Autores UNAM:
JEAN FRANCOIS YVES PIERRE PARROT;

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Autores externos:

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Idioma:

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Año de publicación:
2020

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Palabras clave:

Codes (symbols); Contour measurement; Diffusion; Expansion; Gasoline; Pixels; Surveying; Viscosity; Catastrophic event; Diffusion propagation; Digital elevation model; Directional interpolation; Drainage networks; Pipeline rupture; Soil permeability; Vertical resolution; Pipelines

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Resumen:

Many accidental pipeline ruptures frequently occur in the study region located in the state of Veracruz (Mexico). In relation to the volume involved, the diffusion and extension of the petroleum flux affect this region. For this reason it is necessary to study the eventual extension of the flux when such an event occurs. A high resolution Digital Elevation Model (DEM) is used as a simulation for evaluating the diffusion-propagation of petroleum flux of the Mexican brand in order to assess its consequence at a regional scale. The DEM is generated by an algorithm introduced by Parrot and Ochoa-Tejeda (2005) which is based on a multi-directional interpolation applied to each point located in a hypsometric slice comprised between two successive contour lines. The decimetre vertical resolution partly eliminates artefacts introducing local breaks in the drainage network. Therefore using contour lines of 20 m interval, a 10 m resolution DEM with a 1/10 m vertical resolution is obtained. In the present case, the motion of oil with thickness is related to viscosity depending on the hypsometric value of the neighboring pixels in such a way that extension is able to invade the region around the pipeline rupture. The procedure consists in applying to the DEM the following algorithm. From the starting point that corresponds to the localization of the pipeline rupture (blue point in the figure 1), the motion of the petroleum flux which thickness is related to the viscosity depends on the hypsometric value of the neighboring pixels. At each step, pixels that fulfill the requirements are considered as new starting points. The expansion of the petroleum flux depends on possible displacements in an isotropic environment. In such a way that the extension, contrariwise in a simple flooding process, is able to invade the region downstream and upstream as it can be observed in figure 1. Figure 2 illustrates the progression of the pixel filling. Two neighboring pixels (code 2) are filled by the flux. Four neighboring pixels (code 3) are related to the first code 2. The second code 2 gives rise to a unique connection (code 4). Following this procedure, the algorithm takes into account the first code 3 and so on. The result of the simulation is validated according the observation on the field of a real expansion of to petroleum flux provided by a pipeline rupture. Analysis of the results is focused in two testing cases (Figures 3 and 4). The first one is aimed to show how propagate the petroleum flux into the depression and thereafter to escape following the downstream valley. It is taking account of the viscosity of oil, the soil permeability and the localization of the rupture point. The second one is an alternative way to petroleum flux reaching the sea shore. The simulation corresponds to dry season in a sandy zone so as a high percentage of oil is absorbed. Discussions and comparison between simulations are based on the field of a real expansion of petroleum flux provided by a pipeline rupture. The results of the simulation are validated according to the example cited above. In all cases the thickness of the Mexican brand is evaluated on a flat surface supposed to be equal to 20 cm. It is also supposed the approximation of the expression of petroleum in an isotropic environment and the soil map is not sufficiently precise to really take into account the porosity rate as a consistent parameter. On the other hand, it is possible to simulate the phenomenon at a regional scale, assuming that all points drawing the pipeline can be affected by such a catastrophic event. The resulting maps can indicate at a regional scale all the zones that are concerned by the phenomenon in relation to the total volume of brand mobilized. © MODSIM 2009.All rights reserved.

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Entidades citadas de la UNAM:

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