松辽盆地长岭断陷盆地断陷期构造转换及油气地质意义

Tectonic Transformation of Changling Fault Depression in the Southern Songliao Basin and Its Significance of Hydrocarbon Accumulation

本文以平衡剖面理论为指导,对松辽盆地长岭断陷3条近东西走向的剖面进行了研究。结果表明,长岭断陷盆地在火石岭期初始张裂,沙河子期、营城期断陷强烈扩张,伸展速率均在沙河子期最大,分别为907.50m/Ma、1373.90m/Ma和1100.00m/Ma,两次扩张末期都伴有构造反转。沙河子末期最大缩短量达2.11km,缩短率2.89%;营城末期最大缩短量达2.26km,缩短率3.21%。登娄库期断陷开始向坳陷转化,泉头期—嫩江期为断陷期后热冷却沉降,表现为弱伸展作用,随后进入嫩江末期以挤压作用为主的反转构造发育期。沙河子组、营城组既是主力源岩,又是优质盖层和储层,构成了近烃源自生自储式成藏组合。在沙河子末期、营城末期构造运动形成的大范围的低幅褶皱构造是成藏有利区块。

Three typical near EW trending cross-sections of Changling fault depression in the Songliao basin were studied using the theory of balanced cross-sections. The analysis indicates that rifting of the basin started in Huoshiling period and subsided intensively in Shahezi and Yincheng periods, with extension rates of 907.50 m/Ma, 1373. 90 m/Ma, and 1100. 00 m/Ma respectively, peaking at the Yincheng period. Structural shortening also took place at the end of the two extension periods, with a maximum and ratio of shortening 2.11 km and 2.89% in the former and 2.26 km and 3.21% in the latter. The basin started to transform from faulting depression to subsiding depression in Denglouku period, to post-rifting cooling subsidence in ing the Quantou-Nenjiang period, characterized by weak extension, and to a stage of inverse structure development, characterized by compression at the end of the Nenjiang period. The Shahezi and Yingcheng Groups, as both major rock, and cover/reservoir rocks, formed a unique assemblage for authigenic and self-storing hydrocarbon accumulation. Therefore, large-scale low-magnitude folding structure formed by tectonic activities at the end of Shahezi and Yincheng periods is a favorable zone for accumulation of oil and natural gas.