塔里木盆地塔河油田逆冲背斜区奥陶系古暗河系统发育特征

Development characteristics of Ordovician ancient subterranean river system in thrust anticline area of Tahe Oilfield, Tarim Basin

张长建 蒋林 文欢 吕晶 昌琪

ZHANG Changjian JIANG Lin WEN Huan LÜ Jing CHANG Qi

1. 中国石化 西北油田分公司 勘探开发研究院, 乌鲁木齐 830011; 2. 中国石化缝洞型油藏提高采收率重点实验室, 乌鲁木齐 830011

1. Exploration & Production Research Institute of Northwest Oilfield Company, SINOPEC, Urumqi, Xinjiang 830011, China; 2. SINOPEC Key Laboratory for EOR of Fractured Cavity Reservoirs, Urumqi, Xinjiang 830011, China

塔里木盆地塔河油田古暗河系统研究尚处于初始阶段，主要从暗河的深浅分布、结构样式等特征开展暗河洞穴的划分，较少从构造、断裂、古地貌、地下水位等地质方面综合分析复杂暗河系统的空间发育规律，致使暗河的主次从属关系、空间叠置样式、原始连通关系难以厘清，从而制约了塔河油田开发后期的综合治理研究。为了明确塔河油田主体区逆冲背斜区奥陶系古暗河系统发育特征，利用构造断裂解析、古地貌恢复、地震属性刻画、纵断剖面解读等方法进行了S67井区古暗河的类型识别、系统划分和地质成因研究，尤其首次识别并剖析了潜流回流暗河。结果表明，S67井区处于塔河主体区岩溶台原南缘的低地势区，发育幅差较小的峰丛洼地、溶丘洼地，地表水系下切深度较浅；逆冲背斜为低角度逆冲推覆构造样式，逆冲背斜之上的网格状断裂为多层状暗河系统提供有利溶蚀通道。研究区奥陶系发育相对独立的、树枝状结构的地下水位暗河系统和潜流带暗河系统，地下水位型暗河可分为主干型、支流型和废弃型，潜流回流暗河可分为上升型、对称型。控制逆冲背斜区古暗河发育的主要因素有古地貌、地下水位、逆冲背斜构造和次级断裂网络等。

The study of the ancient subterranean river system in the Tahe Oilfield in the Tarim Basin is still in its initial stage. Subterranean river caves are mainly classified based on the characteristics of the depth distribution and structural patterns of the subterranean rivers. However, there is a lack of comprehensive analysis regarding the spatial development patterns of complex subterranean river systems from geological perspectives such as structure, fault, paleogeomorphology, and water table. This hinders the understanding of primary and secondary relationships of subterranean rivers, spatial superposition patterns, and original connectivity relationships, thereby impeding comprehensive management research in the later stages of Tahe Oilfield development. To address this gap, an investigation was carried out in the S67 well block to clarify the developmental characteristics of the Ordovician ancient subterranean river system in the thrust anticline area of the main Tahe Oilfield. The study utilized methods like structural fault analysis, paleogeomorphology restoration, seismic attribute characterization, and vertical section interpretation to identify river types, classify systems, and examine geological origins. Noteworthy findings include the identification and analysis of a phreatic loop river for the first time. Results show that the S67 well block is located in a low-lying region at the southern edge of the karst platform within the main Tahe Oilfield area. This region features peak cluster depressions and karst hill depressions with minimal amplitude differences and shallow incision depths of surface water systems. The low-angle thrust structural style of the thrust anticline, combined with a network of faults, provides favorable dissolution channels for the multi-layered subterranean river system. In the study area, the Ordovician period is characterized by the emergence of distinct water-table subterranean river systems and phreatic loop river systems, all of which display a dendritic structure. The water-table subterranean rivers are divided into main, branch, and abandoned types, while the phreatic loop rivers are classified as ascending or symmetrical. The formation of ancient subterranean rivers in the thrust anticline area is primarily influenced by factors such as paleogeomorphology, water table levels, thrust anticline structure, and secondary fault networks.

中国石化重大科技项目(P20042-1)资助。

https://doi.org/10.11781/sysydz202402333