Effectiveness Analysis of Slotted Orifice Plate Multiphase Flow Meter Coupled with Venturi Meter and Visualization Study

Abstract

Multiphase flow is a common flow when oil and gas are produced from underground, and in the process of hydrocarbon products transportation. Multiphase flow meters have been one of the most important developments in oil and gas industries. The purpose of inventing a multiphase flow meter is to measure the flow rate of a fluid with multiple phases and/or the fraction of different components in the multiphase fluid. Electrical impedance measurement is a method that has been recently applied so that a new type of multiphase flow meter can be developed. Its principle is to record instantaneous measurements of impedance of a multiphase fluid. After comparing it to the impedance of each component of the fluid, the fractions of each component are known. One of the limitations of this method is that the multiphase flow needs to be well homogenized so that the measurement of impedance is accurate and steady. Therefore, in this study a slotted orifice plate is used to homogenize the multiphase flow. Venturi meters are commonly used to measure the flow rate of a fluid. It uses a converging section of pipe to increase the velocity of the flow which causes pressure drop according to Bernoulli’s theory. Flow rate can be calculated when the differential pressure is measured. Flow visualization is a method to get qualitative or quantitative information of a flow by making the flow patterns visible. In this research, flow rate and gas volume fraction of a water and gas flow is measures by a slotted orifice plate flow meter coupled with a Venturi meter in different orientations. Electrical impedance measurement method is used to obtain the Gas Volume Fraction of the working fluid. Results show that the gains of the signals at 1 MHz frequency have 6th order polynomial correlations with GVF values in both horizontal and vertical orientations, and that phase angles of the signals at 10 MHz frequency have linear correlations with GVF values only in horizontal orientation. The Venturi meter is used to measure the bulk flow rates of the working fluid. The Discharge Coefficients of the Venturi meter is calculated to be 0.97 and 0.89 in horizontal and vertical orientations respectively. In addition, the Discharge Coefficient of the slotted orifice plate is proved to be independent from orientations. At last, a flow visualization study is conducted to show different flow patterns as well as the homogenization ability of the slotted orifice plate. Results of the visualization study show that the slotted orifice plate has remarkable ability to homogenize the water-air mixture in all flow regimes and in both horizontal and vertical orientations.