This is a very important question to consider. The reason schools are asking you this is because they want you to think through the MBA investment. MBA can help open some doors, but it isn’t a magic ticket to senior management.
I didn’t recruit for oil and gas; however, I did get exposure to the oil & gas companies that recruited at Fuqua. The roles they are recruiting for are general finance related (controller, treasury, financial analyst) and management rotations. While there are energy consulting roles out there (Schlumberger), they look for O&G background. My perception is that the daily tasks are similar to what you would do as an engineer moving up in the company, in which case, an MBA is superfluous.
One suggestion that I have, is to talk with people in your company who has an MBA to get some clarity on opportunities available for MBAs in the industry. See what they feel the benefit of having an MBA is. Then ask yourself whether you think an MBA is necessary to get to where you want to be.