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Drilling: Extended problems

Recent research at the University of Stavanger and elsewhere shows that drilling costs have exploded on the NCS in recent years, and that the work is taking much longer. Scientists point to a number of factors, including more use of long wells.

Because existing drilling equipment on many fixed Norwegian installations has been designed and dimensioned for short wells, it is not particularly suited for extended-reach work.

A big commitment is currently being made to long drilling from fixed installations on the NCS. But one well has taken a whole year to complete because of various technical problems.

These include the use of equipment which was insufficiently robust – defined in terms of output – combined with inadequate capacity for storing drill pipe and drilling fluids. But completing the project was cheaper than chartering a mobile rig to drill vertically into the reservoir, installing a template and tying this back to the installation with a flowline.

One reason why extended-reach wells can take so much time is that the drillstring must be pulled out at intervals. This comprises pipes about 10 metres long, which are screwed together.

In a well 10 kilometres long, up to1 000 lengths of drillpipe could accordingly have to be separated and removed/ stacked as the string emerges from the well onto the drill floor.

This number of pipes can present challenges in terms of storage space and the strength of an installation not designed to accommodate them.

When the string is run back into the well to continue drilling, the 1 000 pipes must be screwed together again. The longer the string, the more time such “round trips” take.

The job becomes even more demanding if the string gets stuck in the well. Norwegian regulations require such operations to be automated, keeping people largely away from drill floor risks.

The PSA’s supervisory activities show that storage capacity for drill pipe and equipment containers remains a challenge. Although industry management of such projects appears to be proficient, the development of new, lighter and more robust solutions is slow compared with company ambitions for extended-reach drilling.

A substantial need to upgrade equipment exists.

Some 10-12 projects are currently under way on the NCS to prepare drilling facilities for undertaking long wells.

By Odd Bjerre Finnestad