Former Chairman at Shell was told of issues [link not working]

"A memo, circurlated to Sir Phillip Watts and other senior executives in early 2002, warned that the companies method of booking oil and natural gas reserves appeared to be inconsistent with U.S. Securities and Exchange Commission guidelines, these two people said."
"On Jan. 9, the worlds third-largest publicly traded oil company by market value announced it would cut its oil and gas reserves by about 20%, or 3.9 billion barrels of oil equivalent."
" Just taking the oil portion, the reclassified reserves represent $67.5 billion of potential future revenue, assuming moderate oil prices of $25 a barrel.
The reserves serve as a key gauge of an oil companies future value and are watched closely by analysts and investors. U.S. accounting rules provide specific guidance when companies can book "proved" reserves.