U.S. shale drillers, widely seen as having taken over from OPEC as the swing suppliers to the world, quickly adjusting production as prices ebb and flow, may have just put a $70 a barrel lid on oil. Just months after slashing spending and cutting back on rigs in response to a 60 percent price rout, major domestic producers including bellwether EOG Resources Inc and top Bakken producer Whiting Petroleum Corp are already starting to talk about the price at which they would ramp up production. Others, such as Devon Energy Corp and Noble Energy Inc., are pumping more oil than expected this year after the industry’s deepening drive for more efficient and productive wells yielded better-than-expected results. For some analysts, these are signs of a new price ceiling forming in oil markets and serve warning to traders that a new wave of shale supplies could be quickly […]