Flow Assurance and Production Chemistry for the Na Kika Development

Abstract

The Na Kika base development consists of five oil and gas fields in the Mississippi Canyon area of the Gulf of Mexico tied-back to a central floating oil and gas processing facility. The water depths for each of the fields range from 5800 to 7000 ft and are offset between 6 to 13 miles from the facility. The individual fields have been developed as subsea production systems. The development of the fields had a number of unique features that were challenges for the development project. • Extreme water depths. • Downward sloping flow path for the fields north of the host (Ariel & Kepler). • Relatively low reservoir temperatures. • Complex reservoirs, leading to uncertainty regarding reserves and rates, and in some cases, the nature of expected hydrocarbons. • Subsea flowline design using flow loops and daisy chained wells vs. dual parallel flowlines from a central manifold. • Gas lifting of large diameter risers for production enhancement and slug control. Within these unique features and challenges were a variety of flow assurance concerns. These concerns were addressed by understanding the related production chemistry problems, applying an operating strategy and specialized equipment for mitigation of those problems, and then validating those plans with extensive steady state and transient simulations and testing. The key production chemistry issues anticipated on Na Kika included asphaltene precipitation in the well bore as a result of down hole commingling, paraffin deposition in the flowlines, and hydrate control. Lessons learned during the first year of operation address work-a-rounds because of equipment start-up issues, and differences in production chemistry characteristics from those originally assumed. The operating strategies and equipment employed for mitigation of the production chemistry issues included a combination a various conventional and non-conventional methods such as continuous hydrate inhibition for the gas systems, and heat retention in the oil systems combined with flowline blowdown and oil circulation procedures during unplanned facility outages. Production chemicals would be used for management of corrosion, asphaltene and paraffin deposition. Lessons learned during the first year of operation include subsea equipment performance and associated operating constraints, benchmarking, and results of latest production chemistry analysis. Extensive steady state and transient analyses were performed during the development project to validate operating temperatures and pressures, cool-down times, slugging characteristics, gas lift requirements, and operating parameters, as well as success of transient events (i.e. blowdown, start-ups, etc.). Lessons learned and actual field data for these analyses will be presented. Overview of Na Kika Development. The Na Kika base unit consists of five oil and gas fields in the Mississippi Canyon area of the Gulf of Mexico, developed with 10 production subsea wells and associated subsea facilities that are centrally located to the area. The individual fields are named Ariel, Kepler, Fourier, Herschel, and East Anstey. The five fields are located in water depths ranging from 5800 to 7000 ft depending on the specific well location. The fields are developed utilizing three unique gathering flowloops with their produced fluids routed back to the floating production facility: • Ariel and Kepler oil fields are developed with a 10” x 16” pipe-in-pipe (PIP), 25-mile flowloop to the northwest of the production facility. These fields are developed with five subsea oil wells, each which are daisy chained within the norther loop route. The north loop was unique that the flowline route is generally downhill towards the host. The water depths along the route range from approximately 5800 ft (shallowest) at the well locations to 6340 ft at the host. • The Fourier oil play and the Herschel field are developed with an 8” x 12” pipe-in-pipe, 26-mile flowloop to the south of the production facility. Only two subsea oil wells produce within the south oil loop route. The south oil loop flowline route is generally uphill