Study On Vibration Characteristics Of Submersible Electric Pumps Based On Vibration Measurement Down The Experimental Well

As one of the most important rotating machinery of oil extraction,the vibration and temperature signals of electric submersible pump(ESP)unit contain abundant information related to mechanical failure or assembly quality.Therefore,it is of great significance to research the vibration and temperature characteristic of ESP and submersible motor and the stability evaluation method of the vibration signal of the ESP unit in the test well,so as to judge the assembly quality and the type of the faults.As one of the performance parameters,studying the relationship between flow and vibration of ESP is also instructive for prolonging the service life of electric pump.Therefore,the hardware and software design of downhole vibration signal acquisition system and vibration signal characteristic analysis are important research contents in this thesis.In this thesis,the main work and achievements are as follows:(1)A downhole vibration acquisition and measurement system for downhole submersible motor and electric pump housing vibration and temperature was designed.The vibration acquisition hardware system was designed which take ultra-low power microcontroller STM32L051C6T6,three-dimensional acceleration sensor MMA7361,temperature sensor MAX6608 as the core hardware circuit to measure the vibration and temperature signals of the submersible pump and the motor housing under the surface of the experimental well.(2)The software of vibration and temperature processing was designed by using C# and Matlab mixed programming,which realized the display of historical data,time domain analysis of vibration signal,frequency domain analysis and temperature data analysis,and provided intuitive analysis results for field workers.(3)Experiments on the relationship between vibration and flow were conducted in experimental wells,and the relationship between vibration and flow in different situations was analyzed in time domain and frequency domain respectively.In consideration of the statistical analysis of the RMS values of vibration,it was found that there is a flow ratio in the range where the 3D synthetic vibration has the smallest RMS value within a certain range around the rated flow.The main component of the vibration spectrum of a good pump is the fundamental frequency,and the CZT algorithm is used to analyze the vibration signal under different flow rates.When the variation of the fundamental frequency amplitude is consistent with the timedomain analysis results,the optimal flow value of the vibration is obtained when the electric pump is in good working condition.By this method,the vibration of the electric pump is minimized and the life of the electric pump is extended.(4)The stability evaluation method of the vibration signal of the submersible electric pump was studied and the stability index was defined to quantitatively evaluate the vibration signal stability.Firstly,a sliding window was used to obtain a window signal which can represent periodically the periodic characteristics of the vibration signal.Then the window signal was translated on the vibration signal and autocorrelation analysis is performed to obtain the autocorrelation coefficient sequence.Finally,the autocorrelation coefficient was obtained.The coefficient sequence was processed to obtain the stability index.Simulation and practical results showed that this method can effectively evaluate whether the signal has unstable vibration amplitude or instability of the vibration cycle,and can timely detect the electric pump with potential faults to avoid poor quality pumps from entering the well.