Shale oil and gas discoveries in the U.S. are quickly making us less dependent on OPEC for our energy supplies. How does Arizona fit into the picture? The Arizona Geological Survey has recently begun an assessment of Arizona’s potential contribution with a new report:
Rauzi, S.L. and Spencer, J.E., 2013, A Brief Overview of the Cretaceous Mancos Shale in Northeastern Arizona and its Hydrocarbon Potential. Arizona Geological Survey Open-File Report, OFR-13-08, 8 p. (download for free here, there also is a 100-second-long video here).
An AZGS press release gives an overview:
New developments in horizontal drilling and hydraulic fracture technology are transforming some marginal shale oil and shale gas deposits into economic oil and gas targets. In the Southwestern U.S., the Cretaceous Mancos Shale is part of the stratigraphic sequence in both the San Juan Basin of northwestern New Mexico and Black Mesa in northeastern Arizona. [See map at bottom of this post] It has been the source of much oil and gas in the San Juan Basin, with renewed drilling and hydrofracturing now underway, but has received little attention in Arizona where it underlies the Navajo and Hopi Indian Reservations. In light of this discrepancy, the Arizona Geological Survey reexamined existing well data and rock unit descriptions for the Mancos Shale in northern Arizona.
This new report includes information on the location and availability of existing well logs, cuttings and rock core for seven oil and gas wells drilled at Black Mesa. The absence of geochemical analyses or Total Organic Carbon values of the black, lower shale precludes even crude estimates of the oil or gas content or thermal maturity of the Mancos Shale.
The marine Mancos Shale comprises a lower calcareous, organic-rich shale that grades upward into fine siltstones and sandstones. It is this lower organic-rich unit that holds the greatest potential for economic shale oil and shale gas deposits. The Mancos Shale at Black Mesa ranges in thickness from 720 feet in the north, to only 475 feet in the south. From north to south, the base of the Mancos Shale ranges from ~ 1,500 feet deep to several hundred feet deep.
Black Mesa has been an important source of coal in Arizona since the 1970s. Currently, Peabody Energy strip mines coal from the Wepo Formation near Kayenta on Black Mesa to fuel the 2,250 megawatt Navajo Generating Station.
The Paradox Basin in Utah, just north of the Arizona-Utah border, may serve as an analog for the Black Mesa of Arizona. Last year the U.S. Geological Survey completed a study of the area and concluded that the area has potential for “560 million barrels of undiscovered oil, 12,701 billion cubic feet of undiscovered natural gas, and 490 million barrels of undiscovered natural gas liquids…”