A connection made between a remote well and a main asset (Platform, FPSO).
Due to improving technology, the majority of non process plant i.e. well heads, Christmas trees and manifolds can be manufactured to operate subsea.
This allows multiple small fields with small recoverable reserves to be brought On Stream, Tying them back to a main asset for production.
This saves many billions in field start up costs due to ability to negate platform construction, and makes reserves viable that were previously deemed uneconomical.
A Tieback typically includes import lines as well as export line, running from the main platform to the subsea well, to enable operations like injection.
Traditionally exploration & production companies only concentrated on exploring and developing fields with huge reserves that would last many decades.
This was due to the existence of such large untapped reserves, the cost of building a platform or FPSO to sit above the wells to process the production, and the lack of technology needed to produce remotely.
Today, with the average size of a new reservoir find being less than a tenth of that of the 60s and 70s.