Analysis of Multiple Factors Affecting the Accuracy of Active Magnetic Ranging in Relief Wells

Summary Active magnetic ranging technology used in relief well operations involves a complex excitation process, with various external factors influencing the measured magnetic signal strength. Based on its operational principles, this study performed experiments and numerical modeling to analyze the magnetic field distribution around an accident well. Experiments validated the accuracy of the numerical simulation method. Subsequently, finite element software was used to investigate the effects of 12 parameters, including the formation conductivity, accident well casing properties, injection current intensity, and downhole electrode characteristics, on the magnetic field characteristics. This study analyzed the influence of each parameter and explored the interaction of each parameter with the magnetic field around the accident well casing. The key parameters were ranked using the entropy-weight-gray-fuzzy comprehensive analysis method, with the electrical conductivity of the accident well casing exhibiting the most significant impact on the magnetic field. In addition, this study demonstrated that increasing the length and diameter of downhole electrodes, enhancing drilling fluid conductivity, increasing injection current intensity, placing downhole electrodes and probes in formations with suitable conductivity ranging from 10−3 to 10 S/m, and reducing the spacing between wells can significantly improve magnetic signal strength and ranging accuracy. The findings of this study provide a theoretical basis for understanding the influence of various parameters on the magnetic field of accident wells and offer practical guidance for optimizing magnetic ranging operations and designing related tools in relief well applications.