本文重点研究了直流电阻率测深法在鄂尔多斯盆地沉积相勘探应用中的可行性问 题。目前，对沉积相的探测主要是用到的地球物理方法是测井和地震勘探。测井资料 的获得以钻井为前提，成本高而且效率低。对于鄂尔多斯盆地沉积相勘探，由于其地 域的特殊性，常规的地震勘探方法在这种沟壑纵横、沟梁相间、起伏多变、黄土覆盖 较厚、沉积和岩性相变化比较大的地区，其勘探成本及风险越来越大且难以满足勘探 的需求。故本文就直流电阻率测深法在鄂尔多斯盆地沉积相勘探中可行性进行了研究。 本文在充分了解鄂尔多斯盆地地质情况、沉积环境、沉积相模式的基础上，统计 以往沉积相分析方法所用参数，得出地层电阻率与沉积物颗粒粒径中值、渗透率呈正 相关，与沉积物泥质含量呈反相关的结论；通过对鄂尔多斯盆地测井资料以及地质资 料的统计分析，得到延长组地层纵向电阻率变化范围为 20~45 m；依据测井资料、 地质资料、三角洲前缘沉积相及分流河道沉积相模式建立相应的地球物理模型（电阻 率）。使用直流电阻率法三维有限元数值模拟程序，计算并分析不同部位的视电阻率 测深曲线、断面图及平面图异常特征。研究结果表明：不同沉积相间存在明显的视电 阻率差异，三角洲前缘沉积相及分流河道沉积相其视电阻率偏高，故利用直流电阻率 测深法在鄂尔多斯盆地探测沉积相具有可行性。 通过对鄂尔多斯盆地子北-史家畔工区实测直流电测深资料进行处理、解释，并将 结果与地质资料对比分析，结果表明电测深视电阻率断面图能较好的反应三叠系延长 组地层沉积相纵向展布特征，视电阻率平面图和最大梯度等值线图联合应用能确定分 流河道和河漫滩沉积相的走向及位置，表明直流电阻率测深研究沉积相的展布是有效 可行的。其对于鄂尔多斯盆地沉积相的研究具有一定的意义。 关键词：鄂尔多斯盆地，电阻率测深，沉积相，视电阻率，梯度III Abstract This article focuses on studying the feasibility of using DC resistivity sounding method to explore Ordos basin’s sedimentary facies. At present, the geophysical methods mainly used in detection of sedimentary facies are well logging and seismic exploration. Obtainning logging data is high cost and low efficiency, because drilling is the premise. Due to the particularity of its region, the exploration of Ordos basin’s sedimentary facies which costs and risks of conventional seismic exploration method is big and difficult to meet the needs of exploration on the area which ravines crossbar and beam. Ups and downs and changeful, thick covered by loess and lithological facies change is larger. So this paper studies the feasibility of using DC resistivity sounding method on the exploration of Ordos basin’s sedimentary facies. The paper based on full understanding of geology, sedimentary environments, sedimentary facies model of the Ordos basin, statistics the parameters which are used in sedimentary facies analysis method It is concluded that there was a positive correlation between formation resistivity with diameter median of sediment particles grain, a relevant correlation between formation resistivity with argillaceous sediment content through statistical analysis of the logging data and geological data on Ordos basin, get yanchang formation resistivity variation range is 20~45 m.On the basis of logging data and geological data, establish the corresponding geophysical model (resistivity) on delta front sedimentary facies and distributary channel sedimentary facies. Using DC resistivity method of three-dimensional finite element numerical simulation program, calculation and analysis the different parts of the apparent resistivity sounding curves, profile and the anomaly characteristics of the floor plan. The results show that the apparent resistivity is obvious different between different sedimentary. The apparent resistivity is high on delta front sedimentary facies and distributary channel sedimentary facies. So using DC resistivity sounding method is feasible for the detection of sedimentary facies in ordos basin. Through the processing and interpretation of the banks of the measured dc soundingIV data and analysising of the results and the geologic information, Results show that the electrical sounding apparent resistivity profile can better reaction the formation of the vertical distribution of the formation sedimentary facies of Yanchang group. The joint application of apparent resistivity plan and largest gradient contour map can determine the location of distributary channel and flood land sedimentary facies. Using DC resistivity sounding method is feasible for the study of the distribution of sedimentary facies. It has certain significance for the detection of sedimentary facies in ordos basin. Keywords: Ordos basin, resistivity sounding, sedimentary facies, apparent resistivity, gradientV 目 录 第一章 绪论............................................................................................................................1 1.1 沉积相勘探的发展及现状 ....................................................................................... 1 1.2 课题研究的目的及意义 ........................................................................................... 3 1.3 报告研究思路和主要内容 ....................................................................................... 4 1.3.1 研究思路 ........................................................................................................ 4 1.3.2 研究内容 ........................................................................................................ 4 第二章 鄂尔多斯盆地地质概述............................................................................................6 2.1 地层 ........................................................................................................................... 7 2.2 延长组沉积体系 ....................................................................................................... 9 第三章 鄂尔多斯盆地沉积相地球物理特征........................................................................11 第四章 点源三维电场有限元正演模拟................................................................................16 4.1 点源场的基本方程 ................................................................................................. 16 4.2 点源场的边值问题与变分问题 ............................................................................. 17 4.2.1 边值问题 ...................................................................................................... 17 4.2.2 变分问题 ...................................................................................................... 18 4.3 有限单元法 ............................................................................................................. 19 4.3.1 网格剖分与三线性插值 ................................................................................ 19 4.3.2 单元分析 ........................................................................................................ 21 4.3.3 总体合成与求变分 ........................................................................................ 23 4.4 程序验证 ................................................................................................................. 25 第五章 电阻率法探测沉积相可行性研究..........................................................................27 5.1 模型建立 ................................................................................................................. 27 5.1.1 模型一 ............................................................................................................ 30 5.1.2 模型二 ............................................................................................................ 31 5.2 地表起伏对视电阻率断面的影响 ......................................................................... 32 5.2.1 地表起伏对电场分布的影响 ...................................................................... 32VI 5.2.2 地表起伏情况下，视电阻率断面...............................................................35 5.2.3 地形校正.......................................................................................................35 5.3 模型一正演模拟分析..............................................................................................37 5.3.1 测深曲线分析..........................................