Optimal reservoir recovery demands numerous ideally positioned wells in hydrocarbon-bearing layers.
Injection of water and gas also requires the drilling of dedicated wells.
In addition, there are specialised wells for production and/or for injecting water from shallow formations, and depositing drill cuttings and
CO2 (Sleipner).
The common denominator is the drilling of wells, as a rule, directly from the sea bottom.
Old fields, where all surface drilling possibilities are exhausted, require the construction of new branches stemming from the old wells. In some cases, production is maintained from the old well path, from which a multi-branch well is created.
Individual reservoirs are best exploited when wells are drilled into them in a fishbone pattern. This allows the oil to flow into a common conduit up to the platform.
In some cases, the reserves are a good distance away from the platform, which makes long-reach wells the feasible solution. We have used such wells for many years and presently hold the world's record for the longest reach from a floating platform (Visund).
Statfjord, Gullfaks and Sleipner have also drilled such wells, which have competitively beat out alternative subsea wells.
Optimal directional drilling and well placement are now possible with drilling tools that steer the drill bit in all directions, while the drill string continually rotates.
More and more advanced measuring is done from directly behind the drill bit during drilling, providing necessary data that permits the best possible well placement, in addition to a secure and safe drilling operation.
StatoilHydro is working hard to get the most effective use out of this information by sending downhole data via "broadband" to decision makers on the platforms and rigs, as well as on on land.
