Despite the ongoing concerns about the state of the global economy, OPEC continues to hold an upbeat view on world oil demand, OPEC Secretary General Haitham Al Ghais said on Tuesday. “The economy, despite the challenges, is still doing quite well,” Al Ghais told the Argus European Crude Conference in London, as carried by Bloomberg. “We are positive on demand, we’re still quite robust on demand.” Al Ghais was the keynote speaker at the conference and expressed optimism about global oil demand less than three weeks…