Last time I checked it was 'Exxon Mobil' (no final letter 'e') so it looks, on the face of it, as though you just found another variation on the '419' scam, some deal that you pay up front for but get nothing for in return.
I never heard of a reputable employer for Nigeria who would ask for money from prospective employees for visa fees or whatever. In fact, one would often see people hired at great trouble and expense who only lasted one or two tours.
If it's a straight deal there is no way they would want any money from you first.