Research On Key Technologies Of Three-phase Flow Logging Based On Fiber-optic Vector Hydrophone

Before oil production,the first thing to do is to log.Through logging,various petroleum geological and engineering technical data are obtained,including the location of the oil source and the direction of the oil source,as well as the flow characteristics of the mixed phase of the oil and gas and the composition of each phase,so as to obtain accurate oil production.The fiber-optic vector hydrophone is an important instrument for underwater sound field detection.It has high measurement sensitivity,large dynamic range and excellent directionality.It can be used in petroleum logging to detect weak three-phase flow noise signals in the formation so that has great significance for the study of three-phase flow logging.Based on the basic principle of fiber phase modulation,this thesies proposes a scheme of all-fiber external modulation Michelson interference hydrophone system.Based on this scheme,a fiber-optic vector hydrophone system is designed,and a homo-vibration fiber-optic vector hydrophone probe is developed and the performance is tested.its application in fluid flow rate measurement is studied based on the fiber-optic vector hydrophone.The main contents are as follows:1.A scheme of all-fiber external modulation Michelson interference hydrophone system was proposed.This scheme combines the advantages and disadvantages of traditional internal modulation and external modulation.The narrow linewidth optical signal was directly subjected to high-speed phase modulation,and the unbalanced michelson interferometer is used to preserve the carrier signal.the feasibility of the scheme was verified by experiments.2.An acoustic sensitive probe of same-vibration elastic cylinder structure was designed,and the theoretical formula of the acceleration sensitivity and resonant frequency of the structural probe was deduced.The effects of elastic cylinder material and important structural dimensions on the performance of the probe are simulated and a one-dimensional co-vibration fiber-optic vector hydrophone was developed.The sensitivity and directivity are tested.The sound pressure sensitivity is up to-128 dB,the acceleration sensitivity is up to 41 dB,and the depth of the pit at 2kHz is 27.2dB.3.The PGC demodulation algorithm was optimized based on the all-fiber external modulation Michelson interference hydrophone system scheme.The influence of modulation depth and filter design on the demodulation system in the PGCdemodulation algorithm was simulated and analyzed.The correctness of the algorithm was verified by experiments.4.A fiber-optic vector hydrophone flow rate measurement system was designed and built.Through correlation spectrum analysis,the vertical pipe flow velocity was measured under laboratory conditions,in line with the theory.The measurement results under different sensor spacings were compared,and the relationship between the correlation of the two signals and the sensor spacing was verified.