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20多年来,井下电视测井一直被用于探测井壁特征,但是其解释结果常常受到仪器偏心的影响。特别是因为仪器偏心引起的信号强度变化重叠在振幅图象上,所以不能识别出井壁的细小特征。诸如数据滤波等常规处理方法虽能消除噪声,但也能抹去井壁的细小特征。Menger和Schepers(1988)提出了一种利用井下电视数据确定的声波传播时间计算仪器偏心率的方法。根据仪器在井眼内的位置和实验室测得的仪器特征标定曲线,就几乎能完全重建声波振幅图象而无需做任何滤波。借助于这种判定方法,可以对振幅图象进行仪器偏心校正,同时保留与井壁物理特征有直接关系的细小振幅特征(如地层界面、井眼崩落及裂缝等)。
For more than two decades, downhole TV logging has been used to detect borehole features, but its interpretation is often influenced by instrument eccentricity. In particular, small variations in the borehole wall can not be identified because variations in signal intensity caused by eccentricity of the instrument overlap the amplitude image. Conventional processing methods such as data filtering can eliminate noise but also erase the small features of the borehole wall. Menger and Schepers (1988) proposed a method of calculating the instrument eccentricity using the acoustic propagation time determined by the downhole television data. Depending on the location of the instrument in the wellbore and the laboratory calibration of the instrument characteristics, the acoustic amplitude image is almost completely reconstructed without any filtering. With this method of determination, the amplitude image can be corrected for instrument eccentricity while preserving small amplitude features (such as formation interfaces, borehole breaks and cracks, etc.) that are directly related to the physical characteristics of the borehole wall.