Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (6): 1481-1488.doi: 10.11743/ogg20220616

• Methods and Technologies • Previous Articles     Next Articles

Improvement of method for timing of hydrocarbon migration along source rock-rooted faults and its application: A case of the South Dagang fault in Qikou Sag, Bohai Bay Basin

Guang Fu(), Jiajing Li, Tong Yu   

  1. School of Earth Sciences,Northeast Petroleum University,Daqing,Heilongjiang 163318,China
  • Received:2022-04-01 Revised:2022-09-05 Online:2022-11-21 Published:2022-11-21

Abstract:

Timing of hydrocarbon migration along source rock-rooted faults is critical for understanding the contributions made by the faults to hydrocarbon accumulation. The previous timing has been based only on the activating periods of the related faults, or on both the related faults’ activity period and hydrocarbon expulsion period, and the results obtained often cannot reflect the actual situation underground. In the study, we improve the method for timing of hydrocarbon migration along the source rock-rooted faults by defining the overlapping time of the faulting and hydrocarbon accumulation inside and outside the source rocks, coupled with study on hydrocarbon migration mechanism of source rock-rooted faults. Then a case study on South Dagang fault in Qikou Sag, Bohai Bay Basin, is carried out to comparatively analyze the effects of both the original and improved methods. The results show that the South Dagang fault is estimated as being active in hydrocarbon migration during the depositional period of the Neogene Minghuazhen Formation according to the improved method, which is much shorter than the deposition period of Guantao Formation to Minghuazhen Formation of the Neogene as confirmed to be hydrocarbon migration period of the fault by the original method. Compared to the original one, the hydrocarbon migration period of the South Dagang fault determined with the improved method is more reasonable in explaining the oil and gas distribution discovered in the first member of the Paleogene Shahejie Formation (Es1) near the South Dagang fault. It proves that the improved method is better consistent with the hydrocarbon migration mechanism of the source rock-rooted faults underground.

Key words: lower source rock and upper reservoir combination, hydrocarbon migration period, source rock-rooted fault, South Dagang fault, Qikou Sag, Bohai Bay Basin

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