考虑压电声源-井孔系统的随钻方位声波测井数值模拟

Numerical Simulation of Azimuthal Acoustic LWD Under a Piezoelectric Source-Wellbore System

随钻方位声波测井仪器是一种新型的声波测井仪器,在非均匀性复杂地层的精细勘探与开发中具有应用前景。综合考虑了压电声源-钻铤-井孔系统相互耦合作用,使用有限元ANSYS软件仿真计算了瓦片状声源的随钻方位声波测井仪器响应特征,以及声源的变形、表面不同位置处的振动位移,分析声源的谐振频率与辐射特性。模拟结果表明,声源振动变形复杂,与施加的激励信号存在较大差异。该声源谐振频率位于隔声体阻带之内,钻铤波得到有效压制,且该声源辐射出的能量具有明显的水平、竖直方位指向性。数值模拟了随钻方位声波测井仪器在均匀地层、方位分区变化地层以及过界面地层中的测井响应特征。模拟结果表明,基于该瓦片状声源的随钻方位声波测井仪器可准确测量地层的纵波慢度,识别井周地层方位速度信息,在跨界面地层中通过方位速度差异进行界面识别。研究对于随钻方位声波测井仪器的设计、研发以及使用具有指导意义。

As a new acoustic logging tool,the LWD azimuthal acoustic logging tool is promising in fine exploration and development of heterogeneous reservoirs.By considering a piezoelectric source-drilling collar-wellbore system and using the finite element software,ANSYS,it can simulate the LWD azimuthal acoustic responses from a tile-like sound source,the deformation and displacement of the tile-like source,and analyze the resonant frequency and directivity of the source.The simulation result shows that the vibration of the tile-like source is complex and quite different from the original signal;the working frequency of the source transmitter is in the effective stop band of the isolator so that collar waves can be effectively suppressed;the energy from the source transmitter is directive with horizontal and vertical azimuthal features.Further simulation provided the logging responses from homogeneous,azimuth-variable and cross-interface formations and shows that the LWD azimuthal acoustic tool using a tile-like source can accurately record S-wave slowness and azimuthal velocity,and identify interfaces according to the difference of azimuthal velocity.This research is significant for the design,development and application of the LWD azimuthal acoustic tool.