The main aim of impairment is to adapt the book value to the asset’s ability to produce future benefits, i.e. asset valuation is practiced through the fair value.
I am suggesting below some indicators that might trigger Impairment :
a) The period for which the entity has the right to explore in the specific area has expired during the period, or will expire in the near future, and is not expected to be renewed
b) Substantive expenditure on further exploration for and evaluation of mineral/oil resources in the specific area is neither budgeted nor planned
c) Exploration for and evaluation of mineral resources in the specific areas have not led to the discovery of commercially viable quantities of mineral/oil resources and the entity has decided to discontinue such activities in the specific area
d) Sufficient data exists to indicate that, although a development in the specific area is likely to proceed, the carrying amount of the exploration and evaluation asset is unlikely to be recovered in full from successful development or sale.