井间电阻率成像方法研究

【作者】 沈平；

【导师】 强建科；

【作者基本信息】 中南大学 ， 地球探测与信息技术， 2010， 硕士

【摘要】 井间电阻率成像技术和地表电阻率成像技术相比,因为井间装置的供电电极位于地表以下,对于有一定深度的异常目标体,其分辨能力将远远大于地表装置的分辨率,这特别适用于当今能源和资源勘探中大深度和高分辨率的勘探要求。井间电阻率成像的目的是确定井间异常体的位置及地层真物性参数,本文提出的井间视电阻率几何成像方法可以较准确地确定异常体在井间的纵向位置。基于非全空间直流电场的原理,采用镜像法推导出有别于半空间和全空间的视电阻率计算公式,求出与所有电位对应的视电阻率值,然后以观测井深为纵坐标,供电井深为横坐标绘制视电阻率等值线图,由此得出井间异常体的影像图。应用三维三线性插值有限单元正演模拟方法,计算并分析了几种典型的地质模型,结果表明,由视电阻率等值线形态能够判断异常体的空间形态和准确位置,但井间低阻体表现为高视电阻率异常,井间高阻体表现为低视电阻率异常。该方法垂向分辨率较高,确定深度较准确,但无法分辨异常体的横向位置。为了进一步确定异常体在井间的横向位置,提出一种井间视电阻率网格化交汇成像方法。对井间区域进行网格化以后,求出每一网格节点上的视电阻率平均值,最后以井深为横坐标,井间距离为纵坐标绘制网格化之后的重组视电阻率等值线图。模型计算结果表明可通过该等值线图大致确定异常体的横向位置。井间电磁成像是井间精细结构研究的重要手段之一。论文最后总结了现有的一些井间电磁成像方法并分析了各自的优缺点,指出今后井间电磁成像技术的研究方向将围绕着仪器的研制、金属套管对成像结果的影响及成像反演方法等一些方面进行。最终将采用多分量井间电磁系统探测井间地层的各项异性特征,以达到精确描述井间精细结构的目的。更多还原

【Abstract】 Compared to resistivity image on the surface, the crosshole resistivity image has a better resolution for the target with a certain depth because its current electrode is located below the surface. This method especially meets with the requirements of deep depth and high resolution of energy and resource exploration at present.The purpose of crosshole resistivity image is to ascertain the location of abnormity body and real parameters of the stratum. The geometry image method of crosshole apparent resistivity is put forward in this thesis, which can accurately ascertain the perpendicular position of abnormity body. Based on the theory of direct-current electric field in non-full space, the apparent resistivity formula that is different from half space and full space was deduced by the image method, and all apparent resistivity was solved out, then the apparent resistivity isopleth map was drawn, in which, observation hole depth is ordinate and power-supply hole depth is abscissa. At last, several typical geologic models were simulated by three-dimensional Finite Element Method. The results show, the space shape and precise position of abnormity body can be judged from apparent resistivity isoline shape, but crosshole low resistivity body reflects high apparent resistivity abnormity and crosshole high resistivity body reflects low apparent resistivity abnormity. This method has high resolution in perpendicular direction, and can accurately ascertain the depth, but the transverse position of abnormity body can’t be recognized.To further ascertain the transverse position of crosshole abnormity body, the gridding image method of crosshole apparent resistivity is put forward. After the crosshole area was divided into grids, the average value of apparent resistivity in each grid nodes was calculated. Then the recomposed apparent resistivity isopleth map after gridding was drawn, in which, well depth is abscissa and crosshole separation is ordinate. Model computing result demonstrated the transverse position of abnormity body can be approximately ascertained by this isopleth map. Crosshole electromagnetism image is one of the important means to study crosshole precision configuration. Some crosshole electromagnetism image methods were summarized at the end of this thesis, and its advantages and disadvantages were analyzed. At last, this thesis pointed out the study orientation of crosshole electromagnetism image will be instrument development, the influence of metal thimble and image method, and finally multi-component crosshole electromagnetism system will be adopted to detect the anisotropism characteristic of crosshole stratum, in order to describe crosshole precision configuration accurately.更多还原