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Geoscience ›› 2019, Vol. 33 ›› Issue (06): 1263-1274.DOI: 10.19657/j.geoscience.1000-8527.2019.06.12

• Petroleum Geology • Previous Articles     Next Articles

Classification of Hydrocarbon Accumulation Phases of Yanchang Formation in Southern Ordos Basin

LIU Runchuan1, REN Zhanli1,2(), MA Kan1, ZHANG Yuanyuan1, QI Kai1, YU Chunyong1, REN Wenbo1, YANG Yan1   

  1. 1. Department of Geology,Northwest University,Xi’an,Shaanxi 710069, China
    2. State Key Laboratory for Continental Dynamics, Northwest University, Xi’an,Shaanxi 710069, China
  • Received:2018-06-10 Revised:2018-12-13 Online:2019-12-26 Published:2019-12-27
  • Contact: REN Zhanli

Abstract:

The timing of hydrocarbon accumulation of Yanchang Formation in the southern Ordos Basin is determined, according to the fluid inclusion characteristics and hydrocarbon generation history of source rock and oil maturity. Characteristics of fluid inclusions (under microscope and UV fluorescence) suggest two generations of hydrocarbon inclusions. The first generation comprises yellow or aquamarine liquid hydrocarbon inclusion under fluorescence microscope. These fluid inclusions are low in abundance, and the accompanied saline inclusions homogenized at 100~110 ℃. The second generation includes mainly gas and liquid hydrocarbon inclusions, the former is colorless or light-yellow under polarized light and bright blue under fluorescence. Its abundance is high, and the accompanied saline inclusions homogenized mainly at 130~140 ℃. Integrated with salinity and density analyses, we suggested a one-phase and two-stage model for the major accumulation of hydrocarbons in the Yanchang Formation. Considering the basin thermal evolution history of southern Ordos basin: the first hydrocarbon charging stage occurred in the middle of Early Cretaceous (ca. 125 ~ 115 Ma), whilst the second stage occurred in the late of Early Cretaceous (ca. 97 ~ 105 Ma). These two oil and gas filling stages indicate that the oil and gas accumulation occurred in the Early Cretaceous.

Key words: fluid inclusion, homogenization temperature, hydrocarbon accumulation, Yanchang Formation, Ordos Basin

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