Of geological interest: the Cumnock Formation

I alluded to the geology of the Cumnock Formation in the Sanford sub-basin of the Triassic Basins as being a limiting factor in the ability of gas developers to extract resources safely. I must also acknowledge that the same formation is of significant geological interest in the debate as to whether hydraulic fracturing will be permitted in North Carolina. In their fact sheet on shale gas potential here, the NCGS noted that:

The Cumnock Formation includes a ~800 foot thick interval of Upper Triassic (Carnian) organic-rich black shale.

For comparison, the Marcellus Shale, which extends much further through the Appalachian Basin, ranges in thickness in Pennsylvania of approximately 790 feet in the east to approximately 50 feet in the west. So, the thickness of the Cumnock Formation makes it an attractive possible play. Thomas Murphy of the Penn State Marcellus Center for Outreach and Research reported at the Duke forum in early January that some well developers in Pennsylvania are working on fracturing the Marcellus Shale and the Utica Shale at a lower horizon from the same drill pad. Accessing multiple depths from the same drill pads seems to make mineral extraction more economical. I, for one, would be weary about the well integrity in wells used to access many horizons given that well casing has been shown to break down.

Another difference between the Cumnock and most other gas-rich shale formations is the fact that most of the Cumnock was actually formed in a terrestrial environment, as opposed to a marine environment. It is unclear how much difference that forming environment has in the content of the gas, and the content of other minerals.



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