基于IBC和CBL/VDL测井的微间隙识别方法

Identification Method of Microannulus Based on IBC and CBL/VDL Logging

为了明确微间隙厚度对不同测井仪器固井质量评价结果的影响,研究了CBL/VDL测井的套管波、IBC激发的共振波与挠曲波对微间隙的响应特征,分析了套管与水泥环间微间隙、水泥浆密度等因素对3种模式波的影响规律。分析表明,CBL/VDL测井的套管波对微间隙一直敏感,幅度随微间隙(充液微间隙)厚度增加而增大,厚度0.01 mm的微间隙也会使套管波相对幅度达到30%~50%,此响应结果导致判定水泥胶结差;共振波幅度对厚度小于0.10 mm的微间隙不敏感;挠曲波在套后胶结低阻抗水泥时,衰减稍有降低,但在套后耦合高阻抗水泥(一般指常规水泥和加重水泥)时,微间隙会使衰减明显增大,可见微间隙导致挠曲波的衰减均是高值,在气液固相态识别时会判定为套后介质是固体水泥,因此联合CBL/VDL和IBC测井结果可识别井下微间隙井段。现场多口井试油结果表明,CBL套管波幅度高、但挠曲波衰减值也高的井段在试油过程中均显示了较好的水泥封隔能力,表明该测井结果是微间隙的响应特征。基于IBC和CBL/VDL测井的微间隙识别方法避免了传统的井筒加压测井方式,现场应用效果较好,具有较好的推广应用价值。

To accurately study the influence of microannulus thickness on the evaluation of cementing quality by different logging instruments,this study analyzed the response characteristics of CBL/VDL logging casing waves,IBCinduced resonance waves,and flexural waves to the presence of microannulus.The study focused on how the microannulus between the casing and cement sheath as well as the density of the cement slurry,impacts these three wave modes.The findings reveal that the casing wave in CBL/VDL logging is consistently sensitive to the presence of microannulus,with amplitude increasing as the microannulus thickness(fluid-filled)grows.A microannulus as thin as 0.01 mm can cause the relative amplitude of the casing wave to reach 30%–50%,leading to an assessment of poor cement bonding.The resonance wave amplitude,however,is not significantly affected by microannulus thinner than 0.01 mm,and the attenuation of the flexural wave only slightly decreases when low-impedance cement is cemented behind casing.In contrast,when high-impedance cement(generally conventional cement and heavy cement)is coupled,the presence of microannulus markedly increases attenuation,causing the flexural wave to reach a high attenuation value.In gas-liquid-solid phase identification,the medium behind the casing is likely to be identified as solid cement,making the combination of CBL/VDL and IBC logging results effective for identifying microannulus intervals.Field oil test results from multiple wells show that wells with high CBL casing wave amplitudes and high flexural waveattenuation values consistently demonstrate better cement sealing capabilities, confirming that these logging responsesare characteristic of microannulus. This method of microannulus identification, based on IBC and CBL/VDL loggingavoids the traditional wellbore pressure logging method and obtains a good application effect, and it is worthy ofpromotion and application.