Hydrocarbon Blowdown from Vessels and Pipelines

Abstract

In SPE 26565 presented at the 68th Annual Technical Conference in October, 1993, analysis and experimental results were presented for the blowdown of pipelines and vessels using air, carbon dioxide, and carbonated water. Since then further experiments have been carried out using several hydrocarbon gases including both methane and heavier mixes. The pronounced difference in the blowdown behavior between pipelines and vessels noted in the earlier non-hydrocarbon experiments was confirmed for the hydrocarbon gases tested. In addition, for vessel blowdowns, the presence of condensed hydrocarbon liquid was shown to increase the mass efflux rate over an otherwise equivalent single-phase methane blowdown. By contrast, pipeline efflux rates were found to be virtually insensitive to gas composition over the range of hydrocarbon gases tested. These experimental results were compared to the analytical methods described in the earlier paper, and initial efflux rates were found to agree with measured values within about 20%. In addition, the measured efflux rates can serve as test cases for comparison to other analytical methods.

When does a vessel become a pipe?

“…8 As it may be observed, in the case of the gaseous inventory (Figure 7), at any given time interval following puncture, the drop in the temperature due to its expansion-induced cooling is significantly higher than that for the two-phase mixture (Figure 8). At 20 s following puncture, for example, the maximum drop in the gas temperature is about 22 C. This compares with only 2 C for the two-phase mixture. The higher depressurization-induced cooling of the gas is simply due to its larger Joule Thomson expansion coefficient when compared with the two-phase mixture.…”

“…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.…”