Bryan Sheffield, a third-generation oil wildcatter in Texas ’s Permian Basin, knows what he’ll do if crude drops to $80 a barrel: shut down half his drilling rigs and go on a takeover hunt for weaker rivals. Sheffield is among producers who’ve together invested $150 billion in the Permian since 2010 seeking their piece of an oil trove estimated to be worth as much as $5 trillion. As the money pours in, risks are mounting of a bust as analysts including Marshall Adkins of Raymond James & Associates Inc. forecast crude is heading down to $70 a barrel next year, a price that would slow drilling in the most expensive U.S. shale formation. While traditional wells have been drilled in the Permian since the 1920s, shale producers have become giddy over the potential of the region’s vast overlapping layers of oil-soaked shale rock. Pioneer Natural Resources Co. (PXD) estimated […]