THE PHENOMENON OF NORTH AMERICAN SHALE GAS: GEOLOGY AND DEVELOPMENT

Renewed interest in black shales has occurred in recent years, 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 the large size and stability of the continent for 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 the generation of organic matter was enhanced during both greenhouse and icehouse climates. After the 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 have been 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. As some have noted, what has happened in the North America has been more of an “evolution” than a “revolution,” and because of the unique North American situation, it is uncertain whether similar revolutions will occur elsewhere.