Optimizing Gas Condensate Subsea Tiebacks: Lessons Learned from Unload to Host Operations

Abstract

Gas condensate subsea tiebacks increasingly favor Unload to Host (U2H) operations over traditional Unload to Rig for enhanced execution efficiency and cost reduction. They further eliminate the need for temporary floating production units to partially unload wellbore liquids/solids and introduce first gas with flaring. While U2H brings significant benefits like HSE risk mitigation, it also poses integrity and operability challenges to new and existing facilities. This paper will present case studies and lessons learned from U2H operations conducted on multiple gas condensate subsea tiebacks. Key focus areas include understanding the impact of U2H fluid composition on LNG production, selecting subsea preservation liquids to balance hydrate and corrosion risks, and optimizing liquid handling and inventory management at host facilities. Additional considerations cover solids management during wellbore and pipeline transport, solids filtration at host facilities, and effective production chemistry management with a tailored sampling plan and temporary chemical injection package readiness. The outlined learnings emphasize the critical need for upfront planning on U2H operation, advocating an integrated multidisciplinary approach to influence new facilities designs as well as to minimize last-minute changes during execution. Overall, the aim of this work is to highlight operational excellence for flow back to host where asset integrity and production optimization can assist to unlock value if risks are well-understood and managed.