The disclosure of an O&G company’s reserves should provide a better reflection of the underlying value of the company than its balance sheet. The balance sheet records the historical costs associated with drilling for, development of or acquisition of oil, and not the value of the oil and gas interests. The reserves disclosure, while not perfect, helps investors to fill this information gap. Thus by monitoring movements in the reserves report in terms of both volume and value, the investor should have a clearer understanding of both the current value and the historical performance of the management in adding value (see also reserves report). Some reserves are booked at project sanction – normally a low case number – then more reserves are usually booked during field life as more production data becomes available – these are known as reserves addition or reserves growth. Booking is done in accordance with the US SEC guidelines as well as the national guidelines in some countries. Most important, for booking to take place, the reserves must be economically recoverable using current technology and economic assumptions within a sanctioned project which has all the regulatory approvals in place