Application of the gamma radiation method in analysing the effect of liquid viscosity and flow variables on slug frequency in high viscosity oil-gas horizontal flow

Abstract

Published experimental observations of high viscosity liquid-gas horizontal flows have indicated that hydrodynamic slug flow is the commonest flow regime encountered over a wide range of flow conditions. Since hydrodynamic slugging generates high pressure fluctuations capable of damaging production pipelines, it is necessary to understand the complex characteristics of high viscosity slug flow regime through the analysis of one of its key parameters namely, slug frequency.Investigating slug parameters is crucial, especially when existing slug flow models used in the Petroleum Industry are not suitable for predicting the behaviour of high viscosity oil-gas flow. This is because most existing empirical correlations for predicting slug parameters are based on low viscosity liquid-gas flows which have different hydrodynamic features compared to high viscosity liquid-gas flows.In Cranfield University, an experimental investigation of high viscosity oil-air flow was performed to study the effect of liquid viscosity and flow variables on hydrodynamic slug flow. Experiments were conducted at liquid superficial velocities (V so ) and gas superficial velocities (V sg ) ranging from 0.06 m/s to 2.0 m/s and 0.0 m/s to 4.0 m/s respectively. For each experimental run, a singlebeam gamma densitometer was used to measure slug frequency. The effect of liquid viscosity (μ) on the measured slug frequency was investigated for the range of 1100 cP to 4000 cP. When compared against measured high viscosity slug frequency data, none of the existing empirical correlations used were able to produce accurate predictions. The predicted results tend to diverge from experimental data by several orders of magnitude. Given this context, a new Computational Methods in Multiphase Flow VII 447 empirical correlation for slug frequency was proposed. The new empirical slug frequency correlation was compared against an independent experimental dataset. The comparison indicated that the new empirical correlation performed better than existing correlations in predicting slug frequency of high viscosity liquid-gas flows.

Evolution of High-Viscosity Gas–Liquid Flows as Viewed Through a Detrended Fluctuation Characterization

“…Interestingly, only the estimates obtained from the ad hoc correlation proposed by Gokcal et al [10] compared favourably with the data. The same kind of conclusions were drawn by Okezue [11], who studied high-viscosity oil-gas mixtures (from 1.1 to 4 Pa•s) over a wide range of flow conditions. More recently, Baba et al [12] conducted additional experiments to further characterize the slug frequencies.…”

On gas-liquid intermittent flow in a horizontal pipe: Influence of sub-regime on slug frequency

“…by measuring the slug frequency, at30 D, 60 D, 120 D, 190 D and 260 D from the input, developed another correlation which took into account the pipe length. In recent years, many authors argued that the liquid viscosity has an influence on slug frequency, leading to the developpement of a number of correlations(Gokcal et al (2009), Al-Safran (2009,Schulkes (2011),Okezue (2013),Zhao et al (2013),Archibong (2015),Abulkadir et al (2016),Baba et al (2017),Archibong-Eso et al (…”