Subsea Gas-liquid Separation: Case Studies and Technology Benefits

Abstract Recent deepwater projects are considering Subsea Gas-Liquid Separation aspotential technology to unlock oil reserves. Eni e&p is currently workingon R&D and development studies to evaluate the benefit of this technologyfor a number of representative assets in its deepwater portfolio. The paper presents several findings of this original analysis. Case studies arerepresentative of a wide range of potential applications: from secondarytiebacks in standard deepwater depth to 1500 m water depth oil developmentapplications and heavy/difficult oil cases to condensate/gas fieldsapplications. The results are presented with the comparisons between standard deepwaterarchitectures and configurations based on Subsea Gas-Liquid separation in termsof flowassurance strategy, field layout, capital costs and benefits for theoperators in terms of potential additional recovery and production. SubseaGas-Liquid separation may become an enabling technology for deepwaterdevelopments if oil industry is able to resolve and mitigate possible risksassociated. INTRODUCTION Subsea processing coupled with innovative field architectures are one of themost attractive tools currently being utilized and considered by the oil andgas industry to open new opportunities and achieve more effective exploitationof offshore fields. Every day new oil and gas reservoirs are being discoveredin unconventional and remote areas in deep and ultra-deep water, typically farfrom existing treating and storage facilities. Subsea processing technologiesare becoming faster and faster applicable options to improve technical andeconomic performance of those challenging subsea field developments, improvingthe reserves recovery and operation strategy, and, in some cases, reducing theassociated development CAPEX. The term " subsea processing" can be defined as any treatment of the producedfluids performed on the seabed prior to reaching the offshore installation andthe conventional surface process facility. Different devices have beenqualified and installed to boost the raw wellstream, like subsea multiphasepumps and wet gas compressors. In the last ten years, technologies to separatethe gas phase from a liquid stream and produced water from hydrocarbons rapidlyevolved thanks to great efforts on qualification program and testing campaign. Moreover, a few installations of separation and boosting devices have beenachieved, presenting really encouraging results but not neglecting operationalissues they have encountered during field life.