井下金属套管应力磁记忆检测信号的处理

Detection signal treatment for stress and magnetic memory of downhole metal casing

由于地质和工程方面的原因,井下套管受到非均匀载荷的作用易产生塑性变形。用金属磁记忆检测技术可有效判断套管的应力集中区域,为套管损坏进行早期诊断。井下的干扰和噪声对金属磁记忆检测数据影响很大。因此,磁记忆信号的处理与分析技术是磁记忆法检测与评价井下金属套管应力的技术关键与难点。在实际检测中,磁记忆信号属于随机信号、不具有平稳性,宜采用小波技术分析磁记忆信号。该文介绍了在磁记忆信号定量分析中开发的小波消噪信号处理方法,采用Db4小波函数、分解层数4层及其信号数字滤波、信号反演等相关技术,该方法有效地消除了各种噪声的干扰,依据处理后的磁记忆信号可精确分析判断套管的受力位置。

By the reason of geology and engineering, downhole casing is affected on heterogeneous load easily generates plastic deformation. Metal magnetic memory testing technique can effectively distinguish stress concentration zone of casing, which can develop early diagnose for casing damage. Downhole interference and noise has serious effects on metal magnetic memory test data, thus treatment and analysis techniques for magnetic memory signal are technical key and difficulty for magnetic memory method testing and evaluating downhole metal casing stress. In actual testing, magnetic memory signal belongs to random signal without stationarity, adjusting adopting wavelet technique to analyze magnetic memory signal. This paper introduces wavelet denoising treatment method in quantitative analysis and adopts several relative techniques including Db4 wavelet function, resolving layers, signal and digital filtering and signal inversion. This method effectively eliminates various noisy interferences. Based on magnetic memory signal after treatment, force site of casing can accurately be analyzed and determined.