Research On Structure Optimization And Drive Circuit Of The Oil Well Downhole Small Diameter Electromagnetic Flowmeter

The multiphase flow system is widespread in nature and industrial production, andthe parameter detection of oil-water two-phase flow is always one of the hot problems inmodern petroleum industry. The flow is a significant parameter to measure the oil-watertwo-phase flow. Because of the complexity of the fluid flow condition in oil welldownhole, it becomes quite difficult to measure the flow. Oil-water two-phase flowmeasurement for oil well downhole based on small diameter electromagnetic flowtransducer is deeply studied in this paper.Firstly, aiming at the lower accuracy for response characteristics of small diameterelectromagnetic flow transducer in two-dimensional case, the theoretical model of smalldiameter electromagnetic flow transducer in three-dimensional case when multipleoil-gas bubbles exist is established, and the analysis of response characteristics ofdifferent oil-water bubbles in cross section and vertical section is performed. It comes toa conclusion about the influence rules of the non conductive materials virtual currentdistribution, laying a theoretical foundation for the structure optimization of smalldiameter electromagnetic flow transducer.Secondly, considering the uneven distributions of the inner magnetic field inelectromagnetic flow transducer and big difference of non conductive materials formeasurement, optimum design method for small diameter electromagnetic flowtransducer is studied. Simulation experiment is conducted for three different types ofstructures of the magnet coils and cores and the optimal designof setting a porous plate atthe flow inlet position is done, reducing the influence of oil-gas bubbles impact on thesensor, as well as improving the sensitivity of the sensor.Finally, a kind of oil well downhole small diameter electromagnetic flowtransducer was developed and the drive circuit of the transducer is designed.Low-frequency square wave is used to excite the transducer, with which constitutes theelectromagnetic flowmeter. Then simulation well experiments in Daqing oilfield isconducted, including clear water measurements in vertical simulation wells, oil-water two-phase flow measurements in vertical simulation wells and oil-water two-phaseflow measurements in level simulation wells. The accuracy of the small diameterelectromagnetic flow transducer and drive circuit is verified in the end.