National oil companies rarely lack reserves in the ground. It is capital that can be harder to come by. So emerging markets’ slide from honored guest to social pariah in many a portfolio presents a problem, and not just for these national champions. Oil-services companies could suffer, too. Petróleo Brasileiro, known as Petrobras, exemplifies all this. Three years ago, it sported a market value of $213 billion. Today, that is a mere $78 billion. The Brazilian national champion’s fall from grace is stunning, but it isn’t alone. In 2007, when both oil and emerging markets ran hot, the PFC Energy 50, a ranking of companies by market value, had four national oil companies in its top 10: PetroChina , Gazprom , Sinopec and Petrobras. Their combined value of $1.55 trillion was actually higher than the total for the five Western integrated oil majors in the top 10 that year. […]