Abstract
Liquid holdup is one of the most significant parameters in multiphase flow. Accurate measurement of liquid holdup is required to calculate pressure drops in oil and gas wells which is essential in analyzing the well production, performance, well designing and optimization. This study reviewed different methods used in measuring liquid holdup and highlighted the most effective methods currently used in multiphase combinations. More importantly, liquid holdup measurements using capacitance sensors in slug flow, bubble flow, churn flow, annular flow and coaxial flow are discussed. The features considered during the review include, electrode material, angle of rotation, curvature and guard electrodes. The operational issues observed when using capacitance based sensors were highlighted. In single capacitance sensors like the helical arrangement which has high sensitivity, error in symmetry and inability to measure fluids with lower dielectric constants were however observed. Concave sensors are more accurate for phase shift detection but lower sensitivity compared to the helical type. From the knowledge and technical gaps identified from literature, this study proposed Electrical Capacitance Tomography tool with dual capacitance sensor for effective liquid holdup measurement in oil and gas transportation pipelines because of its ability to determine the dielectric permittivity distribution inside the pipeline from external capacitance measurements with real-time imaging of the multiphase flow.
Highlights
Accurate prediction of the pressure gradient is crucial for production, design and optimization of oil and gas wells
From the knowledge and technical gaps identified from literature, this study proposed Electrical Capacitance Tomography tool with dual capacitance sensor for effective liquid holdup measurement in oil and gas transportation pipelines because of its ability to determine the dielectric permittivity distribution inside the pipeline from external capacitance measurements with real-time imaging of the multiphase flow
Capacitance sensors are widely used in multiphase flows
Summary
Accurate prediction of the pressure gradient is crucial for production, design and optimization of oil and gas wells. The most important parameter in calculating multiphase pressure drops in wells is Liquid Holdup [1]. A value for Liquid Holdup cannot be calculated analytically. It must be determined from empirical correlations and is a function of variables such as gas and liquid properties, flow pattern, pipe diameter and pipe inclination. Calculation of holdup is complicated by the phenomenon of gas/liquid slip. It is essential to be able to determine liquid holdup to calculate such things as mixture density, actual gas and liquid viscosities, effective viscosity and heat transfer. It can be used to estimate the hold-up in a given section of the pipe, taking advantage of the different permittivity values of the two liquids or the multiphase flow
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