Research On Acoustic Reflection Characteristics Of Drilling Fluid Surface And Depth Adaptive Calculation Method

During the drilling operation,the real-time monitoring of the dynamic fluid surface depth of the mud helps to understand and monitor abnormal working conditions such as lost circulation and kick,and helps engineers quickly identify possible well control problems and take corresponding measures to improve the efficiency and safety of drilling operations.However,the current methods for calculating the dynamic liquid surface depth mostly use manual or semi-automatic ones,and it is difficult to realize real-time monitoring.In this paper,the numerical simulation calculation studies the propagation and reflection mechanism of sound waves in the water hole and the annular space in the complex environment of the drill sleeve,and the adaptive calculation method of the dynamic liquid level depth.The research results provide a theoretical basis for the development and application of the intelligent dynamic liquid level monitoring system.The main research content and results of the paper are as follows.The first part studies the characteristics of reflected waves in the drill pipe water hole.Based on the COMSOL Multiphysics finite element software,a sound wave propagation model in the drill pipe water hole is constructed to study the mechanism and characteristics of the acoustic wave reflection signal in the drill pipe water hole under the excitation of different polarity acoustic wave signals,and reflected signal characteristics and reflected signal characteristics at the interface under different liquid depths and different mud densities.The results show that when the positive(negative)polarity acoustic wave signal and the positive and negative polarity superimposed acoustic wave signals are used as the transmitting signal respectively,the polarity of the reflected wave is the same as that of the transmitting signal;the liquid level depth and mud density have an influence on the amplitude of the reflected signal,but have no effect on the waveform;liquid level depth and mud density have no effect on the signal amplitude and the waveform at the interface between air and mud.The second part studies the characteristics of reflected waves in the annular space of the drill sleeve.Use COMSOL software to establish the propagation model of the sound wave in the annular space of the drill sleeve,and analyze the mechanism and characteristics of the acoustic wave reflection in the annular space of the drill sleeve when the acoustic wave signals of different polarities are used as the transmitting signal,and the response characteristics of the coupling signal under the four conditions of mud density,coupling radius,coupling length and coupling number.The results show that when the positive(negative)polarity acoustic wave signal is used as the transmitting signal,the response of the coupling signal is first positive and then negative(first negative and then positive);when the positive and negative polarity superimposed acoustic wave signal acts as the transmitting signal,its reflected wave signal is the superposition response generated when the positive and negative polarity acoustic waves are respectively excited;the mud density and the coupling radius have an influence on the amplitude of the reflected wave,but have no effect on the waveform;the longer the coupling length,the greater the distance between the peak and peak values of the coupling signal,and the waveform changes;the more the number of couplings,the more the number of coupling reflected waves,and the waveform changes.The third part studies the adaptive calculation method of dynamic liquid surface depth.According to the change law of the sound wave propagation response in the downhole,a method for automatically identifying the reflected wave of the dynamic liquid surface and calculating the depth of the liquid surface is designed based on the Graphical User Interfaces of the MATLAB software,and the adaptive calculation of the dynamic liquid surface depth is realized.Through this interface,the user can intuitively monitor the dynamic liquid level surface depth,the measurement waveform and other parameters to judge the corresponding drilling operation conditions,and take corresponding measures to improve the efficiency of production operations.