140
results show that the dispersion pathway of the different droplet types varies significantly. Indeed, some droplet types remain suspended in the subsea over months,
while others accumulate in the surface layers. In addition, the decay rate of oil
pseudo-components significantly alters the dispersion, denoting the importance of
more biodegradation and dissolution studies of chemically and naturally dispersed
live oil at high pressure. This new modeling tool shows the potential for improved
accuracy in predictions of oil partition in the water column and of advancing impact
assessment and response during a deepwater spill.
Keywords Far-field model · Near-field model · Coupling · Deepwater well
blowout · Coupled near-field and far-field models · Oil transport prediction ·
Model parameterization
9.1 Introduction
During deepwater oil spills, it is fundamentally important to account for both the
complex dynamic processes occurring in the near-field, a couple hundred of meters
above the wellhead, and the continuing transport and biological processes occurring
in the far field, up to kilometers away from the source. The near-field refers to the
dynamic, buoyant mixture of oil, gas, entrained seawater, and potentially gas hydrate
ascending through the water column after release from a broken wellhead, leaking
pipe, or distributed seafloor release. In this chapter we focus on localized sources,
and as this near-field plume ascends in the water column, the lighter fractions of the
gas bubbles and live oil droplets dissolve. Eventually, the ocean density stratification arrests the buoyant plume, forming an intrusion layer, and petroleum fluids
having a weathered composition enter the far-field domain, where ocean currents
and particle motion dominates. Tracking of the oil droplets beyond the near-field is
referred to as far-field modeling. These domains are typically modeled separately
since they occur at different spatiotemporal scales. However, to accurately simulate
the fate and transport of oil and gas emitted from deep-sea blowouts, it is necessary
to enable a smooth transition between near- and far-field models.
When gas and oil are released from an accidental deepwater oil well blowout or
similar highly localized source, models must track the dispersal and dynamics of the
live oil, simulating the generation of the turbulent, buoyant jet caused by the mixture of ambient seawater and gas and oil existing the source, and the subsequent
breakup of the jet into small gas bubbles and oil droplets (Bandara and Yapa 2011;
Johansen et al. 2013; Zhao et al. 2014, 2015, 2017; Nissanka and Yapa 2016; Li
et al. 2017; Wang et al. 2018). After the initial jet breakup, a buoyant plume of gas
bubbles, oil droplets, and entrained seawater develops (Zheng et al. 2003; Socolofsky
and Dissanayake 2016; Dissanayake et al. 2018). The spatial scale of such plumes
is small, in the order of meters; thus, specialized models are adapted to simulate
processes at these small scales. Beginning at the oil spill source, near-field models
track the evolution of spilled oil and gas throughout the region dominated by local,
A. C. Vaz et al.
results show that the dispersion pathway of the different droplet types varies significantly. Indeed, some droplet types remain suspended in the subsea over months,
while others accumulate in the surface layers. In addition, the decay rate of oil
pseudo-components significantly alters the dispersion, denoting the importance of
more biodegradation and dissolution studies of chemically and naturally dispersed
live oil at high pressure. This new modeling tool shows the potential for improved
accuracy in predictions of oil partition in the water column and of advancing impact
assessment and response during a deepwater spill.
Keywords Far-field model · Near-field model · Coupling · Deepwater well
blowout · Coupled near-field and far-field models · Oil transport prediction ·
Model parameterization
9.1 Introduction
During deepwater oil spills, it is fundamentally important to account for both the
complex dynamic processes occurring in the near-field, a couple hundred of meters
above the wellhead, and the continuing transport and biological processes occurring
in the far field, up to kilometers away from the source. The near-field refers to the
dynamic, buoyant mixture of oil, gas, entrained seawater, and potentially gas hydrate
ascending through the water column after release from a broken wellhead, leaking
pipe, or distributed seafloor release. In this chapter we focus on localized sources,
and as this near-field plume ascends in the water column, the lighter fractions of the
gas bubbles and live oil droplets dissolve. Eventually, the ocean density stratification arrests the buoyant plume, forming an intrusion layer, and petroleum fluids
having a weathered composition enter the far-field domain, where ocean currents
and particle motion dominates. Tracking of the oil droplets beyond the near-field is
referred to as far-field modeling. These domains are typically modeled separately
since they occur at different spatiotemporal scales. However, to accurately simulate
the fate and transport of oil and gas emitted from deep-sea blowouts, it is necessary
to enable a smooth transition between near- and far-field models.
When gas and oil are released from an accidental deepwater oil well blowout or
similar highly localized source, models must track the dispersal and dynamics of the
live oil, simulating the generation of the turbulent, buoyant jet caused by the mixture of ambient seawater and gas and oil existing the source, and the subsequent
breakup of the jet into small gas bubbles and oil droplets (Bandara and Yapa 2011;
Johansen et al. 2013; Zhao et al. 2014, 2015, 2017; Nissanka and Yapa 2016; Li
et al. 2017; Wang et al. 2018). After the initial jet breakup, a buoyant plume of gas
bubbles, oil droplets, and entrained seawater develops (Zheng et al. 2003; Socolofsky
and Dissanayake 2016; Dissanayake et al. 2018). The spatial scale of such plumes
is small, in the order of meters; thus, specialized models are adapted to simulate
processes at these small scales. Beginning at the oil spill source, near-field models
track the evolution of spilled oil and gas throughout the region dominated by local,
A. C. Vaz et al.