The wireless sensor networks can enable the real-time monitoring in the pipeline environments, which can facilitate important applications such as structure identification and fault diagnosis. The magnetic induction (MI)-based techniques provide efficient and reliable wireless communications among sensor nodes in such challenging environments. This paper proposes a localization strategy for MI-based wireless sensor network in the complex pipeline environment without requiring any additional infrastructure. The proposed localization strategy analytically captures the unique pipeline system effects, including antenna orientations, absorption of fluid medium, reflections on pipe walls, node's position on the pipe cross section, and the pipe turns and branches. The numerical evaluation shows the proposed strategy can provide high resolution position estimation for small wireless mobile sensor nodes with arbitrary orientation and position inside the pipelines.