塔里木盆地哈拉哈塘地区奥陶系良里塔格组古地貌与岩溶洞穴特征

Characterization of paleo-topography and karst caves in Ordovician Lianglitage Formation,Halahatang oilfield,Tarim Basin

塔里木盆地哈拉哈塘地区奥陶系良里塔格组发育典型的表生岩溶体系,形成特征性的喀斯特地貌及地下岩溶洞穴系统。首先利用地震资料表征了良里塔格组顶部喀斯特地貌,然后应用岩心、镜下及测井资料研究了地下岩溶洞穴系统的基本特征,并通过RMS振幅和方差融合技术刻画了岩溶洞穴系统的展布。结合本区地质背景,探讨了岩溶体系发育的控制因素。研究表明,良里塔格组顶部喀斯特发育岩溶高地、岩溶斜坡、岩溶槽谷和落水洞等地貌要素,不同的地貌要素具有不同的分布特征;其内部岩溶洞穴系统发生垮塌、充填及压实,岩溶洞穴通道呈直线形态并交织成复杂网状。控制该区岩溶体系发育的因素有:低水位期海平面下降、先存断裂及裂缝、地表河流体系。

The typical eogenetic karsts developed in the Ordovician Lianglitage Formation of the Halahatang area,Tarim Basin,are characterized by the featured paleokarst topography and subsurface paleokarst cave systems.This study initiates from the characterization of the karst terrain on top of the Lianglitage Formation with seismic data and then turns to the analysis of basic features of collapsed karst cave systems by core and thin section observation and log interpretation.In addition,the distribution pattern of the karst cave system is depicted through RMS amplitude and variance attribute fusion;and the factors controlling the development of the karst cave systems are explored against the paleogeological background therein.This study shows that the karst landform on top of the Lianglitage Formation consists of typical elements such as karst highlands,karst ramps,karst troughs and valleys as well as dolines,each with a different distribution pattern.The internal cave systems in the Lianglitage Formation underwent distinctive collapse,filling and compaction,leading to the pathways inside the systems occurring in rectilinear pattern and interweaving into reticular structure.The factors controlling the karst system development include extensive subaerial exposure during the LST period,pre-existing faults and fractures and surficial fluvial systems.