Investigation of a shallow alluvial aquifer using geoelectrical methods: a case from Turkey

Near-surface geophysical methods are commonly used to solve a wide class of geological, engineering and environmental problems. In this study, a geoelectrical survey was performed to investigate an alluvial aquifer. The study area is located in the southwest of the Çubukluda? graben, situated in the south of ?zmir, Turkey. The geophysical studies included the electrical resistivity imaging and self-potential (SP) methods. The resistivity data were acquired along eight profiles in the northern part of the study area by a Wenner-Schlumberger electrode configuration and the data processing was achieved by a tomographic inversion technique. The SP data were collected by gradient technique along 16 profiles. Total field values were calculated for each profile by addition of the successive gradient values, then a total field SP map was obtained. The water-saturated zone in the northern part of the study area was clearly revealed by the electrical resistivity imaging and the SP survey yielded useful information on the subsurface fluid movement.     

Evaluation of landfill disposal boundary by means of electrical resistivity imaging

This paper deals with an employment of electrical resistivity imaging (ERI) for survey of leachate content on the waste disposal site in Northern Israel. The research consisted of conducting ten ERI lines and drilling investigation wells. Data simulation used a 2D EarthImager inversion program. Analysis of 2D ERI interpretation results shows that determination of the boundary between the landfill body bottom intensively saturated with leachates and underlying layers of highly water saturated fat nonconsolidated clays presents a challenge. However, statistical analysis of ERI data indicates that standard deviation and confidence interval of a set of resistivity data measured in the landfill body are significantly larger than those in underlying clays. Moreover, maximum changes of these parameters are found on the boundary between landfill body and underlying soil, thus reflecting natural differences in scattering of resistivity data measured in these two objects.     

Combined analysis of electrical resistivity and geotechnical SPT blow counts for the safety assessment of fill dam

Electrical resistivity survey and the geotechnical SPT blow counts (N value) method were simultaneously analyzed to investigate the stability of a center-core type earth-fill dam against the seepage phenomenon. The coupling of these heterogeneous field methods provided a chance to understand the status of underground material by comparing the geophysical and geotechnical view. The analysis shows that the zones with low resistivity value generally have low N value, which means low stiffness. However, some zones with a high resistivity pattern are not accompanied by an increase of its N value, and are even showing a lower N value. These results imply that one should be careful to directly correlate resistivity value with the real status of the core material of a fill dam. And a highly resistive zone may be in poor status due to the effect of increase of resistivity value as a result of the piping condition. Additional laboratory tests show that there is a deficiency of fine soil particles believed as the clay at the troubled region, which means an increase in resistivity value. Therefore, multiple explorations should be planned to reduce the uncertainty in application of geophysical methods to dam safety evaluation in order to compensate the resistivity information of core material.     

油气电法勘探综述

在直接找油气的物探方法中，电法作为一类重要的非地震地球物理方法，越来越受到人们的重视与关注。本文对其中几种主要的方法，如激发极化法、电场差分法和自然电场法等，从原理、发展概况和应用效果方面进行了简要论述。另外，对用来解决地质构造问题的非直接找油气的建场测探法、大地电磁法和可控源音频大地电磁法等，本文也作了扼要介绍。     

Multiscale segmentation of well logs

Examination of well logs leads to the observation that they exhibit characteristic behavior over a wide range of scales, differing from a foot to hundreds of feet. This behavior is not accounted for in conventional segmentation methods. The segmentation method that is proposed here aims to solve this problem. It is based on a multiscale representation of the well log. This is a representation of the well log at different levels of smoothness. The behavior of edges, which are associated with extrema of the first derivative, across scales is of great importance in the segmentation. Analysis of this behavior leads to a multiscale segmentation of the well log, in which a fine-scale segment is a part of one coarse scale segment only. In this way the geologist is able to analyze the log at different scales simultaneously. An extension of this approach is not to preserve all fine-scale information but to zoom in only on parts of the log where it is considered to be of interest.     

湖北襄樊—福建罗源的大地电磁测量与地壳上地幔电性特征研究

湖北襄樊—福建罗源一千多公里的剖面上作了23个大地电磁测深点。该剖面穿过不同的地质构造单元。 大地电磁测深的结果清楚地反映了剖面内地壳和上地幔的电性结构特征。例如构造单元的形态、边界、断层位置、地壳和上地幔的高导层发育情况等。结果对于了解该区的深部构造背景、探讨深浅构造之间的关系提供了有益信息     

测井技术在泰安姚庄油页岩勘探中的识别应用

油页岩是一种很有前景的油气资源,测井技术是油页岩矿勘探开发的关键技术。该文依托姚庄地区油页岩矿钻孔的测井工作,通过对典型钻孔zk002的测井资料进行分析对比,得出测井曲线的变化与岩层有机质含量的关系,识别出地层岩性,并定出含油页岩层厚度,其结果与地质岩心钻探结果基本一致,因此,测井技术能较好地识别含油页岩层。     

The present-day stress field of New South Wales,Australia

The Australian continent displays the most complex pattern of present-day tectonic stress observed in any major continental area. Although plate boundary forces provide a well-established control on the large-scale (>500 km) orientation of maximum horizontal stress (S_Hmax), smaller-scale variations, caused by local forces, are poorly understood in Australia. Prior to this study, the World Stress Map database contained 101 S_Hmax orientation measurements for New South Wales (NSW), Australia, with the bulk of the data coming from shallow engineering tests in the Sydney Basin. In this study we interpret present-day stress indicators analysed from 58.6 km of borehole image logs in 135 coal-seam gas and petroleum wells in different sedimentary basins of NSW, including the Gunnedah, Clarence-Moreton, Sydney, Gloucester, Darling and Bowen–Surat basins. This study provides a refined stress map of NSW, with a total of 340 (A–E quality) S_Hmax orientations consisting of 186 stress indicators from borehole breakouts, 69 stress measurements from shallow engineering methods, 48 stress indicators from drilling-induced fractures, and 37 stress indicators from earthquake focal mechanism solutions. We define seven stress provinces throughout NSW and determine the mean orientation of the S_Hmax for each stress province. The results show that the S_Hmax is variable across the state, but broadly ranges from NE–SW to ESE–WNW. The S_Hmax is approximately E–W to ESE–WNW in the Darling Basin and Southeastern Seismogenic Zone that covers the west and south of NSW, respectively. However, the present-day S_Hmax rotates across the northeastern part of NSW, from approximately NE–SW in the South Sydney and Gloucester basins to ENE–WSW in the North Sydney, Clarence-Moreton and Gunnedah basins. Comparisons between the observed S_Hmax orientations and Australian stress models in the available literature reveal that previous numerical models were unable to satisfactorily predict the state of stress in NSW. Although clear regional present-day stress trends exist in NSW, there are also large perturbations observed locally within most stress provinces that demonstrate the significant control on local intraplate sources of stress. Local S_Hmax perturbations are interpreted to be due to basement topography, basin geometry, lithological contrasts, igneous intrusions, faults and fractures. Understanding and predicting local stress perturbations has major implications for determining the most productive fractures in petroleum systems, and for modelling the propagation direction and vertical height growth of induced hydraulic fractures in simulation of unconventional reservoirs.     

基于水资源生态足迹的浑河流域水资源利用评价

用水资源生态足迹模型计算浑河流域2005~2013年水资源生态足迹和水资源生态承载力,并基于各评价指标对浑河流域水资源利用情况进行评价。结果表明:2005~2013年浑河流域水资源生态足迹呈现不显著的下降趋势,水资源生态承载力呈现波动变化;流域一直处于水资源生态赤字状态,仅在2010年出现盈余;流域水资源生态足迹指数低于可持续发展足迹指数范围,但万元GDP水资源生态足迹持续下降。总体来看,流域水资源利用处于不可持续状态,但2010年后流域水资源利用效率明显提高,并向着可持续的方向发展。