The control effect of normal faults and caprocks on hydrocarbon accumulation: A case study from the Binhai fault nose of the Huanghua Depression, Bohai Bay Basin, China

• Published in: Journal of petroleum science & engineering 2022-11, Vol.218, p.110918, Article 110918
• Main Authors: Dong, Yuyang, Zeng, Jianhui, Dong, Xiongying, Li, Chuanming, Liu, Yazhou
• Format: Article
• Language: English
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/j.petrol.2022.110918

An exploration breakthrough was made in the Paleogene strata in the Binhai fault nose of the Huanghua Depression, but the distribution of hydrocarbons remained insufficient to understand. A series of fault-controlled traps were formed around the Gangdong fault, especially a large number of fault-block traps, which gave us a unique opportunity to use seismic data to study the distribution of the hydrocarbons under the control of normal fault and caprocks. By analysing the vertical and lateral changes of the fault throws (T-x and T-z plots), combined with the expansion index (EI), the characteristics of the Gangdong fault were studied and the evolution process of the fault was reconstructed. The fault has undergone the evolution process of lateral and dip linkage, and finally, the Gangdong fault was formed. The reconstruction of the evolution process and determination of charging stages found that the Gangdong fault was formed dip linkage just before late Neogene, providing an excellent vertical pathway for hydrocarbon migration. Besides, when the fault throw exceeds than 39 m, hydrocarbons were found near the fault, indicating a lower limit of fault throw. However, there were differences in the spatial distribution of hydrocarbons in the study area, which may be related to the integrity of the caprock. A lower thickness limit was found by analysing the relationship between the difference in hydrocarbon distribution above and below the regional caprock and the effective caprock thickness. When the effective caprock thickness is greater than this lower thickness limit, hydrocarbons can only accumulate below the caprock. When the effective caprock thickness is less than this lower limit, there is hydrocarbon accumulation above the caprock. This work highlights the evolution of normal fault and the control effect of fault-caprocks on hydrocarbon accumulation and further understands the spatial distribution of petroleum near the fault. •The invested normal fault has experienced lateral and dip linkage.•Two hydrocarbon charging events occurred, the second charging stage is more important.•Fault linkage before the second charging provides a channel for hydrocarbon migration.•A method for evaluating the effectiveness of the caprock is proposed.