柴达木盆地东部石炭系页岩三维裂缝网络模型研究  

Study on three-dimensional fracture network models of Carboniferous shale in Eastern Qaidam Basin

作　　者：张成[1] 夏露[1] 李英杰[1] 于青春[1] 

机构地区：[1]中国地质大学(北京)水资源与环境学院,北京100083

出　　处：《地学前缘》2016年第5期184-192,共9页Earth Science Frontiers

基　　金：国家自然科学基金项目(41272387);中央高校基本科研业务费专项资金项目(2652015001;2652015237);中国地质调查局地质调查项目(12120113040000-3;1212011120964)

摘　　要：裂缝既是页岩气的聚集空间,同时也是页岩气的运移通道,对页岩气成藏起着重要控制作用。裂缝的产状、密度、组合特征等很大程度上决定了页岩气是否具有开发价值。该研究对柴达木盆地东部的13个露头的岩石裂缝进行了野外观测统计,实测裂缝1 000多条,选取了三个具有代表性的页岩露头进行统计分析建模。通过野外观测和室内统计分析发现,工作区页岩裂缝发育有三组(某些地段一组不发育),各组裂缝的方向满足Fisher分布,迹线长度满足对数正态分布。确定了各组裂缝方向、长度的均值和方差,以及各组裂缝的密度,建立了三维裂缝网络模型,绘出了模拟的三维裂缝网络图。裂缝三维模型为圆盘模型,即假设单个裂缝三维空间上具有圆盘形状。建模过程采用了逆建模方法,其基本原则是通过拟合实测的二维露头观测数据,优化裂缝三维大小和密度参数,使模型能够准确再现野外所观测到的实际现象,包括露头面上不同裂缝的数量、密度和长度。该研究对柴达木盆地东部石炭系页岩裂缝描述达到了定量化,为研究页岩中油气运移提供了很好的基础数据。Fractures provide both the gathering space and migration pathways for shale gas. They play a significant role in controlling shale gas reservoir. The occurrence, density and combination characteristics of fractures play a decisive role in determining whether the region has exploitation value for shale gas. More than one thousand fractures from thirteen outcrops in six areas of Eastern Qaidam Basin were observed in this study. Detailed statistical analyses of the fractures from three typical shale outcrops were carried out, and the corresponding discrete fracture networks were built. Three groups of fractures were determined in this area through statistical analyses and field observations （one group did not appear in part of the area）. The mean and standard deviation of the orientation, length and density of each fracture group were determined, and the three dimensional fracture network models were constructed. The disk model was used in this study, which assumes that each fracture has a single disk shape in three-dimensional space. An inverse modeling method was used in the modeling process. The basic principle was based on fitting the observed data of the outcrops to optimize the size and density of the fractures in the three-dimensional parameters of the model in order to accurately reproduce the observed actual field data, including the number, density and length of the fractures. The study presented in this paper quantitatively measured the fractures in the shale of Eastern Qaidam Basin and provides essential data for studying the migration of oil and gas in shale.

关 键 词：柴达木盆地东部 石炭系页岩 裂缝模型 

分 类 号：P618.130.2[天文地球—矿床学] P534.45[天文地球—地质学]