"A 2008 Chevron blowout appears in hindsight to have been a rehearsal for Deepwater Horizon and its design problems. Like BP, Chevron was in the final stages of drilling a well aboard Transocean rig Discoverer Deep Seas. Because of the blowout, drillers lost 500,000 gallons of drilling mud into the earth below the wellhead, and spilled 293 gallons onto the ocean floor."
Full article: "Deadly Gulf blowouts persist"
-Houston Chronicle, July 20, 2010