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1.
The city of Burdur, which is built on an alluvium aquifer, is located in one of the most seismically active zones in southwestern
Turkey. The soil properties in the study site are characterized by unconsolidated and water-saturated sediments including
silty, clayey and sandy units, and shallow groundwater level is the other characteristic of the site. Thus, the city is under
soil liquefaction risk during a large earthquake. A resistivity survey including 189 vertical electrical sounding (VES) measurements
was carried out in 2000 as part of a multi-disciplinary project aiming to investigate settlement properties in Burdur city
and its vicinity. In the present study, the VES data acquired by using a Schlumberger array were re-processed with 1D and
2D inversion techniques to determine liquefaction potential in the study site. The results of some 1D interpretations were
compared to the data from several wells drilled during the project. Also, the groundwater level map that was previously obtained
by hydrological studies was extended toward north by using the resistivity data. 2D least-squares inversions were performed
along nine VES profiles. This provided very useful information on vertical and horizontal extends of geologic units and water
content in the subsurface. The study area is characterized by low resistivity distribution (<150 Ωm) originating from high
fluid content in the subsurface. Lower resistivity (3–30 Ωm) is associated with the Quaternary and the Tertiary lacustrine
sediments while relatively high resistivity (40–150 Ωm) is related to the Quaternary alluvial cone deposits. This study has
also shown that the resistivity measurements are useful in the estimation of liquefaction risk in a site by providing information
on the groundwater level and the fluid content in the subsurface. Based on this, we obtained a liquefaction hazard map for
the study area. The liquefaction potential was classified by considering the resistivity distributions from 2D inversion of
the VES profiles, the types of the sediments and the extended groundwater level map. According to this map, the study area
was characterized by high liquefaction hazard risk. 相似文献
2.
Pervaiz Sikandar Allah Bakhsh Muhammad Arshad Tariq Rana 《Environmental Earth Sciences》2010,60(5):1113-1129
A geoelectrical resistivity survey using vertical electrical sounding (VES) was conducted at Chaj Doab (land between rivers
Jhelum and Chenab, Pakistan) and Rachna Doab (land between rivers Chenab and Ravi, Pakistan), with the objective of investigating
groundwater conditions. A total of 90 sites were selected with 43 sites in Chaj and 47 sites in Rachna Doabs. The resistivity
meter (ABEM Terrameter SAS 4000, Sweden) was used to collect the VES data by employing a Schlumberger electrode configuration,
with half current electrode spacings (AB/2) ranging from 2 to 180 m and the potential electrode (MN) from 1 to 40 m. The field
data were interpreted using the Interpex IX1D computer software and the resistivity versus depth models for each location
was estimated. The outputs of subsurface layers with resistivities and thickness presented in contour maps and 3-D views by
using SURFER software were created. A total of 102 groundwater samples from nearby hydrowells at different depths were collected
to develop a correlation between the aquifer resistivity of VES and the electrical conductivity (EC) of the groundwater and
to confirm the resulted geophysical resistivity models. From the correlation developed, it was observed that the groundwater
salinity in the aquifer may be considered low and so safe for irrigation if resistivity >45 Ω m, and marginally fit for irrigation
having resistivity between 25 and 45 Ω m. The study area has resistivities from 3.9 to 2,222 Ω m at the top of the unsaturated
layer, between 1.21 and 171 Ω m, in the shallow aquifers, and 0.14–152 Ω m in the deep aquifers of the study area. The results
indicate that the quality of groundwater is better near the rivers and in the shallow layers compared to the deep layers. 相似文献
3.
The occurrence, movement and control of groundwater, particularly in hard-rock areas, are governed by different factors such
as topography, lithology, structures like fractures, faults and nature of weathering. An attempt is made in the present study
to investigate the extent of the influence of structures such as fractures and thereby delineate the nature of subsurface
lithology with the help of an electrical resistivity method. For this study, the Upper Gunjanaeru River basin, Cuddapah district
Andhra Pradesh was chosen to determine groundwater potentials. In order to understand the significance of the fracture pattern,
geological, hydrogeomorphological and lineament maps were prepared based on the field data and also from the LANDSAT TM imagery.
Further, electrical resistivity surveys were conducted to determine the subsurface lithology and also to confirm the studies
of LANDSAT imagery. The isoresistivity contour map has been prepared based on the 45 VES conducted to determine the resistivity
variations in the study area. The isoresistivity contours obtained were found to conform to the structural trends obtained
by geological studies and also confirm the relationship between the structure and secondary porosity present in the rocks.
The lineaments in the area have two preferred directions. One set is a NE-SW direction (N 30°–70° E; S 30°–70° W) and another
is a NW-SE direction (N 0°–30° W; S 0°–30° E and N 60°–80° W; S 60°–80° E). The water-table contour map shows that the direction
of groundwater flow is south to north.
Received: 3 March 1997 · Accepted: 17 June 1997 相似文献
4.
Surface electrical and electromagnetic surveys were conducted on top of a solid waste facility in Unguwan Dosa, Kaduna State,
Northwest Nigeria. The aim of the geophysical survey was to detect vertical and subvertical fractures that may provide pathways
for groundwater and contaminant transport. Results from the 2D electrical resistivity imaging showed vertical and subvertical
contacts overlain by 6–10 m thick overburden. Quantitative interpretation of the VLF-EM data correlates well with the results
of the 2D resistivity imaging delineating the vertical and subvertical contacts as good and weak conductors (fractures zones)
with resistivity values of 40–220 and 300–420 Ω m, respectively. Azimuthal Schlumberger VES measurements yield apparent anisotropy
values ranging from 1.01 to 1.47 for electrode spacings of 1–45 m with the highest value recorded at spacing of 2 m. However,
azimuthal variations at large spacings (30–45 m) showed no fracture anisotropy due possibly to the array’s low sensitivity
to anisotropy at these spacings. The result of the study showed that pollutants in the leachate can reach and contaminate
the groundwater. Therefore, urgency for leachate treatment at this site is recommended to prevent contamination of groundwater. 相似文献
5.
Delineation of saltwater intrusion into the freshwater aquifer of Lekki Peninsula,Lagos, Nigeria 总被引:2,自引:0,他引:2
A. A. Adepelumi B. D. Ako T. R. Ajayi O. Afolabi E. J. Omotoso 《Environmental Geology》2009,56(5):927-933
Recently, the deterioration of water quality in the coastal zones of Lekki Peninsula area of Lagos due to saltwater infiltration
into the freshwater aquifer has become a major concern. With the aim of providing valuable information on the hydrogeologic
system of the aquifers, the subsurface lithology and delineating the groundwater salinity, vertical electrical resistivity
(VES) sounding survey was carried out utilizing surface Schlumberger electrode arrays, and electrode spacing varying between
1 and 150 m. The DC resistivity surveys revealed significant variations in subsurface resistivity. Also, the VES resistivity
curves showed a dominant trend of decreasing resistivity with depth (thus increasing salinity). In general, the presence of
four distinct resistivity zones were delineated viz.: the unconsolidated dry sand (A) having resistivity values ranging between
125 and 1,028 Ωm represent the first layer; the fresh water-saturated soil (zone B) having resistivity values which correspond
to 32–256 Ωm is the second layer; the third layer (zone C) is interpreted as the mixing (transition) zone of fresh with brackish
groundwater. The resistivity of this layer ranges from 4 to 32 Ωm; while layer four (zone D) is characterized with resistivities
values generally below 4 Ωm reflecting an aquifer possibly containing brine. The rock matrix, salinity and water saturation
are the major factors controlling the resistivity of the formation. Moreover, this investigation shows that saline water intrusion
into the aquifers can be accurately mapped using surface DC resistivity method. 相似文献
6.
Ahmad Neyamadpour W. A. T. Wan Abdullah Samsudin Taib 《Journal of Earth System Science》2010,119(1):27-40
The objective of this paper is to investigate the applicability of artificial neural networks in inverting quasi-3D DC resistivity
imaging data. An electrical resistivity imaging survey was carried out along seven parallel lines using a dipole-dipole array
to confirm the validation of the results of an inversion using an artificial neural network technique. The model used to produce
synthetic data to train the artificial neural network was a homogeneous medium of 100Ωm resistivity with an embedded anomalous
body of 1000Ωm resistivity. The network was trained using 21 datasets (comprising 12159 data points) and tested on another
11 synthetic datasets (comprising 6369 data points) and on real field data. Another 24 test datasets (comprising 13896 data
points) consisting of different resistivities for the background and the anomalous bodies were used in order to test the interpolation
and extrapolation of network properties. Different learning paradigms were tried in the training process of the neural network,
with the resilient propagation paradigm being the most efficient. The number of nodes, hidden layers, and efficient values
for learning rate and momentum coefficient have been studied. Although a significant correlation between results of the neural
network and the conventional robust inversion technique was found, the ANN results show more details of the subsurface structure,
and the RMS misfits for the results of the neural network are less than seen with conventional methods. The interpreted results
show that the trained network was able to invert quasi-3D electrical resistivity imaging data obtained by dipole-dipole configuration
both rapidly and accurately. 相似文献
7.
Surface geophysical investigations of landslide at the Wiri area in southeastern Korea 总被引:1,自引:1,他引:0
A geophysical survey was undertaken at Wiri area of the Andong in southeastern Korea to delineate subsurface structure and
to detect the fault zone, which affected the 1997 mountain–hill subsidence and subsequent road heaving initiated by the intense
rainfall. Electrical resistivity methods of dipole–dipole array profiling and Schlumberger array sounding and seismic methods
of refraction and reflection profiling were used to map a clay zone, which was regarded as the major factor for the landslide.
The clay zone was identified in electrical resistivity and seismic sections as having low electrical resistivity (<100 Ωm)
and low seismic velocity (<400 m/s), respectively. The clay zone detected by using geophysical methods is well correlated
with its distribution from the trench and drill-core data. The results of the electrical and seismic surveys showed that slope
subsidence was associated with the sliding of saturated clay along a fault plane trending NNW–SSE and dipping 10°–20° SW.
However, the road heaving was caused by the slope movement of the saturated clay along a sub-vertical NNE-trending fault. 相似文献
8.
We propose a discretization technique using non-fitting grids to simulate magnetic field-based resistivity logging measurements. Non-fitting grids are convenient because they are simpler to generate and handle than fitting grids when the geometry is complex. On the other side, fitting grids have been historically preferred because they offer additional accuracy for a fixed problem size in the general case. In this work, we analyse the use of non-fitting grids to simulate the response of logging instruments that are based on magnetic field resistivity measurements using 2.5D Maxwell’s equations. We provide various examples demonstrating that, for these applications, if the finite element matrix coefficients are properly integrated, the accuracy loss due to the use of non-fitting grids is negligible compared to the case where fitting grids are employed. 相似文献
9.
Diesel transport monitoring in simulated unconfined aquifers using miniature resistivity arrays 总被引:2,自引:0,他引:2
The principal aim of this study is to assess the scope of monitoring diesel plume migration in a scaled aquifer model with
a miniaturised electrical resistivity array. Respectively 1000 and 500 ml of diesel were injected in both the unsaturated
and water-saturated zones of a sand body overlying a clay aquitard, and diesel migration was monitored with a miniature electrode
array and an off-the-shelf resistivity meter. Inverted time-lapse electrical resistivity tomography (ERT) data reflect downward
and lateral spreading of the diesel plume away from the injection point in the unsaturated zone. Diesel was also imaged to
spread upwards and laterally away from the injection point in the saturated zone, as controlled by capillary rise. In both
cases later-time ERT images reflected preferential pooling of diesel on the water table, as well as vertical smearing of pooled
diesel in response to simulated water-table fluctuations. Repeat fluid electrical conductivity (EC) and dissolved oxygen (DO)
measurements validate the observed changes in bulk resistivity caused by both diesel injections. Artefacts introduced by 2D
inversion of 3D contaminant transport were abound. Time-lapse ERT imaging of diesel transport is therefore inferred to be
feasible and well-suited to complementing conventional techniques of intrusive site investigation, although time-lapse 3D
or 4D ERT imaging is strongly advocated. 相似文献
10.
Ángel Rodríguez-Rozas David Pardo Carlos Torres-Verdín 《Computational Geosciences》2018,22(5):1271-1281
We develop a rapid 2.5-dimensional (2.5D) finite element method for simulation of borehole resistivity measurements in transversely isotropic (TI) media. The method combines arbitrary high-order \(H^{1}\)- and \(\mathbf {H}\)(curl)-conforming spatial discretizations. It solves problems where material properties remain constant along one spatial direction, over which we consider a Fourier series expansion and each Fourier mode is solved independently. We propose a novel a priori method to construct quasi-optimal discretizations in physical and Fourier space. This construction is based on examining the analytical (fundamental) solution of the 2.5D formulation over multiple homogeneous spaces and assuming that some of its properties still hold for the 2.5D problem over a spatially heterogeneous formation. In addition, a simple parallelization scheme over multiple measurement positions provides efficient scalability. Our method yields accurate borehole logging simulations for realistic synthetic examples, delivering simulations of borehole resistivity measurements at a rate faster than 0.05 s per measurement location along the well trajectory on a 96-core computer. 相似文献
11.
In situ soil micro electrical resistivity measurements were carried out in a pilot plot within the Teaching and Research Farm of Ekiti State University with the aim of establishing relationships between such measurements, soil horizons, and textural classifications. The vertical electrical sounding (VES) technique was adopted for horizon mapping, while the horizontal profiling (HP) technique was used to determine the spatial distribution of in situ soil electrical resistivity of the topmost horizon. Twenty-five VES points were occupied with the Wenner electrode array and electrode spacing that was varied from 2 to 128 cm (0.02 to 1.28 m). The VES data were interpreted by partial curve matching and computer assisted 1-D forward modeling with the IPI2Win software. HP data were also acquired with the Wenner electrode array with a constant electrode separation of 8 cm and station interval of 1 m. Resistivity measurements were taken at 729 stations. The HP data were classified into resistivity-derived soil classes using a standard table. Eighty-one soil samples were collected from the topmost (0–3 cm) horizon and textural classification was derived from the particle size distributions. The resistivity range of values for the identified three layers was 38–590, 328–5222, and 393–900 Ω·m respectively. The average resistivities of the three layers were 263, 2554, and 703 Ω·m, with respective thicknesses of 2.85 cm, 45.52 cm, and infinite. The above resistivity regimes of the three horizons were attributed to responses from the O, A, and B soil horizons. The resistivity values of the O-horizon ranging from 210 to 750 Ω·m were classified as clayey sand while values greater than 750 Ω·m were classified as sand. The soil textural classifications obtained within the horizon were the sandy loam and loamy sand types. The cross-tabulation and spatial pattern comparison of resistivity-derived soil classes and textural classifications showed that whereas there existed some overlapping relationships, the sandy loam textural class had stronger association with the resistivity-derived clayey sand soil type, and the loamy sand textural class had stronger association with the more resistive sand soil type. This study therefore established that in situ soil electrical resistivity can be used for soil horizon mapping and textural classification. 相似文献
12.
Magnetotelluric investigations have been carried out in the Garhwal Himalayan corridor to delineate the electrical structure
of the crust along a profile extending from Indo-Gangetic Plain to Higher Himalayan region in Uttarakhand, India. The profile
passing through major Himalayan thrusts: Himalayan Frontal Thrust (HFF), Main Boundary Thrust (MBT) and Main Central Thrust
(MCT), is nearly perpendicular to the regional geological strike. Data processing and impedance analysis indicate that out
of 44 stations MT data recorded, only 27 stations data show in general, the validity of 2D assumption. The average geoelectric
strike, N70°W, was estimated for the profile using tensor decomposition. 2D smooth geoelectrical model has been presented,
which provides the electrical image of the shallow and deeper crustal structure. The major features of the model are (i) a low resistivity (<50Ωm), shallow feature interpreted as sediments of Siwalik and Indo-Gangetic Plain, (ii) highly resistive (> 1000Ωm) zone below the sediments at a depth of 6 km, interpreted as the top surface of the Indian plate,
(iii) a low resistivity (< 10Ωm) below the depth of 6 km near MCT zone coincides with the intense micro-seismic activity in the
region. The zone is interpreted as the partial melting or fluid phase at mid crustal depth. Sensitivity test indicates that
the major features of the geoelectrical model are relevant and desired by the MT data. 相似文献
13.
Mapping groundwater conditions in different geological environments in the northern area of UAE using 2D earth resistivity imaging survey 总被引:1,自引:1,他引:0
A. M. Ebraheem M. M. Al Mulla M. M. Sherif O. Awad S. F. Akram N. B. Al Suweidi A. Shetty 《Environmental Earth Sciences》2014,72(5):1599-1614
A water resources database was developed and used to characterize the geological and hydrogeological settings of groundwater aquifers in the northern part of the United Arab Emirates. An intensive 2D Earth Resistivity Imaging (ERI) survey was conducted in selected areas to assess the available groundwater resources and delineate the salt-water intrusion. Drilling information of the existing monitoring wells as well as their records of water table elevations and groundwater salinity were used to measure the horizontal and vertical variations in lithology, degree of saturation, and groundwater salinity and thus to improve the interpretation of ERI data. The results of the chemical analyses of water samples collected from the wells along with the 2D ERI survey profiles were used to obtain an empirical relationship between the inferred earth resistivity and the amount of total dissolved solids. This relationship was used along with the true resistivity sections resulting from the inversion of 2D ERI data to identify and map three zones of water-bearing formation (fresh, brackish, and salt-water zones) in the coastal areas. The results indicated that the depth to the fresh-brackish interface exceeded 50 m at the upstream of the wadies and was in the order of 10 m or less in the vicinity of shoreline. Because of the high resistivity contrast between dry and water saturated fractured rocks; this method was very successful in detecting water-filled fractures and cavities in the carbonate aquifer. The application of this method was unsuccessful in clayey aquifers as it was not possible to isolate lenses of gravel and/or saturated with saline or brackish water from the surrounding clayey materials. 相似文献
14.
B. S. Badmus O. D. Akinyemi J. A. Olowofela G. M. Folarin 《Journal of the Geological Society of India》2012,80(6):845-854
Geological structures are 3-Dimensional (3D) in nature, thus 1-Dimensional and 2-Dimensional surveys cannot adequately model them. However, sophisticated 3D survey equipment are very expensive. In this study, a singlechannel ABEM SAS 300B Terrameter was used to obtain 3D models of the subsurface. This survey was carried out at three different locations within Abeokuta, a basement complex terrain of southwestern Nigeria. The area falls within longitudes 3.35° and 3.38° East and latitudes 7.22° and 7.46° North respectively, with coordinates of 2550.0 m North and 1724.2 m East. A manual 4-electrode system was used in the Electrical Resistivity Tomography survey at the three locations. Each location was marked into 7 by 7 square grids with 1 m, 3 m and 5 m unit electrode spacings in succession. The pole-pole array was used with the two remote electrodes placed at distances of 23 m, 40 m and 65 m from the grids of 1 m, 3 m and 5 m unit electrode spacings respectively, to reduce their telluric effects on the measured apparent resistivity values. To reduce survey time consumption, the cross-diagonal survey method was adopted. The data obtained were analysed using a 3D inversion software called RES3DINV and 3-Dimensional models of the subsurface were also generated using Slicer Dicer graphics software. The study revealed layers extending to depths of 7.75 m, 23.2 m and 38.7 m for unit electrode spacings of 1 m, 3 m and 5 m respectively. It revealed resistivity values ranging from 7.3 Ωm to 300 Ωm for electrode spacing of 1.0 m; 13.8 Ωm to 200 Ωm for electrode spacing of 3 m and 3.9 Ωm to 200 Ωm for electrode spacing of 5 m at the first location. At the second location, it revealed resistivity values ranging from 0.53 Ωm to 120.0 Ωm for electrode spacing of 3 m and 0.30 Ωm to 100 Ωm for electrode spacing of 5 m. For electrode spacings of 1 m, 3 m and 5 m, resistivity values ranging from 6.1 Ωm to 600 Ωm, 12 Ωm to 600 Ωm and 0.85 Ωm to 1700 Ωm were obtained respectively at the third location. Generally, this study revealed lithologies composed of lateritic soil, sand, sandstone, sandyclay, clayeysand, weathered rock, fractured rock, clay and fresh basement; to a depth of about 39 m. Also, location 3 was discovered to have good groundwater prospects; though not as good as for locations 1 and 2. 相似文献
15.
Wells are seldom modeled explicitly in large scale finite difference reservoir simulations. Instead, the well is coupled to the reservoir through the use of a well index, which relates wellbore flow rate and pressure to grid block quantities. The use of an accurate well index is essential for the detailed modeling of nonconventional wells; i.e., wells with an arbitrary trajectory or multiple branches. The determination of a well index for such problems is complicated, particularly when the simulation grid is irregular or unstructured. In this work, a general framework for the calculation of accurate well indices for general nonconventional wells on arbitrary grids is presented and applied. The method entails the use of an accurate semianalytical well model based on Green's functions as a reference single phase flow solution. This result is coupled with a finite difference calculation to provide an accurate well index for each grid block containing a well segment. The method is demonstrated on a number of homogeneous example cases involving deviated, horizontal and multilateral wells oriented skew to the grid. Both Cartesian and globally unstructured multiblock grids are considered. In all these cases, the method is shown to provide results that are considerably more accurate compared to results using standard procedures. The method is also applied to heterogeneous problems involving horizontal wells, where it is shown to be capable of approximating the effects of subgrid heterogeneity in coarse finite difference models. 相似文献
16.
《Russian Geology and Geophysics》2015,56(8):1194-1200
The processing algorithms for high-frequency induction resistivity data are applied to logs acquired at different stages of well construction. Open-hole induction logging while reaming of vertical wells provides a priori information on geology and resistivity distribution. The resulting resistivity model can make reference in geosteering for deviated and horizontal drilling. Algorithms for inversion of high-frequency induction responses from layered media are used in a software package for processing LWD data. The software provides real-time inversion to recover resistivities and depths to layers in oil and gas reservoirs penetrated by wells of a complex trajectory. It also allows checking the inversion quality by analyzing the sensitivity of tool responses to model parameters with reference to the tool specifications. 相似文献
17.
The effectiveness of secondary recovery methods in reservoir development studies depends on the knowledge about how fluid-carrying regions (i.e. good-quality rock types) are connected between injection and production wells. To estimate reservoir performance uncertainty, comprehensive simulations on many reservoir model realisations are necessary, which is very CPU consuming and time demanding. Alternatively, we can use much simpler and physically based methods such as percolation approach. Classic percolation assumes connectivity between opposite 2-D faces of a 3-D system; whereas, hydrocarbon production is achieved through active wells that are one-dimensional lines (e.g. vertical, horizontal or deviated wells). The main contribution of this study is to analyse the percolation properties of 3-D continuum percolation models with more realistic well representations during secondary recovery. In particular, the connection of randomly distributed sands (i.e. good-quality rock types) between two lines (representing two wells) located at two corners of the system are modelled by Monte Carlo simulations. Subsequently, the connectivity and conductivity of such a line-to-line well representation is compared with that of face-to-face well representations in the previously published results. The critical percolation properties of those systems as well as the universality concept are also investigated. As there are many rooms for connections in 3-D models, we found that the principal percolation properties will not be altered significantly when the problem with a face-to-face connection is transformed to a line-to-line connection model. 相似文献
18.
Aquifers in the arid alluvial basins of the southwestern U.S. are recharged predominantly by infiltration from streams and
playas within the basins and by water entering along the margins of the basins. The Tucson basin of southeastern Arizona is
such a basin. The Santa Catalina Mountains form the northern boundary of this basin and receive more than twice as much precipitation
(ca. 700 mm/year) as does the basin itself (ca. 300 mm/year). In this study environmental isotopes were employed to investigate
the migration of precipitation basinward through shallow joints and fractures. Water samples were obtained from springs and
runoff in the Santa Catalina Mountains and from wells in the foothills of the Santa Catalina Mountains. Stable isotopes (δD
and δ18O) and thermonuclear-bomb-produced tritium enabled qualitative characterization of flow paths and flow velocities. Stable-isotope
measurements show no direct altitude effect. Tritium values indicate that although a few springs and wells discharge pre-bomb
water, most springs discharge waters from the 1960s or later.
Received, February 1997 · Revised, September 1997 · Accepted, September 1997 相似文献
19.
水平井和大斜度井中阵列侧向测井响应数值模拟 总被引:1,自引:0,他引:1
针对水平井和大斜度井中阵列侧向电极系的工作原理,利用多电场叠加方式进行电场合成,采用三维有限元方法模拟仿真各个分电场的场分布,进而利用电场线性叠加原理得到阵列侧向测井响应。在基于计算机仿真的基础上,得到阵列侧向五条测井曲线的径向探测深度,阵列侧向径向探测深度要小于深侧向探测深度。考察了三维地层模型下井斜和侵入深度变化对阵列侧向测井响应的影响,分析了水平井和大斜度井中阵列侧向测井响应特征。模拟结果表明,在井斜小于15°时,阵列侧向测井响应受井斜影响小,可以不进行井斜校正;井斜超过60°的大斜度井以及水平井中,阵列侧向测井响应视地层厚度逐渐增大,测井响应值与直井条件下响应值差别较大,必须进行井斜校正。 相似文献
20.
Case study: a 3D resistivity and induced polarization imaging from downstream a waste disposal site in Brazil 总被引:2,自引:2,他引:0
Andréa Teixeira Ustra Vagner Roberto Elis Giulliana Mondelli Lázaro Valentin Zuquette Heraldo Luiz Giacheti 《Environmental Earth Sciences》2012,66(3):763-772
A contaminated site from a downstream municipal solid waste disposal site in Brazil was investigated by using a 3D resistivity and induced polarization (IP) imaging technique. This investigation purpose was to detect and delineate contamination plume produced by wastes. The area was selected based on previous geophysical investigations, and chemical analyses carried out in the site, indicating the presence of a contamination plume in the area. Resistivity model has successfully imaged waste presence (ρ < 20 Ωm), water table depth, and groundwater flow direction. A conductive anomaly (ρ < 20 Ωm) outside wastes placement was interpreted as a contamination plume. Chargeability model was also able to imaging waste presence (m > 31 mV/V), water table depth, and groundwater flow direction. A higher chargeability zone (m > 31 mV/V) outside wastes placement and following conductive anomaly was interpreted as a contamination plume. Normalized chargeability (MN = m/ρ) confirmed polarizable zone, which could be an effect of a salinity increase (contamination plume), and the clay presence in the environment. 相似文献