Exploration Geophysics
Volume 49 Number 5 2018
EG17049Synthetic modelling and analysis of CSEM full-field apparent resistivity response combining EM induction and IP effect for 1D medium
Full-field apparent resistivity response combining EM induction and IP effect for layered earth were modelled using the Cole–Cole model. The influence of chargeability is greater than that of the other two parameters, time constant and frequency dependent coefficient. The layered model was distorted seriously by using the inversion algorithm ignoring IP effect.
EG17053The magnetotelluric tensor: improved invariants for its decomposition, especially ‘the 7th'
Measurements of natural time-fluctuating magnetic and electric fields at the surface of Earth produce magnetotelluric data, most of which can be expressed as quantities invariant to the directions of field measurement. Such invariants give information on geological structure.
EG17053 Abstract | EG17053 Full Text | EG17053PDF (736 KB) Open Access Article
EG17110The relationship between normalised horizontal-to-vertical spectral ratios (HVSRs) of microtremors and the F distribution
This paper shows that a method used to identify a peak of horizontal-to-vertical spectral ratios (HVSRs) of microtremors, which was proposed in 2001, is unreliable, and clarifies the reason for the unreliability. Because of the resemblance between the distribution of normalised HVSRs and the F distribution, we frequently fail to detect the deviation between them.
EG17104A simple inversion algorithm to estimate a linearly increasing velocity model for microseismic monitoring
In this study, we suggest a simple algorithm to estimate 1D velocity gradient for microseismic monitoring. The proposed algorithm is based on the analytically-derived ray formulas for a linearly increasing velocity model and the Gauss–Newton method. Numerical examples show that the proposed algorithm is robust to picking errors and initial guess.
EG17048Seismic facies-controlled prestack simultaneous inversion of elastic and petrophysical parameters for favourable reservoir prediction
This paper describes the development of a deterministic prestack inversion for estimating elastic and petrophysical parameters. The Gassmann equation is used to construct the relationship between the seismic data and petrophysical parameters. Seismic facies constraints were introduced to improve the accuracy. The very fast-simulated annealing method is used to quickly find the optimal solutions.
EG16134Velocity analysis of CMP gathers acquired by an array GPR system ‘Yakumo’: results from field application to tsunami deposits
Velocity analysis is applied to explore the capability of a multi-static ground penetrating radar (GPR) system to estimate a vertical profile of dielectric constants of stratified tsunami layers. Both laboratory and field experiments demonstrate that multi-static GPR can accurately delineate the layered geological structures.
EG17093The Marine Vibrator Joint Industry Project: four years on
The Marine Vibrator Joint Industry Project (MVJIP), sponsored by Shell, Total and ExxonMobil, has been ongoing for four years. This paper discusses the history, motivation, technology and latest developments from the project.
EG17077Estimation of reservoir properties from seismic data through a Markov Chain Monte Carlo-AVA inversion algorithm
We formulate the amplitude versus angle (AVA) inversion in terms of a Markov Chain Monte Carlo algorithm and apply it for reservoir characterisation and litho-fluid facies prediction in offshore Nile Delta. A blind test, based on available well log information, demonstrates the applicability of the proposed method and the reliability of the results.
EG17057Channel edge detection using 2D complex shearlet transform: a case study from the South Caspian Sea
Channel detection plays a significant role in seismic interpretation. Shearlet transform as a multi-scale and multi-directional transformation is capable of detecting anisotropic singularities. We applied complex-valued shearlet edge measure to synthetic and real seismic time-slices from the South Caspian Sea. The proposed algorithm outperformed both Sobel and Canny edge detectors.
EG16028Compensation for aircraft effects of magnetic gradient tensor measurements in a towed bird
We present a compensation model of aircraft effects for full magnetic gradient tensor data acquired in a towed bird. Training flight tests were designed so that aircraft compensation parameters could be estimated. The feasibility of the compensation method was verified by modelling and by a flight simulation test.
EG16124Correction and compensation of an airborne fluxgate magnetic tensor gradiometer
In this paper, the correction coefficients of a fluxgate magnetic tensor gradiometer and the magnetic properties of an aircraft are determined. A recursive method is used to combine the magnetic interference model and the error model into a unified calibration model. The method is significant as there will be a greater use of airborne magnetic tensor gradiometers using a wide range of aircraft.
This paper demonstrates the magnitude of change that results when different information (relating to calibration factors, time zones and time changes, height, geodetic datums and gravity datums) is introduced at various stages of the gravity reduction process. The differences range from below 0.01 mGal to over 16.0 mGal.
EG17094 Abstract | EG17094 Full Text | EG17094PDF (226 KB) | EG17094Supplementary Material (177 KB) Open Access Article
EG16156Estimation of elastic anisotropy from three-component ultrasonic measurements using laser Doppler interferometry
Laser Doppler interferometers were previously employed to detect ultrasonic waves propagating in different directions and to estimate elastic anisotropy from these measurements. Our numerical simulations and laboratory measurements show that the recorded wavefield contains converted PS-waves, which need to be taken into consideration to obtain robust estimates of anisotropy.
EG16154The archaeological site of Sagalassos (Turkey): exploring the mysteries of the invisible layers using geophysical methods
The ancient Roman city of Sagalassos (Turkey) is covered by layers of eroded soil that have preserved many secrets waiting to be revealed. A geophysical campaign was planned to highlight the buried structure. Geophysics revealed evidence of a clay quarry, a number of tombs related to the Byzantine period and defensive walls.
EG17032Improving bitumen detection in resistivity surveys by using induced polarisation data
A hydrogeophysically and geologically complex bitumen deposit in western Iran was investigated by means of resistivity and induced polarisation (IP) methods. The results show the high potential of IP data to improve bitumen detection. It was also proven that saline water can sometimes be useful in target identification in mineral explorations.
EG16135Sensitivity of shale anisotropic parameters to core cutting rotation error
In laboratories, core cannot always be cut exactly along the axis of symmetry (normal to the bedding plane), which leads to a minor core cutting rotation error. This paper investigates the sensitivity of Thomson’s anisotropic parameters, epsilon (ε), gamma (γ) and delta (δ), to the cutting error.
EG17055A constrained spectral inversion method based on compressive sensing in order to distinguish high-quality shale
Distinguishing high-quality shale effectively is a difficult exploration problem. We propose a constrained spectral inversion method based on compressive sensing to handle this challenge. This method can help us improve the resolution and continuity of the profiles and enhance our ability to discover high-quality shale.