For perspective on shale’s impact, rewind to 2007, when some industry leaders saw world demand hitting a wall once it rose to 100 million barrels a day—a level they thought supplies would have trouble matching. “Where is all that going to come from?” said James Mulva, the former chief executive of ConocoPhillips, that year, when the world produced and consumed about 85 million barrels a day. In August, global oil demand reached 100 million barrels a day , and the world hardly noticed. What happened? Shale. Using techniques such as hydraulic fracturing and horizontal drilling, U.S. oil drillers figured out how to get crude oil from ultradense shale rocks in North Dakota, Texas and Oklahoma. U.S. oil output rose from 5 million barrels a day in 2007, when Mr. Mulva raised his concerns, to a record of nearly 11 million a day in August, a remarkable increase that has […]