General statement

Many of the earliest oil and gas provinces of the late nineteenth and early twentieth centuries were in thrustbelts, where discoveries were based on the presence of surface seeps and prominent structures. These include the allochthonous Alleghany Plateau in the Appalachians, the Canadian Foothills belt, the transpressional basins of Southern California, the northern Andes, the Zagros fold belt and the Middle Caspian region. Since these early, relatively easy discoveries, the petroleum exploration in thrustbelts has been driven in cycles in which the sustained product price coincides with technical advances that reduce the generally higher costs and risks of finding and developing hydrocarbons in this setting. The last major cycle of thrustbelt exploration was in the 1970s and 1980s, resulting in the discovery of prolific new provinces such as the Wyoming Thrustbelt, the El Furrial trend in eastern Venezuela, the sub-Andean basins of Peru, Bolivia and northern Argentina, Papua New Guinea, to name just a few. This was also the time of expansion of hydrocarbon plays in the Canadian Foothills belt, the northern Andes and other established thrustbelt provinces. As industry attention shifted to the deep-water continental margins during the 1990s (Esser, 2001), the few new thrustbelt discoveries of significance were all in established petroleum provinces. The sole exception was the discovery of large petroleum accumulations in toe thrusts at the base of the Niger fan (Zafiro field) and the Mississippi fan fold belt beneath the Gulf of Mexico salt canopies (e.g., Mad Dog, Neptune and Atlantis fields). These discoveries point to a whole new class of highly prospective, but high-risk, thrustbelt plays.