The USGS revised its oil and gas resource assessment for the Bakken and Three Forks formations for the first time since 2008.

Over 4,000 wells have been drilled and more than 450 million bbls of oil have been produced since the last update.

In 2008, the USGS estimated the Bakken could technically yield a mean estimate of 3.65 billion bbls. That didn't change in this estimate, but the Three Forks was added and is estimated to hold 3.73 billion bbls oil. That's a mean estimate of 7.38 billion barrels of technically recoverable oil from the Bakken and Three Forks.

The Bakken and Three Forks are also estimated to hold 6.7 Tcf of natural gas and 0.53 billion barrels of NGLs. That's up from just 1.8 Tcf and 0.15 billion barrels in 2008.

The USGS numbers quoted the most include a mean estimate. The USGS actually provides a range of probability. The organization estimates that technically recoverable reserves range from 5.2 Billion boe to 14.3 Billion boe. That means a best or high case could be double what you see quoted in most places.

Read the full press release at USGS.gov