摘要
以Isolation Scanner的工作方式为背景,采用有限差分方法模拟中心频率为250kHz的超声脉冲波自井内流体中斜入射于套管内壁界面时产生的各种模式波的声学特征与水泥环性质之间的关系。研究发现,当水泥环声阻抗不同时,接收波列的各种模式波的幅度有很大的差异,即随着水泥环声阻抗的依次降低,套管中S0模式的Lamb波逐渐增强,A0模式的Lamb波逐渐减弱;A0模式Lamb波的声衰减与水泥环声阻抗的关系是随着水泥环声阻抗的减小其声衰减系数增加。结果表明,根据A0模式Lamb波的幅度和衰减信息可以判断水泥环声阻抗的大小,为评价套管外介质的声阻抗提供了依据。通过接收波列的时域波形直接识别第Ⅱ界面是不现实的,但通过对接收波形的频谱分析有望反演水泥环的厚度。
Based on the principle of Isolation Scanner, the characteristics of waves produced by an ultrasonic pulse with centre frequency as 250 kHz on the interface of borehole fluid and case are simulated by a finite difference method, and the influence of case properties on received wave- forms is analyzed by comparing the results of different cement cases. Results indicate that large difference appears for cements with different acoustic impedance, as acoustic impedance of ce-ments decreases, amplitude of SO Lamb mode increases, whereas amplitude of A0 Lamb mode de-creases; the relationship of A0 Lamb mode with cement acoustic impedance is that the attenuation of A0 mode increases with the decreasing of cement acoustic impedance. This study shows that the cement acoustic impedance can be evaluated by the amplitude and attenuation of A0 mode, but the thickness is hard to be exactly extracted by the recorded waveforms of this measurement.
出处
《测井技术》
CAS
CSCD
北大核心
2012年第5期460-464,共5页
Well Logging Technology
关键词
固井质量
水泥环
声阻抗
斜入射
超声脉冲反射波
有限差分
cementing quality, cement sheath, acoustic impedance, oblique incidence, ultrasonic pulse, finite-difference
