Do women get paid less than men for doing the exact same job and do they have the exact the same qualifications, experience, competency?

I know for a fact, since I work in the oil industry, that  it's 95% men who are working in the field away from home for long periods of time. Hence they are paid a premium. The very few women in the field are paid the same as men, as far as I know. In fact I wouldn't be surprised if they're paid a little bit more.