Well blowout rates in oil fields undergoing thermally enhanced recovery (via steam injection) in California Oil and Gas District 4 from 1991 to 2005 were on the order of 1 per 1,000 well construction operations, 1 per 10,000 active wells per year, and 1 per 100,000 shutin/idle and plugged/abandoned wells per year. This allows some initial inferences about leakage of CO2 via wells, which is cons...