井环境对阵列感应测井响应的影响分析

The analysis of effect of the borehole environment on responses of array induction logging

阵列感应测井资料经常出现与井眼环境有关的质量问题.采用三维矢量有限元法分别在椭圆形井眼、仪器偏心及斜井条件下的阵列感应测井原始响应进行了模拟,并对环境校正和合成聚焦后的数据进行了分析.结果表明,线圈距较短的原始测量信号更易受井眼椭圆度、仪器偏心、泥浆电阻率及与地层电阻率反差的影响;而合成聚焦后的浅探测曲线虽然经过了环境校正和合成聚焦等数据处理,但仍然受这些因素的影响,这反映出阵列感应测井的数据处理是不完善的或采用的校正模型是理想化的;在井斜影响方面,浅探测曲线受井斜角大小影响相对较小,深探测曲线在井斜角为60°以上时受其影响较大而必须进行进一步处理.

The quality problems related with the borehole environment olten appear for array induction logging data. The raw responses of array induction logging are separately simulated by the 3-D vector finite element method in different borehole environments including the elliptical borehole, tool eccentricity, and slant borehole, and processed by environment correction and synthesis and focus to get the logs. The results show that the influence of the ellipticity of borehole, the tool＇s eccentricity, the mud resistivity, the contrast between the formation resistivity and the mud resistivity is bigger on the raw responses of short-distance coils than that of long-distance coils. The shallow-investigation logs are still influenced by those factors in spite of being processed by environment correction, synthesis and focus, which demonstrates that the data processing of array is imperfect or the used correction model is ideal. The influence of the borehole slope is relatively smaller on the shallow-investigation logs than deep-investigation logs. When the borehole slope is greater than 60°, its influence is very serious on array logs and the correction to them must be done further.