The rating action affects $1.85 billion of outstanding notes.
In addition, Fitch has assigned a BBB ranking to the company's issuer default rating, which reflects DEFS' ability to meet financial commitments on a timely basis.
The outlook is stable.
According to Fitch, the medium quality investment-grade ratings reflect the company's conservative capital structure, significant scale of operations, geographic diversity of assets and highly discretionary capital spending.
Also recognized in the rating is the company's financial exposure to fluctuations in commodity prices.
