Property, plant and equipment comprise oil and gas properties, and vehicles and office equipment and others.
(a) Oil and gas properties
For oil and gas properties, the successful efforts method of accounting is adopted. The Group capitalizes the initial acquisition costs of oil and gas properties. Impairment of initial acquisition costs is recognized based on exploratory experience and management judgement and charged to profit and loss as exploration expenses. Upon discovery of commercial reserves, acquisition costs are transferred to proved properties. The costs of drilling and equipping successful exploratory wells, all development expenditures on construction, installation or completion of infrastructure facilities such as platforms, pipelines, processing plants and the drilling of development wells and the building of enhanced recovery facilities, including those renewals and betterments that extend the economic lives of the assets, and the related borrowing costs are capitalized. The costs of unsuccessful exploratory wells and all other exploration costs are expensed as incurred.
The Group carries exploratory well costs as an asset when the well has found a sufficient quantity of reserves to justify its completion as a producing well and where the Group is making sufficient progress assessing the reserves and the economic and operating viability of the project. Exploratory well costs not meeting these criteria are charged to expenses. Exploratory wells that discover potentially economic reserves in areas where major capital expenditure will be required before production would begin and when the major capital expenditure depends upon the successful completion of further exploratory work remain capitalized and are reviewed periodically for impairment.
Producing oil and gas properties are depreciated on a unit-of-production basis over the proved developed reserves. Common facilities that are built specifically to service production directly attributed to designated oil and gas properties are depreciated based on the proved developed reserves of the respective oil and gas properties on a pro-rata basis. Common facilities that are not built specifically to service identified oil and gas properties are depreciated using the straight-line method over their estimated useful lives. Costs associated with significant development projects are not depreciated until commercial production commences and the reserves related to those costs are excluded from the calculation of depreciation.
Capitalized acquisition costs of proved properties are depreciated on a unit-of-production method over the total proved reserves of the relevant oil and gas properties.
(a) Vehicles, office equipment and others
Vehicles, office equipment and others are stated at cost less accumulated depreciation and impairment losses. The straight-line method is adopted to depreciate the cost less any estimated residual value of these assets over their expected useful lives. The useful lives of vehicles, office equipment and other assets are in line with their beneficial periods.
Where parts of an item of property, plant and equipment have different useful lives, the cost of that item is allocated on a recoverable basis among the parts and each part is depreciated separately.
Residual values, useful lives and the depreciation method are reviewed and, adjusted if appropriate, at each reporting date.
Any gains and losses on disposals of property, plant and equipment (calculated as the difference between the net disposal proceeds and the carrying amount of the asset) are recognized in profit or loss.