe stirred vessel r5378). Arithmetic mean droplet diameters decreased monotonically from 344 to 125 μm over this range, with maximum droplet sizes decreasing from 708 to 441 μm. A model tuned to the measured oil-in-water data was used to predict a mean droplet size on the order of 80 μm for Deepwater Horizon conditions; when incorporated into far field blowout simulations, this droplet size data enables quantitative assessment of the impact of dispersant injection at the blowout site. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction In deepwater blowout scenarios, such as a ruptured subsea oil pipeline, a positive pressure difference between the reservoir and hydrostatic water column adjacent to the blowout point results in the uncontrolled release of hydrocarbon to the environment. The contact between the dispersing hydrocarbon and aqueous bulk phase results in the dispersion of liquid and gaseous hydrocarbon in water. Gas bubbles are unlikely to remain trapped in the water column for a prolonged period, due to both the substantial density difference between gas and water, and the rapid dissolution of light hydrocarbons in seawater (Chen et al., 2013). Conversely, numerical studies by Paris et al. (2012) suggest that small oil droplets may naturally stratify at depths beyond 1000 m, enabling extensive subsea lateral transport. To correctly predict the fate of entrained oil, fundamental models of oil droplet size distributions during blowout are required over a range of dispersing fluid types and shear conditions. Kolmogorov Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ces Chemical Engineering Science http://dx.doi.org/10.1016/j.ces.2015.01.058 0009-2509/& 2015 Elsevier Ltd. All rights reserved. n Corresponding author. Tel.: þ61 8 6488 3078. E-mail address: zachary.aman@uwa.edu.au (Z.M. Aman). Chemical Engineering Science 127 (2015) 392–400