【作者】 冯杰；

【导师】 刘天佑；

【作者基本信息】 中国地质大学 ， 地球探测与信息技术， 2010， 博士

【摘要】 随着国家现代化建设和国民经济的发展,矿产资源消耗迅速,我国多数矿山的浅部资源已被开采殆尽,找矿目标转向矿山的外围和深部。因此,近年来,深部找矿成了我国地质勘探的热点。由于老矿山多年开采,地面磁测受浅部及地表干扰十分严重,再加上深部矿体引起的地面磁异常较弱,难以识别。如果用单一地面磁测资料进行反演解释,结果往往不尽人意。井中磁测是一种有效的找矿方法,它能够避开地面及浅部磁性体的干扰,在钻孔中实现全方位测量,有很高的纵向分辨率和精度。如果单独用井中资料反演,可以根据各分量的矢量线簇发散情况来确定矿头和矿尾的大概位置,但是对于空间形态和准确位置的确定仍然有一定困难,而且井中磁测受钻井的限制,它所控制的范围非常有限,因此单一井中资料的反演解释难以满足实际需要。为了更好地寻找深部矿体,我们必须找到一种更为有效的方法,能够将地面磁测和井中磁测资料结合起来,准确反演定位地下矿体的空间位置和形态。本文针对上述深部找矿过程中存在的问题开展了井地磁测联合反演研究工作,主要包含以下几点：1、本文实现了三维空间的井地联合磁化率成像反演。介绍了地下三维空间模型单元划分的方法和原则,将下半空间划分为诸多小的长方体,每个长方体的磁化率为常数,但磁化率大小可以不同。在成像反演过程中,采用Occam’s反演方法,利用了预优共轭梯度算法求解磁化率成像大规模线性方程组。给出了单一倾斜板状体和组合倾斜板状体两个模型实例,分别进行了3D地面磁化率成像反演、3D井中三分量磁化率成像反演和3D井地联合磁化率成像反演,并将反演结果进行对比和分析。通过对比发现,单一地面磁化率成像反演中,可以从横向上区分开两块倾向相反的板状体,具有较高的分辨率,但在纵向上却反演出两个大小相同的板状体,且位置和形态与理论模型不符。井中磁测资料的单一成像反演,在纵向上大致可以区分开两个大小不同的板状体,但横向上却十分模糊,无法区分开两个板的水平位置。3D井地磁测联合成像反演后,反演结果在横向和纵向上都具有非常清晰的边界,很容易识别出两个大小不同、倾向相反的板状体。通过模型实例,证明了3D井地磁测资料的联合成像反演,可以充分发挥地面磁测资料横向分辨率高和井中磁测资料纵向分辨率高的优点,反演结果更加清晰,符合实际情况。2、以BG理论为基础,从理论上讨论了进行3D井地磁测联合反演的必要性,说明了平均函数A(ξ-ξ0)的形态取决于核函数的性质,也就是说取决于地球物理问题的本质。核函数的性质不同,它随深度的衰减特性也不同,必然会影响平均函数的属性。在浅部衰减殆尽的核函数,主要决定平均函数的浅部性质；反之,衰减缓慢的核函数主要影响平均函数的深部特性。对于地面磁测资料而言,对浅部的分辨力较高,对深部的分辨力低；对于井中磁测资料而言,在井附近分辨力高,在周围远的地方分辨力低。因此从理论上来说,3D井地磁测联合反演的分辨力要比单一资料反演的分辨力高。并以一个球体模型的实例来说明,证实了井地磁测资料的联合反演要优于地面或井中磁测资料的单一反演。3、本文详细阐述了3D井地联合人机交互反演的基本原理和实现步骤,介绍了3D空间地面和井中磁异常的正演计算公式,讨论了在积分间距相等和不等情况下,如何用三维数值积分来求取正演异常,如何利用三维可视化技术建立3D地质模型和相邻剖面之间的连接成图方案等,并将3D井地联合人机交互反演应用于国家危机矿山深部找矿中。本文以湖北大冶铁矿尖林山-象鼻山矿段为例,通过详细整理矿区的岩石物性资料、已有地质和钻孔资料,对前人的工作成果进行了分析和比较,然后对尖林山-象鼻山矿段的6条测线(17线、18线、19-0线、19-1线、21线和22线)和3个钻孔(ZK18-12、ZK19-1-15和ZK22-16)做了3D井地联合人机交互反演,并得出该矿区内铁矿赋存位置在标高上具有明显的“台阶”特征的重要结论。最后,本文给出了两个实例,论证了3D井地联合人机交互反演要优于单一资料的反演,它不但减少了反演的多解性,而且改变了2.5D反演中地质体形态沿y方向无法改变的问题,更加符合实际情况,是一种深部找矿非常有效的理论和方法。更多还原

【Abstract】 With the country’s modernization construction and national economic development, consumption of mineral resources increased rapidly, and the majority of our resources in shallow mines have been mined and exhausted, exploration targets have turned to the external and deep mines. Thus, in recent years, deep exploration become our geological hot spot.Years of exploitation of the old mines, the ground magnetic survey of the shallow and surface disturbance is very serious, coupled with magnetic response of deep ore bodies on the ground are weak, hard to be identified. Inversion results are often unsatisfactory by single ground-magnetic survey data inversion interpretation.Borehole magnetic measurement is an effective method of magnetite ore, and it can avoid ground and shallow magnetic body interference, achieve all-round measurement in borehole, high vertical resolution and accuracy. If borehole magnetic data is used to inverse alone, according to the various components of the vector line maps to determine the head and tail of the mine, but not avail to determinate spatial patterns and the exact location. And the magnetic measurement is restricted by drilling, the scope of its control is very limited, so a single inversion of borehole data interpretation is sometimes difficult to meet the actual needs.In order to search for deep deposits better, we must find a more effective way to combine the ground and well magnetic measurement data, so as to inverse the spatial location and forms of the underground ore accurately. This paper mainly carried out the following research work for the deep prospecting problems:1. The ground-borehole joint magnetic susceptibility imaging inversion was carried out in this article. The principle and rule for dividing the underground 3D spatial model were introduced, which divide the semi-space underground into many little cuboids, each magnetic susceptibility value of which was a constant, but could be different. In the process of imaging, use the Occam’s inversion method and the pre-optimum conjugate gradient algorithm to solve the large scale linear equation group. The practical examples of single inclined plate and combined plates models were presented, performed 3D ground magnetic susceptibility imaging inversion,3D borehole 3 components magnetic susceptibility imaging inversion and 3D ground-borehole joint magnetic susceptibility imaging inversion separately, through compared and analyzed the results, we found that we could distinguish two plates with different inclines from the horizontal direction by the single ground magnetic susceptibility imaging inversion, which was with higher resolution, while the results of two similar plates from the vertical direction were different from the theoretical models. The plates could be approximately distinguished from the vertical direction by the single borehole magnetic susceptibility imaging inversion, but it was very fuzzy in the horizontal direction, and couldn’t separate the horizontal positions. It was very clear and easy to distinguish two plates with different sizes and opposite inclines both in the horizontal and vertical directions with the ground-borehole joint magnetic susceptibility imaging inversion. Through the model test, we proved 3D ground-borehole joint magnetic susceptibility imaging inversion could utilize advantages of the high horizontal resolution of ground magnetic susceptibility imaging inversion and high vertical resolution of borehole magnetic susceptibility imaging inversion, and it was more clear, which was more coincident with the practical situation.2. Based on BG theory, the necessary of 3D surface and borehole magnetic joint inversion is discussed theoretically. Form of average function depends on the character of the kernel function, which is the essence of geophysical problem. Kernel functions are different in nature, its attenuation with depth is different, and will affect the character of the average function. Kernel functions which depleted in the shallow, decides the shallow nature of the average function; the other hand, the slow decay of the kernel function mainly affects the deep features of the average function. For surface magnetic measurement data, the shallow resolution is high, and the deep resolution is low; well for the borehole magnetic measurement data, the resolution near the borehole is high and low far from the borehole. Therefore, in theory, resolution of 3D surface and borehole joint inversion is much better than a single data inversion. An example of sphere model is given to prove that surface and borehole joint inversion is superior to the single surface, or borehole inversion.3. The basic principle and performed steps of 3D ground-borehole joint human-computer interactive inversion was described, the forward formula of 3D spatial ground-borehole magnetic anomaly was introduced and how to compute the forward anomaly and build 3D geological model as well as the linked precept between adjacent profiles when with the same or different integral offsets were discussed, and 3D ground-borehole joint human-computer interactive inversion for the deep prospecting of the national crisis ore mine was applied in this article.In this paper, Jianlin hill-Elphant trunk hill mining block in Daye, Hubei province was shown as an example, by sorting out the petrophysics data as well as the known geological and borehole data, we analyzed and compared the predecessors’achievements, then did 3D ground-borehole joint human-computer interactive inversion for the 6 profiles(line 17,18,19-0,21,22) and 3 borehole(ZK18-12,ZK19-1-15,Zk22-16) here, as a result, we concluded it was with obvious "step" characteristics of the iron mine in the elevation hosting position. Finally, we present 2 practical examples and proved that 3D ground-borehole joint human-computer interactive inversion was prior to single data inversion, which not only reduced the multi-plicity of the solutions, but also improved the difficulty problem in 2.5D inversion for changing geological body’s form along y direction, and it was more coincident with the practical situation, so it is a very effective theory and method for deep prospecting.更多还原