Parameter Design And Optimization Of Nuclear Magnetic Resonance Two-phase Flow Measurement Sensor

Downhole two-phase flow information detection is the core and basis of the intelligent reservoir production system.The precise measurement of its parameters directly affects the results of optimized production of the reservoir.Due to the variability and complexity of flow characteristics such as two-phase flow pattern,flow rate and the content of each phase,the traditional methods are not ideal in the measurement process of two-phase flow,and there are still many technical defects.The application of NMR method overcomes the limitation of traditional measurement methods that are influenced by external macroscopic materials,and provides a new idea for the comprehensive and accurate acquisition of two-phase flow process parameters.This paper considers the oil-water two-phase flow characteristics,and designs a three-stage nuclear magnetic resonance magnet sensor and an integrated transceiver sensor suitable for oil-water two-phase flow.Compared with traditional nuclear magnetic resonance sensors suitable for static media,this design improves the magnetization efficiency and ensures the uniformity of the magnetic field and the sensitivity of detection.And the specific parameter research work was carried out for the sensor optimization problem existing in the two-phase flow measurement of nuclear magnetic resonance.Finally,the nuclear magnetic resonance transmission circuit system was designed and produced,and the relevant verification experiments were carried out.The specific work of the thesis is as follows:Design and optimization of magnet parameters for nuclear magnetic resonance sensors.First,this paper studied the relationship between the magnetization efficiency and the magnetization length under the oil-water two-phase flow parameters,thereby determining the pre-polarization range and ensuring the magnetization efficiency.Based on the research of the finite element simulation method,the sensitivity analysis was fused,and the influence of the Halbach array parameters used by the nuclear magnetic resonance sensor on the magnetic field distribution was explored in detail.Further,in order to solve the problem of poor uniformity of the magnetic field caused by the rapid decrease of the magnetic field at the end of the detection area,a new and improved structure of the compensation magnet was proposed.Finally,the parameter optimization of the magnet structure of each part of the sensor was completed for the 50 mm diameter oil pipe used in the laboratory.Aiming at the research and parameter optimization of radio frequency coils of nuclear magnetic resonance sensors.In this paper,first,a theoretical model of the integrated solenoid coil for transmission and reception was established.For the uniformity of the RF magnetic field in the transmission mode,based on the traditional solenoid coil,two optimization schemes was proposed,which are a segmented structure and a compensation coil.For the receiving mode,the relative signal-to-noise ratio and quality factors are used as the optimization objectives,and the optimal parameters of the receiving coil were determined by the particle swarm optimization algorithm in combination with the segmented optimization scheme.The simulation results show that the optimized coil performance is effectively improved.Based on the DDS technology,the design work of the transmission unit circuit system including the signal source circuit,power amplification circuit and matching bleeder circuit was completed,which ensures the controllability and stability of the signal quality of the radio frequency system.Use the designed nuclear magnetic resonance sensor to build an experimental platform,and carried out relevant verification experiments such as circuit system testing and sensor performance analysis.The results show that all the indexes meet the theoretical requirements,which further verifies the excellent performance of the designed NMR sensor and the feasibility of the system scheme.Through the above parameter optimization and experimental research work of the NMR sensor,it provides a theoretical basis for the research on the dynamic online measurement of the two-phase flow of the NMR,and provides a reference value for the efficient and accurate production of oil wells in the future.