ional Society of Offshore and Polar Engineers Preliminary results of the probabilistic modeling show an ability to predict: the probability associated with a specific value or range of slug frequency, slug frequency interval for a given probability value, and the expected range of slug frequency under normal operation. In addition, a slug frequency empirical correlation is proposed to predict the mean slug frequency in a horizontal pipeline, which is used in Poisson probability modeling. This time interval, normally called Delay Constant Parameter, is a tuning parameter in slug tracking models, such as OLGA, which require a probabilistic distribution to quantify its uncertainty. Another important application of slug frequency probabilistic modeling is the calculation of the time interval between two initiated slugs and its probability. In addition, these values are important in properly designing corrosion inhibitor injection rates and their economical evaluation. These probability values can be propagated in a mechanistic model to predict the expected, low- and high-end values of pressure gradient and liquid holdup for proper pipeline design and optimum operation. Such modeling can predict the P10, P50, and P90 accuracy of slug frequency predictions for a given flow condition. For this reason, probability modeling is necessary to quantify the uncertainty and calculate the probability associated with slug frequency predictions. A comprehensive study by Zabaras (2000) and a recent study by Al-Safran (2009) showed that the error in existing slug frequency correlations' predictions averages around 75% for horizontal flow and 115% for horizontal and inclined flows. Conversely, slug frequency is the least accurately predicted parameter in two-phase flow, due to the high uncertainty of slug frequency predictive empirical correlations and models. Their model is based on a slug formation process in which a smallĪBSTRACT: Slug frequency is a critical characteristic of two-phase slug flow for predicting pressure gradient, erosion/corrosion rates, pipeline structural integrity and designing downstream separation and process facilities. Horizontal pipes, relating slug frequency to the time taken for a slug to be initiated at the This suggested that the slug frequency can be correlated to a Froude number.cy in They showed that there are direct and inverseĭependenc.ies of slug frequency on liquid superficial velocity and pipe diameter, Gregory and Scott conducted two-phase flow experiments using 1.9-cm ID pipe andĬarbon dioxide and water as the fluids. Α Gas Void Fraction.nce it is related to serious operational problems such asįlooding of downstream facilities, severe pipe corrosion, pipeline structural instabilityĪnd wellhead pressure fluctuation. Quantify the uncertainty and calculate the. For this reason, probability modeling is necessary to Slug freq.verages around 75% for horizontal flow and 115% for Kuwait University, Petroleum Engineering Department, Kuwait Probabilistic modeling of slug frequency in gas/liquid
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