The Mancos shale of the Piceance basin in Colorado holds mean undiscovered, technically recoverable resources of 66 tcf of shale natural gas, 74 million bbl of shale oil, and 45 million bbl of NGLs, according to an updated assessment by the US Geological Survey.
The previous USGS assessment of Mancos was completed in 2003 as part of a comprehensive assessment of the greater Uinta-Piceance province. That estimate amounted to 1.6 tcf of shale gas.
“We reassessed the Mancos shale in the Piceance basin as part of a broader effort to reassess priority onshore US continuous oil and gas accumulations,” explained USGS scientist Sarah Hawkins, lead author of the assessment. “In the last decade, new drilling in the Mancos shale provided additional geologic data and required a revision of our previous assessment of technically recoverable, undiscovered oil and gas.”
Tight gas in the younger, shallower parts of the Mancos is produced primarily from vertical and directional wells in which the reservoirs have been hydraulically fractured. Shale oil and gas in the older and deeper intervals are produced mostly from horizontal wells that have been fraced.