| Affected by the multi-dynamic source geological context of mantle upwelling and plate collision,complex fault system was developed in Bohai Sea in Cenozoic.And together with the intensive Cenozoic strike-slip activity of NNE Tanlu fault zones and NWW Zhangjiakou-Penglai and Qinhuangdao-Lvshun fault zones,the induced structures such as strike-slip duplex were abundant in Bohai Sea.The research about the evolution mechanism and distribution law of strike-slip duplex could not only enrich the theoretical system of structural geology but it also provide us with a new method to research and acknowledge internal structure characteristic and evolution mechanism of strike-slip basin.Based on the abundant three-dimensional seismic data of Bohai Sea,this paper utilized coherence slice recognition method,seismic profile recognition method,fault system plane recognition method and three dimensional picture recognition method to recognize comprehensively the strike-slip duplexes of Bohai Sea and discussed evolution mechanism of strike-slip duplexes applying structure physical modelling analogy,faults activity analysis,balanced section.Eventually,this paper identified the distribution law and development types of strike-slip duplex in Bohai Sea and described briefly about the petroleum geological significance of strike duplex with the help of exploration practice.The evolution mechanism of strike-slip duplexes in Bohai sea are complicated and it has multiple types.Duplexes at offsets include the northern part of Liaodong uplift formed due to dextral strike-slip and left stepping of Liaodong fault and Liaozhong 2 fault,Liaozhong sag duplex caused by dextral strike-slip and right stepping of Liaozhong 1 fault and Liaozhong 2 fault,Jinxian 1-1 duplex and Kenli 6-5 duplex at the offsets of Liaozhong 1 branch faults and east Laizhou branch faults respectively and Bonan strike-slip duplex formed as a result of right stepping in Bonan segment of Tanlu fault.Duplex on straights is Penglai 3 strike-slip duplex which was formed because of the reverse strike-slip zone of Tanlu fault zone.Duplex at bends is shabei 1 strike-slip duplex formed owing to the bend of Shabei 1 fault.The strike-slip duplexes in Bohai Sea were much more in the east area and Neogene than in the west area and Paleogene.The wide range of spatial and temporal distribution and the variety of size strike and maturity provide us with opportunity to study strike-slip duplex more comprehensively.Five enlightenments from this study could be gained.(1)Strike-slip duplex at offsets is easier to form than the other types.(2)Extensional strike-slip duplex is easier to form than contractional one.(3)Secondary faults can lead to the formation of main boundary faults,thus constituting strike-slip duplex.(4)The ratio of the distance between two boundary faults and strike-slip distance plays a vital role in the development of internal structures.(5)The internal secondary structure is not Riedel shear but extensional or compressional fault.The stress increasing area of contractional strike-slip duplex contributes to the formation of effective fault traps because of the better lateral sealing and the faults in stress-decreasing area are favorable to vertical migration of oil.Furthermore,extensional strike-slip duplex tends to form hydrocarbon generation sag.These features are critical for the hydrocarbon accumulation. |
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