Banks have sold off recently on a variety of perceived woes, some real, some not so real.  One of them is their exposure to energy loans.  This article shows the exposure the major banks have.  CiitiGroup has 3.48% of their loan portfolio, JPM 5.56%,BAC 2.48%,and WF C 1.91%.  All in all this looks manageable to me.

Banks are clashing with regulators over loan reviews that could crimp the flow of new credit to the oil patch.

Source: Energy Lending Caught in a Squeeze