TABLE OF CONTENTS The modelling of an accidental scenario associated with gas and oil starts with the leaking medium. This may be from many sources, such as:
pipes and associated fittings
vessels
pipelines/risers.
The phase of the leaking medium is the next important aspect:
1 phase flow i.e., gas or oil (liquid) phase
2 phase flow i.e., usually gas and oil (liquid) mixed
3 phase flow i.e., gas, oil, water.
Different models suitable for the different phase compositions and different sources (mainly reflecting the difference between outflow from a vessel or from a pipeline or pipe section) have to be used. The models are primarily aimed at determining the flow rate as a function of time.
The Petroleum Safety Authority [Norway] has the last six years collected considerable amounts of experience data for the Norwegian Continental Shelf, in particular for hydrocarbon leaks from process equipment and operations. The last annual update is presented in PSA (2006a and b). Details are only available in Norwegian; the summary report is also published in English. The scientific approach has been discussed in Vinnem et al. (2006b).
There is actually data available for a ten year period, 1996 2005 for all installations on the Norwegian Continental Shelf. The quality of the data is good for the period 2001-2005, and this should be the main data basis. The overview of all leaks exceeding 0.1 kg/s leak rate from all installations in the Norwegian sector is shown in Figure 6.20.
