The following commentary comes from an independent investor or market observer as part of TheStreet's guest contributor program, which is separate from the company's news coverage.NEW YORK ( Trefis) -- Exxon Mobil ( XOM) and other vertically integrated oil majors, such as Chevron ( CVX), ConocoPhillips ( COP) and BP ( BP), may see their revenues decline in the next few quarters. Concerns over the slowing pace of the global recovery and production from Libya easing supply have led to oil falling to $76 this week. The bearish sentiments were strengthened by news of rising U.S. crude inventories and falling GDP growth estimates from analysts. Revenues from the sale of oil and natural gas liquids are an important source of income for oil majors. We have a $93 price estimate for Exxon Mobil, which implies a 30% premium to its current market price.