"The U.S. Securities and Exchange Commission requires drillers to calculate the value of their oil reserves every year using average prices from the first trading days in each of the previous 12 months."
Because oil didn’t start its freefall to about $45 till after the OPEC meeting in late November, companies in their latest regulatory filings used $95 a barrel to figure out how much oil they could profitably produce and what it’s worth.
Of the 12 days that went into the fourth-quarter average, crude was above $90 a barrel on 10 of them.
So Continental Resources Inc., led by billionaire Harold Hamm, reported last month that the present value of its oil and gas operations increased 13 percent last year to $22.8 billion.
For Devon Energy Corp., a pioneer of hydraulic fracturing, it jumped 31 percent to $27.9 billion.
Read more: Companies use the first-trading-day-of-every-month calculation to estimate future cash flow and to tally how much crude can be profitably pumped out of the ground.