碳酸盐岩岩溶古河道发育特征与成因演化:以塔里木盆地塔河油田12区中——下奥陶统为例

Development Characteristics and Genetic Evolution of Carbonate Karst Ancient River:Example from the Middle-Lower Ordovician in Block-12 of Tahe Oilfield,Tarim Basin

为了明确塔里木盆地塔河油田12区中—下奥陶统顶面古河道的成因,利用地震剖面分析、地震属性提取等技术,结合钻井资料刻画了古地貌、古水系发育特征,定量描述古河道的河曲特征,并基于现代岩溶理论建立了古河道成因演化模式。结果表明:中—下奥陶统顶面古河道为“深切河曲”古岩溶地貌,深切河曲特征表现为河谷主要呈“V”字形,两侧河谷坡岸对称,谷壁陡峭,发育由于截弯取直形成的离堆山、天生桥等标志性地貌;中—下奥陶统顶面古河道发育“高弯曲率”河曲形态,深切河曲的单个河曲弯曲率C值都在2.20以上,平均值为4.27,SN向河曲带弯曲率C值为1.87,EW向河曲带的弯曲率C值为2.38;塔河油田12区中—下奥陶统顶面深切河曲经历志留系沉积期、自由河曲期、深切河曲期等3个演化阶段,其成因与华力西早期运动构造作用关系密切。

In order to clarify the origin of the ancient river channel on the top of the Middle and Lower Ordovician in Block 12 of Tahe Oilfield,the Tarim basin,using techniques of seismic profile analysis and seismic attribute extraction,combined with drilling data,the development characteristics of the ancient landform and ancient water system are depicted,the meander characteristics of the ancient river channel are quantitatively describe,and the genetic evolution model of the ancient river channel is established.The results show that the an cient channel on the top of the Middle and Lower Ordovician is entrenched meander river,and the entrenched meander is characterized by a"V"shape of the valley,symmetrical slope banks on both sides of the valley,steep valley walls,and the development of the meander core and natural bridge formed by process of natural cutoff.The ancient channel on the top of the Middle-Lower Ordovician developed a"high curvature"meander shape.Statistical meander parameters indicate that the meander ratio C values are larger than 2.20,with an average value is 4.27,the C value of the whole North-South meander is 1.87,and the C value of the whole East-West meander is 2.38.The evolution of meandering superimposed Valley in block-12 has three stages:Silurian sedimentary period,free-meander and entrenched-meander,and its genesis is closely related to the early Hercynian movement.