Halliburton is a leader in the oil services industry as a provider of engineering and construction services for oil extraction and development. After separating from Kellogg, Brown & Root (KBR) in 2007, it is no longer in the business of providing military logistics support.
Chevron is the world's fifth largest global energy company and engages in oil exploration and production; refining, marketing and transport; chemicals manufacturing and sales; and power generation. The company is currently embroiled in major lawsuits for the contamination of Ecuador (Aguinda v. Chevron) and alleged crimes in Nigeria (Bowoto v. Chevron).
With operations in more than 100 countries, Royal Dutch Shell is one of the handful of massive companies that dominate the global petroleum industry. In 2008 it was the largest corporation on earth, based on its nearly half a trillion dollars in revenue. Formerly an unusual Dutch-British hybrid with two boards of directors, the company was reorganized in the wake of a scandal involving inflated reporting of its oil reserves.
