The original objective wasn't to "store CO2 underground", but to enhance oil recovery in existing fields.
Perhaps there needs to be another line in their accounting, that being the amount of CO2 that would be produced in re-drilling and refraccing those fields, instead of merely injecting CO2 to enhance recovery, which could be subtracted from the CO2 produced by burning the oil (assuming it is even burned, when some goes for chemical industry feedstocks).
Counting the CO2 produced by the oil recovered when it is used (because of the enhanced recovery of oil) against the amount of CO2 required to be sequestered to recover that oil is just bullshit.
The objective has been restated to placate the CO2 phobics, but the objective was to more efficiently recover oil from existing oil fields.
If that oil was never burned, more CO2 would go in the ground than the oil produced would emit.