This article, written by Technology Editor Dennis Denney, contains highlights of paper OTC 18384, "Flow-Assurance Lessons: The Mica Tieback," by A.L. Ballard, SPE, BP America Inc., prepared for the 2006 Offshore Technology Conference, Houston, 1-4 May. Flow assurance plays a significant role in asset development. In the case of ultradeep water, the role is major. The Mica field uses the longest tieback in the Gulf of Mexico and has been in operation for more than 4 years. The Mica wells are tied back through two 29-mile flowlines (one for gas and one for oil) to a major facility (Pompano). A review of Mica, comparing original flow-assurance-design strategies with current operational strategies, revealed several learnings, particularly involving paraffin, corrosion, erosion, hydrates, and slugging. Introduction The Mica field is in 4,350 ft of water. First production was in 2001. It was decided early on that the Mica wells would be tied back to an existing platform. Three zones in the reservoir were deemed producible. The shallowest zone is a saturated-gas and -oil zone with a gas/oil ratio (GOR) of 1,330 scf/STB, oil gravity of 32°API, and a wax cloud point of 93 to 100°F. The middle zone is a near-critical fluid with a GOR greater than 3,000 scf/STB, oil gravity of 37°API, and a wax cloud point of 90 to 94°F. The deepest zone is a dry gas with a condensate yield of 5 STB/MMscf and condensate gravity of 44°API. Peak capacity from the reservoirs was expected to be 150 MMscf/D of gas and 15,000 STB/D of oil. Pompano Tie-In. Pompano is a steel-jacket structure in 1,290 ft of water. Weight on the platform was not a major issue, so it was decided to construct a new process system for the Mica wells. Because a relatively small amount of oil was expected compared to gas, a separate gas-export pipeline was built for the gas while the oil was tied into the Pompano crude treater. New equipment built for the Mica wells includes a high-pressure (HP) separator, intermediate-pressure (IP) separator, low-pressure (LP) separator, turbine-driven centrifugal compressor, glycol-dehydration system, and turbine-driven generator. Fig. 1 shows the process system. The compressor suction is drawn from the IP separator at 450 psig and discharged to the gas-export line at 1,300 psig. The LP separator feeds into the Pompano compressors at 150 psig. Design Challenges Paraffin. With the cloud-point temperatures of the oil, paraffin issues were expected in the wells and in the insulated oil flowline. For a tieback of this length, it was not feasible to keep the fluids in the flow-line above the wax-appearance temperature during production. Pipe-in-pipe (PIP) insulation was designed for the oil flowline to spread out the deposited paraffin in the flowline as the oil cooled.