Have you ever seen an oil rig walk ? Some of the newest rigs can travel hundreds of yards to the next well under their own power, lurching along like 150-foot-tall robots on pneumatic legs that raise the equipment five inches at a time, nudging forward at about a foot per minute. While that sounds slow, it is faster and cheaper than dismantling a rig and trucking the parts to a new site nearby. More efficient drilling rigs that cost a third less than just a year earlier are changing the face of the U.S. shale industry, helping boost per-rig output in the four largest fields by at least 40 percent since the crude price plunge began in 2014. While helping producers pump more oil, the new rigs have a downside. Companies such as Helmerich & Payne Inc., Nabors Industries Ltd. and Patterson-UTI Energy Inc. that provide the equipment […]