I would think a petroleum engineer would be a valuable asset to any of the large number companies, big and small, working in Marcellus shale. It does seem a bit premature to assume that your chosen field is a failure, though. Domestically, oil and natural gas are competing resources. As oil has steadily crept down over the last 5-7 years, natural gas has picked up. But the industry itself is rather volatile, because energy is a global and politically charged market.
In any case, I wouldn't give up so soon on your career choice. If being employed right now isn't an urgency for you, I would take the down time to combine your degree with an MBA (as you suggested) or something that makes you all that much more marketable in the likely event of a rebound in energy.
In any case, I wouldn't give up so soon on your career choice. If being employed right now isn't an urgency for you, I would take the down time to combine your degree with an MBA (as you suggested) or something that makes you all that much more marketable in the likely event of a rebound in energy.