How Do Oil, Gas, and Water Interact Near a Subsea Blowout?
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University of South Florida Scholar Commons C-IMAGE Publications C-IMAGE Collection 8-2016 How Do Oil, Gas, and Water Interact Near a Subsea Blowout? Scott A. Socolofsky Texas A&M University E. Eric Adams Massachusetts Institute of Technology Claire B. Paris-Limouzy University of Miami Di Yang University of Houston Follow this and additional works at: https://scholarcommons.usf.edu/cimage_pubs Part of the Marine Biology Commons Scholar Commons Citation Socolofsky, Scott A.; Adams, E. Eric; Paris-Limouzy, Claire B.; and Yang, Di, "How Do Oil, Gas, and Water Interact Near a Subsea Blowout?" (2016). C-IMAGE Publications. 67. https://scholarcommons.usf.edu/cimage_pubs/67 This Article is brought to you for free and open access by the C-IMAGE Collection at Scholar Commons. It has been accepted for inclusion in C-IMAGE Publications by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. OceTHE OFFICIALa MAGAZINEn ogOF THE OCEANOGRAPHYra SOCIETYphy CITATION Socolofsky, S.A., E.E. Adams, C.B. Paris, and D. Yang. 2016. How do oil, gas, and water interact near a subsea blowout? Oceanography 29(3):64–75, http://dx.doi.org/10.5670/ oceanog.2016.63. DOI http://dx.doi.org/10.5670/oceanog.2016.63 COPYRIGHT This article has been published in Oceanography, Volume 29, Number 3, a quarterly journal of The Oceanography Society. Copyright 2016 by The Oceanography Society. All rights reserved. USAGE Permission is granted to copy this article for use in teaching and research. Republication, systematic reproduction, or collective redistribution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The Oceanography Society. Send all correspondence to: [email protected] or The Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA. DOWNLOADED FROM HTTP://TOS.ORG/OCEANOGRAPHY GoMRI: DEEPWATER HORIZON OIL SPILL AND ECOSYSTEM SCIENCE How Do Oil, Gas, and Water Interact Near a Subsea Blowout? By Scott A. Socolofsky, E. Eric Adams, Claire B. Paris, and Di Yang 64 Oceanography | Vol.29, No.3 At low flow rates into seawater, oil jets are laminar and break up into droplets having nearly uniform diameters… However, for higher flow rates, the“ jet is turbulent, and the oil becomes atomized into a spectrum of smaller droplets whose diameters decrease with increasing flow rate. ABSTRACT. Oil and gas from a subsea blowout shatter into droplets and bubbles that was near complete dissolution of methane,” rise through the water column, entraining ambient seawater and forming a plume. Local significant dissolution of small hydrocar- density stratification and currents eventually arrest this rising plume, and the entrained bon molecules (Ryerson et al., 2011), and water, enriched with dissolved hydrocarbons and some of the smaller oil droplets, near complete oxidation of methane in forms one or more subsurface intrusion layers. Beyond the plume and intrusion the water column (Du and Kessler, 2012). layer(s), droplets and bubbles advect and diffuse by local currents and dissolve and These measurements highlight the impor- biodegrade as they rise to the surface, where they are transported by wind and waves. tance of subsurface processes to hydro- These processes occur over a wide range of length scales that preclude simulation by carbon fate, yet there remain significant any single model, but separate models of varying complexity are available to handle uncertainties in the processes responsible the different processes. Here, we summarize existing models and point out areas of for these effects. ongoing and future research. To bridge this gap, studies of trans- port processes in the nearfield (where INTRODUCTION small-scale processes that transport oil vertical plume rise is significant) and far- The Deepwater Horizon (DWH) acci- and gas near a subsea blowout. field (where bubbles and droplets advect dent demonstrated in dramatic fashion Most observations made during DWH independently) are underway by sev- the wide range of processes that affect oil were beyond the 5 km response zone— eral groups, many funded by the Gulf of droplets and gas bubbles released from hence, beyond the region of major droplet/ Mexico Research Initiative (GoMRI). To a subsea blowout. These processes begin bubble dynamics—and primary observa- communicate research quickly among with breakup of the blowout jet into small tions were of the spill’s dissolved signature this network of colleagues, the Nearfield droplets and bubbles, followed by their within the water column (e.g., Valentine, Modeling Listserv was created (near- vertical transport as a buoyant plume, et al., 2010; Kessler, et al., 2011; Du and [email protected], mod- horizontal transport within intrusion lay- Kessler, 2012). As in all spills, droplet size erated by author Socolofsky), and the ers caused by local density stratification, distribution is critical to predict the oil’s user group has hosted three work- advection and diffusion by local currents, fate and transport. For DWH, significant shops. This group identified five areas for and additional mixing near the surface quantities of chemical dispersants were study: (1) bubble and droplet generation, due to wind and waves. Simultaneously, applied subsurface, directly at the spill (2) plume modeling, (3) intrusion forma- dissolution and biodegradation alter the source, to promote formation of smaller tion and coupling to circulation models, oil and gas mixtures. How these pro- oil droplets (Brandvik et al., 2013). (4) particle tracking models, and (5) bub- cesses occur, their rates, and what man- However, no measurements of bubble ble and droplet fate modeling (an inte- agement strategies may affect them are or droplet size distributions were made grative topic present in each of the pre- important questions as we look to under- in situ at the source. The few measure- vious four areas). Here, we discuss the stand the impact of DWH on the Gulf ments made inside the response zone con- first four topics and touch on dissolution of Mexico and to seek mitigation strate- firmed the strong plume behavior of the (topic five), showing how oil and gas mix gies for potential future oil spills. Here, oil and gas jet (Camilli et al., 2011), deter- and are dispersed from a subsea blowout. we discuss our present understanding mined the emission composition (Reddy, For farfield transformation, see Tarr et al. of, and the ongoing research addressing, et al., 2011), and demonstrated that there (2016, in this issue). Oceanography | September 2016 65 MODELING DEEPWATER atomized into a spectrum of smaller observed median droplet diameters d50, BLOWOUTS droplets whose diameters decrease with measured in laboratory experiments with Droplet Generation increasing flow rate (Figure 1). The tran- oil jetted into seawater (e.g., Brandvik The sizes of bubbles and droplets gener- sition from laminar to turbulent jet et al., 2013), to the Weber number using ated in a subsea blowout affect hydrocar- breakup depends on a Weber number the orifice diameter and velocity as bon transport and fate in several ways. (Tang and Masutani, 2003), length and velocity scales in Equation 1. First, oil and gas are buoyant, causing the ρU2 D The simplest equation in this empirical We =–0 , (1) hydrocarbons to rise toward the surface as σ approach is a plume (see section on Nearfield Plume where ρ = oil density, U = exit velocity, d 0 –50 = AWe –3/5 (2) Dynamics, below). Second, depending D = orifice diameter, and σ = interfacial D , on their sizes, the droplets and bubbles tension. At the time of DWH, no consen- where A is a fitting coefficient. Following may separate from the entrained sea water, sus models were available to predict actual Wang and Calabrese (1986), Johansen resulting in different pathways to the droplet sizes in the atomization regime. et al. (2013) modified Equation 2 to surface (see section on Intrusion Layer Under these energetic conditions, tur- account for viscosity (which resists drop- Formation and Farfield Tracking Models, bulent pressure fluctuations cause oil to let breakup when interfacial tension is below). And third, droplets and bubbles break up into increasingly smaller drop- reduced due to the use of dispersants). provide the surfaces across which hydro- lets until they reach a critical size at which They also accounted for the presence of carbon constituents are dissolved into sea- breakup is resisted by interfacial tension gas mixed with the oil. For a given oil flow water and ultimately degraded. Chemical (Brandvik et al., 2013). Coalescence due rate and orifice, the gas increases the exit dispersants, designed to reduce interfacial to droplet collision may also play a role. velocity of oil; it also increases the down- tension and, thus, droplet size, override For decades, chemical engineers have stream buoyancy of the jet relative to a this process. The effectiveness of disper- studied such processes under equilib- pure oil jet. Johansen et al. (2013) thus sants depends on how much smaller they rium conditions, and developed correla- predict median droplet size as a function can make the droplets, and how much dif- tions of characteristic droplet size with of a modified Weber number, ferently smaller droplets are transported a Weber number, choosing values for U0 –3/5 d50 We compared with larger, undispersed drop- and D appropriate for a stirred reactor – = A –– , (3) D 1 + BVi (d /D) lets. While both droplets and bubbles are (Hinze, 1955). However, except for a short [ 50 ] important, we focus here on oil droplets. distance of several orifice diameters from where We is now based on Uc = a corrected At low flow rates into seawater, oil jets the source, oil emanating from a blowout exit velocity to account for gas and buoy- are laminar and break up into droplets is not in equilibrium, but instead exhibits ancy, Vi = µUc /σ, µ = dynamic viscosity of having nearly uniform diameters, com- rapidly decreasing turbulence and droplet oil, and A and B are empirical coefficients.