Abstract
This paper presents a low-pressure experimental validation of a two-phase transient pipeline flow model. Measured pressure and flow rate data are collected for slug and froth flow patterns at the low pressure of 6 bar at the National University of Singapore Multiphase Flow Loop facility. The analyzed low-dimensional model proposed in comprises a steady-state multiphase flow model in series with a linear dynamic model capturing the flow transients. The model is based on a dissipative distributed parameter model for transient flow in transmission lines employing equivalent fluid properties. These parameters are based solely on the flowing conditions, fluid properties and pipeline geometry. OLGA simulations are employed as an independent method to validate the low-dimension model. Both low-dimensional and OLGA models are evaluated based on the estimated two-phase pressure transients for varying gas volume fraction (GVF). Both models estimated the two-phase flow transient pressure within 5% mean absolute percent error of the laboratory data. Additionally, an unavoidable presence of entrained air within a pipeline is confirmed for the case of 0% GVF as evidenced by the pressure transient estimation. Thus, dampened oscillations in the simulated 0% GVF case exists owing to an increase in the fluid compressibility.
Highlights
Multiphase flow is the simultaneous flow of two or more phases/components of gas, liquid, and/or solids
For the case of highpressure high-temperature (HPHT) subsea tiebacks, accurate prediction and assessment are required in order to be able to predict and appropriately mitigate flow assurance issues such as corrosion, hydrates formation and slugging that are directly related to the variation of flow regimes along long subsea pipelines [2]
The liquid holdup distribution and the slug unit frequency estimated. This between and the friction losses effect. This phenomenon wasare captured will enable the derivation of a relationship between the slug flow structure parameters by the Low-D and the OLGA models
Summary
Multiphase flow is the simultaneous flow of two or more phases/components of gas, liquid, and/or solids This category of flow has a wide range of applications ranging from medical and biological to the automotive, aerospace, power generation and oil and gas industries. Multiphase production and transportation systems are characterized by the presence of serious challenges when considering the effect of slugging flow. Such issue is highlighted, as described in [1] by the occurrence of unstable flow regimes where liquid can cause the blockage of the gas phase leading to severe consequences such us flow rates, pressure and temperature oscillations. Since multiphase flow models are crucial for the achievement of a wide range of applications within this industry, having an accurate and reliable prediction tool is crucial to overcome these different challenges
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