Study On Petroleum Accumulation Systems In Tabei Uplift

Petroleum accumulation system(PAS) theory was introduced into the study ofTabei uplift in this paper. Beginning with the static elements analysis, laying emphasison dynamic accumulation process, this paper divided Tabei uplift into different PASs,analyzed the dominating factors and accumulation modes through contrasting study.Then the geologic and resource assessment was conducted quantitatively and thepotential prospecting areas were pointed out.In vertical, there are lower-Paleozoic, upper-Paleozoic, and Mesozoic-Cenozoic oiland gas bearing groups in Tabei uplift. In plane, every group can be divided into severalPASs: Luntai, Yingmaili, Donghetang-Yakela, Akekule, and Caohu-Akekule inlower-Paleozoic;Donghetang, Akekule, and Caohu in upper-Paleozoic;Luntai-Yingmaili and Akekule in Mesozoic-Cenozoic.Analysis of hydrocarbon accumulation phases indicated that in lower-PaleozoicPASs, the main hydrocarbon charging times are late Caledonian period, late Hercynianand Himalayan period. in which the latter two were valid accumulation phases forcurrent oil&gas pools. The accumulation phase of Donghetang reservoir is lateHercynian, and that of Kalashayi reservoir is Himalayan period. In Mesozoic toCenozoic PASs, the accumulation phase is Himalayan period in which more than oncehydrocarbon accumulating and adjusting happened..Through hydrocarbon tracing research and accumulation condition analysis, themigration characteristics in Akekule PASs were recognized. In Ordovician, the mainmigration direction during later Hercynian was SSW-NNE, while the predominatingmigration directions are multiple in Himalayan period. In Carboniferous and Triassic,petroleum migration is controlled by faults and inclination of sandstone layers, and thepetroleum migration directions are more complex.In the same oil and gas bearing group, the great differences between the South andNorth PASs exist in source systems and migration framework types, while thedifference between the East and west PASs exit in the development of migrationpathways, their combination styles, and the distance of source to pool. The dominatingaccumulation factors in upper and lower-Paleozoic PAS are reservoir and trap firstly,migration pathways and hydrocarbon source secondly, while in Mesozoic to Cenozoicaccumulation system are migration pathways and hydrocarbon source firstly, sandstonebody and low amplitude anticline group secondly.Based on the assessment results of geologic condition and resource,lower-Paleozoic PAS in Akekule is the most beneficial accumulation system in Tabeiuplift, with 936 million undiscovered resources,one oil pool bigger than 5 million tonand 15 to 27 oil pools with reserve of 10-50 million to be discovered. Luntai-Yingmailiand Akekule Mesozoic-Cenozoic PASs are also promising areas.