The ratings on Irving, Texas-based ExxonMobil Corp. reflect the company's "excellent" business risk, based on outstanding competitive positions in all facets of the oil and gas industry, and its "minimal" financial risk. ExxonMobil operates in three primary business segments: upstream, downstream, and chemicals. Upstream (its exploration and production unit) by far contributes the most to profitability and cash flow. In 2011, the exploration and production (E&P) segment accounted for over 80% of the company's consolidated net income. At year-end 2011, ExxonMobil's proved reserves totaled 25 billion barrels of oil equivalent (bboe)--the largest among the supermajors (the six largest nonstate-owned oil companies in the world). A long reserve life (about 15 years) and a large resource base (estimated at more than
