You're absolutely correct that oil and gas extraction activities need to be properly decommissioned, and that is expensive. But that's a separate activity from

You're absolutely correct that oil and gas extraction activities need to be properly decommissioned, and that is expensive. But that's a separate activity from shutting down electric power plants. Oil rigs will continue to operate even if all gas and oil power plants were shut down tomorrow, since only about 25% of all oil and gas is used for electricity generation.