Research On NMR Sensor Technology Of Oil-gas-water Multiphase Flow

Crude is one of the world’s most important energy, and plays a key role in the development of industries. Because of its multi-component composition and complex flow processes, making multiphase flow detection without separation is still a problem.The measurement target is to determine three phase fractions of oil-gas-water respectively. On the basis of literature study, a multiphase flow measurement model based on nuclear magnetic resonance (NMR) is studied, and an NMR sensor of oil-gas-water multiphase flow is designed according to the measurement model. The main contents and innovations of this thesis are as follows:(1) Based on analysis of the NMR principle, the measurement project of multiphase flow fractions is studied.(2) An NMR sensor system is designed, including uniform magnetic field design and circuit design. A simple Halbach magnet array is designed with four cuboid permanent magnets, which has advantages of relatively uniform magnetic field and easy installation. Based on the existing formulae, some important parameters of the NMR system are estimated, so as to determine the parameters of various components of the circuit according to the calculated value.(3) With regard to the high-frequency white noise in NMR measurement signal introduced by the circuit system, an Empirical Mode Decomposition (EMD) filter algorithm based on the Pearson correlation coefficient is studied. This filter algorithm has strong noise immunity and adaptability.