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Research Papers: Pipeline Systems

New Developments for the Description of Oil Leakages by Advective Migration From Submarine Pipelines

[+] Author and Article Information
Renan Martins Baptista

Petrobras R & D Center, Cidade Universitária, Ilha do Fundão, Quadra 7, 21949-900 Rio de Janeiro, Brazil

Ricardo Antonio Francisco Machado, Marintho Bastos Quadri, Ariovaldo Bolzan, André Lourenço Nogueira, Toni Jefferson Lopes

Department of Chemical Engineering, Federal University of Santa Catarina, Caixa Postal 476, Trindade Florianópolis, 88040-000 Santa Catarina, Brazil

J. Pressure Vessel Technol 131(3), 031701 (Apr 06, 2009) (8 pages) doi:10.1115/1.3089499 History: Received January 15, 2007; Revised January 14, 2009; Published April 06, 2009

The significant growth in offshore operations increases the risk of a pipeline rupture, even considering the high standards of safety involved. Throughout a submarine leakage, four different amounts of oil may be accounted. The first one is the oil volume released until the leakage detection. The second one is the volume leaked throughout mitigation initiatives (e.g., pump shutdown and valve closure). The third parcel is the amount released by gravitational flow. Finally, the fourth and last amount of oil is released due to the water-oil entrainment, generally known as advective migration. Normally, a considerable amount of oil is released in this step. It begins just after the internal pipeline pressure becomes equal to the external one. The present work continues to introduce a mathematical alternative approach, based on the theories of perturbation and unstable immiscible displacement, to accurately estimate the leakage kinetics and the amount of oil released by the advective migration phenomenon. Situations considering different hole sizes and thicknesses were tested experimentally and through simulations. Additional experiments were accomplished using smooth and rough edge surfaces, besides different slopes (using the horizontal plane as reference). Those experiments permitted a preliminary evaluation of the importance of these factors. The results obtained with the model showed good agreement with the experimental data in many situations considered.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Detailed scheme of the experimental apparatus: (a) initial condition with a plane interface, (b) perturbed interface after a rotation of 180 deg of the apparatus, and (c) real horizontal situation simulated with the experiments

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Figure 2

Experimental test using a slab with a circular hole (Rh=1.0 cm) after the steady state achievement: (a) original photography; (b) white lines highlighting water and oil fingers, besides the area boundaries of both fingers; and (c) oil finger penetrating the water phase

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Figure 3

Experimental test using a slab with a rectangular hole (4.61×1.54 cm2) after the steady state achievement: (a) formation of a pair of opposite and contiguous fingers; (b) formation of two oil fingers close to the hole smaller edges and one water finger in the central region

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Figure 4

Effect of the hole geometry on the leakage kinetic (maintaining constant the constant ratio between rectangular and circular perimeters=1.30 and thickness=0.4 cm): (a) hole area of 3.14 cm2, equivalent to Rh=1.0 cm; (b) 7.07 cm2, equivalent to Rh=1.5 cm; and (c) 12.57 cm2, equivalent to Rh=2.0 cm

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Figure 5

Effect of the presence of grooves on the leakage kinetic: (a) Rh=1.0 cm, (b) Rh=1.5 cm, and (c) Rh=2.0 cm

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Figure 6

Effect of the hole thickness on the leakage kinetic, considering a smooth wall: (a) Rh=1.0 cm, (b) Rh=1.5 cm, and (c) Rh=2.0 cm

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Figure 7

Effect of the hole plane inclination on the leakage kinetic (Rh=2.0 cm and thickness of 0.4 cm)

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Figure 8

Experimental leakage flow for different hole radii (Rh) and thicknesses (σ) as a function of the effective interfacial tension adjusted by the model

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Figure 9

Pareto’s chart of standardized effects; variable: leakage flow 2 three-level factors, 1 block, 26 runs; MS Pure Error: 1.177695

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Figure 10

Experimental versus statistical model results of the steady state leakage flow for different holes radii (Rh) and wall thicknesses (σ)

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Figure 11

Illustration of the water/oil interface for circular holes with thin (a) and thick (b) walls

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