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Episodes 2024; 47(2): 265-278

Published online June 1, 2024

https://doi.org/10.18814/epiiugs/2024/024007

Copyright © International Union of Geological Sciences.

Fluid inclusions and hydrocarbon accumulation stages of the Chang 73 sub-member in the Zhijing-Ansai area in the Ordos Basin

Yulin Chen1, Nan Wu1*, Yong Feng2, Jian Wang2

1 School of Geosciences, Yangtze University, Wuhan 430100, China
2 Key Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, School of Geosciences, Yangtze University, Wuhan 430100, China

Correspondence to:*E-mail: wuuse@foxmail.com

Received: December 26, 2023; Revised: April 14, 2024; Accepted: April 14, 2024

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Influenced by Late Cretaceous tectonic uplift, fluid inclusion techniques were employed to determine the hydrocarbon accumulation stages of the Chang 73 sub-member in the Zhijing-Ansai area. There were two fluorescent oil inclusions in the Chang 73 sub-member. The green fluorescent oil inclusions indicated the relatively low-maturity oil, the homogenization temperatures of coeval aqueous inclusions were 83.8-89.5℃. The blue fluorescent oil inclusions indicated the relatively high-maturity oil, the homogenization temperatures of coeval aqueous inclusions exhibited two peaks which were 90.6-109.4℃ and 110.1-137.4℃. Combining the burial-thermal history of four wells, there were three stages of hydrocarbon accumulation. A small-scale charging of the relatively low-maturity oil occurred around 131-122 Ma. During the large-scale charging of the high-maturity oil, the hydrocarbon generation of source rock peaked (c. 114 to 100 Ma). Late tectonic uplift resulted in an oil adjustment stage (88-72 Ma), corresponding to the high-maturity oil charging time.