Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (3): 553-565.doi: 10.11743/ogg20220306

• Petroleum Geology • Previous Articles     Next Articles

Theory on genesis of coaliferous petroleum in the China Sea

Gongcheng Zhang1,2(), Ying Chen1, Zengxue Li2(), Youchuan Li1, Lei Lan1, Shixiang Liu1, Rui Sun1   

  1. 1.CNOOC Research Institute,Beijing 100029,China
    2.College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266590,China
  • Received:2021-05-18 Revised:2022-03-21 Online:2022-06-01 Published:2022-05-06
  • Contact: Zengxue Li E-mail:zhanggch@cnooc.com.cn;lizengxue@126.com

Abstract:

The study systematically analyzes coaliferous petroleum in a giant coal-bearing basin belt consisting of 14 coal-bearing basins in the China Sea and its surroundings. The evolution of the giant coal-bearing basin belt spanned five periods of coal formation, that is the Paleocene, the Eocene, the Early Oligocene, the Late Oligocene and the Miocene-Pliocene, in coal-forming environments of deltas, fan deltas and tidal flat-lagoons. The coaliferous source rocks dominate in the giant basin belt, featuring a “dual structure” of coaliferous and marine source rocks development. Experimental analysis of source rock, gas condensate, and natural gas samples indicates that the coal-bearing basin belt is characterized by a “four-stage” hydrocarbon generation model, and the coal-generating limit of the coaliferous source rocks (reflectance of vitrinite Ro) can reach up to 4.38 %, greatly expanding the lower limit of natural gas generation. The coaliferous source rocks in the basin belt feature two modes of hydrocarbon accumulation, that is, accumulation of hydrocarbons from the coal measures on the margin of the sag and that from the terrigenous marine source rocks within the sag, under the guidance of which multiple large-scale coaliferous hydrocarbon enrichment zones are developed.

Key words: hydrocarbon generation mode, dual structure, coal forming environment, coal-accumulating domain, coal-bearing basin belt, China Sea and its surroundings

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