Fault growth and linkage: Implications for trap integrity in the Qi'nan area of the Huanghua Depression in Bohai Bay Basin, China. (November 2022)

• Record Type: Journal Article
• Authors: Wang, Haixue; Fu, Xiaofei; Fan, Mingxing; Wang, Shunyu; Meng, Lingdong; Du, Wei
• Is Part Of: Marine and petroleum geology. Volume 145(2022)
• Publication Date: 2022-11
• Subjects: Bohai bay -- Fault growth and linkage -- "Like-dipping" and "oppositely-dipping" faults -- Oil preservation -- Trap integrity; Submarine geology -- Periodicals; Petroleum -- Geology -- Periodicals; Géologie sous-marine -- Périodiques; Pétrole -- Géologie -- Périodiques; Petroleum -- Geology; Submarine geology; Periodicals; Electronic journals; 551.468
• DOI: 10.1016/j.marpetgeo.2022.105875
• Languages: English
• ISSNs: 0264-8172

Abstract

Abstract: Based on comparisons between fault growth histories and the distributions of paleo-oil and existing oil accumulations, the fault growth and linkage processes have been proposed as being critical in determining the location, timing, and oil preservation of "like-dipping" (with inclinations the same as those of the corresponding strata) and "oppositely-dipping" (with inclinations opposite to those of the corresponding strata) fault-bound traps in the Qi'nan area of the Huanghua Depression in Bohai Bay Basin. The critical fault throw is a key factor determining the leakage behavior and integrity of these traps. "Oppositely-dipping" fault-bound traps are developed at the throw maxima of the footwalls; these throw maxima are located at the trap crests. Once the throw exceeds the threshold, the oil columns in the traps become fully breached (emptied). "Oppositely-dipping" fault-bound traps with preserved oil are found in almost all single-layer systems (either fully preserved or fully breached). However, "like-dipping" fault-bound traps are found where interacting fault segments are hard-linked, and the throw minima are located at the trap crests. A closure bounded by a "like-dipping" reactivated fault might still retain hydrocarbons when the throw of crest is below the established threshold. "Like-dipping" fault-bound traps with preserved oil are found in single-layer and multilayer systems (either partially preserved or partially breached). Therefore, a trap integrity model is constructed on the basis of the aforementioned observations. The results of this model exhibit great consistency with the results derived from 31 drilled fault-bound traps containing petroleum fluid inclusions in the Qi'nan area. The model successfully explains the complex distributions of paleo-oil and preserved oil columns in the "like-dipping" and "oppositely-dipping" faults. In addition, the mechanisms proposed in the model may be applicable to other plays or basins. Highlights: 1. The critical fault throw was a key factor in determining the leakage behavior. "Oppositely-dipping" fault-bound traps are developed at the throw maxima of the footwall, the throw maxima are located at the crest of trap. Once throw exceed the threshold, the oil columns in the traps become fully breached (empty). Therefore, the "oppositely-dipping" fault-bound traps with preserved oil are almost always found in single-layer systems (either fully preserved or fully breached). The "like-dipping" fault-bound traps are located where interacting fault segments are hard-linked, the throw minima are located at the crest of trap. A closure bounded by a "like-dipping" reactivated fault might still retain the hydrocarbon when the throw of crest is less than the threshold. Therefore, the "like-dipping" fault-bound traps with preserved oil are found in single-layer systems or multilayer systems (partially preserved and partially breached). 2. A trap integrity model, comprising a series of temporal and spatial evolution of fault-bound traps and hydrocarbon vertical leakage risk, is constructed, and it effectively explains the reason behind the aforementioned discrepancies. The results of the proposed model have a good degree of consistency with the drilling results from 31 individual fault-bound traps containing petroleum fluid inclusions in the Qi'nan area.