套管-水泥界面微间隙的检测方法及应用

声幅及变密度测井检测油、水固井质量中、套管-水泥界面微间隙与窜槽两种胶结状态在测井资料上表现出相似的特征，即套管波具有中等幅度。为了找出两种胶结状态在套管波幅度上的特征和差别，进而将其区分开，在套管与水泥环间存在不同厚度的流体环的情况下，对井孔声场及套管波幅度进行了理论研究，提出了利用声波测井资料、伽马密度测井资料对套管-水泥界面微间隙进行综合评价的解释方法；编写了相应的解释软件。实验结果表明，套着-水泥界面存在的流体环随着其厚度的增加，套管波幅度逐渐升高；水泥缺失和窜槽将导致伽马密度测井探测到的套管外介质密度值降低，而套管-水泥环间存在微间隙的情况下，其测量的密度值仍然是正常的水泥密度。在水泥胶结模拟井中进行了室内实验，在大庆油田的4口井中进行了现场实验，应用效果良好。

Identification Method and Application Examples of the Annulus Between Casing and Cement Sheath

When we use VDL data to evaluate cement bond quality, the microannulus between casing and cement sheath show similar feature as channels, i.e., pipe wave presents moderate amplitudes. In order to find the differences of the amplitude and feature of pipe wave, and furthermore, to distinguish the microannulus from channels, we studied the pipe wave amplitude under the condition that there is fluid between casing and cement sheath. When the thickness of the fluid sheath is about 0 1 mm, the amplitude of pipe wave is consistent and we call it the feature amplitude, this value is connected with the thickness of casing, etc. On the basis of theoretical study and analysis of the cause of microannulus, we propose a comprehensive method that using the material of acoustic logging and Gama-density logging to interpret the first interface microannulus. A corresponding interpretation software has been programed. Lack of cements and cement channelings may result in lower densities of media outside the casings in Gamra-density logging, while there exist micro-annulus between the casing and cement sheath, the measured densities are still the normal cement density. We had experimented this method in model well. This method got expected effect in four wells in Daqing Oilfield including well 3-1x.