Pipeline and processing companies, known as the midstream sector in the flow of oil and gas from well to consumption, were late to feel the effects of the 50% drop in oil prices because they typically operate under fee-based, long-term contracts. Recently, however, they've been looking for new sources of revenue as oil and gas become less profitable and producers pump and transport less of it. "Investors are concerned about the growth opportunities going forward," said Riccardo Bertocco, a partner with Bain & Company in Dallas who focuses on the midstream. "Companies that have the opportunity and the financial strength to grow by acquisition will do so."