Novel Four-Electrode Electromagnetic Flowmeter for the Measurement of Flow Rate in Polymer-Injection Wells

Abstract

In this article, a novel four-electrode electromagnetic flowmeter (EMF) is proposed for flow rate measurement in polymer-injection wells. The ideal response model of the four-electrode EMF is established. In this model, the weight function and intensity of magnetic field are both derived, according to which numerical calculations are conducted. The calculation results show that in the annular area between the flowmeter and oil tubing, the weight function and magnetic field are both symmetrically distributed near the measurement electrodes and magnetic poles, respectively, and are rapidly attenuating along the radius direction. The potential difference is calculated for several kinds of flow velocity profiles in the annular area, and the calculation results show that the output of the four-electrode EMF is sensitive to the distribution of the flow profile. The experimental results obtained by using the multiphase flow loop facility show that when the four-electrode EMF is used in polymer solutions, the instrument constant of the four-electrode EMF differs from that used in tap water and remains unchanged with the concentration of the polymer solutions. The flow patterns of tap water and polymer solutions are various, leading to the change of the instrument constant of the four-electrode EMF. On-site experiments show that the four-electrode EMF is suitable for the polymer-injection wells developed in short durations. For the wells developed in long durations, the four-electrode EMF is limited because of the contamination, distortion, and corrosion of the oil tubing.