鄂尔多斯盆地上三叠统延长组7段埋藏期热液活动对页岩油储层的影响

The influence of hydrothermal activities on shale oil reservoirs during the burial period of the Upper Triassic Chang 7 Member， Ordos Basin

王梓毅 付金华 刘显阳 李士祥 张昌虎 梁新平 董琳

Ziyi WANG Jinhua FU Xianyang LIU Shixiang LI Changhu ZHANG Xinping LIANG Lin DONG

目前针对鄂尔多斯盆地上三叠统延长组7段（长7段）热液作用的研究较多，主要聚焦于长7期的热水沉积作用。长7段在埋藏期也可能受到热液作用的影响，但相关的研究极为有限。为揭示长7段埋藏期热液活动的期次、时代及其对页岩油储层的影响，利用光学/电子显微镜观测、电子探针分析、显微激光拉曼光谱分析及包裹体均一温度测试等手段，对长7段热液黄铁矿以及固相和流体包裹体开展研究。结果表明，长7段发育多种类型的黄铁矿，其中脉状或团块状、透镜状、他形-半自形晶散布状和半自形-自形晶斑块状黄铁矿的Co/Ni元素含量比值均大于1，指示其为热液成因。根据显微观测结果及区域构造史和埋藏史-热演化史模拟，推断长7段埋藏期至少存在两期热液活动，其中一期发生于早白垩世。与黄铁矿包裹体伴生的盐水包裹体均一温度表明，注入瑶页1井区长7段的热液温度最高可达270.5 ℃以上；基于Easy%动力学模型的计算结果表明，热液注入后地层经历了较快的降温过程，这可能是页岩有机质热演化程度较低（ = 0.70 %）的重要原因之一。

The hydrothermal activity of the Upper Triassic Chang 7 shale in the Ordos Basin has been extensively studied in previous studies， with a focus on hydrothermal sedimentation during the depositional period of Chang 7 Member. However， there is limited research on the impact of hydrothermal activities during the corresponding burial stage. This study aims to investigate the stages and ages of hydrothermal activities and their impact on shale oil reservoirs during the burial stage of the Chang 7 shale. An integration of multiple techniques， including optical/electronic microscopy， electronic probe， micro-laser Raman spectrum and inclusion homogenization temperature analysis is applied to study the hydrothermal pyrite and solid phases and fluid inclusions in the Chang 7 Member. The results reveal that there contains many types of pyrite with Co/Ni greater than 1 exhibiting a variety of morphologies， including veins， lumps， lenticular shape as well as xenomorphic-hypidiomorphic scattered and hypidiomorphic-euhedral massive forms， indicating hydrothermal origin. Based on the analyses of microscopic observation， regional tectonic history， as well as the simulation of burial-thermal evolution history， it is inferred that there were at least two phases of hydrothermal activities during the burial period of the Chang 7 Member， with one of them occurring in the Early Cretaceous. The maximum temperature of the hydrothermal fluid injected into the Chang 7 shale in well Yy1 may reach up to 270.5 ℃ based on the homogenization temperatures of aqueous inclusions associated with pyrite inclusions. The calculation based on the Easy% kinetic model indicates that the Chang 7 shale underwent a rapid cooling process after hydrothermal injection， which may be one of the important reasons for the lower-degree thermal evolution of shale organic matter （ = 0.70 %）.

10.11743/ogg20230408