KKR is a big believer, an investor, in the shale boom.

The private equity firm has pumped billions of dollars into shale-related deals, from a 2009 investment in Pennsylvania gas producer East Resources that brought a $1.5bn return a year later, to last year's KKR-led $7.2bn buyout of oil producer Samson to a tie-up this year with shale pioneer Chesapeake Energy to acquire drilling rights across the US.