New drilling techniques have helped operators access more than 2.2 billion bbl of oil equivalent, previously thought inaccessible, in Northwest Europe's fields during 1990-95.
Horizontal and extended reach drilling in particular have enabled development of many marginal North Sea fields with combined reserves of 2.5 billion bbl of oil equivalent in the same period.
Those are the findings of Smith Rea Energy Analysts Ltd., Canterbury, U.K. Smith Rea gauges the economic effect of new drilling technologies by attributing to them capital and savings of more than 1 billion ($1.5 billion).
The analyst identified a number of key projects that could influence future drilling technology.
Rig conversion
Norway's Saga Petroleum AS is leading a joint industry project known as EfEx, intended to cut exploration costs by converting a second generation semisubmersible rig to drill slimline wells in deep water.
Smith Rea said converting a rig would cost about 150 million kroner ($22 million). But hiring a second generation rig would cost about $40,000-75,000/day, compared with $80,000-115,000/day for a fourth generation rig normally used for deepwater drilling.
Another idea, which Smith Rea said may soon be overtaken by events, is the multiple bit magazine proposed by Denmark's Ingenjorsfirman Daniteknik AS. This is envisaged to cut drilling costs by 25%.
The magazine would carry four or five bits, and each time a bit wears out it would be swiveled sideways to cut a short sidetrack, where it would be dumped. A new bit would then take over drilling.
Coiled tubing has potential to be improved by metallurgical developments, said Smith Rea, with titanium alloys and resin/fiber composites being developed to extend life.
Coiled tubing, with its ability to carry hydraulic, electrical, and optical fiber links to the downhole assembly, could enable microprocessor control of bit direction. This is exemplified by the Royal Dutch/ Shell "Neurobot" system, which is undergoing feasibility study.
"This would be a fully automated system that can steer on an optimized course and at the same time keep the driller informed of the parameters it is using," Smith Rea said.
Oil price link
Jim Jenner, drilling consultant based in Weybridge, U.K., reckons the momentum behind innovations in drilling will continue so long as the margin between oil price and production costs remains relatively low.
"Any increase in the oil price will reduce the economic pressure for innovation," Jenner said. "The day rate for rigs is currently too low to encourage contractors to invest in new building or extensive reequipping to handle dramatically new technology.
"The most successful developments are most likely to be extensions of existing technology: improved measurement and logging while drilling tools, downhole steering/continuous information systems, longer lasting and improved performance bits, mud motors, and drill string components, and low cost, high performance, environmentally acceptable drilling fluids. All these can be handled by existing rigs, as can slimline or reduced hole/casing size drilling programs."
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