松辽盆地北部徐家围子断陷断裂构造特征及对深层天然气的控制作用

Characteristics of Fault Structure and Its Control on Deep Gas Reservoir in Xujiaweizi Fault Depression,Songliao Basin

系统分析徐家围子断陷断裂构造特征,研究了断裂系统对深层天然气成藏条件的控制作用。徐家围子断陷发育5套断裂系统,徐西早期走滑伸展断裂系统、徐中走滑长期活动断裂系统、徐东走滑断裂系统、早期伸展晚期张扭长期活动断裂系统以及晚期张扭断裂系统。断裂活动时期主要为断陷期和泉头组沉积晚期—青山口组沉积时期。徐西走滑伸展断裂系统控制了沙河子组烃源岩的展布,徐中及徐东走滑断裂控制了下白垩统营城组一段和营城组三段火山岩体的展布,长期活动断裂为天然气垂向运移提供良好垂向通道。断裂对登二段区域性盖层破坏程度小,使得徐家围子断陷深层天然气主要富集在下白垩统登娄库二段之下的营城组地层中。断层两盘岩性对接关系为火山岩—砂泥岩,断层侧向封闭;火山岩—火山岩对接,断层侧向不封闭。晚期构造反转较弱,使得断裂对气藏的破坏程度较小,对天然气的保存有利。

the characteristics of development and activity of fault in the Xujiaweizi fault depression,Songliao Basin,were analyzed. The control of fault on deep gas reservoir was investigated. Five cases of fault system were developed in the Xujiaweizi fault depression,including the western Xujiaweizi early extensional strike-slip fault system,central Xujiaweizi strike-slip long-term active fault system,eastern Xujiaweizi strike-slip fault system,early extensional and later tenso-shear long-term active fault system,later tenso-shear fault system. Fault activity periods are fault depression period,from K1q deposition to later stage——K1qn deposition period. The Xuxi early extensional strike-slip fault system control the distribution of K1sh source rock,the Xuzhong and Xudong strike-slip fault system control the distribution of K1yc1 and K1yc3volcanic,later-term activity fault was well vertical pathway of gas vertical migration. Fault destructiveness to K1d2 region cap-rock is poor,gas mainly accumulate k1yc formation in Xujiaweizi fault depression,the relationship of lithological juxtaposition was volcanic—sand shale,the fault was lateral seal,the relationship of lithological juxtaposition was volcanic—volcanic,the fault was not lateral seal,later structural reverse was poor,the damage degree of hydrocarbon by fault was poor,it was better to hydrocarbon conserve.