Booking, unbooking and rebooking oil sands reserves
ExxonMobil reduced its 2016 proved oil reserves to 20 million barrels of oil equivalent, down 3.3 billion barrels from 2015.
Under US Securities and Exchange Commission (SEC) rules, proved reserves can only include oil and gas fields that can be produced economically within the next 50 years.
As part of the write-down, Kearl's entire 3.5 billion barrels of reserves was deemed unprofitable at 2016 prices and debooked from the balance sheet. In addition to the Kearl volumes, another 800 million barrels of oil equivalent across North America were also debooked due to low oil prices.
However, Exxon noted that 2017 prices are already substantially higher than last year, and those volumes will likely be rebooked in the future. Exxon also says reserve revisions do not affect the company's operations or outlook.
In a similar vein, ConocoPhillips also cut its proved oil sands reserves in half, from 2.4 billion to 1.2 billion barrels. In all, the company unbooked 1.7 billion barrels of oil equivalent. The company owns a stake in the Surmont, Christina Lake, Foster Creek and Narrows Lake leases south of Fort McMurray. If current oil prices hold, the company also says it will likely rebook part of those barrels.