Study On Anti-collision Technology Of Complex Structure Well Based On Magnetic Anomaly

This article is derived from the major science and technology projects of the 13th Five-year Plan.In this paper,the geometric space and physical model of a single well drilling casing in a cluster well are established,and this model is based on the theory of magnetic anomaly detection,by using COMSOL multi-physics finite element software.Then,the magnetic field distribution around the drilling in passive magnetic anomaly detection and active magnetic detection is studied by using Finite Element Analysis.And the following work has been carried out.First,in the method of passive magnetic anomaly detection,a drilling casing model is established,the appropriate boundary value is selected,and the specific magnetic field distribution in the surrounding space after the magnetization of the borehole casing is analyzed;The variation of the surrounding magnetic field distribution with changing the three factors,such as the diameter,thickness and relative permeability of the casing,were studied respectively,the above is a theoretical reference for determining the existence of drilling.Second,in the method of active magnetic detection,a drilling casing model with permanent magnet source is established,the appropriate boundary value is selected,the specific magnetic field distribution of the casing drilling with permanent magnet source in the surrounding space is analyzed,and the influence of drilling casing's magnetic field distribution is analyzed too,by changing casing diameter,thickness and relative permeability;At the same time,A new formula for calculating magnetic field of permanent magnet is derived,according to the Biot-savart's law,magnetic theory and so on,and the influence of geometry which affect its magnetization capacity,like the radius R,the length L,and the ratio of the length to the radius squared is L/R~2,is confirmed by using COMSOL multi-physics software and Matlab software,and the conclusion can be used to provide theoretical and simulation basis for the magnetization capacity of the permanent magnet.Third,in this paper,a simulation test to verify the correctness of passive magnetic anomaly detection is designed,and the correctness and feasibility of simulation and the model which built by COMSOL multi-physics are verified,the above experiment can be a good foundation for the research and development of borehole anti-collision tool by using passive magnetic anomaly detection method.