塔里木盆地顺南地区中-下奥陶统深成岩溶特征

Characterization of hypogenic karst systems in the Middle-Lower Ordovician of Shunnan area,Tarim Basin

基于热液运移通道低连续弱振幅和热液作用区高连续强振幅"串珠体"两种截然相反的地震反射特征,建立振幅地震属性分级-断裂体系解释-拾取-三维刻画-融合技术,有效刻画热液运移通道和热液作用区二者空间耦合关系,进而建立深成岩溶的发育模式。通过对塔里木盆地塔中SN4井鹰山组上段深成岩溶系统的刻画,认识到热液作用区(深成岩溶系统发育区)的形成与分布和热液运移通道系统具有密切关系。1热液运移通道系统一般由主干断裂、次生断裂以及横向输导层(近地表岩溶系统、孔隙层以及孔洞层)组成,其中主、次断裂合成树枝状形态构成垂向运移通道。深部热液先沿垂向运移通道运移,接着沿横向输导层运移,形成"纵横结合"的热液运移通道系统。2深部热液在次生断裂的顶部汇聚后加剧,沟通了先存的"单串珠"状的近地表岩溶系统,使得原先"单串珠"点状分布的近地表岩溶系统沟通演变成连片分布的"串珠体"深成岩溶系统,呈现"枝状疏导、层状分布、指状交互"特征。

By contrasting two opposite seismic reflection features of hydrothermal conducting pathways （low continuity and weak seismic amplitudes） and hydrothermal zones （high continuity and strong seismic amplitudes） of data gathered from hypogenic karst systems in the Middle-Lower Ordovician of Shunnan area in Tarim Basin,we developed a new seismic characterization workflow consisting of seismic amplitude thresholding,fracture system interpretation,pick up,and merge display,to effectively describe the coupling relationship between spatial distribution of hydrothermal zones （hypogenic karst system＇ zones） and hydrothermal conducting pathways （fracture systems）,and then to establish development modal of the hypogenic karsts.Characterization of the hypogenic karsts from the Yingshan Formation of Well SN4 in central Tarim Basin shows a close relationship between the formation and distribution of the areas affected by hydrothermal fluids and the migration pathways of the fluids.The migration pathway system is usually composed of primary and secondary faults,and lateral carriers （epigenic karst systems,porous layers and vuggy layers）,among which,the primary and secondary faults together form vertical migration pathways.Fluids from the deep usually move upwards along the vertical pathways first and then flow along the lateral carriers-a criss-cross migration system.The accumulation of fluids from the deep at the top of the secondary faults makes it possible for the scattered epigenic karst systems of individual bead string type to communicate with one another and form a massive hypogenic karst system of ＂bead string commplex＂ type with such features as branched carriers,layered distribution and interfingered bead strings.