Precision engineering - oil drilling for TV, please

Materials World magazine
,
2 Apr 2012

Engineering programmes have never had better TV exposure, but the oil industry is still saddled with images of crude-covered birdlife and burning rigs. Could the sector learn something from its high-flying, high-tech aerospace cousins?

Precision engineering is a phrase frequently used to describe machined parts with exceptional tight tolerances, repeatability and reliability. An excellent example was recently shown on the BBC/Open University collaborative series, ‘How to Build a Jet Engine’, that showed how Rolls-Royce engineers in Derby, UK, designed, built and tested the Trent 1000 jet engines for the Boeing 787 Dreamliner.

The statistics are quite incredible. These huge 2.85 metre diameter turbofan engines have fan blades manufactured from a high-grade titanium inflated with an inert gas to create an extremely high strength-to-weight ratio honeycomb structure. The blades are manufactured to a 125 micron radial and 50 micron lateral tolerance, and rotate at more than 3,000rpm with only a fraction of a millimetre clearance between the tip of the fan blade and the casing. The development test programme was equally extreme and culminated in a controlled explosion to remove a fan blade at maximum rpm to confirm that the casing would remain intact. Once installed on an aircraft, a wide range of in-flight operating parameters are streamed real-time to the Rolls-Royce engine management centre, allowing engineers to identify anomalies and advise corrective actions to suit.

Not surprisingly, this level of design and technology doesn’t come cheap. Each engine takes approximately 20 days to assemble and costs up to £11 million, at list price.

The aerospace industry has always presented itself as high tech and cutting edge, and has no trouble attracting the best and brightest engineers to join. It’s easy to see why the oil industry has sometimes struggled to do the same, being a sector that still uses feet, inches, barrels and pounds per square inch, and where the stock-in-trade library footage shows roughnecks covered in oil throwing tongs around a piece of pipe on a wet, windy rig in the middle of the North Sea. But those men on the rig floor are at the sharp end of what is equally precision engineering, albeit in a slightly different guise. Here’s how.

Typical North Sea wells can reach measured depths of around 6,000 metres and are drilled with 126-millimetre OD drillpipe. That’s a length to diameter ratio of nearly 48,000 to one. Given geological uncertainty and increasingly smaller oil accumulations, the drillers are expected to hit a target within a 30 metre tolerance. It’s like taking a piece of wire the diameter of a coat hanger, pushing it through the ground and hitting a dart board nearly 100 metres below – as one of my colleagues described it, ‘Like threading spaghetti through a key hole’. Precision engineering is what I call it. Meanwhile, data is streamed real-time from an array of sensors close to the drill bit, and onward to regional operating centres where drilling engineers and data analysts identify potential problems and advise corrective actions.

Not surprisingly, these wells sport a hefty price tag. Even a relatively straightforward appraisal well will take at least 20 days to drill and cost up to £11 million, depending on the rig-rate. Aerospace and drilling engineering have more in common than you might think.

Perhaps the next BBC series could include a ‘How to... Drill an Oil Well’ and update the library footage to reflect how far directional drilling has come.