塔河油田良里塔格组迷宫型岩溶洞穴系统发育特征

Characteristics of Maze Karst Cave System in Lianglitage Formation of Tahe Oilfield,Tarim Basin

为了明确塔河油田上奥陶统良里塔格组迷宫型岩溶洞穴系统的样式和结构,利用古地貌恢复、古水系刻画、测井地层对比、构造断裂解析、地震属性刻画等方法,进行了塔河油田11区的古水文地貌恢复、岩溶层组格架构建、岩溶洞穴识别和成因模式分析。结果表明:塔河油田南部加里东运动中期Ⅱ幕古地貌西北高、东南低,发育北北西—南南东向树枝状地表深切沟谷,良里塔格组发育近水平状分布、闭合管道结构及溶蚀强度较高的迷宫型岩溶洞穴系统;良里塔格组岩溶洞穴系统与澳大利亚Judbarra地区Bullita洞穴系统成因相似,属于典型的表生岩溶扩散下渗型迷宫型岩溶洞穴系统;上奥陶统恰尔巴克组泥岩段为隔水层,控制了良里塔格组迷宫型岩溶洞穴系统的侧向溶蚀作用;沟通地表水系的断裂为岩溶水主要下渗溶蚀通道,随着区域基准面下降,岩溶水沿断裂下渗进入中奥陶统,中奥陶统一间房组形成断溶体。塔河油田加里东运动中期Ⅱ幕表生岩溶“双层”迷宫型岩溶洞穴系统的认识对上奥陶统油藏开发具有重要意义。

To understand the styles and structures of the maze karst cave system in the Upper Ordovician Lianglitage formation in the Tahe oilfield,Tarim basin,the palaeohydrological and geomorphological restoration,karst framework construction,karst cave identification,and genetic model analysis were performed for Block 11 of the oilfield by using the methods such as paleolandform restoration,paleo-water system characterization,log-based stratigraphic correlation,structural fracture analysis,and seismic attribute characterization.The results show that during the EpisodeⅡof the Middle Caledonian,the southern Tahe oilfield was higher in the northwest than in the southeast geomorphically,with developed NNW-SSE dendritic incised valleys.A subhorizontal maze karst cave system with closed conduit structures and high intensity of erosion are found in the Lianglitage formation,which is a typical maze karst cave system formed by epigenetic karst diffusion and infiltration and shares similarities in genesis with the Bullita karst cave system in the Judbarra region of Australia.The mudstone interval in the Upper Ordovician Qiaerbake formation serves as an aquiclude,which controls the lateral erosion of the karst cave system in the Lianglitage formation.The faults connecting surface water systems provide primary channels for karst water infiltration and erosion.As the regional base level drops,karst water infiltrates downwards along the fractures into the Middle Ordovician strata,forming fault-karst reservoirs in the Yijianfang formation.Understanding the“double-layer”maze epigenetic karst cave system of the EpisodeⅡof the Middle Caledonian in the Tahe oilfield is crucial for the development of Upper Ordovician reservoirs.