Shearing the unshearable

July 1, 2011

The 5 million barrels of oil that spilled into the Gulf of Mexico last year from the BP-operated deepwater Macondo well after a bad shear job played heavily on Radoil president Benton Baugh's mind. An inventor at heart, he knew there had to be a way to shear the unshearable. Baugh discusses his latest creation with Jennifer Pallanich.

Like many inventors, Benton Baugh spent much of his childhood figuring out how things work. ‘I always sort of fixed stuff,' he says. While in high school, he invented an automatic transmission. ‘It was great for shifting up, but it wasn't so great at shifting down,' he says.

Baugh's first personal commercial success dates back to devising a drilling choke in 1965. Baugh, a mechanical engineer, started Radoil in 1981 as a consultancy. ‘I mostly make stuff now,' says the holder of 107 patents, fanning out 13 business cards, each bearing his name and the Radoil logo, as well as an image of one of his inventions. Some are targeted to the oil industry, but Baugh has also turned his attentions to issues such as floods, hurricanes, mass transit, and beach cleanup And last year, when Transocean's Deepwater Horizon exploded and the Macondo well was leaking millions of barrels of oil into the deepwater Gulf of Mexico, Baugh is one of the experts who testified before a congressional committee about whether subsea drilling equipment provides an adequate level of safety for deepwater drilling operations.

It got him thinking: all of the shear rams on the market ‘can shear pipe. Some can shear the coupling. But nobody can shear a drill collar,' Baugh says, pausing to add, ‘until now'.

The drill collar – as much as 1000ft of heavy, thick-walled steel tube between the drill pipe and the drill bit that provides the weight on bit – has long been an unshearable component. ‘Drill collars are the strongest things known to man,' Baugh jokes. ‘It's probably 50 times stronger than it needs to be.' Conventional wisdom might call for stronger and larger shear rams. But, he reasoned, applying a new philosophy might make the otherwise impossible possible. The traditional drill collar design relies on a high-strength material with a solid metal-to-metal seal, and a heavy weight cross section to provide the necessary weight on bit for drilling operations.

Baugh wondered if he could redesign the typical drill collar using different materials to provide the key characteristics of strength and weight, which would result in a drill collar that was strong enough for the job and provided the needed weight on bit, but that the average shear ram could cut through easily.

The resulting Shearable Drill Collar – patent pending – features a lead-filled skin that provides the weight and needed strength but no real opposition to the cutting power of shear rams.

‘We made the drill collar not out of a thick cross-section but out of a thin cross-section that is the same thickness as the drill pipe above it,' Baugh says.

The drill collar doesn't really need to be stronger than the drill pipe, he notes, only as strong as the drill pipe above it; it was the need for weight that led to the use of a thicker cross section of steel. Baugh's design uses the steel skin for the strength with a lead filling for the needed weight.

Baugh acknowledges the industry's concern about using lead: in his design, he says, ‘the lead is fully encapsulated, so it is not exposed to the mud'. The lead also is costlier than steel, but less length would be needed to reach the required weight on bit, according to the company.

Robert Taylor, an engineer who started Teacups consultancy, was working at the Radoil facility on a riser centralizer project for a supermajor while Radoil was working out the finer points of the Shearable Drill Collar. ‘I looked at that and thought, "what a good idea",' he says. While some in the industry avoid making equipment from lead, he says, when strategically applied it can make sense. ‘Of course there will be a cost associated with it.' The ‘weaker but denser' concept is a good one, Taylor says. The concept will likely take off once the industry decides that being able to shear drill collars is important, he adds.

John Vozniak, Radoil director of business development, says he's seen a great deal of interest in the prototype; an easily manufacturable design, he says, could see use by the industry. Testing of the drill collars will focus on issues like how much vibration the new design can take, he says, as well as whether the design will ‘torque to the limit or be more or less rigid as drill pipe'.

He expects Radoil to license the patent to an existing drill collar manufacturer because such a company would be able to more quickly supply the equipment. Baugh agrees, saying ‘the presumption is that a major drill collar manufacturer would take these and go to town . . . rather than us being a new drill collar manufacturer. But we're flexible.'

Testing, testing
Radoil fabricated the prototype 6.75inOD drill collar with a 0.5in wall shell and an inner 2.157in, 0.109 wall bore pipe with the lead-filled interstitial space at its Houston facility. The design weighs 141.9lb/ft, compared with traditional solid steel drill collars, which weigh in at 108.3lb/ft.

This year, on 19 April at GE Oil & Gas' drilling and production test facility in Houston, a Hydril ram shear carried out the trial run of cutting through the prototype drill collar.

The Hydril Pressure Control Compact Ram blind shear system with 3000psi bonnet and 22in operator sheared the drill collar during the test. The Hydril unit used 1725psi and allowed the subsequent BOP sealing of the new drill collar. The BOP has a seal pressure test of 10,000psi.

On 6 June, Cameron also sheared the Shearable Drill Collar. This test was carried out with 950psi on a 22in operator and had a successful low and high pressure test afterwards, Baugh says. Cameron used an 183/4in 15k AWKS BOP for the testing. ‘The lead shears like butter, and so the drill collar shears like the drill pipe above it does,' he says. As a result, he adds, everyone who can shear drill pipe can also shear the new drill collar. ‘This is not an obvious solution. It's been a problem for a long time.'

Baugh says the Shearable Drill Collar will make wells safer. Additionally, he notes, the drill collar is reusable unless it is sheared; even then, he says, the lead can be reused. Baugh hopes the supermajors will begin specifying this type of drill collar for future drilling operations. ‘The biggest part of invention is to recognize the need, and identify what the actual constraints are . . . and matching a solution to a need and actual constraints,' Baugh says. OE



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