Research On The Flow Measurement Of Oil-water Two-phase Flow And Its Application To The Flow Measurement Of Oil-gas-water Three-phase Flow

Multiphase flow exists in various kinds of fields, such as petroleum, chemistry and metallurgy. And its parameter measurement plays an important role in resource exploration, production safety and industrial process control. A great deal of attention has been paid to this field, which has become a leading subject both home and abroad. Since multiphase flow is a complex process, it is quite difficult to measure its parameters, of which flow rate is the most important and proves rather difficult to measure. This thesis deals with oil-water flow rate measurement using a venturi and develops a differential pressure-based two-phase flow rate measurement model, which does a terrific job with the use of a water fraction device. Meanwhile, Coriolis flow rate meter is also studied in the oil-water two-phase flow measurement and a SVM-based single-phase flow rate prediction method is proposed, realizing the prediction of single-phase flow rates. To overcome the disadvantages of both venturi and Coriolis flow meters, a double parameter measurement method is put forward, which combines the two meters and solves the problem of oil-water flow rate measurement. Last but not least, on the basis of the study of two-phase flow, a device for the separation of gas and liquid is designed and realizes the flow rate measurement of three-phase flow as oil, gas and water. Much of the work done and the initiative points are listed as follows:1. Considering the asymmetric distribution of oil-water two-phase flow density will affect the flow rate measurement and the density will have to be revised, a mass flow rate measurement model is developed, based on the differential pressure of the two ends of venturi and water fraction. Venturis with different diameters are applied to the oil-water flow using the flow measurement model. Experiments show this model can measure the total flow rate of the mixture quite well and the measurement error of the model is influenced by water fraction to only a little extent within the range of oil-water ratio.2. The mass flow rates of both the oil-water mixture and the single phase as well as the real density are studied with the use of a double U Coriolis flow meter. On the basis of the mass flow rates and density obtained, a direct SVM-based prediction method is put forward for single-phase mass flow rate measurement, avoiding the study of the complex relationship among slip velocity, water hold-up and water fraction, etc. Experimental results show the mass flowrate measurement error for the two-phase mixture can be kept within ± 1.5% and for single phases within ± 8% with water fraction varying from 5%--95%.3. Through the analysis of the advantages and disadvantages of both Venturis and Coriolis flow meters, a double parameter measurement method is put forward with the combination of them both. Meanwhile, according to the need of Venturis, a SVM-based water-oil flow pattern identification method is given, with which characteristic vectors can be obtained and used to identify flow patterns, thus giving good results of both separated and distributed flow pattern identification. With the combination of the double parameter measurement method and the separated flow pattern obtained through SVM, single-phase mass flow rate measurement of the oil-water flow can be done even better.4. Based on the basic thought of partial separate measurement, a gas-liquid separation device is designed. In calculational methods, the aforementioned mass flow rate measurement model is adopted to measure the two-phase flow, which is based on differential pressure. It is proved with experiments of the oil-gas-water three-phase flow, the average square root error of the total volume flow rate measurement of gas is less than 3% and that values of the mass flow rates of both oil-water two-phase flow and singe phases are less than7.5%.