| 套管井贴壁声源激发的非轴对称声场的有限差分模拟及结果分析 |
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| 引用本文： | 陈雪莲,唐晓明,张聪慧,魏涛,董兴蒙,魏周拓.套管井贴壁声源激发的非轴对称声场的有限差分模拟及结果分析[J].地球物理学报,2015,58(1):318-326. |
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| 作者姓名： | 陈雪莲 唐晓明 张聪慧 魏涛 董兴蒙 魏周拓 |
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| 作者单位： | 1. 中国石油大学(华东)地球科学与技术学院, 青岛 266580;2. 中海油田服务股份有限公司 油田技术事业部, 北京 101149 |
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| 基金项目： | 国家自然科学基金资助项目(40804020),中央高校基本科研业务费项资金(14CX05010A)资助. |
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| 摘 要： | 套管井贴壁声波测井仪器在固井质量评价中的应用越来越广泛.本文利用三维交错网格高阶有限差分方法首次研究了贴壁声源在套管井中激发的非轴对称声场特征,给出了测井声源在贴壁固体弹性介质中激发时的数值模拟方法,模拟的全波波形与测井仪器在实际井中记录的波形吻合较好,这为利用数值模拟方式开发贴壁声波仪器的潜在应用奠定了基础.通过对套管井不同胶结状况下的数值模拟,得到了贴壁声源在套管井中激发的声场特征和传播规律,模拟结果显示加载声源的贴壁滑板的存在大大压制了套管中弯曲型Lamb波的幅度;套管中传播的拉伸波的幅度相对较强,其泄漏到水泥中的声波传播到水泥和地层界面时发生反射,反射波的幅度和相位特征携带了水泥环第二界面的胶结信息.数值计算结果为利用贴壁声源激发接收的波形实现水泥环第二界面井周不同角度上的胶结评价奠定了理论基础.
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| 关 键 词： | 套管井 声波测井 三维有限差分 贴壁声源 非轴对称声场 |
| 收稿时间： | 2014-01-24 |
Finite-difference numerical simulation and analysis on nonaxisymmetric acoustic fields in cased borehole |
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| CHEN Xue-Lian,TANG Xiao-Ming,ZHANG Cong-Hui,WEI Tao,DONG Xing-Meng,WEI Zhou-Tuo.Finite-difference numerical simulation and analysis on nonaxisymmetric acoustic fields in cased borehole[J].Chinese Journal of Geophysics,2015,58(1):318-326. |
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| Authors: | CHEN Xue-Lian TANG Xiao-Ming ZHANG Cong-Hui WEI Tao DONG Xing-Meng WEI Zhou-Tuo |
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| Institution: | 1. School of Geosciences, China University of Petroleum, Qingdao 266580, China;2. Oilfield Technology Department, China Oilfield Services Limited, Beijing 101149, China |
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| Abstract: | It is difficult to evaluate the cement bonding quality between the cement and the formation. Cased-hole sidewall acoustic logging tools have been widely used in cement bonding quality evaluation. The feasibility is verified using the waveform data, which is recorded by cased-hole sidewall acoustic logging tool, to evaluate the cement bonding quality between the cement and the formation.#br#The acoustic field excited by cased-hole sidewall acoustic logging tool is non-axisymmetric. This work applies the 3D interleaved grid high-order finite difference method to study the characteristics of the non-axisymmetric acoustic field excited by a source on the fluid-filled cased-hole sidewall, which provides a numerical simulation method to simulate the wave field excited by a source on the sidewall of the casing pipe. The model size is 0.4 m×0.4 m×0.8 m. Cased-hole sidewall acoustic logging tool is regarded as the SBT (Segmented Bond Tool). There are six pads uniformly positioned in contact with the interior casing wall. They provide compensated attenuation measurement. The model consists of water, six pads, casing pipe, cement annulus, and formation from inner to outer. The outer diameter and thickness of casing pipe are 0.178 m and 0.01 m, respectively. The thickness of the cement annulus is 0.04 m. The finite differential grid spacing and time step are 0.001 m and 0.0834 μs, respectively. The cosine envelope pulse source of the central frequency of 100 kHz is used.#br#The simulation results show that the existence of the sidewall pad with the source significantly suppresses the amplitude of flexural (asymmetric) Lamb waves in the casing pipe, and the amplitude of extensional (symmetric) Lamb waves is relatively enhanced. So a logging tool has a great effect on casing waves, and should be considered in numerical simulation. The simulated waveforms are in good agreement with the full waveforms recorded by the SBT. The dispersion curves of extensional and flexural waves extracted from the simulated waveforms are consistent with analytical dispersion curves. The waveforms and the snapshots are simulated. The snapshots show that the extensional Lamb waves can radiate cement compressional waves and shear waves into the cement, which generate reflection at the second interface of the cement sheath. A comparison of waveforms between the bonded condition and debonded condition demonstrates that the amplitude and phase characteristics of the reflected waves from the interface between cement and formation indicate the bonded conditions. If the second interface of the cement sheath is a debonded condition, the amplitude of reflected waves increases. The simulated results provide a theoretical foundation for using the recording waveforms to evaluate cement bonding quality of the cement-sheath second interface. The debonded condition is modeled using a 5 mm-thick water annulus between cement and formation.#br#Finite-difference numerical simulation and analysis on non-axisymmetric acoustic fields of cased borehole can be regarded as the beginning of developing potential applications of the sidewall acoustic logging tools. By analyzing numerical simulation results, we can conclude that the cement bond integrity in six angular segments around the second interface between cement and formation can be evaluated by the recorded waveforms. Further study on processing methods should be carried out. |
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| Keywords: | Cased well Acoustic logging 3D finite difference Sidewall source Non-axisymmetric acoustic field |
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