Value of SNE, page-67

Ya,

it would be fair to say that sunk costs are not a reliable method to calculate "fair value" of an oil and gas asset.

closer would be:

PV10 of forecast production at current fwd curve * by whatever risks factors one wishes to use (geological / political etc)

so, in very simple terms:

at discovery - asset is worth "barrels in the ground" (say 3-5)
after appraisal (5-7)
at FID - 7-9
after capital spent (15-25+)

all of these are oil price dependant, as it deterims the net cash flow (as do the terms of the PSC in this case).

rgds
V_H