An active magnetic ranging method for drilling cluster wells based on casing current excitation

Abstract

Multiple wellheads are required to be constructed in a confined space for drilling cluster wells, so it is necessary to take high-precision cross-well ranging measures to prevent borehole collisions. To solve the problem of ranging between the drilling wells and multiple adjacent wells, a new method of ranging between adjacent wells based on the casing current excitation of adjacent wells is proposed, in which low frequency excitation current is injected into the casing in adjacent wells with time-division or frequency-division excitation mode, and the ranging tool in the drilling well is used to detect the magnetic induction intensity generated by the casing current around the formation, so as to determine the distance between adjacent wells. In this paper, the algorithm for determining distances and directions between adjacent wells is established, and the key factors affecting the ranging model are analyzed by numerical simulations. The results show that with the increase of well depth, the magnetic induction decreases at the exponential rate of exp, and high formation resistivity and low excitation current frequency are beneficial to enhance the magnetic induction. The experimental results show that within the range of 10 m, the measured value of magnetic induction intensity matches well with the theoretical value, and the directional measurement error is less than 1°, which validates the effectiveness and accuracy of this method, and provides theoretical guidance and experimental basis for the development of anti-collision measurement while drilling system for cluster wells.