IHS Inc., Englewood, Colo., (NYSE: IHS) has acquired Norwalk, Conn.-based John S. Herold Inc. for approximately $48 million in cash. John S. Herold is a research firm that provides analyses and key financial and operational data on more than 400 global oil and gas companies. Its services include providing online transaction databases and deal analyses essential to understanding and executing energy mergers and acquisitions and capital markets transactions.