Research On Multiphase Flowmeter Of Oil, Gas And Water

On-line measurement of multiphase flow of the oil, gas and water mixture is significantly valuable to the exploitation of oil fields, especially located on the sea or far from the city. But it is very difficult to develop multiphase flowmeters due to the complexity of flow regimes and inconstancy of flow composition at flowing conditions, thus far there are few practicable multiphase flowmeters available.A study of on-line measurement of multiphase flow is shown in this paper. It presents a new measurement method based on the capacitance, conductance, RF (radio freqency) and cross-correlation measurement technique after investigating and analyzing the materials of many multiphase flowmeters home and abroad.The paper deduced the relations between the phase fractions of the multiphase flow and measured signals, such as the dielectric constant from the capacitance sensor, the electrical conductivity from the conductance sensor, and the ratio of absorption from the RF sensor. It also describes these signals' individual process circuits, and represents the measuring method about the cross-section phase fractions of the multiphase flow on the basis of above techniques. By taking advantage of the complementarity of the capacitance and the conductance measurement, the design extends the water cut measurement range from 0 to 100 percent.By employing the capacitance and conductance arrays, the multiphase flow velocities are obtained by cross-correlation technique and a practicable method of the cross-correlation calculation based on the digital signal processing technique is discussed in detail.A prototype of this design using digital signal processor (TMS320LF2407) was developed and some static tests based on this prototype were carried out. The experimental data roughly demonstrate that it is effective to measure multiphase flow by combining these techniques. The design has the characteristics of high accuracy, low cost and wide measuring range, and thus offers a reference for further developing practical multiphase flowmeters of non-radioactivity pollution, low press loss and non-moving components.