WorldWide Drilling Resource

77 WorldWide Drilling Resource ® DECEMBER 2016 Mancos Shale Redefines its Worth in New Assessment Adapted from Information Provided by U.S. Geological Survey The U.S. Geological Survey (USGS) recently conducted the second-largest assessment ever of potential shale and tight gas resources in Colorado. The Mancos Shale Formation, located in Colorado’s Piceance Basin, is purported to contain ap- proximately 66 trillion cubic feet of shale natural gas, 74 million barrels of shale oil, and 45 million barrels of natural gas liquids. This is an update to a prior assessment completed in 2003, which only estimated about 1.6 trillion cubic feet of shale natural gas. “We reassessed the Mancos Shale in the Piceance Basin as part of a broader effort to reassess priority onshore U.S. continuous oil and gas accumulations,” said Sarah Hawkins, USGS scientist, and lead author of the report. “In the last decade, new drilling in the Mancos Shale provided addi- tional geologic data and required a revision of our previous assessment of technically recoverable, undis- covered oil and gas.” Within the Marcos Shale, more than 2000 wells were drilled and completed since the previous assess- ment. Over 4000 feet thick, the Mancos Shale contains intervals acting as the source rock for shale gas and oil - meaning petroleum was gener- ated in the formation. Conventional reservoirs both above and below the formation, as well as tight reservoirs within the Mancos, have been primed with oil and gas, which migrated out of the source rock. Oil and gas have also remained in the Mancos’ continuous shale gas and shale oil reservoirs. Tight gas in the younger, more shallow areas of the Mancos Shale is produced chiefly from vertical and directional wells, in which the reservoirs have been hydraulically fractured. Shale oil and gas in the older, deeper sections are produced primarily from horizontal wells also hydraulically fractured. The USGS Energy Resources Program also got involved, drilling a research well in the southern Piceance Basin which provided meaningful new geologic and geochemical data used to refine the 2003 assessment. Sarah Hawkins examines a core drilled by the USGS Core Research Center. USGS scientists drill a test core for the report. ! " # !