As much as 400,000 barrels a day of oil production is at risk as U.S. shale companies like Samson Resources Co. run out of money and are forced to slow drilling. Total debt for half of the companies in a Bloomberg index of more than 60 producers has risen to a level that represents 40 percent of their enterprise value. It’s a sign of distress that shows equity values falling in the face of oil’s crash, said Rob Thummel, a managing director and portfolio manager at Tortoise Capital Advisors LLC who helps manage $15.6 billion. The companies facing high debt loads, which include Encana Corp. and Chesapeake Energy Corp., produced 1.1 million barrels of oil a day in the second quarter of this year, according to data compiled by Bloomberg. If more companies file for bankruptcy as Samson did Wednesday, or embrace the kinds of draconian […]