采用数值模拟与刻度井群测井相结合的方法进行套管井声场研究,分析套管井窜槽角度、Ⅱ界面（水泥与地层胶结界面）胶结质量对声波-变密度测井的影响,在此基础上对利用CBL/VDL测井资料评价固井质量的方法进行改进,提出新的评价标准。分别采用实轴积分法和2.5维有限差分算法对轴对称声场与非轴对称声场进行数值模拟,并与刻度井测井数据对比后发现：数值模拟方法可靠;随着窜槽角度减小,套管首波幅度减小,且水泥浆密度越大,套管波衰减越快;声波测井能辨别的最小窜槽角度为45°;通过波形图在时域内很难提取地层波信息,可利用主频识别地层波,且在灰岩地层中当Ⅱ界面环隙宽度较小时地层波才可作为首波接收。依据套管井声场研究结果,建立了新的基于声波-变密度测井的固井质量评价标准。图8表3参20
A new method of cement bond quality evaluation was proposed by combining numerical simulation and calibrated cased hole acoustic logging data. The effects of the cement channel angle and the quality of the second bond interface (the interface of cement with formation) on acoustic variable density logging data were analyzed. Based on the analysis result, a new cement bond evaluation standard was presented after revising the traditional CBL/VDL method. The axisymmetric acoustic field was simulated by real axis integral method, while the non-axisymmetric acoustic field was simulated by 2.5-D finite differential method. After comparing with the calibrated cased hole acoustic logging data, the research has the below results: the numerical simulation result matches with the calibrated well logging data very well and the new method is reliable; the amplitude of the first acoustic arrival in the case hole decreases as the angle of cement channel decreases, and the denser the cement is, the faster the amplitude of cased hole acoustic waveform decays; the lower limit of cement channel angle is around 45 degrees which can be detected by acoustic logging; the formation acoustic waveform is not easy to be detected in time domain, however it is easy to be detected in frequency domain, especially in limestone formation, the first arrival only can be detected when the annulus width of the second bond interface is small. According to the research result of the numerical simulation of cased hole acoustic field and acoustic variable density logging data, new evaluation criteria of cement bound quality were presented.
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