Palynological evidence for identification of nonmarine petroleum source rocks, China

Abstract

Fossil spores and pollen, some of which carry microscopic metallic minerals, are found in crude oils collected from various oil fields of the inland petroliferous basins of China. The palynological evidence of Carboniferous to Tertiary aged palynomorphs in the crude suggests that the source rocks are nonmarine. A comparison of spores and pollen in crude oils with those of the assemblages within the regional strata shows a widespread existence of potential petroleum source rocks in many of the inland sedimentary basins of China. Carboniferous and Permian rocks in the Junggar Basin, Triassic rocks in the Junggar, Tarim and Ordos Basins, Jurassic rocks in the basins of West China, and Paleogene rocks in the basins of East China contain previously unrecognized petroleum source rocks. Problems with basic principles and processing methods, the possibility of misinterpretation because of reworked spores and pollen and methods to eliminate this problem, the character of spores and pollen that allow them to be expelled with liquids from source rocks and to migrate into reservoir rocks, and petroleum migration mechanisms are discussed. The wide occurrence of fossil spores and pollen in crude oils is demonstrated to be caused by petroleum migration rather than by resedimentation.