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The Rescue of the Chilean Miners, Using Plan B – Who Were the Real Heroes?

November 10th, 2011

In August 2010, Chilean President Sebastian Piñera officially confirmed rumors that the 33 miners trapped in the depths of a San José mine were alive and well — in a refuge chamber almost a half mile underground. The news brought relief and joy to the miners’ families, but it also presented a difficult challenge: figuring out the best way to rescue the miners as soon as possible, which would involve technical and human challenges no one had faced before. Several options were considered, including drilling a rescue shaft with a raise borer, a machine designed to cut mine ventilation shafts.

But Chilean government authorities and the group of professionals in charge of the rescue did not rule out alternate solutions. Soon, two more ideas were suggested. One included widening an existing pilot hole using a water drilling rig; the other called for using oil field drilling technology with an oil-drilling rig. The three options were named Plans A, B and C, respectively.

In the end, Plan B was the first to reach the target.

The professionals, technicians and operators at Geotec Boyles Bros., an experienced drilling company already working at the San José mine, came up with Option B. They determined that their approach had one major advantage: By using one of the existing pilot holes, it was almost guaranteed further boring would connect with the target, unlike the other two methods.

Executives at Geotec contacted two nearby copper miners to ask if their drill rigs could be used for the task of widening the shaft. These companies also funded the project and provided a team of technical personnel led by three geologists.

Geotec also made the critical decision to use large-diameter air hammers instead of tricone bits to sink the hole faster and brought in four specialists from its U.S. affiliate, Layne Christensen.

On August 26, Geotec put Plan B into action, first ensuring the pilot hole was oriented as accurately as possible to reach the area of the underground workshop. In order to avoid flooding the space in which the survivors were living, the team drilled without downhole motors to direct the drill string, as this technology uses large quantities of water. Instead, rigid bars were introduced into the hole to guide the drill.

The miners provided information indicating where the drill had broken through, and the Geotec team began the second stage of the operation. Using the newly completed hole as a guide, they wanted to widen it to 28 inches, the diameter necessary to allow passage of a rescue capsule. They brought in a larger capacity machine typically used to drill deep water wells.

Advancing at a rate of 65 feet per day, the new rig had the advantage of using a previously drilled hole to facilitate the first stage of its job: drilling a 12-inch diameter bore. The team then had to figure out how to widen the shaft, an unprecedented challenge for the drill. It normally had the capacity to lift 130,000 pounds. The engineers from Schramm and Geotec performed an engineering study that showed them how to modify the hydraulic pressure to reach a capacity of 170,000 pounds.

The initial team coordination meeting was held at Geotec on September 5, and the Plan B drill team was ready to begin the following day. Over the next 33 days, Geotec’s operations were far from trouble-free. Four days in, drilling came to a halt when the nose of the hammer bit broke. The final 130 feet meant drilling through particularly hard and abrasive rock, forcing rig operators to fine-tune the drill several times.

On Saturday, October 9, the Plan B drill rig finally reached the underground workshop, creating the avenue of escape that would allow the rescue of the 33 miners to begin.

Who were the real heroes here? The trapped miners, or the engineering professionals who designed and accomplished their rescue?

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