海西早期大型树枝状岩溶暗河发育条件与地质模式——以塔里木盆地塔河油田B94井区为例

Development conditions and geological models of large dendritic karst conduit in early Hercynian: a case study of B94 well block of Tahe Oilfield, Tarim Basin

汪彦 高济元 杨德彬 张恒 蔡忠贤 何新明 金燕林 刘遥 王明

中国石油化工集团公司碳酸盐岩缝洞型油藏提高采收率重点实验室，新疆 乌鲁木齐 830011 中国石化西北油田分公司勘探开发研究院，新疆 乌鲁木齐 830011 湖北省油气勘探开发理论与技术重点实验室，湖北 武汉 430074 中国地质大学（武汉）资源学院，湖北 武汉 430074

塔河油田奥陶系发育类型多样的古岩溶缝洞型储集体，其中，海西早期大型岩溶暗河系统是最重要的储集空间之一。基于三维地震和钻井资料，利用地震属性提取技术，重建了B94井区奥陶系古构造、古地貌和古水文条件，描述了该区岩溶暗河的空间展布特征，揭示了岩溶暗河形成的地质控因，建立了岩溶暗河发育的地质模式。研究表明：塔河油田B94井区奥陶系位于2个次级鼻凸之间的向斜部位；该区处在海西早期岩溶作用区，主要发育中高幅度的岩溶地貌，呈现东高西低、北高南低的地势坡降，地表水系异常发育，呈近对称的树枝状，且从北向南汇流，最终汇入一条岩溶峡谷；该区岩溶暗河平面分布范围广，呈树枝状展布，垂向发育深度相对稳定，主要分布在T56以下120 ms；由于地表水向地下的转化频繁，岩溶暗河内部充填较为严重，暗河中下段充填更加明显；显著的地势坡降、次级背斜之间的向斜构造和NNE，NNW向走滑断裂共同控制了岩溶暗河的发育，形成了向斜汇流型岩溶暗河发育模式。这一认识可直接指引B94井区奥陶系的井位部署工作。

Various types of palaeokarst fractured?鄄vuggy reservoirs are developed in the Ordovician of Tahe Oilfield. Among them, large karst conduit formed during the early Hercynian are one of the most important reservoirs. Based on three dimensional seismic and drilling data, the palaeostructure, palaeogeomorphology and palaeohydrology conditions of the Ordovician in B94 well block were reconstructed by utilizing seismic attribute extraction technology. The spatial distribution characteristics of karst conduits in this area were investigated, the geological control factors for the development of karst conduits were revealed and the geological model of them was established. The research results show that the Ordovician in B94 well block of Tahe Oilfield is located in a syncline between two secondary nose?鄄shaped structures. The area is located in the early Hercynian karstification region, which mainly develops medium and high relief karst geomorphology, showing a terrain gradient of high in the east and low in the west, and high in the north and low in the south. The surface water system is abnormally developed and distributed in a nearly symmetrical dendritic pattern, which converges from north to south and eventually flows into a karst canyon. In this area, the karst conduit is characterized by wide plane distribution and shows dendritic morphology. It has relatively stable vertical depth and is mainly distributed at 120 ms below T56. Due to the frequent transform of surface water to underground water system, the inner filling of karst conduit is serious, and the filling in the middle and lower reaches of the conduits is more obvious. The significant terrain gradient, synclinal structure between secondary anticlines, and NNE and NNW strike?鄄slip faults jointly control the development of karst conduit, and a synclinal confluence karst conduits development model is established. These results can directly serve the well deployment of Ordovician in B94 well block. 

10.6056/dkyqt202305008