Research On An Array-type Electromagnetic Correlation Flowrate Measuring Method For Oil-gas-water Three-phase Flow In Oil Well

Multiphase flow exists in various kinds of fields, such as petroleum, chemistry, pharmaceutical industry, environmental protection, city water supply and drainage. With the deepening of oilfield development, oil-gas-water three-phase flow becomes a more and more common phenomenon in well logging, and flow is a parameter that must be measured and controlled. But the fluid flow state is very complex in downhole, which results in flow measuring is very difficult, and currently the online measurement of oil-gas-water three-phase flow is a challenging research task in oilfield development.Based on the background of application in production logging, to solve the underground oil-gas-water three-phase flow measuring problem, the research work carried out in this dissertation are listed as follows:First, for the specific measuring environment in oil well, to solve oil-gas-water three-phase flow measurement problem, organically combining the electromagnetic measuring technology, cross-correlation measuring technology and data fusion technology, a new method basing on an array-type electromagnetic correlation sensor is proposed, a structure model of the array-type electromagnetic correlation sensor is established. The designed array-type electromagnetic correlation sensor has the advantages of small volume, non intrusive, no radiation, no moving parts, wide measuring range and low cost etc. Two indicators the direction parallel degree and intensity uniform degree of the induced magnetic field are proposed, and the induced magnetic field generated by excitation coils of different shape are simulated and analyzed numerically, which provides a reference for the optimization design of excitation coil of the array-type electromagnetic correlation sensor.Second, the weight function is an important concept in electromagnetic flow measuring theory. It reflects the contribution to the whole flow measuring signal of liquid medium unit in different place of pipeline. Using finite element method, the weight function distribution in the pipe cross section of a multi-electrode electromagnetic flowmeter and the influence of discrete non conductive phase are studied. Then the response characteristic of the multi-electrode electromagnetic flowmeter is analyzed. It provides a basis for further study for structure optimization of the array-type electromagnetic correlation sensor.Third, adopting finite element numerical analysis method, the optimization design of structural parameters on the array-type electromagnetic correlation sensor is carries on. Basing on the uniformity of the distribution of induced magnetic field, excitation structure parameters of the sensor are designed, mainly including the angle of magnetic core, the angle of exciting coil, thickness and axial length of magnetic core. Basing on the homogeneity of the weight function distribution in sensor’s measuring region, electrode structure parameters of the sensor are designed, including the electrode number, electrode size, and the distance between upper electrodes and lower electrodes. Optimization design of the sensor structure parameters plays an important role in improving measuring accuracy of oil-gas-water three-phase flow.Fourth, to improve measuring accuracy, data fusion technique of the array-type electromagnetic correlation sensor is studied. A method basing on support degree and adaptive weighted for multi-sensor data fusion is presented, calculating the comprehensive support degree and weighting factor of each data in measuring sequence of a single sensor, then calculating the weighting factors corresponding to measuring sequences in an adaptive way, which makes the total mean square error the minimum. Then a data fusion method basing on multi-scale principal component analysis and adaptive weighted is proposed, by eliminating noise a better effect could be got. The two methods above are validated through simulation experiment.Finally, for real-time measuring oil-gas-water three-phase flow, an array-type electromagnetic correlation measuring system is designed. The system’s drive circuit, analysis software and a flowmeter prototype are introduced. Then an experiment platform of oil-gas-water three-phase flow is built, and experiments with the designed array-type electromagnetic correlation measuring system are carried out, afterwards the data of experimental results is analyzed.