Bringing the 1st BP Operated Subsea to Shore Gas Field into Production: Flow Assurance Lessons Learned

Abstract

Abstract Taurt field located in the Mediterranean Sea in 108 m water depth is the 1st BP operated subsea to shore gas development. Phase 1 of the project consists of two subsea wells producing directly from the subsea manifold to the onshore gas processing plant via a 68 km, 20-in pipeline. The field has been brought into production and ramped up to 230 MMscfd successfully despite facilities constraints during initial start-up. The main flow assurance issues experienced during the initial start-up are hydrate risks due to J-T cooling and liquid production handling onshore particularly due to potential completion brine return. The experience during initial start-up highlights the importance of collecting good fluid samples during exploration and appraisal, and also the down hole and wellhead pressures and temperatures during flow back. Confirming the condensate yield helps prediction of liquid holdup in the pipeline which in turn will affect the prediction of liquid production coming to onshore during ramp-up. More accurate prediction of the wellhead temperature affects the requirement for hydrate inhibitor which in turn also affects the liquid holdup in the pipeline and liquid production coming onshore. Transient simulations help in selecting the dewatering strategy to be either pigged or pig less operation by predicting the amount of remaining water and how it impacts the production ramp up. Simulations also help prediction of the liquid production for setting up temporary liquid handling facilities to prevent the possibility of completion brine return upsetting the processing plant. Comparison with the actual liquid production data suggests that simulations should have been performed with less conservative condensate yield, although predicting the completion brine return onshore is still difficult. After obtaining the latest fluid composition and the actual operating conditions, the hydrate management strategy has been re-visited and resulted in operations cost saving and simpler operating procedures.