Smaller field size, together with difficult recovery characteristics such as geological complexity, low or very high permeability, poor oil mobility or remote location, may all result in marginal economic attractiveness.

In the mature parts of the North Sea, the development of small, satellite fields can lead to further utilisation of the existing offshore processing and transportation infrastructure. Tie-back of sub-sea wells to existing platforms over distances of up to 10 km has been achieved. However, approximately 30 small discoveries on the UK Continental Shelf (each with less than 50 million barrels of oil) located within 30 km of existing platforms await development.

In addition to any uncertainties surrounding reservoir volume and recovery factors, issues such as multiphase fluid handling during transportation, costs of pipeline deployment and maintenance, and the cost of power for pumping are all issues which impact upon the attractiveness of small field developments adopting a tie-back strategy as distances increase (see also Section 4.5 on deepwater/remote development issues).

Advances in the engineering of drilling and production systems are providing improved technology options for both mature and frontier situations. Extended reach drilling may provide an alternative to sub-sea satellite wells. In addition to the tie-back option, the use of sub-sea wells with semi-submersible rigs and export via pipeline, and sub-sea well to floating production, storage and offshore loading (FPSO) facilities are now viable for hydrocarbon accumulations more distant from platform infrastructure. Extended well testing and flexible, staged development strategies also contribute to reducing risk and improving project economics.

Economic cut-off will be reduced further if re-useable production systems for short term service on small fields can be developed, especially if used in parallel with non-interventionist/remote sensing techniques for reservoir and fluid imaging. It is possible that future production from small oil pools may be achieved over short time frames from a single well development.

RTD topics relevant to marginal field developments are listed in Sections 5.2, 5.3 and 5.4.