Comportamento bidimensional da pluma de óleo e gás oriunda de um blowout na região da bacia potiguar

Abstract

Mathematical modeling of underwater oil spills contributes to the understanding of oil migration, prediction of affected areas and provides a technical basis for the choice, development and application of efficient containment actions. Accidents such as the Deepwater Horizon platform in 2010 highlight the importance of safe monitoring and prediction models. The accuracy of mathematical models is closely linked to near-field information and the incorporation of details of the environment, including the processes occurring immediately at the spill site and the dynamics of the plume. The study of such factors is relevant for estimating results and improving response methods, for example, the underwater application of dispersants at the source. In blowout scenarios, factors such as the influence of ocean currents, high pressures and interaction with the underwater environment cause difficulties in modeling the occurrences before their observation on the surface. In this context, the present work aims to improve the understanding of the processes involved in modeling submarine leaks, applying this analysis to the Potiguar Basin, in northeastern Brazil. Recent knowledge in near-field modeling is applied to develop a case study of an underwater oil and gas plume simulating a blowout scenario in the analyzed region, in order to map variables such as the time and distance expected for contamination to reach the surface, compositions and distribution of particle diameters throughout the generated plume. The methodology employs the open-source model Texas A&M Oil Spill Calculator (TAMOC), which uses a Lagrangian approach for integral modeling of oil and gas particles in submarine plumes. For a depth of 1 km, simulations were carried out for two horizontal velocities of ocean currents (v1 = 0,09 m/s and v2 = 0,2 m/s). The estimated minimum time for contamination to reach the surface was 1,1 h for v1, at a horizontal distance of 414,47 m from the source; and 1,37 h for v2 at approximately 1 km horizontal distance from the source. Particles released at time t = 0 s, depending on their composition and size, can take up to 13,4 h to emerge (appearing on the surface 4,48 km from the origin) for v1, and up to 14,4 h (10,8 km from the origin) for v2. The pattern of compositions when the particles reach the surface predicts higher fractions of benzene, toluene and ethylbenzene in regions closer to the source and higher percentages of n-heptane and n-decane in particles that emerge last. The difference in horizontal velocities of the environment does not significantly impact the composition, but it was observed that the percentages of mass lost throughout the water column are more significant for the higher drag speed. The particles range in size from 0.63 mm to 16.19 mm, presenting a distribution with d50 = 5.873 mm. The results provide the visualization of the expected magnitude of critical plume variables during the first hours after the blowout occurrence and the influence of current speeds on these parameters.