Shortly after bagging big profits on a Pennsylvania drilling deal, George Roberts traveled to Houston to meet with the banker who had brought the prospect to his private-equity firm, KKR & Co. Mr. Roberts, KKR’s co-founder, asked about other opportunities in shale drilling. Ralph Eads unfurled maps on a conference-room table and pointed out the country’s emerging drilling fields. “We want to be your first call,” Mr. Roberts told the Jefferies Group LLC banker. KKR went on to complete a couple of relatively small but hugely profitable shale deals before Jefferies in 2011 pitched the big one: Samson Investment Co., one of the largest closely held energy producers in the U.S. KKR bit, in the biggest-ever buyout of an oil-and-gas company. Now, the investment is deep in the red, as falling oil prices amplify struggles Samson has […]