Abstract: The array induction logging tool adopts the basic combination of shielded and receiving coil pairs wound in opposite directions, effectively eliminating direct coupling signals and measuring rich wellbore and formation characteristics, suitable for resistivity measurement in medium to low resistance shale formations. When using oil-based drilling fluids in high-resistance carbonate formations, high temperatures and weak background signals cause a large number of negative anomalies in the original signal of array induction logging, resulting in extremely low signal-to-noise ratios. Traditional software focusing algorithms produce results that neither reflect reservoir characteristics nor can be used for hydrocarbon evaluation. To address this issue, numerical simulations reveal the intrinsic relationship between high-temperature deformation and weak signal backgrounds in high-resistance formations and abnormal original signals. Analyzing the signal quality differences at different source distances, a new approach is proposed:calculating multi-frequency conductivity averages in thick dense layers and correcting anomalies using the theoretical lower limit of induction logging signals. By combining four long-source-distance sub-array signals for synthetic processing, the accuracy of resistivity measurements in such complex wellbore environments in carbonate formations is significantly improved. The relevant methods have been validated using multiple actual well logs.

Key words: carbonate, array induction logging, oil-based drilling fluid, ultra-deep formation, logging interpretation

摘要： 超深层碳酸盐岩高阻地层钻探过程采用油基钻井液,井筒高温环境及地层本身极低的电导率常常导致阵列感应测井短源距子阵列原始信号产生大量的负值异常,信噪比低,传统软件聚焦算法输出的阵列感应电阻率曲线饱和平直,不能用于油气评价。以高分辨率阵列感应测井仪(high definition array induction log,HDIL)为例,利用数值模拟手段揭示出,高温下线圈微小位移导致的短源距子阵列屏蔽效果下降以及仪器制造过程针对高温的刻度校正不充分是导致原始信号异常的根本原因。通过分析不同源距的信噪比差异,提出一种新思路:优选长源距高频、高信噪比电导率信号,在井底厚层致密层段针对多频电导率平均值开展理论下限值异常校正,最后对校正后的长源距子阵列信号进行合成处理。该方法显著提高了复杂井筒环境下碳酸盐岩地层的电阻率测量精度,并且得到了多口实测井资料的验证。

关键词: 碳酸盐岩, 阵列感应, 油基钻井液, 超深层, 测井解释