In late September, during the peak of fall borrowing base redetermination , many oil and gas companies got their first glimpse of just how bad their liquidity would get when as a result of collapsing commodity prices, the value of their collateral crashed when PV-10s plunged by up to 80% Y/Y as of December 2015...
... and resulted in plunging access to secured liquidity as borrowings bases were eviscerated as much as 38% (for those unfamiliar with the basics of the semiannual redetermination process, the WSJ has a handy and brief 101).