徐家围子断陷营城组火山岩分布特征及火山喷发机制的新认识

A new understanding about the volcanic distribution characteristics and eruption mechanism of Yingchen Formation in Xujiaweizi fault depression

基于深层钻井和连片处理三维地震资料,结合同位素测年,本文对松辽盆地北部徐家围子断陷白垩系营城组火山岩的分布特征及其喷发机制进行了研究。本区火山岩分布广、厚度大、沿深大断裂串珠状分布;纵向上分为下部营一段和上部营三段两套;营一段分布于断陷中部及其以南地区,岩性以酸性为主;营三段分布于断陷中部及其以北地区,酸性和中、基性火山岩均有发育。本区断裂类型及其组合复杂,正、逆、走滑和花状断裂都有发育;两组断裂交汇部位是火山喷发的主要通道。深大断裂与火山岩时空展布关系显示,营一段火山岩主要受徐中断裂控制,由北向南依次喷发,岩性以酸性为主;营三段火山岩主要沿着徐东花状断裂带由南向北依次喷发,表现为基性与酸性交替的双峰式。营城组火山岩喷发类型有三种:裂隙式、中心式与复合式。徐家围子断陷营城组火山岩储集性能优良且毗邻烃源岩,与断裂、源岩及盖层有利匹配,可构成有利的生储盖组合,具有良好的天然气勘探前景。

Based on well data and concatenating processed 3D seismic data of the deep layer in Xujiaweizi fault depression,also with the isotopic age determination technique,a research about volcanic distribution characteristics and volcanic eruption mechanism is carried out.The volcanic rock of Yingcheng Formation is widely distributed along each large fault in Xujiaweizi fault depression, Songliao basin,like a string of beads with great thickness.The volcanic rock of Yingcheng Formation is divided into two sets:The lower set is the first member and the upper set is the third member.The first member distributes in the middle and north area of the depression,with a predominantly acidic volcanic lithology.The third member distributes in the middle and south area of the depression,with acidic,intermediate and basic volcanics developed.The fault structures and its combined characteristics in Xujiaweizi fault depression are very complicated.Normal fault,reverse fault,strike-slip fault and flower-pattern fault are all developed in this area.The convergence area of the faults of two directions is the main magma eruption channel.The time-space distribution relations of the large deep faults and volcanic rocks show that Xuzhong fault controls the magma eruption and the volcanic distribution of the first member of Yingcheng Formation.The magma mainly erupted from north to south in turn.During the third member period,the magma mainly developed along Xudong flower-pattern fault zone,erupting from south to north in turn,with basic and acidic volcanics developed alternately.Meantime,the volcanic eruption pattern of Yingcheng Formation can be summarized as fissure volcanic eruption, central volcanic eruption and compound volcanic eruption.The volcanic rock of Yingcheng Formation in Xujiaweizi fault depression has an excellent storage capability and is adjacent to the source rocks.It is suited well with fault,source rock and cap rock,building up a favorable source-reservoir-cap combination,which reveals a better prospect for gas exploration.