Transfer of unprocessed oil from a reservoir to a platform over distances up to 25 km is commonplace, and recent projects have implemented schemes for over 50 km. Most such installations use one or several thermally insulated flowline(s) for the purpose of keeping the well fluids hot in the steady state such as to avoid formation of hydrates, wax and asphaltenes.
Most such installations use a dual flowline configuration, thus facilitating circulation of stabilized crude oil in the flowline system prior to a planned shutdown, thereby eliminating sensitivity to the undesirable effects of low temperatures. On restarting production, methanol or other chemical means of hydrate inhibition is injected into the well stream to prevent hydrates as the well stream is cooled by the cold flowline pipe. Alternatively, circulation of hot stabilized crude oil is used to heat the flowlines.
For cases of extreme offsets (say for instance in the order of 100 km) use of a dual flowline system for production (in addition to a water injection pipeline) can be uneconomical.