Gas Shales: A largely North American Phenomenon?

Abstract

Black shales are back in the “limelight” again, largely in response to the so-called “shale-gas revolution.” This revolution has changed the nature of global diplomatic relations and encouraged other countries to seek their own shale-gas revolutions. In fact, the EIA developed estimates of possible shale-gas reserves for countries across the world, again spawning hopes for “revolutions,” energy independence, and a surge in the use of cleaner fuels. A closer look at the situation, however, suggests that the U.S. shale-gas revolution was not really a revolution at all, and that abundant shale gas may largely be a North American phenomenon related to geology and developmental factors. Geologically, North American has more than 30 recognized shale-gas basins, and the development of so many basins probably reflects large size and stability of the continent through nearly 500 Ma. Continental deformation, when it did occur, only occupied continental margins, and in the process, generated many foreland, intracratonic and yoked basins that served as repositories for the organic-rich sediments generated in the process of basin formation. Moreover, during Paleozoic and Mesozoic time, when most organic-rich sediments were accumulating, critical parts of North American were situated in the tropics or subtropics, where generation of organic matter was enhanced during both greenhouse and icehouse climates. After Triassic and Jurassic breakup of Pangea, even more repositories were generated in the form of rift and rift-margin basins along the eastern and southern continental margins. As important as geological factors were, developmental factors since 1975 were just as important. These factors include more than 40 years of research into the nature of eastern and central US gas shales, economic factors that reflect private ownership, abundant water, and adaptable political and social institutions, as well as technological factors that reflect the work of many small independent operators, supporting contractors and infrastructure. In truth, as some have noted, the situation in North America reflects more of an “evolution” than a “revolution.” Whether or not the same alignment of factors that has occurred in North America can happen elsewhere, I am doubtful. Hence, similar “revolutions” in other parts of the world are unlikely.

AAPG Datapages/Search and Discovery Article #90258 © 2016 AAPG Eastern Section Meeting, Lexington, Kentucky, September 25-27, 2016