塔里木盆地塔河油田TH12402井区中下奥陶统古岩溶洞穴发育模式*

塔里木盆地塔河油田TH12402井区位于志留系覆盖区,发育典型的古岩溶缝洞型储集层,是塔河油田西北部奥陶系主要的产建阵地之一。基于三维地震数据、测井和钻井资料,并结合地震属性提取技术,对该区下奥陶统岩溶发育条件和储集层发育特征进行了研究,探讨了岩溶洞穴的控制因素和发育模式。结果表明: TH12402井区处于北西向次级鼻状构造的南翼,该区发育加里东中期Ⅲ幕古岩溶作用,岩溶地形以低幅度的溶丘和洼地为主,地表水系呈南北向汇流且分支水系相对欠发育;岩溶储集空间以大型迷宫状岩溶管道和分散的孤立状洞穴为主,主要分布在不整合面以下40~100m,且以未充填为主;近东西向的走向断层、次级鼻状构造以及上奥陶统地层尖灭线联合控制了古岩溶洞穴的发育,形成了平缓岩溶地貌区走向断裂汇流型岩溶洞穴模式。上述成果为相似井区的古岩溶储集层预测和井位部署提供了理论依据。

Development model of paleokarst caves in the Middle-Lower Ordovician of TH12402 well area in Tahe oilfield,Tarim Basin

The TH12402 well area of the Tahe oilfield that is located in silurian overlying area is characterized by typical paleokarst fractured-cave reservoirs. It is one of the main production and construction sites of the Ordovician in the northwest of Tahe oilfield. Based on 3D seismic data,well logging data and drilling data and pickup technique of seismic attribute,the karst development conditions and reservoir development characteristics of the Lower Ordovician in this area were studied,and the dominant factors and development patterns of karst caves were illustrated. The result shows that the TH12402 well area is located in the south wing of a secondary nose-like structure oriented in the NW direction. This area records the karstification during the third phase of the Middle Caledonian,where the karst landform is mainly composed of low-relief dissolved hills and depressions,the surface water system extends from north to south without abundant branch water system. The karst reservoir space is composed of large maze karst caves and separated single caves that are unfilled,which are mainly located at 40~100m under the unconformity. Strike faults approximately oriented in WE direction,secondary nose-like structure and pinch-out lines of the Upper Ordovician together catrolled the development of paleokarst caves. A karst cave pattern is established considering the influence of strike faults on water concentration in areas within relatively flat karst landforms. These results provide a theoretical basis for paleokarst reservoir prediction and well location deployment in other well regions with similar conditions.