A Theoretical Model of Residual Magnetic Field around a Pre-Magnetized Casing String

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.

Experimental Study of Measuring Algorithm Accuracy of the Electromagnetic Distance Measurement Anticollision Tool

“…Based on the pseudo-analytical equation of electromagnetic log for layered formation, an optimal boundary match method was proposed to adaptively truncate the encountered formation structures [19][20][21]. e inverted results of field data demonstrated that the real-time interactive inversion method was capable of providing the accurate boundaries of layers around the wellbore from the LWD EM, and it will benefit the wellbore trajectory optimization and reservoir interpretation [22][23][24]. erefore, it is necessary to develop an electromagnetic anticollision detection tool for adjacent wells.…”