Simulation Research Of Flow Field And Acoustic Field Characteristics Of Oil Casing Leakage

The leakage of oil casing in natural gas well will pose a serious threat to the production of natural gas.It is of great significance for the safety and economy of natural gas production to study the detection technology of oil casing leakage so as to realize the accurate location of leakage.Because of the high sensitivity,strong adaptability and high accuracy of acoustic detection,it can be used for oil and casing leakage detection.In this paper,natural gas well casing as the research object,the casing pipe leakage sound mechanism is studied,and the numerical simulation method is used to analyze the leakage flow field and sound field characteristics,to explore the feasibility of oil casing leakage ultrasonic detection.The main research contents are as follows:(1)According to the theory of fluid mechanics,the characteristics of the flow field when the pipeline leaks are analyzed.It is determined from the theory that the turbulent flow area of the fluid is mainly located in the leak hole and the annulus,and this area is the sound source area of the leakage noise.Then,according to the aerodynamic noise theory,the characteristics of the sound source when the pipeline leaks are analyzed,and the sound source composition of the leakage noise is determined.(2)The flow field and sound field simulation theory of pipeline leakage are studied,and appropriate calculation models and methods are selected in combination with the specific working conditions of pipeline leakage,which lay the foundation for the following simulation calculations.(3)A simulation model of gas well tubing leakage is established.First,the flow field of tubing leakage is numerically simulated.Subsequently,the calculation results of the flow field are imported into the sound field simulation model,and the sound field when the oil pipe leaked is numerically simulated.The influence of the pressure difference between the inside and outside of the pipe and the diameter of the leak hole on the characteristics of the leakage noise source and the sound field distribution in the oil pipe is analyzed.The results show that ultrasonic detection can be applied to pipeline leakage detection,and the sound source and sound field have similar sound pressure level spectrum characteristics.The frequency corresponding to the peak of the leakage noise sound source spectrum can be set as the center frequency of ultrasonic detection;as the pressure difference increases,the sound source and sound field of the oil pipe leakage increase,but the frequency corresponding to the peak on the spectrum curve does not change;with the increase of the leakage aperture,the sound source and sound field of the oil pipe leakage the sound pressure level increases,and the frequency corresponding to the peak value gradually decreases.(4)A simulation model of gas well casing leakage is established,and the flow field and acoustic field of casing leakage are numerically simulated.The results show that with the increase of the pressure difference between the inside and outside of the pipe,the energy of the sound source and the sound field of the casing leakage increases,and the frequency corresponding to the peak of the spectrum curve has no influence;with the increase of the leakage aperture,the sound pressure level of the leakage sound source and the sound field of the casing increases first and then gradually tends to the same,and the frequency corresponding to the peak value gradually decreases.