Abstract
In the field of petroleum drilling engineering, passive magnetic ranging technology is generally used for specialized drilling operations such as connecting relief wells, preventing wellbore collisions, guiding parallel horizontal wells, etc. Although pre-magnetized casing strings have been used to improve the detection distance and accuracy, the theoretical mechanism is not well understood. Based on the equivalent current model of a permanent magnet, a theoretical magnetic field model around the pre-magnetized casing string was established by using the vector potential method and vector superposition principle and validated by the COMSOL Multiphysics software. Our results show that connecting pre-magnetized individual casings with homogeneous magnetic poles can enlarge the magnetic induction intensity around the total casing string. Furthermore, the magnitude close to the casing coupling is significantly larger than that close to the middle of the individual casing. Connecting pre-magnetized individual casings with heterogeneous magnetic poles results in a low magnetic induction intensity around the total casing string. In order to improve the detection distance and accuracy of the magnetic ranging, the pre-magnetized individual casings should be connected with homogeneous magnetic poles. The results of this study can provide guidelines for the development of passive magnetic ranging technology.
Highlights
In the field of oil-drilling engineering, magnetic ranging technology is used in special drilling operations, such as connecting relief wells [1,2,3], preventing wellbore collisions [4,5,6], guiding parallel horizontal wells or U-shape well [7,8], etc
Because the magnetic field of the adjacent casing string is due to the remanence produced by the pre-magnetization, and its intensity and distribution characteristics are known in advance, the detection accuracy is relatively high, and the detection distance is relatively large
In order to develop the passive magnetic ranging technology independently, a robust theoretical magnetic field model around the pre-magnetized casing string is to be established by the modern electromagnetic theory and validated by COMSOL Multiphysics software in this article
Summary
In the field of oil-drilling engineering, magnetic ranging technology is used in special drilling operations, such as connecting relief wells [1,2,3], preventing wellbore collisions [4,5,6], guiding parallel horizontal wells or U-shape well [7,8], etc. The relative position of the adjacent casing string is determined by applying an electromagnetic excitation signal in one well and detecting it in another well by additional magnetic instrument. The self-induced magnetic field intensity of the adjacent casing string itself is relatively small and exhibits more uncertainties This method is still restricted by relatively low detection accuracy and small detection distance [1,2,9,10]. Because the magnetic field of the adjacent casing string is due to the remanence produced by the pre-magnetization, and its intensity and distribution characteristics are known in advance, the detection accuracy is relatively high, and the detection distance is relatively large. In order to develop the passive magnetic ranging technology independently, a robust theoretical magnetic field model around the pre-magnetized casing string is to be established by the modern electromagnetic theory and validated by COMSOL Multiphysics software in this article
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