A large number of gas fields have recently been discovered offshore in depths of up to 3000 m, far away from the nearest coast and in countries with little or no oil and gas infrastructure. In addition to the field development strategies including large surface facilities for processing and export to shore, or floating LNG plants, the industry may in the future be seeing more subsea-to-shore developments for these fields.
Total and Aker Solutions have completed a study for a challenging notional gas field development located at 2500m water depth, 300 km from shore, that is to be developed using only subsea technology. The vision is a fully autonomous subsea production system with tie-back to shore.
This paper describes the flow assurance challenges with long-distance subsea tie-backs to shore, from deep offshore fields, and the work done to identify the wide range of subsea processing schemes that may improve the gas transport. Two of these schemes were selected and studied in detail: one consisting of pushing the envelope of multiphase transport to shore with the aid of a subsea compression system, and the other of developing a system for subsea gas dehydration to avoid the use of Mono Ethylene Glycol (MEG) for hydrate inhibition. The main challenges of using these technologies are presented and discussed.
