A major US driller delivered a message to OPEC last week in Vienna, urging the oil ministers to increase production to prevent a price spike that would damage both groups and trigger yet another boom-and-bust cycle.  Scott Sheffield, chairman of Pioneer Natural Resources, said the conditions are set for prices to cross $100/b, and that would be terrible for OPEC and West Texas alike.  Sheffield spoke with Capitol Crude after addressing the OPEC International Seminar.  Decisions made in Washington and West Texas were a huge topic at the conference, especially sanctions against Iran and Venezuela, and US-China trade tensions.  Analyst Joe McMonigle and author Daniel Yergin also joined Capitol Crude on the sidelines of the Vienna event to put those issues into context.