Field measurement of slug characteristics is conducted using gamma-densitometers in a 30-in gas-oil-water three-phase pipeline. The pipeline is quite flat with minor elevation changes. The gas, oil, and water flow rates are 66.859 sm3/s (204 mmscfd), 0.078 sm3/s (42,650 sbpd), and 0.151 sm3/s (82,000 sbpd), respectively. The operating pressure is relatively low, about 200 psia. The collected information includes slug frequency, slug length, translational velocity, and pressure. Liquid holdup in slug body and bubble region could also be estimated, but the uncertainty may be high, due to the way in which the gamma-densitometer is calibrated. The measured data indicates that only one large slug exists in the pipeline at a given time. After the previous large slug exits from the pipeline, a new large slug is formed. The explanation of this observation is investigated in this paper. The commercial multiphase flow simulator, OLGA®, is run and results are compared to the field data. It is found that the OLGA model using the default delay constant significantly over-predicts slug frequency, and under-predicts slug length. After the model is tuned by changing the delay constant, much better agreement is achieved. This work shows that the use of the default value of delay constant may give less conservative results in terms of slug length and surge volume for large scale pipelines.

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