"The U.S. Geological Survey (USGS) recently completed a comprehensive assessment of in-place oil in oil shales of the Eocene Green River Formation of the Uinta Basin of eastern Utah and western Colorado."
"The total in-place resource for the Uinta Basin is estimated at 1.32 trillion barrels. This is only slightly lower than the estimated 1.53 trillion barrels for the adjacent Piceance Basin, Colorado, to the east, which is thought to be the richest oil shale deposit in the world." [from the publication ReadMe file]
That's a total of 2.85 trillion bbls in the Uinta basin. To put this in perspective, the world has used less than 1 trillion barrels since the first commercial oil well was completed in 1859 (one calculation puts it at 875 billion bbls so far) Ref: U.S. Geological Survey Oil Shale Assessment Team, 2010, Oil shale resources of the Uinta Basin, Utah and Colorado: U.S. Geological Survey Digital Data Series DDS–69–BB, 7 chapters, pages variable.