A high-precision guidance method of wellbore trajectory based on the rotary magnetic dipole

As traditional measurement-while-drilling (MWD) techniques can not meet the high-precision guidance requirement of complex structure wells, such as horizontal intersection wells and steam assisted gravity drainage (SAGD) parallel wells in heavy oil development, the present paper proposed a high-precision guidance method based on the rotary magnetic dipole model, aiming at directly measuring the relative position and orientation between drill-bit and target-point. By investigating signal propagation rules of the rotary magnetic dipole, the paper demonstrated that the rotary magnetic dipole could be an equivalent of two perpendicular magnetic dipoles, and there existed a characteristic magnetic intensity signal, which could position the rotary magnetic dipole and be determined with the phase demodulation and amplitude demodulation of triaxial measureable magnetic signals by using the Hilbert Transform. The simulation results showed that the closer the rotary magnetic dipole to the target point, the smaller the positioning error, and the more accurate the orientation. The high-precision guidance method of wellbore trajectory based on the rotary magnetic dipole was of great value in drilling SAGD parallel wells in heavy oil development and horizontal intersection wells in coalbed methane development as well as in soluble salt mine development.