| 套后介质声学性质对套管中三种模式波影响的对比分析 |
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| 引用本文： | 陈雪莲,唐晓明.套后介质声学性质对套管中三种模式波影响的对比分析[J].地球物理学报,2019,62(4):1565-1572. |
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| 作者姓名： | 陈雪莲 唐晓明 |
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| 作者单位： | 中国石油大学(华东)地球科学与技术学院, 青岛 266580 |
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| 基金项目： | 国家自然科学基金（41774141）资助. |
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| 摘 要： | 由于套管的厚度小于目前声波测井仪器工作频率下的波长,声波仪器工作时可在套管中激发Lamb波或SH模式波.目前评价水泥胶结质量的声波测井仪器主要是利用套管中的对称Lamb波(拉伸波,S0模式)或反对称Lamb波(泄漏弯曲波,A0模式)的相对幅度或衰减评价套管与水泥之间的胶结程度.Lamb波可看作是纵波和横波在套管边界的耦合形成的,在套管中还存在另一种非耦合的SH横波,偏振方向与套管轴向平行沿着周向传播.本文基于定向声源辐射技术,实现了对称Lamb波、反对称Lamb波的分波模拟技术,数值研究了套管后耦合不同声阻抗介质时,对称Lamb波、反对称Lamb波以及SH横波的测井响应,通过频散衰减曲线以及模式波的波形响应幅度的直观显示表明,由于套管中的SH波仅向固体水泥中辐射剪切波,这一传播特征与套管中的Lamb波相比可以极大提高套管-水泥界面胶结状况的测量灵敏度.Lamb波的固有缺陷是套管与两侧介质的较大声阻抗反差使得在井中测量套管后面水泥界面的灵敏度受到相当大的限制.
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| 关 键 词： | 套管井 Lamb波 SH波 衰减 灵敏度 |
| 收稿时间： | 2017-12-12 |
Study on three mode-wave sensitivities to material acoustic property behind casing in a cased well |
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| CHEN XueLian,TANG XiaoMing.Study on three mode-wave sensitivities to material acoustic property behind casing in a cased well[J].Chinese Journal of Geophysics,2019,62(4):1565-1572. |
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| Authors: | CHEN XueLian TANG XiaoMing |
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| Institution: | School of Geosciences, China University of Petroleum, Qingdao 266580, China |
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| Abstract: | Because the casing thickness is less than the wavelength during the log working frequency range, the Lamb modes or SH mode can be induced in the casing. The attenuation or relative amplitude of the Lamb mode wave including symmetric Lamb wave (S0, extensional wave) and antisymmetric Lamb wave(A0, flexural wave) can be used to evaluate cement bonding quality. Lamb wave is the result of the coupling or superposition of compressional waves and shear waves in the casing. SH wave is uncoupled mode, which is polarized along the axial direction and propagates along the circumferential direction of the casing. Based on the technique of the oriented source radiation, three mode-wave logging responses are simulated respectively. The dispersion and attenuation curves and waveforms are calculated corresponding to different acoustic-impedance materials behind casing in a cased well. The results show that SH mode, compared to Lamb modes, is more advantageous for differentiating high performance lightweight cements from liquids because SH wave only radiate shear wave in the solid materials. The sensitivity of SH mode to acoustic impedance behind casing is higher than that of Lamb waves. The large acoustic impedance contrast between casing and coupled materials restricts the detecting sensitivity of Lamb waves to the acoustic property of the medium behind casing. |
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| Keywords: | Cased well Lamb wave SH wave Attenuation Sensitivity |
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