Research On Pipeline Flow Monitoring Technology Based On Distributed Fiber Optic Acoustic Sensing

Pipeline flow monitoring is of great importance in modern industrial production.In the fields of oil and gas recovery,accurate measurement of the flow parameters inside the pipeline can provide a precise understanding of the flow situation and help to construct an industrial profile,enabling effective control of the oil and gas production in each layer.In addition,pipeline flow monitoring can ensure safe pipeline operation,improve pipeline operating efficiency,optimize pipeline design,and refine pipeline management,while also providing certain protection for the environment near the pipeline.Traditional flow monitoring schemes are difficult to apply in the complex underground production environment due to their inherent limitations,and they often involve single-point monitoring,making network construction and fluid production profiling challenging.As an emerging monitoring technology,distributed fiber-optic acoustic sensing technology has the characteristics of electromagnetic interference resistance,high temperature and high-pressure resistance,and corrosion resistance,making it suitable for monitoring requirements in the oil and gas recovery industry.This thesis focuses on the demand for flow monitoring in the oil and gas recovery industry,combined with the technical characteristics of distributed fiber-optic acoustic sensing technology,proposing an energy-based monitoring scheme and a sound velocity-based monitoring scheme that combine fiber-optic distributed acoustic sensing technology with pipeline flow monitoring.The fiber-optic sensor is used to achieve intrusive and non-intrusive monitoring of pipeline flow,and has good application prospects in constructing fluid production profiles in oil and gas recovery.The main research contents are as follows:(1)The working principle of distributed fiber-optic acoustic sensing system is introduced from a theoretical perspective.The relationship between acoustic pressure and phase is analyzed based on the acoustic phase modulation principle,and the conclusion that there is a linear relationship between acoustic pressure and phase is obtained.Based on the theory of distributed fiber-optic spatial differential interference,a distributed fiber-optic spatial differential interference model is established,which accurately obtains the amplitude and phase of the external acoustic field based on information such as monitoring point location and frequency.(2)Based on the distributed fiber-optic acoustic sensing system,an energy-based monitoring theoretical model for pipeline flow is established,and the relationship between flow rate and internal pressure of the pipeline is analyzed,constructing a corresponding linear relationship between flow rate,internal pressure and phase.COMSOL Multiphysics software is used for simulation analysis of the relationship between flow rate and pressure,verifying the theoretical model of energy-based monitoring.Intrusive and non-intrusive monitoring methods for energy-based monitoring are analyzed,and the feasibility of both monitoring methods is verified.The frequency variation of co-directional and counter-directional sound velocity propagation is simulated,verifying the theoretical model of sound velocity-based monitoring.(3)The energy-based monitoring research based on distributed fiber-optic acoustic sensing technology is conducted,and a pipeline flow monitoring experimental system is constructed to compare intrusive and non-intrusive monitoring methods.A galvanized steel pipe with a radius of 2 cm is used for intrusive and non-intrusive monitoring in the flow rate range of 0.258-0.349 m/s.The results show that intrusive monitoring is slightly better than non-intrusive monitoring,with the best fit of R~2=0.99432 for intrusive monitoring and R~2=0.98770 for non-intrusive monitoring,and the best relative measurement error is less than 1%.At the same time,a sound velocity-based flow monitoring system with a radius of 5 cm is constructed,the flow rate of 1.41 m/s and 1.5 m/s is monitored and analyzed.The monitoring results show that there is a certain measurement error in micro-flow velocity measurement using sound velocity-based monitoring,but this monitoring method is not dependent on the calibration of other flow meters and is suitable for installation in pipelines where flow meter installation is difficult.