The regional Hydrogen Index (HI) of the upper Bakken Shale, based on public domain data accessible from the U.S. Geological Survey, supplemented by in-house data. Hot colors are low HI values indicative of greater levels of thermal maturity; cooler colors are higher HI values indicative of lower thermal maturity. Named project areas highlight Whiting’s Williston acreage holdings; the productive Pronghorn zone is the southern-most entity on the map.