There does exist a company in Doha with the name Doha Petroleum Construction Co. Ltd. (DOPET) and here is the link:
http://www.dopet.com/dopet/index.php/contactus
But it makes me wonder why they are asking you to pay them advance money for a visa. That sounds a bit fishy. Suggest you contact them through email and find out more about this matter. I would not give a single riyal.