油基钻井液环境下电成像测井的快速定量反演研究

The electrical imaging logging technology in oil-based drilling fluid environment is one of hotspots in logging field. The poor conductivity of oil-based drilling fluid makes it a key and difficult problem to obtain the imaging that can be compared with that obtained in the water-based drilling fluid environment, restricting its development. Fast quantitative inversion imaging method for the three parameters (i.e., formation resistivity, formation dielectric constant, and the thickness of mudcake) based on electrical imaging logging in oil-based drilling fluid environment is researched. Based on the interaction between the stimulus signal and oil-based drilling fluid and formation, using finite element numerical simulation method, the variation of measured current signal is studied systematically with the clear influencing factors. On this basis, the equivalent circuit models are established and further optimized, computing models of the three parameters are developed with application scope analysis. Furthermore, the fast quantitative inversion method based on forward modeling data for three parameters is established using the multidimensional data combination, compression and geophysical inversion method. Furthermore, to satisfy the actual requirement, the fast quantitative inversion method is evaluated and optimized by means of typical formation models. The research has important significance and application prospect in the development and application for the future electrical imaging logging in oil-based drilling fluid environment.

油基钻井液环境下电成像测井技术是目前测井领域的研究热点之一。油基钻井液导电能力差，使得在油基钻井液环境下获得与在水基钻井液环境中相媲美的成像效果成为重点和难点问题，成为制约其发展的瓶颈。本项目研究油基钻井液环境下基于电成像测井的三参数（地层电阻率、地层介电常数和泥饼厚度）快速定量反演成像方法。基于激励信号与油基钻井液和地层的作用关系，利用有限元数值模拟方法，系统研究测量电流信号的变化规律，明确其影响因素；在此基础上，建立并优化仪器等效电路模型，确定三参数的计算模型，并分析其适用范围；进而利用多维数据组合、压缩及地球物理反演方法，建立基于正演数据包的三参数快速定量反演方法；结合典型地层模型，对三参数快速反演方法进行评价和优化，使其满足实际测井要求。研究成果对今后油基钻井液环境下电成像测井技术的发展和应用具有重要的指导意义和应用前景。

油基钻井液环境下电成像测井技术是目前测井领域的研究热点之一，尤其是在国内尚未形成成熟的理论方法体系和广泛的工程应用，与国外相关测井技术之间还存在相当大的差距。与水基钻井液电成像测井技术相比，在油基钻井液环境中，制约电成像测井技术发展的主要难点是油基钻井液电阻率高，需要采用更高频率的激励信号，才可以使得电流能够以电容耦合的方式穿过高阻泥饼层进入地层。此时影响测量信号的主要因素有泥浆电阻率、泥浆介电常数、泥饼厚度、频率大小、地层电阻率和地层介电常数等。本项目研究油基钻井液环境下基于电成像测井的三参数（地层电阻率、地层介电常数和泥饼厚度）快速定量反演成像方法。基于激励信号与油基钻井液和地层的作用关系，利用有限元数值模拟方法，系统研究测量电流信号的变化规律，明确其影响因素；在此基础上，建立并优化仪器等效电路模型，确定三参数的计算模型，并分析其适用范围；进而利用多维数据组合、压缩及地球物理反演方法，建立基于正演数据包的三参数快速定量反演方法；结合典型地层模型，对三参数快速反演方法进行评价和优化，使其满足实际测井要求。研究结果建立了油基钻井液环境下电成像测井方法体系，明确了测井响应的变化规律，基于正演数据包和机器学习算法率先建立了快速定量反演方法，可实时地给出定量的地层电阻率、地层介电常数和泥饼厚度等三个参数。研究结果可服务于国内油基钻井液环境下电成像测井仪器研发和工程应用，具有重要的指导意义和应用前景。