Single-Phase or Multiphase Blowdown of Vessels or Pipelines

Abstract

In order to predict the consequences of a leak or rupture of a pipeline or vessel, or to design a controlled pressure release system, a method of predicting the mass efflux is required. Although a large body of literature exists on blowdown simulation for vessels or short pipes, relatively little analysis and experimentation has been performed for the depressurization behavior of pipelines. In addition, the impact of the thermodynamics of multicomponent hydrocarbon fluids has been relatively unexplored. A mechanistic homogeneous equilibrium model applicable to both vessels and pipelines has been written. Since fluid thermodynamics are evaluated external to the model, single or multicomponent fluids can be simulated as well as single or multiphase flows. In addition, a series of small scale blowdown experiments has been made using both gas bottles and coiled tUbing. The coiled tubing has a length to diameter ratio of SO,OOO, comparable to that encountered in field piping. Air, carbon dioxide, and carbonated water have been used in the experiments.Excellent agreement between the model and experiments has been obtained, along with excellent agreement with at least one field data set.

When does a vessel become a pipe?

“…Norris, 21,22 for example, proposes a 'unified outflow model' for vessels and pipelines. Apart from the steady-state flow assumption, the model ignores wave dynamics and pipe/wall heat-transfer effects.…”

“…In an attempt to address the long computational workloads associated with simulating pipeline ruptures, a number of authors have proposed simplistic pipeline models based on steady-state flow assumptions for which analytical solutions are obtainable. Norris, 21,22 for example, proposes a 'unified outflow model' for vessels and pipelines. Apart from the steady-state flow assumption, the model ignores wave dynamics and pipe/wall heat-transfer effects.…”

Leak Detection in Subsea Pipeline: A Mechanistic Modeling Approach With Fixed Pressure Boundaries

“…A softwarebased leak-detection method identifies a pipeline leak which occasionally causes several immediate detectable effects in terms of fluctuations in the monitoring pressures and/or flow rates (Mastandrea et al 1990;Bonn 1998). Earlier studies usually focused on the drastic change in flow conditions resulting from the blowdown and rupture of subsea vessels or pipelines (Norris and Puls 1993;Norris and Hissong 1994). It is clear that such a relatively large leak can predict the failure of multiphase flowlines reasonably well.…”