摘要
与其他岩类不同,黄土岩遇水后有明显的湿陷特征,进而引发宏观的地质灾害现象,而这些现象的产生与黄土内部矿物、孔隙分布以及渗透率各向异性关系密切。因此,进一步深入研究黄土岩内部结构,对分析黄土湿陷性特征产生的原因具有重要的科学意义,并可为除黄土岩性外其他岩性提供一种探究矿物、孔隙、渗透率之间关系的研究思路。基于此,选取A地区黄土样品,采用微米CT(computed tomography)图像,综合分析黄土中矿物成分、矿物形状,模拟了黄土岩孔隙网络分布,并基于Navier-Stokes方程及达西渗流公式描述流体运动形式,分别确定了12个孔隙体绝对渗透率大小,对不同方向的渗透率大小进行分析。结果表明:①黄土岩中石英、长石、重矿物、云母等不同矿物之间形状差别大,矿物长轴长度与其磨圆度、体积组分之间有较好的对应关系;②各类矿物分布规律性不强,黄土岩中孔隙分布分散,孔隙喉道之间连接方式变化大,孔隙空间分布非均质性强。③相对石英、长石以及重矿物,云母由于其形状特性,极大的影响黄土岩中孔隙的形成及后期赋存,也间接对其渗透率各向异性的产生起着至关重要的作用。
Different from other rock types,loess rock has obvious characteristics of collapsibility after encountering water,which in turn triggers macroscopic geological disasters.The occurrence of these phenomena is closely related to the internal minerals,pore distribution and permeability anisotropy of the loess.Therefore,further study the internal structure of loess rock has important scientific significance for analyzing the causes of collapsibility characteristics of loess,and can provide a way to explore the research ideas of the relationship between mineral shape and porosity and permeability in addition to loess lithology.For these reasons,loessite samples of A region were selected to analyze the components and shape of mineral by using micro-CT(computed tomography)images,the pore network distribution of loess rocks was simulated,and the fluid motion form was described based on Navier-Stokes equation and Darcy seepage flow formula.Twelve pore subvolumes(360μm×360μm×360μm)what were extracted from the segmented pores were used to analyze penetrating quality in different orientation.The results prove that the shapes of different minerals such as quartz and feldspar,heavy minerals and mica in loessite vary greatly,there is a good correspondence between long axis and psephicity,volume components.The distribution regularity of all kinds of minerals is not strong in loess rocks,the pore distribution is very scattered,the connection mode between pore and throat varies greatly,and the pore space distribution is highly heterogeneous.Compared with quartz,feldspar and heavy minerals,mica,due to its shape characteristics,greatly affects the formation and later occurrence of pores in loess rocks,and indirectly plays a crucial role in the generation of anisotropy of permeability.
作者
王超
吴丰
陈义国
李广涛
吴凤
WANG Chao;WU Feng;CHEN Yi-guo;LI Guang-tao;WU Feng(Research Institute Shaanxi Yanchang Petroleum(Group) Co., Ltd., Xi’an 710075, China;School of Geosciences and Technology, Southwest Petroleum University, Chengdu 610500, China)
出处
《科学技术与工程》
北大核心
2021年第27期11527-11535,共9页
Science Technology and Engineering
基金
油气藏地质及开发工程国家重点实验室(西南石油大学)开放基金(PLN201719)。
关键词
微米CT
矿物成分
孔隙赋存
云母颗粒
各向异性
micro-CT images
mineral composition
pore occurrence
mica grains
anisotropy
