Groundwater Exploration Using AEM in Structurally Complex, Inverted Sedimentary Basins and Paleovalleys, Kimberley Regio

Application of Vertical Electrical Sounding (VES) with Schlumberger array as a low-cost technique and veritable method in groundwater exploration is more suitable for hydrogeological survey of sedimentary basins. This method is regularly used to solve a wide variety of ground water problems and hydraulic parameters. The main objective of this research therefore, is to evaluate aquifer porosity and hydraulic conductivity using the empirical equations of porosity and hydraulic conductivity with resistivity conducted in the continuation of the adjacent Sharazoor basin. For this purpose, four profiles were taken in studied area (Piramagroon district), and each profile includes five VES points of measurements. Then each VES was interpreted manually as well as by IPI2 win program for determining aquifer depth ranging from (40 m.) to (80 m.) in piramagroon district) and resistivity values range between (37.0 Ω.m) to (102 Ω.m), which are substituted in the empirical porosity-resistivity and hydraulic conductivity-resistivity equations for evaluating aquifer porosity and hydraulic conductivity of the studied area. The estimated aquifer porosity values range along the studied area range between (21%) to (39 %), and for hydraulic conductivity values range from (1 m/day) to (4 m/day), which shows the increasing of the both aquifer porosity from the top of uplifted subsurface layers underlying the piramagroon district toward both limbs according to increasing of rock fragments (gravel, pebble) and (sand sediments) and decreasing of clay content overlying upper part of Middle Tanjero Formation.

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Variogram analysis of helicopter magnetic data to identify paleochannels of the Omaruru River, Namibia

Geophysics ◽

10.1190/1.1444588 ◽

1999 ◽

Vol 64 (3) ◽

pp. 785-794 ◽

Cited By ~ 11

Author(s):

Stefan Maus ◽

K. P. Sengpiel ◽

B. Röttger ◽

B. Siemon ◽

E. A. W. Tordiffe

Keyword(s):

Geomagnetic Field ◽

Sedimentary Basins ◽

Source Model ◽

High Accuracy ◽

Groundwater Exploration ◽

Magnetic Data ◽

Magnetic Signal ◽

Variogram Analysis ◽

Power Spectral ◽

Basement Depth

The geomagnetic field over sedimentary basins is very sensitive to variations in basement depth. Therefore, magnetic surveys are widely used to map basement topography in petroleum and groundwater exploration. We propose variogram analysis as a more accurate alternative to power spectral methods. Data variograms are computed from aeromagnetic flight‐line data. To estimate depth, the data variograms are compared with model variograms for a range of source depths. We use the exact space domain counterparts of a fractal power spectral model as model variograms. To demonstrate the utility of this method for groundwater exploration, we map the basement topography of the Omaruru Alluvial Plains in Namibia. A comparison with electromagnetic (EM) resistivities and drilling information confirms the high accuracy—but also the limitations—of variogram analysis depth. Variogram analysis makes maximum use of short‐wavelength contributions to the magnetic signal, which is the key to the resolution of shallow basement topography. Moreover, by using a realistic source model and avoiding extensive data preconditioning and the transform to wavenumber domain, variogram analysis is likely to provide improved magnetic depth estimates even for deep basins.

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Joint inversion of seismic refraction and resistivity data using layered models — Applications to groundwater investigation

Geophysics ◽

10.1190/geo2013-0476.1 ◽

2015 ◽

Vol 80 (1) ◽

pp. EN43-EN55 ◽

Cited By ~ 12

Author(s):

Niklas Juhojuntti ◽

Jochen Kamm

Keyword(s):

Case Studies ◽

Joint Inversion ◽

Seismic Refraction ◽

Sedimentary Basins ◽

Groundwater Exploration ◽

In Situ Tests ◽

Seismic Reflection Data ◽

Near Surface ◽

Resistivity Data ◽

Geotechnical Investigations

We developed a method for joint inversion of seismic refraction and resistivity data, using sharp-boundary models with few layers (typically three). We demonstrated the usefulness of the approach via examples from near-surface case studies involving shallow groundwater exploration and geotechnical investigations, although it should also be applicable to other types of layered environments, e.g., sedimentary basins. In our model parameterization, the layer boundaries were common for the resistivity and velocity distributions. Within the layers, only lateral variations in the material parameters (resistivity and velocity) were allowed, and we assumed no correlation between these. The inversion was performed using a nonlinear least-squares algorithm, using lateral smoothing to the layer boundaries and to the materialparameters. Depending on the subsurface conditions, the smoothing can be applied either to the depth of the layer boundaries or to the layer thicknesses. The forward responses and Jacobian for refraction seismics were calculated through ray tracing. The resistivity computations were performed with finite differences and a cell-to-layer transform for the Fréchet derivatives. Our method performed well in synthetic tests, and in the case studies, the layer boundaries were in good agreement with in situ tests and seismic reflection data, although minimum-structure inversion generally has a better data fit due to more freedom to introduce model heterogeneity. We further found that our joint inversion approach can provide more accurate thickness estimates for seismic hidden layers.

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