Volume 48 Number 4 2017
EG15077Relationship between bulk mineralogy and induced polarisation responses in iron oxide-copper-gold and porphyry copper mineralisation, northern Chile
We have studied the correlation between bulk mineralogy and induced polarisation (IP) responses in iron oxide-copper-gold (IOCG) and porphyry copper concealed mineralised systems in northern Chile. Data analyses show that bulk sulphide concentration is the first order factor that explains variation in the IP effect, even for the case of magnetite-related IOCG mineralisation.
EG15074Divergence correction schemes in finite difference method for 3D tensor CSAMT in axial anisotropic media
This paper presents a study on divergence correction in the finite difference method for 3D tensor controlled-source audio-frequency magnetotellurics (CSAMT) in an axial anisotropic media. We show how divergence correction can be performed more efficiently and the study results can be used to help accelerate a whole 3D tensor CSAMT forward modelling and inversion.
EG15095Short-offset grounded-wire TEM method for efficient detection of mined-out areas in vegetation-covered mountainous coalfields
The objective of this study was to overcome the limitations in using the loop-source TEM method and realise the efficient detection of mined-out areas using the short-offset grounded-wire TEM (SOTEM) method in vegetation-covered mountainous coalfields. The feasibility of SOTEM is verified by the drilling result in the field test.
EG15059Ground resistivity method and DCIP2D forward and inversion modelling to identify alteration at the Midwest uranium deposit, northern Saskatchewan, Canada
Forward and inverse modelling are used to demonstrate that the resistivity method can detect alteration above the Midwest uranium deposit in Canada. The inverse section of the field data is similar to the inverse section of a synthetic model when alteration is present, but dissimilar when there is no alteration.
EG15078Near-surface high resolution imaging of a metallogenic zone in the northern fringe of Dalma volcanics in eastern India using electrical resistivity tomography
An ERT survey was conducted over a defined conducting zone through a magnetotelluric survey in the Dalma volcanics, India. The resistivity models resolved four major zones and the results corroborate well with the geological succession. The resistivity values of less than 1 Ωm at a depth of ~25 m correspond to the deposit.
We obtained the shallow S-wave velocity profile distributions in the Bandung Basin, Indonesia, from the inversion of the observed Rayleigh wave phase velocity spectra using a microtremor survey. The profiles will be used for calculation of the average S-wave velocity of the upper 30 m and site amplification factors for seismic hazard evaluation in the area.
Subsurface-property estimation from remote geophysical measurements is subject to non-Gaussian errors. We propose to minimise the misfit with a robust error measure, which is based on a generalised Gaussian distribution. A suboptimal solution is proposed through a mixed-norm functional combination of the l1 and l2 norms.
EG15097Simultaneous seismic interpolation and denoising based on sparse inversion with a 3D low redundancy curvelet transform
This paper introduces a low redundancy curvelet transform which can reduce the redundancy to 10 for three dimensional data and simultaneously interpolate and denoise. Numerical experiments on synthetic and field data demonstrate that the low redundancy transform can provide reliable results while at the same time improving the computational efficiency.
EG15112Improved reservoir characterisation using fuzzy logic platform: an integrated petrophysical, seismic structural and poststack inversion study
In this study, petrophysical properties, seismic structural and poststack seismic inversion results are integrated using the fuzzy logic AND operator to characterise the Tensleep Sandstone Formation at Powder River Basin, Wyoming, USA. The 3D seismic cube and logging datasets of 17 wells are used for enhancing the seismic and petrophysical evaluation.
Benefitting from the forward modelling studies, the phenomenon of spatial mispositioning in apparent reflections caused by the symmetry axis orientation of the TI overburden was demonstrated. Numerical manipulations show the imaging problems can be well described by the TERF method and properly handled by the RAKTM method.
A new parameterisation using P-wave velocity, Poisson’s ratio and density is proposed for multi-parameter full waveform inversion (FWI) for isotropic elastic media. By introducing Poisson’s ratio, the virtual source for the P-wave velocity generates additional S-waves in the partial derivative wavefields, which increases the spatial resolution of FWI.
EG16031Separation of prestack seismic diffractions using an improved sparse apex-shifted hyperbolic Radon transform
We have developed an improved sparse apex-shifted hyperbolic Radon transform with Fourier-kernel Stolt-based modelling and imaging operators to separate seismic diffractions from reflections. The time axis is stretched to overcome the limitation of the multi-velocity model and a sparsity-promoting inversion is implemented to enhance the resolution of the Radon panel.
EG16020Identification of small-scale discontinuities based on dip-oriented gradient energy entropy coherence estimation
We have proposed a dip-oriented gradient energy entropy (DOGEE) coherence method to detect subtle faults and structural features. Theoretical synthetic datasets and a real dataset show that our proposed method is not only robust to noise, but also improves the clarity of small-scale discontinuities.
EG15107Analysis of crooked-line 2D seismic reflection data recorded in areas with complex surface and subsurface conditions
A crooked-line 2D seismic reflection dataset recorded in the northern part of the Eastern Pannonian Basin was processed to obtain a high-resolution seismic image for the area of interest. Refraction interferometry was used to enhance the first arrivals and to compute static corrections with good accuracy.
Depth variation of scattering attenuation by applying single events to multiple lapse time window analysis (MLTWA) was recently shown; however, this application inevitably combined several events due to insufficient data. This study demonstrated that a flexible range window can be applied successfully to solely single events in MLTWA.
EG15021Radiogenic heat production in Rudeis Formation, Lower Miocene, Belayim marine oil field, Gulf of Suez, Egypt
This study describes radiogenic heat production (RHP) estimated from two sets of well logging data recorded in Rudeis Formation, Belayim marine oil field. Cross-correlation of the estimated RHP (AR and ABR) yielded a moderate fit of 0.75. The three-dimensional (3D)-slicing of the reservoir shows that the northern and north-western parts of the study area have higher RHP compared to other parts.
EG16010The research on the buried public monumental complexes of Lupiae (Lecce) by geophysical prospecting
This paper presents a case study that involves a geophysical survey employing the surface 3D ground penetrating radar (GPR) techniques, in order to archaeologically characterise the areas located in the south-western sector of the historical centre of Lecce (Italy). GPR measurements significantly contributed to reconstruction of the complex subsurface properties in these modern urban areas.