It doesn't have to be. The technology of injection is well known. For decades, oil companies have boosted production by raising the pressure in depleted fields with CO2 injections.
Only a small percentage of the CO2 created in burning fuel is needed to re-pressurize wells. It would require a terrific waste of energy and money for infrastructure to compress all the CO2 created at power plants and pipe it back to the oil wells or into the sea.
This is nothing but appeasement of the global warming crowd and it will not work. As we see here, they will find plenty of bogus objections to this bypass of their cash cow (carbon trading credits).