Oil & Gas Geology ›› 2024, Vol. 45 ›› Issue (3): 710-721.doi: 10.11743/ogg20240310

• Petroleum Geology • Previous Articles     Next Articles

Segmented growth of low-angle normal faults in the western Bonan swell,Bohai Bay Basin and its petroleum geological significance

Rui LOU1,2(), Yonghe SUN1,2(), Zhongqiao ZHANG3   

  1. 1.School of Petroleum Engineering,Chongqing University of Science & Technology,Chongqing 401331,China
    2.Chongqing Key Laboratory of Complex Oilfield Exploration and Development,Chongqing 401331,China
    3.Tianjin Branch of CNOOC (China) Limited,Tianjin 300459,China
  • Received:2024-01-10 Revised:2024-05-15 Online:2024-06-30 Published:2024-07-01
  • Contact: Yonghe SUN E-mail:lorii0504@163.com;syh79218@163.com

Abstract:

A fine characterization of the segmented growth process and differential evolution characteristics of these faults is conducted using the latest 3D seismic data to investigate the segmented growth-induced spatiotemporally differential evolution and mechanisms governing hydrocarbon accumulation of the low-angle normal faults in the Bonan swell within the Bohai Bay Basin. Furthermore, we explore the genetic mechanisms of these faults and their controlling effects on hydrocarbon accumulation while considering the regional tectonic setting. The findings indicate that faults F1 and F2 at the southern boundary of the Bonan swell are low-angle normal faults. Both originated from the Mesozoic NWW- to nearly-EW-trending pre-existing thrust faults, which underwent negative inversion and subsequent reactivation during the Cenozoic. Fault F1 exhibits segmented connections laterally and multiple episodes of activity vertically; its central segment inherits continuous activity from the original fault plane, while its western and eastern segments vertically overlap with the NEE-trending fault newly formed during the rifting episode Ⅱ and the nearly-EW-trending fault during the rifting episode Ⅲ, respectively. These collectively create the present morphology of fault F1. The controlling effects of the low-angle normal faults on hydrocarbon accumulation are as follows: (1) The fault-controlled sides exhibit a large sedimentary scale, thus providing sufficient spaces for deposition. Consequently, large-scale sand bodies on steep slopes are developed. (2) The low-angle normal faults, which have remained active for a prolonged time, provide channels for vertical hydrocarbon migration and determine the horizons of vertical hydrocarbon enrichment. The multiphase activity of these faults has transformed the physical properties of deep reservoirs, with the activity intensity being closely related to the formation of high-quality reservoirs.

Key words: differential evolution, segmented growth, mechanism governing hydrocarbon accumulation, low-angle normal fault, Bonan swell, Bohai Bay Basin

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