OPEC ponders how to co-exist with U.S. shale oil

First, they ignored each other. Then, they went into a bruising fight. Finally, they are talking, albeit with opposing agendas.

The history of the relationship between OPEC and the U.S. shale oil industry has evolved a great deal since the cartel discovered it had a surprise rival emerging in a core market for its oil around five years ago.

U.S. shale bankers came to Vienna this week and OPEC is readying a trip for its top officials to Texas in a bid to understand whether the two industries can co-exist or are poised to embark on another major fight in the near future.