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The leakage over time becomes less likely they said because the gas dissolves other particles, and becomes heavy enough. However, the time scale for that happening was many years, from what I recall.

Also, the reason they are looking at this at all there, was due to pumping out more oil, not to store away the CO(2).

There’s considerable energy use to the process, making power from coal more expensive. To equal an old-style coal plant, you’d have to build a larger plant than normal, and burn even more coal. The number of places which are stable geologically enough to try this tech are limited. This also determines where power plants can be built, which is not necessarily where the power is needed, forcing expensive grid expansions. CO2 piopelines have been suggested, but this also adds to the cost. There are also problems with the pressurized CO2 causing geological changes toi the container rock itself, which can make an apparently safe storage site unsafe over time. Even with a secure site, it is not clear how longer the CO2 will stay done. If it leaks, what’s the point?

Harper is pushing big subsidy bucks into this, but it’ll likely be a rarely-used white elephant. In the meantime, he’ll keep proclaiming that this technology will justify burning coal and drilling oil wells.