为了解套管井下声场的特点以及影响套管波幅度的因素,利用COMSOL软件对套管井下声场进行模拟,模拟并计算了 自由套管、胶结良好、Ⅰ、Ⅱ界面微环隙等情况下套管波波形.研究发现,频率增大时,套管波首波的幅度先增大后减小,声源频率为15 Hz时有利于声波水泥胶结测井评价,可以通过提取相应的波形来确定地层纵波和横波的速度,从而判断地层的岩心和孔隙度.套管厚度仅影响套管波首波的到达时间,对于幅度的变化影响较小.井眼尺寸对于套管波幅度的影响仅在水泥环胶结良好时较为明显,并且井眼尺寸越小,地层波幅度越小,当井眼尺寸为80 mm时,地层波几乎看不见.Ⅰ、Ⅱ界面窜槽的厚度对井内波形的影响均较小,但是CBL/VDL可以通过其到达时差来区分.
In order to understand the characteristics of downhole acoustic field in cased wells and the factors affecting casing wave am-plitude,COMSOL software was used to simulate the downhole acoustic field in cased wells,and the casing wave waveforms were simula-ted and calculated under the conditions of free casing,good cementation and micro-ring gap at the Ⅰ and Ⅱ interfaces.It is found that when the frequency increases,the amplitude of the first wave of the casing wave first increases and then decreases.A sound source fre-quency of 15 Hz is beneficial for evaluating acoustic cement bonding logging,and the corresponding waveform can be extracted to deter-mine the velocity of the longitudinal wave and the transverse wave of the formation,and the core and porosity of the formation can be judged by using them.The thickness of the casing only affects the arrival time of the first wave of the casing wave,and has little effect on the amplitude change.The influence of wellbore size on casing wave amplitude is only more significant when the cement sheath is well cemented,and the smaller the wellbore size,the smaller the formation wave amplitude.When the wellbore size is 80 mm,the formation wave is almost invisible.The thickness of interface channeling has little effect on the waveform in the well,but CBL/VDL can be distin-guished by their arrival time difference.