Study on draining and drying scheme for T-type subsea natural gas pipeline with different diameters

Author of the article:TAN Hongying, GAO Mingzhi, LEI Zhenming, SI Hongtao, LIU Jian

Author's Workplace：Offshore Oil Engineering Co., Ltd., Tianjin,　300451, China

Key Words：Natural gas pipeline; T-type subsea natural gas pipeline with different diameters; Draining; Drying; Pigging; Purge

Abstract：For the T-type subsea natural gas pipeline of different diameters, the conventional draining and drying procedure cannot be implemented. To address this problem, based on gas field pipeline network project in the South China Sea, this study first analyses the layout characteristics of that T-type subsea gas pipeline before proposing two schemes of draining and drying the pipeline; namely draining and drying with dry gas purging, and draining with dry gas purging follow by TEG drying respectively. These two schemes are compared and evaluated from the perspectives of technical feasibility, implementation complexity, economics, environmental protection and risks. Finally, it is recommended to adopt the increased dry gas purging volume as the optimal scheme for draining and drying subsea pipeline, and specific implementation plan and technical requirements are also given to provide reference for development of draining and drying schemes for similar subsea natural gas pipeline projects in the future.