重力勘探及其应用
涂 承 林
区域重力调查方法技术中心
目 录
序言：
第一章 重力勘探的基础理论
一、地球的重力场
二、正常重力场与重力异常 三、岩（矿）石密度
第二章 重力仪
一、概述
二、石英弹簧重力仪 三、金属弹簧重力仪
第三章 重力勘探的工作方法
一、工作设计主要内容和技术要求 二、重力资料的整理 三、重力异常图
第四章 重力异常的数据处理
一、引起异常的主要原因 二、数据处理
三、区域异常和局部异常的划分方法 四、重力异常的解释延拓 五、重力异常的二阶导数
第五章 重力异常的正反演问题
一、基本概念
二、规则形体异常的正反演问题 三、任意形体异常的正反演问题 四、选择法解反演问题
五、密度界面的正反演问题
第六章 重力勘探的应用
一、基础地球物理调查—区域重力调查 （一）概况 （二）成果 （三）应用
二、重力勘探在油气勘查中的应用 三、重力勘探在煤田中的应用
四、重力勘探在其他地质勘探方面的应用 五、我国重力勘探工作概况
序 言 ································································································································· 1 第一章 重力勘探的基础理论 ························································································· 1 一、地球的重力场········································································································ 1 二、正常重力场和重力异常························································································ 3 三、岩石和矿石的密度································································································ 5 第二章 重力仪 ·················································································································· 6 一、概述························································································································ 6 二、石英弹簧重力仪···································································································· 7 三、金属弹簧重力仪···································································································· 7 第三章 重力勘探的工作方法 ························································································· 8 一、工作设计的主要内容和技术要求········································································ 8 二、重力资料的整理·································································································· 10 三、重力异常图·········································································································· 12 第四章 重力异常的数据处理 ······················································································· 13 一、引起异常的主要原因·························································································· 13 二、数据处理·············································································································· 15 三、区域异常和局部异常的划分方法······································································ 16 四、重力异常的解析延拓·························································································· 18 五、重力异常的导数·································································································· 19 第五章 重力异常的地质解释及应用 ·········································································· 19 一、重力异常解释的基本概念·················································································· 20 二、重力异常解释基本方法和步骤·········································································· 20 三、重力勘探的应用·································································································· 21 四、重力勘探在其他地质勘探方面的应用······························································ 22 五、我国重力勘探工作概况······················································································ 23
序 言
重力勘探是地球物理勘探方法之一。是研究地球表面及其周围空间重力变化的物理现象。地表及其周围空间重力变化原因之一是由于地球内部各种岩石密度的不同而引起的，而岩石密度不均匀往往与地下地质构造、矿产分布等地质原因有关。由于某种地质原因或矿产赋存而引起的重力变化称重力异常，这种情况下的重力场称为重力异常场。研究重力异常的变化特征，从而得到地下地质构造、岩石分布和矿产赋存的地球物理信息，就是重力勘探的实质和任务。
重力勘探在研究深部构造、进行地质构造分区，圈定盆地，岩浆岩体（隐伏），勘查石油、天然气，圈定煤系地层分布范围、寻找含水地层等工作中发挥了它应有作用。
第一章 重力勘探的基础理论
一、地球的重力场
1、重力的概念
重力是最常见的地球物理现象之一。当地球表面及其周围空间存在有质量的物体时，就要受到地球质量对他的引力作用，同时还受到地球自转而产生的惯性离心力的作用，这两种力的合力就是物体所受的重力。如下图所示。图中F表示地球的引力，C表示离心
力，P表示重力，则有 P=F+C
地球空间到处存在着重力作用，因此这个空间就存在重力场。显然，它是引力场和离心力场的叠加。
物体所受的重力作用，不仅与物体在重力场中的位置有关，而且与物体的质量大小有关。
当物体受重力作用而自由降落时，将产生重力加速度g，根据牛顿第二定
律，它与作用在质量m的物体上的重力p有如下关系：
p=mg
用m除上式两边，得 p/m=g 1
按照场强定义，单位质量所受的重力就是重力场强度（ p/m ）。可见重力场强度和重力加速度，虽然它的物理概念不同，但其数值和量纲完全相同，而且方向一致。因此，在重利勘探中常用“重力”二字代表重力加速度或重力场强度。在以后的讨论中，对两者不再区别。所谓重力测量，就是测量重力加速度或者重力场强度。
在国际单位制中，重力加速度的单位为米/秒2，以它的十万分之一为通用重力单位即10-5m/s2（毫伽）
1Gal=100mgl=10000μgl=10-2m/s2
2、重力场
地球的重力场包括引力场和离心力场 1）引力场
宇宙中任何物体之间都存在万有引力作用，引力大小是根据牛顿万有引力定律计算的。
由于引力场是一个矢量场，所以采用直角坐标系，这样任何矢量的大小和方向都可用它的三个坐标轴上的投影来表示。坐标系原点位于地球中心，Z轴与地球自转轴重合，X，Y在赤道平面内（下
图）
设dm为地球内部的某一质量
单元，其坐标为（ξ，η，ζ ）
A为地球外部的某一点，其坐标为
（x,y,z）。A点到dm的距离r?(x??)2?(y??)2?(z??)2 则质量单元dm对A点处单
位质量的引力为
F?Gdm r2式中G为万有引力常数，等于6.67×10-11m3/(kg.s2)。 F方向是由A点指向质量元dm。 2）离心力场
地球为一个自旋的天体，设自旋速度矢量为ω，设地表任一点A（x,y,z）到地球自转轴的距离为L，则A点单位质量所受到的离心力为
C=ω2L
2