The Recruiter is the best method to get in the door, since they have close relationships already established. the recruiting firm will interview you first to determine if your experience matches the job profile, which is normal. Managers ask questions about what you know what to do, and how did you solved difficult situations before... and if they like your answers you are in... Not too intrusive. You should be respectful and do your homework about Oil and Gas before going to the interview to guarantee success.