Banks have begun to tighten requirements on revolving lines of credit, an essential lifeline for smaller companies, as these institutions revise estimates on the value of some shale reserves held as collateral for loans to producers, according to people familiar with the matter. Some large financial institutions, including Capital One Financial Corp. and JPMorgan Chase JPM -0.08% & Co., are likely to decrease the size of current and future loans to shale companies linked to reserves as a result of their semiannual reviews of the loans, the people say. The banks are concerned that if some companies go bankrupt, their assets won’t cover the loans, the people say. JPMorgan Chase declined to comment. Capital One COF -0.01% didn’t respond to requests for comment. The tightening financial pressure on shale producers is one of the reasons many are facing a reckoning going into next year. Chevron Corp. said Dec. 10 […]