鄂尔多斯盆地旬宜地区下古生界走滑断裂特征与油气勘探意义

Characteristics of Lower Paleozoic strike-slip faults and their significance for oil and gas exploration in Xunyi-Yijun area, Ordos Basin

王启超 刘光祥 吴疆 岳欣欣 孙自明 张军涛 高晓鹏 刘玲 鲁锴 张仲培

WANG Qichao LIU Guangxiang WU Jiang YUE Xinxin SUN Ziming ZHANG Juntao GAO Xiaopeng LIU Ling LU Kai ZHANG Zhongpei

1. 中国石化 石油勘探开发研究院, 北京 102206; 2. 中国石化 深部地质与资源重点实验室, 北京 102206; 3. 中国石化 河南油田分公司, 河南 南阳 473400

1. SINOPEC Petroleum Exploration and Production Research Institute, Beijing 102206, China; 2. Key Laboratory of Deep Geology and Resources, SINOPEC, Beijing 102206, China; 3. Henan Oilfield Company, SINOPEC, Nanyang, Henan 473400, China

近年来随着勘探和认识程度的加深，鄂尔多斯盆地不再被认为是“铁板”一块，盆地内多期多套断裂系统对油气成藏的控制作用越来越受重视。选取盆地南部旬邑—宜君(旬宜)地区，基于最新三维地震资料与钻井资料，应用走滑断裂理论模型，开展了断裂几何学与运动学分析，预测了断裂形成机制，并探讨了其对深层碳酸盐岩成储、成藏的控制作用。旬宜地区发育3套断裂系统，且存在深、浅层脱耦现象，下古生界走滑断裂在剖面上呈高陡直立、倾向摆动、“花”状构造等典型特征，平面上表现为“北西部挤压剪切、中部拉张剪切、主干断裂分段变形”。下古生界走滑断裂经历了两期构造活动，其中晚奥陶世至志留纪活动强度较大，为断层主要发育期，中—晚二叠世活动强度较弱，断层呈继承性走滑，形成北东、北西走向两组左行走滑断裂。鄂尔多斯盆地南部可能存在北东和北西向的基底薄弱带，加里东期Ⅱ幕洋盆俯冲闭合向盆内传递应力，斜向挤压导致旬宜地区基底断裂活化，是下古生界走滑断裂系统形成的主要动力机制。下古生界走滑断裂可有效改善深层碳酸盐岩储层物性，形成岩溶型或构造裂缝型优质储层，沿走滑断裂带形成“上生下储—旁生侧储”型成藏组合，是旬宜地区深层油气勘探值得关注的重点领域。

In recent years, the Ordos Basin has undergone a reevaluation, transitioning from a perception of a single block to a focus on understanding the influence of multiple stages and fault systems on hydrocarbon accumulation. This study utilizes the latest 3D seismic and drilling data alongside a theoretical model of strike-slip fault to analyze fault geometry and kinematics in the Xunyi-Yijun area of the basin’s southern region. The mechanisms of fault formation are predicted and the related impacts on the formation and accumulation of deep carbonate rocks are also discussed. The results indicate the presence of three fault systems in the Xunyi-Yijun area, with decoupling between deep and shallow layers. The Lower Paleozoic strike-slip faults exhibit distinct characteristics, including high vertical structure, dip swing, and a “flower-shaped” structure in the section. The faults display “compression shear in the northwest, tension shear in the center, and segmental deformation on trunk fractures” on their planes.Moreover, the Lower Paleozoic strike-slip faults experienced two stages of tectonic activities with greater intensity observed from the Late Ordovician to the Silurian, marking the primary period of fault development. The activity intensity during the Middle to Late Permian was relatively weaker, with faults exhibiting inherited strike-slip characteristics. These faults formed two groups, one with a NE strike and the other with a NW strike. Additionally, during the second stage of the Caledonian period, ocean subduction and closure lead to stress being transferred to the basin interior. It is believed that the NE and NW strike basement weak zones existed in the southern Ordos Basin. As a result, the Lower Paleozoic strike-slip fault system likely formed due to the activation of oblique compression. This fault system has the potential to enhance the physical properties of deep carbonate reservoirs and create high-quality karst or tectonic fracture reservoirs in the Xunyi-Yijun area. Moreover, The formation of the “upper source and lower reservoir-lateral source and lateral reservoir” combination along the strike-slip fault belt is an area of interest for deep oil and gas exploration in the Xunyi-Yijun region.

国家自然科学基金企业创新发展联合基金项目(U19B6003)和中国石化科技部项目(P21088-1)联合资助。

https://doi.org/10.11781/sysydz202402342