断裂对断陷盆地火山岩天然气的成藏与控制作用——以松辽盆地徐家围子断陷为例

Controlling of Faults to Gas Accumulation of Volcanic Rock in Depression Basin:An Example from Xujiaweizi Depression of Songliao Basin

通过断裂发育及分布特征、火山岩中天然气分布规律和二者之间时空匹配关系研究得到,徐家围子断陷主要发育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。断裂的主要活动时期为火石岭组至营三段沉积时期和泉头组沉积晚期至青山口组沉积时期。火山岩中天然气分布具有纵向分布层位多、深度范围大和平面上分布于生气凹陷内或附近,且沿断裂带分布的特征。断裂对火山岩天然气成藏与分布的控制作用表现在:火山岩天然气源岩的形成与分布,火山岩体和其内部裂缝形成与分布,火山岩天然气藏形成的层位及火山岩圈闭的形成与分布。

There are mainly 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,and later tenso-shear fault system according to the study of development and distribution of faults,gas distribution regularity in volcanic rocks and their relationship in Xujiaweizi depression.The main active periods of the faults are K1h-K1yc3 and the later of K1q2 to K2qn.There are many distribution layers in vertical,much depth range,located in or near gas source depression in plane and along faults on gas distribution features in volcanic rocks.Control roles of gas accumulation and distribution in volcanic rocks are manifested in the following areas： faults control formation and distribution of gas source rocks;faults control formation and distribution of volcanic rock body and fractures within them;faults control formation and distribution of gas traps in volcanic rocks;faults control formation layers of gas reservoirs in volcanic rocks.