Just for the sake of clarity, Halliburton and Schlumberger aren't "oil" companies. They're service companies.
Petrobras has a shore base in Fourchon.To be a cartel it would require that there is a cornered market done by a small group of companies, couldn't be further from the truth. In fact, we just had an Irish company start it's first division in the U.S. here in Louisiana. If it were a true cartel there wouldn't be outsiders coming in and contracting.