I think I was wrongfully terminated

I have a felony record. On July 18, 2005, I was hired by Ceja Corporation out of Tulsa, Oklahoma, for a position on their Ponca City seismic crew. I was hired by the Ponca City supervisor. During the hiring process, which included an interview, no mention was made of my criminal history. No inquiries, no questions. Naturally, I didn't volunteer any information, but would have had any kind of question regarding background been asked. As the position was a little rough and tumble, the employees a little rough themselves, I thought that no inquiries had been instituted because personal history was not germaine to employment with the seismic team. On September 26, 2006, I was notified by the Ponca City crew supervisor that I was being terminated because of my felony background. My question is this: If my background was not an issue during the hiring process, nor an issue during the ensuing 14 months of service, how can it be an issue warranting termination? Does merit exist to file a suit for wrongful termination?