Enrichment Patterns of Various Coexisting Energy Resources and their Correlation in Ordos Basin, NW China
Ordos basin, the second largest sedimentary basin located in the central part of China, was transformed into westward declination monocline with only about 2-3°dip angle in later cretacious where a large amount of various energy resources have been found. It is concluded that the strutural evolution in Ordos basin can be classified as the following several stages: riftsyncline, giant composite craton depression, large inland depression and margional fault depression. This unique structural evolution of the basin leads to the particular various energy minerals spatio-temporal distributions. As a result, the basin is prolific in oil, gas, coal and uranium resources. Vertically, oil, coal and uranium distribute mainly in Jurassic, while gas distributes mainly in Permian and Ordovician; natural gas is located below oil and uranium, and closely above and/or below the Permo-Carboniferous coal measures. Laterally, oil distributes in the central and southern parts of the basin, uranium deposits are located in the northern and western edges of the basin, natural gas and coal distribute in the whole basin, and recoverable coals distribute in the basin margin. Gas distributions in Lower and Upper Paleozoic have been controlled by the palaeokarsts formed in the late Caledonian to Hercynian fossil weathered crusts, and the widely distributed large braided river delta front sediments respectively. The accumulation of coal has been controlled by the turning stage of tectonism and palaeoclimate, and the enrichment of uranium has been controlled by oxidation-reduction environment. The minerogenic evolutions of various energy resources in the basin are characterized by their obvious phasic development, and the commercial energy resources have been accumulated in a sequence of coal→uranium→gas→oil. Yishan slope area is favorable for exploration of oil, gas, coal and unconventional gas; Tianhuan depression and the thrust belts on the western edge of the basin are favorable for joint exploration of oil, gas, coal and uranium; Yimeng uplift and Weibei and Jinxi flexural fold belts are favorable for joint exploration of coal, coalbed methane and uranium.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013