BETTER drilling methods are making the single biggest contribution to improving recovery from Norway’s offshore fields, according to StatoilHydro.
Riserless intervention in 2009 alone is expected to deliver more than £1.4billion of additional revenues from previously under-performing subsea wells.
The group says its “substantial” commitment to research and technology development in order to improve its drilling and well operations is paying off.
There is an imperative as StatoilHydro operates some 500 subsea wells on the NCS, which account for more than 40% of its oil&gas production. Downhole intervention and drilling sidetracks from existing wells are seen as the most effective ways of recovering more oil&gas, especially from subsea fields.
Head of subsea technology Oystein Haland says adopting new solutions in these areas also yields substantial reductions in operating costs.
As in other mature provinces such as the US Gulf of Mexico and the UK North Sea, more and more discoveries on the Norwegian Continental Shelf are being developed with subsea installations. At the same time, production is declining from mature fields.
Wells need workovers to maintain their output by removing deposits and halting water intrusion. But until the advent of the deepsea intervention vessel barely a handful of years ago, subsea well intervention designed to boost output was pretty much a no-go area.
StatoilHydro played a key role in encouraging development of competent tonnage and systems – notably with the Norwegian company, Island Offshore – and has now adopted light well intervention (LWI) vessels on a large scale, with two such ships in operation all year round on the NCS.
The company calculates that, compared with the use of traditional drilling rigs, these units cut the cost of well intervention work for the group by 50-70%. They are also more nimble and therefore faster to redeploy to new jobs.
During light well intervention activities, downhole equipment is remotely operated via a wireline from the surface and – unlike rigs – without a riser.
So far, StatoilHydro has conducted more than 90 such interventions, with all deemed successful, and has been pursuing riserless wirelining on subsea wells since 2003. Earlier this autumn, the company also reported a successful first use of through tubing rotary drilling (TTRD) for a sidetrack drilled directly out from the production tubing in an existing well.
Now StatoilHydro is out to the market seeking a rig purpose-built for such operations, and hopes to have this new unit in place by 2012-13. That way, Haland expects that this technology will allow the company to cut costs for such well interventions by 40%.