Eccentric array-based borehole transient electromagnetic system for NDT of multipipe strings in sidetrack well

Abstract

In the middle and late stage of oilfield development, the sidetracking technology is widely used for restoring the production of stripper well, damaged well and abandoned well. In this paper, we present an eccentric array-based borehole transient electromagnetic (TEM) system for nondestructive testing (NDT) of multipipe strings in sidetrack well. Using the borehole TEM signal model, the response of eccentric sensor is analyzed, which contains more information in the direction of eccentricity. On this basis, multiple eccentric sensors with different depths and different angles are utilized to form an eccentric array, which can be used to determine the direction of sidetracking and to detect the multiple pipes in hanging casing strings. The performance of the proposed system was verified by applying it to sidetrack wells in Shengli oilfield. In addition, field experiments were conducted, and the results demonstrated the effectiveness of the proposed method.