Successful Late Life Subsea Gas Field Management: Extending Life of Giza Fayoum in Challenging Flow Assurance Environment, Without Subsea Intervention

This paper describes the late life flow assurance challenges faced Giza Fayoum (GF) subsea gas field, where total production dropped below pipeline turndown rate, leading to liquids accumulation in the pipeline increasing back pressure on wells and eventually 30 days field shut down. Despite system constraints of depleting reservoirs and limited liquid handling capacity, the team put together a practical methodology to dewater the trunkline and restore production without the need for an expensive subsea intervention. The team studied few scenarios for pipeline dewatering considering wells potential, location, liquids inventory and its distribution along the pipeline, onshore constraints of liquid handling, as well as impact on resources and ultimate recovery from the field. Through Integrated discussion supported by dynamic modelling using OLGA, the team has decided on the most promising approach for removing about 12000 bbl of water from the pipeline via cycling a group of wells distributed along the pipeline. The initial operation involved flaring and frequent plant shut-ins and restarts, so a temporary operating procedure was written and reviewed by multidisciplinary team before execution. Early dewatering operation targeted 5 to 6 short production cycles (6-10 hours) at minimum onshore pressure by sending gas to flare to help remove 12000 bbl of water with an expected total flared volume of 150 mmscf. During execution, actual system performance was very close to expectations from the dynamic modelling, and team managed to remove the required amount of water after only four cycles with 65% savings in flared gas. In addition, the success of the concept allowed further optimization and removal of more water from the pipeline by completing another 6 production cycles through the export route and stopped flaring. The dewatering process resulted in lowering system pressure by 10 bar which enabled field restart and resuming production for ~3 years till the time of writing this paper at an average cyclic production rate of 45 mmscfd. It has also allowed better understanding of the subsea system's performance and limitations, which set the basis for the ongoing improved longer term operating strategy for the field. The approach described in this paper offers a practical and cheap solution for one of the most common late life flow assurance challenges that can be applied in similar gas fields to dewater the pipeline, increase production, and extend field's life when the economics do not support a subsea vessel intervention to pig and dewater the pipeline.