韩同城1,2,,,
符力耘1,2
1. 中国石油大学(华东)地球科学与技术学院, 山东 青岛 266580
2. 青岛海洋科学与技术试点国家实验室海洋矿产资源评价与探测技术功能实验室, 山东 青岛 266071
基金项目: 国家自然科学基金（41821002，41874151），中央高校基本科研业务费（18CX05008A）资助
详细信息
作者简介: 包宏帅, 男, 1997年生, 硕士在读, 主要从事岩石物理电学性质研究.E-mail: 2059349384@qq.com
通讯作者: 韩同城, 男, 1982年生, 教授, 博士生导师, 主要从事岩石物理学、岩石声电联合性质、岩石和沉积物的物理性质研究.E-mail: hantc@upc.edu.cn
中图分类号: P631收稿日期:2020-11-11
修回日期:2021-01-11
上线日期:2021-05-10
Calculation method of digital rock electrical conductivity based on two-dimensional images
BAO HongShuai1,,HAN TongCheng1,2,,,
FU LiYun1,2
1. School of Geosciences, China University of Petroleum(East China), Qingdao Shandong 266580, China
2. Laboratory for Marine Mineral Resources, Pilot National Laboratory for Marine Science and Technology, Qingdao Shandong 266071, China
More Information
Corresponding author: HAN TongCheng,E-mail:hantc@upc.edu.cn
MSC: P631--> Received Date: 11 November 2020
Revised Date: 11 January 2021
Available Online: 10 May 2021
摘要
摘要:电导率是表征岩石电学性质的重要物理参数，在地质资源勘查和测井解释等领域发挥着巨大作用.快速、准确地确定岩石电导率具有重要的理论和实践意义.作为近年来发展的一种岩石物理数值模拟工具，数字岩心技术在定量计算电导率等物性参数方面应用广泛.三维微观结构的准确获取是数字岩心技术计算岩石电导率的关键，但传统获取岩石三维微观结构的方法较为复杂费时.为了方便快速地通过数字岩心技术计算岩石的电导率，本文研究了岩石二维与三维数字岩心的电导率联系.我们基于微米级X射线CT扫描得到的三个砂岩样品的微观结构信息建立了三维数字岩心，并通过有限元法计算的三维数字岩心电导率与实验数据的对比验证数值计算方法的有效性.随后我们数字地扩展了岩石的孔隙，产生了较大孔隙度的三维数字岩心样本，在此基础上，计算了三维数字岩心和相应二维数字岩心的电导率，并通过Archie公式分别拟合了电导率与孔隙度之间的关系，得到了相应的胶结系数.结果表明，三维数字岩心的胶结系数小于二维数字岩心的胶结系数，且二者的比值与岩石实测孔隙度呈线性负相关关系.以该联系为纽带，通过二维图像快速计算得到的电导率与孔隙度关系，确定了三维数字岩心的电导率与孔隙度关系，并进一步通过三维数字岩心的孔隙度计算其电导率.该方法计算得到的人工砂岩样品的电导率与其三维数字岩心电导率相关系数高于96%，验证了基于二维图像的数字岩心电导率计算方法的有效性.本文的研究结果为快速、准确地计算岩石电导率提供了新的思路，在油气勘探开发中有广阔的应用前景.
关键词: 数字岩心/
电导率/
有限元/
二维图像
Abstract:Electrical conductivity is an important geophysical parameter to characterize the electrical rock properties, which play a significant role in geological resource exploration and logging interpretation. It is of great theoretical and practical importance to determine the electrical conductivity of rocks quickly and accurately. Digital rock physics technique is a kind of numerical simulation tool of rock physics developed in recent years that has been widely applied in quantitative calculation of rock conductivity and other geophysical parameters. The accurate acquisition of three-dimensional (3D) microstructure of rock is the key to the calculation of the electrical conductivity by digital rock physics technique. However, it is complicated and time-consuming to obtain the 3D microstructure by traditional methods. In order to calculate the electrical conductivity of rock conveniently and quickly by digital rock physics technique, the conductivity relationship between two-dimensional (2D) digital rock samples and 3D digital rocks is studied in this paper. Based on the 3D microstructure of 3 sandstones obtained by micro X-ray computer tomography, we have established the original digital rocks. The validity of the numerical calculation method is verified by comparing the electrical conductivity calculated by finite element method with the experimental data. New 3D digital rock samples with larger porosity are generated by expanding the pores of rocks digitally. On this basis, the electrical conductivity of the 3D digital rock samples and the corresponding 2D digital rocks are calculated by using finite element method, and we further characterize the relationship between rock electrical conductivity and porosity by Archie equation, and the corresponding cementation coefficients are obtained. The results show that the cementation coefficient of 3D digital rocks is smaller than that of 2D digital rocks, and the ratio of them has a negative linear correlation with the measured rock porosity. Taking the connection between 2D and 3D cementation coefficient as a link, the relationship between the conductivity and porosity of 3D digital rocks can be determined through the relationship between conductivity and porosity obtained from fast calculation of 2D images, and the conductivity of 3D digital rocks can then be calculated. The electrical conductivity of a synthetic sandstone shows great correlation (correlation coefficient better than 96%) with that calculated from 3D images using finite element method, which verifies the validity of the proposed calculation method of digital rock electrical conductivity based on 2D images. The results provide a new idea for determining rock electrical conductivity and have broad application prospects in oil and gas exploration and development.
Key words:Digital rock/
Electrical conductivity/
Finite element method/
2D images
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