Drilling advances

	Vol. 231 No. 12
JIM REDDEN, CONTRIBUTING EDITOR

Don’t count out aluminum drill pipe just yet

Many of you may remember when aluminum drill pipe was touted as the Holy Grail, capable of overcoming with a single joint the myriad technical obstacles the industry faced as it first ventured into deeper waters and then into drilling of longer extended reach wells.

Unfortunately, the shouts quickly turned to whispers once the accountants got involved. When it came to their attention that aluminum drill pipe carried a 50% to 150% higher price tag, they got a severe jolt of sticker shock. That was all it took for the powers-that-be to decree that good old steel would continue to work just fine, thank you.

Today, however, it appears aluminum drill pipe is emerging as the drilling industry’s answer to Mark Twain—in that reports of its death may have been grossly exaggerated. Over the past few years, the use of drill pipe and other oilfield tubulars fabricated with aluminum alloy has been in the throes of a renaissance of sorts. It’s been a quiet revival, no doubt, but its proponents tell anyone who will listen that aluminum drill pipe remains the ultimate solution for the complexities of today’s highly demanding drilling environments. Proponents concede that even with improved manufacturing and design processes, aluminum drill pipe remains much more expensive than conventional steel. At the same time, they argue that the price tends to decline appreciably when you factor in the reduced nonproductive time and the fact that operators can construct deeper and more complex well geometries.

One advocate who never lost the faith is Russia’s Aquatic Co. At the 1997 SPE/IADC Drilling Conference in Amsterdam, Aquatic Co. and Fugro Engineers B.V. co-authored a paper extolling the benefits of large-diameter aluminum drill pipe in deep water. They focused on its success in extending the weight limitations that geotechnical and other scientific research vessels dealt with when working in deeper waters.

Aquatic Co., which Weatherford International acquired in December 2007 and reorganized into a new Global Department for Aluminum Alloy Tubulars, remains a fan today. The company made its mark in designing, manufacturing and applying aluminum drill pipe for oilfield and ultra-deep scientific drilling projects. Today, the company designs and manufacturers a range of lightweight aluminum alloy drill pipe, as well as non-magnetic BHA components, casing, tubing and drilling risers.

Aquatic went full bore, so to speak, in aluminum drill pipe when Russian operators began drilling deeper and longer wells. Owing to the weight restrictions of the older rigs in the area, with conventional steel drill pipe, they were limited to a maximum of about 8,200 ft (2,500 m). By using aluminum drill pipe, the company says, an operator in Megion City, Western Siberia, was able to use the same 125-ton-capacity rig and drill a wellbore to 13,780 ft (4,200 m). Using a steel drillstring to penetrate a similar depth would have required a 250-ton rig, Aquatic Co. contends.

Despite the clear weight advantage, a scan of the technical literature shows few, if any, major technical presentations on the subject since the 1997 paper, until earlier this year—and, once more, the IADC/SPE Drilling Conference was the venue. During the February confab in New Orleans, Fugro Engineers once again promoted the operational benefits of aluminum drill pipe, this time teaming up with Alcoa Oil & Gas. The two companies presented the paper “Field tests show aluminum drill pipe can extend operating envelope for extended-reach drilling,” which, they contend, is an obvious advantage in sensitive ecosystems. Being able to drill ultra-long horizontal reaches with the rig located farther away, they say, will allow more wells to be constructed in environmentally fragile locations with a minimal footprint.

Both Alcoa and Fugro readily acknowledge that drill pipe fabricated with aluminum alloy has its share of drawbacks, not the least of which is the accountant-shocking price tag. Aluminum drill pipe, they concede, tends to have higher buckling tendencies than steel, as well as lower yield and tensile strengths and higher susceptibility to corrosion when exposed to pH values in excess of 11 for any prolonged period.

At the same time, they argue that the benefits have plainly offset the disadvantages in various field experiences. For one thing, as illustrated in Western Siberia, Alcoa and Fugro said the reduced equivalent derrick loads provide an opportunity to reach longer targets from a single location without expensive rig upgrades. In the field trials, they also observed a reduction in drillstring torque and drag. A key advantage seen was the ability to cut down on drillstring weight while increasing the strength-to-weight ratio.

Alcoa said it has high hopes for aluminum oilfield tubulars. In mid-October, the company backed up that optimism by retaining K&B Machine Works to install a state-of-the-art manufacturing center in Houston specifically to assemble aluminum drill pipe. The facility will include a next-generation machining cell for threading aluminum alloy tube, a dedicated steel tool joint threading unit and a semi-automated assembly unit for steel tool joint installation.

Alcoa spokesperson Jay Grissom said the company is in the commercialization mode of what he called “an interesting market.” He said Alcoa is setting up its production facility, perfecting assembly techniques and conducting tests to evaluate performance under various conditions, such as with different fluids.

“We are really focusing on the ultra-extended reach wells, and we’re also in the process of introducing a new product for shale gas drilling,” Grissom said. “We’ve completed the design and testing of what we call a spud well pipe. Basically, it’s a steel tool joint with a 4½-in. aluminum tool body. It will allow shale drillers to go much deeper without having to retrofit the rigs. What we really didn’t expect, however, was all the interest we received from the geotechnical survey sector.”

With capability to decrease torque and drag while reducing the hook load up to 35%, these diverse applications may just be the tip of the iceberg for aluminum drill pipe.