Ultra Petroleum (UPL)is one such firm. Oh man, what a debt load they have.
http://fuelfix.com/blog/2015/03/17/quicksilver-resources-seeks-bankruptcy/
Quicksilver CEO Glenn Darden said the firm didn’t have any viable alternatives to bankruptcy – including asset sales after a period of marketing – that would fix its liquidity and capital structure issues.
The firm’s voluntary petition indicated it has $1.2 billion in assets and $2.4 billion in liabilities. It had skipped an interest payment in February.