PETROLEUM GEOLOGY OF SHELVES VERSUS GEOSYNCLINES

While the United States has only 13 percent of the actual Free World oil reserves, the largest known potential oil resource in the world lies in the oil shales of the Tertiary Green River Formation, Piceance Yoked Basin, Colorado. Examining these supplies is timely in planning for the national needs. Similary the Arabian Gulf Basin area including Arab States and Iran has 70 percent of the Free World proven reserves, mainly in Mesozoic rocks. Petroleum is found underground by prospecting and wildcat drilling. The amount of oil recovered by new methods is only 50-60 percent. A geosyncline is like a large sediment-filled, elongate, asymmetric basin. Shelves are the most stable areas of the craton that are periodically flooded by marine waters. It is found that 58 percent of world's oil is produced from Tertiary beds, 18 percent from Cretaceous and 24 percent from beds of all other periods combined. Yet, basins are the most prolific areas for petroleum.