In our analysis of how that sector could become carbon neutral by 2020, we considered a number of scenarios that combined purchasing offsets—in other words, financing emission reductions elsewhere to offset the industry's emissions—with deployment of carbon capture and storage at various different levels. I don't have the exact range of results in front of me, but to achieve that target, the middle range of the numbers was in the low single figures of dollars per barrel of oil.
On February 20th, 2007. See this statement in context.