Research On The Laser Doppler Measurement Technology For The Length Of Continuous Oil Tubes

At present, workers still mainly use the traditional manual method to measure the length of oil tubes going down into wells in the oil production. They measure every tube by pulling a tape and record the total number. This way has been in use since wells emerged. Not only it is inefficient, labor-intensive, but also its measurement accuracy is low. In addition to manual measurement, some oil fields need to use special instruments to measure the exact location of downwell tools, again. Even if someone poposed to make use of sound, light or other methods to measure tubes length, but these methods or techniques have not still been widely applied because of low accuracy, complex structure and many other questions.Therefore, It is obvious that the research and development of online intelligent measurement apparatus for tubes going down, can not only improve the measurement accuracy, reduce labor intensity, but also save production costs, improve production efficiency and economic profits.Laser Doppler measurement technology is widely used and developed due to its many characteristics, such as high precision, good linearity, fast dynamic response, wide measurement range, as well as non-contact measurement, etc. Particularly in the fluid flow rate measurement the results are satisfactory. Laser online measurement technology has become a focus of the current industrial applications LDV technology research and development.In this thesis, according to the practical requirement, it is designed that an online length measuring system for continuous oil tubes based on the principle of Laser Doppler Velocimetry. This system takes dual-beam optical structure. It uses the semiconductor laser as light source, and takes the photomultiplier tube to receive the scattered lights from the surface of the moving oil tubes. Based on data acquisiting and signal processing system, we can measure the Doppler shift, and then calculate the length of the continuous oil tubes. The measuring system has some characteristics such as high precision, simple structure, stable performance, being suitable for the requirements of field operations, and so on. So it has a broad application prospect. The thesis describes the measurement principle and each unit design and implementation case. It laid the foundation of theory and practice for further research. This is a new attempt to use laser Doppler velocimetry measurement technology in measuring the length of continuous tubes. If the system is successfully developed, people can get a new kind of online length measurement equipment with more superior performance to continuous tubes.