Low oil prices are leaving many oil and gas companies with difficult debt loads, causing them to default at an extraordinary rate. On top of that, rating firm Moody's forecasts the default rate will increase. "The energy sector remains the most troubled, accounting for almost a quarter of the 79 defaults so far this year," said Sharon Ou, Moody's Credit Policy Research senior credit officer. The strain on the oil patch comes after years of borrowing heavily at the start of the domestic energy renaissance.