(1) Subject to subsections (5) and (16), where a person carrying on a petroleum trade has incurred any exploration expenditure (not being expenditure which has been or is to be met directly or indirectly by any other person) there shall be made to him for the chargeable period related to the expenditure an allowance equal to the amount of the expenditure.
(2) Where a person carrying on a petroleum trade has incurred any exploration expenditure in respect of which an allowance has been made to him under subsection (1) and he disposes of assets representing any amount of that expenditure, a charge (hereafter in this section referred to as a "balancing charge") equal to the net amount or value of the consideration in money or money's worth received by him on the disposal shall be made on him for the chargeable period related to the disposal or, if the disposal occurs after the date on which the trade is permanently discontinued, for the chargeable period related to the discontinuance