Piper Jaffray Cos. agreed to buy Houston-based energy investment banker Simmons & Co. International for $139 million to expand into the energy sector. Piper, based in Minneapolis, plans to operate the unit from Simmons’ Houston headquarters and Aberdeen, Scotland. Simmons was founded in 1974 and has executed more than 830 advisory transactions and 330-plus private and public transactions, which together represent a total transaction value of $260 billion. The firm employs more than 170 people. Fred Charlton is to be appointed chairman of energy investment banking and serve as co-head of energy investment banking with James Baker. Bill Herbert would become head of global energy research, while Will Britt would continue to lead specialized energy equity sales. Simmons generated revenue of $96 million in the fiscal year ending June 30.