scholarly journals Least-squares path-summation diffraction imaging using sparsity constraints

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. S187-S200 ◽  
Author(s):  
Dmitrii Merzlikin ◽  
Sergey Fomel ◽  
Mrinal K. Sen
Keyword(s):  
Plane Wave ◽  
Field Data ◽  
Reservoir Characterization ◽  
Forward Modeling ◽  
Small Scale ◽  
Separation Procedure ◽  
Seismic Reservoir ◽  
Sparsity Constraints ◽  
Diffraction Imaging ◽  
Separation Results

Diffraction imaging aims to emphasize small-scale subsurface heterogeneities, such as faults, pinch-outs, fracture swarms, channels, etc. and can help seismic reservoir characterization. The key step in diffraction imaging workflows is based on the separation procedure suppressing higher energy reflections and emphasizing diffractions, after which diffractions can be imaged independently. Separation results often contain crosstalk between reflections and diffractions and are prone to noise. We have developed an inversion scheme to reduce the crosstalk and denoise diffractions. The scheme decomposes an input full wavefield into three components: reflections, diffractions, and noise. We construct the inverted forward modeling operator as the chain of three operators: Kirchhoff modeling, plane-wave destruction, and path-summation integral filter. Reflections and diffractions have the same modeling operator. Separation of the components is done by shaping regularization. We impose sparsity constraints to extract diffractions, enforce smoothing along dominant local event slopes to restore reflections, and suppress the crosstalk between the components by local signal-and-noise orthogonalization. Synthetic- and field-data examples confirm the effectiveness of the proposed method.

scholarly journals Least-squares diffraction imaging using shaping regularization by anisotropic smoothing

Geophysics ◽  
2020 ◽  
Vol 85 (5) ◽  
pp. S313-S325
Author(s):  
Dmitrii Merzlikin ◽  
Sergey Fomel ◽  
Xinming Wu
Keyword(s):  
Plane Wave ◽  
Least Squares ◽  
Field Data ◽  
Forward Modeling ◽  
Edge Diffraction ◽  
Sparsity Constraints ◽  
Diffraction Imaging ◽  
Least Squares Migration ◽  
Anisotropic Smoothing

We have used least-squares migration to emphasize edge diffractions. The inverted forward-modeling operator is the chain of three operators: Kirchhoff modeling, azimuthal plane-wave destruction, and the path-summation integral filter. Azimuthal plane-wave destruction removes reflected energy without damaging edge-diffraction signatures. The path-summation integral guides the inversion toward probable diffraction locations. We combine sparsity constraints and anisotropic smoothing in the form of shaping regularization to highlight edge diffractions. Anisotropic smoothing enforces continuity along edges. Sparsity constraints emphasize diffractions perpendicular to edges and have a denoising effect. Synthetic and field data examples illustrate the effectiveness of the proposed approach in denoising and highlighting edge diffractions, such as channel edges and faults.

Poststack impedance inversion considering the diffractive component of the wavefield

Geophysics ◽  
2020 ◽  
Vol 85 (1) ◽  
pp. R11-R28 ◽  
Author(s):  
Kun Xiang ◽  
Evgeny Landa
Keyword(s):  
Specular Reflection ◽  
Low Frequency ◽  
Velocity Model ◽  
Forward Modeling ◽  
Small Scale ◽  
Fracture Detection ◽  
Frequency Model ◽  
New Approach ◽  
Impedance Inversion ◽  
Diffraction Imaging

Seismic diffraction waveform energy contains important information about small-scale subsurface elements, and it is complementary to specular reflection information about subsurface properties. Diffraction imaging has been used for fault, pinchout, and fracture detection. Very little research, however, has been carried out taking diffraction into account in the impedance inversion. Usually, in the standard inversion scheme, the input is the migrated data and the assumption is taken that the diffraction energy is optimally focused. This assumption is true only for a perfectly known velocity model and accurate true amplitude migration algorithm, which are rare in practice. We have developed a new approach for impedance inversion, which takes into account diffractive components of the total wavefield and uses the unmigrated input data. Forward modeling, designed for impedance inversion, includes the classical specular reflection plus asymptotic diffraction modeling schemes. The output model is composed of impedance perturbation and the low-frequency model. The impedance perturbation is estimated using the Bayesian approach and remapped to the migrated domain by the kinematic ray tracing. Our method is demonstrated using synthetic and field data in comparison with the standard inversion. Results indicate that inversion with taking into account diffraction can improve the acoustic impedance prediction in the vicinity of local reflector discontinuities.

Diffraction imaging of ground-penetrating radar data

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. H1-H12 ◽  
Author(s):  
Hemin Yuan ◽  
Mahboubeh Montazeri ◽  
Majken C. Looms ◽  
Lars Nielsen
Keyword(s):  
Ground Penetrating Radar ◽  
Field Data ◽  
Velocity Structure ◽  
Velocity Estimation ◽  
Small Scale ◽  
Imaging Method ◽  
Surface Reflection ◽  
Diffraction Imaging ◽  
Saturated Media ◽  
Ground Penetrating

Diffractions caused by, e.g., faults, fractures, and small-scale heterogeneity localized near the surface are often used in ground-penetrating radar (GPR) reflection studies to constrain the subsurface velocity distribution using simple hyperbola fitting. Interference with reflected energy makes the identification of diffractions difficult. We have tailored and applied a diffraction imaging method to improve imaging for surface reflection GPR data. Based on a plane-wave destruction algorithm, the method can separate reflections from diffractions. Thereby, a better identification of diffractions facilitates an improved determination of GPR wave velocities and an optimized migration result. We determined the potential of this approach using synthetic and field data, and, for the field study, we also compare the estimated velocity structure with crosshole GPR results. For the field data example, we find that the velocity structure estimated using the diffraction-based process correlates well with results from crosshole GPR velocity estimation. Such improved velocity estimation may have important implications for using surface reflection GPR to map, e.g., porosity for fully saturated media or soil moisture changes in partially saturated media because these physical properties depend on the dielectric permittivity and thereby also the GPR wave velocity.

Diffraction imaging using shot and opening-angle gathers: A prestack time migration approach

Geophysics ◽  
2014 ◽  
Vol 79 (2) ◽  
pp. S23-S33 ◽  
Author(s):  
Jianfeng Zhang ◽  
Jiangjie Zhang
Keyword(s):  
Field Data ◽  
Opening Angle ◽  
Small Scale ◽  
Time Migration ◽  
Crucial Problem ◽  
Diffraction Imaging ◽  
Prestack Time Migration ◽  
Angle Gather ◽  
Fresnel Zones ◽  
Migration Velocities

We have developed a migration scheme that can image weak diffractions in time. This significantly contributes to conventional interpretation in detecting small-scale faults and heterogeneities. The proposed scheme images diffractions using the shot and opening-angle gathers generated by prestack time migration (PSTM). Here, the shot and opening-angle gather represents a 2D migrated gather in terms of shot locations and opening angles between the incident- and scattered-rays. We muted the Fresnel zones related to reflections, corrected phases of diffractions, and enhanced diffractions in the migrated gathers. As a result, the proposed diffraction PSTM can image diffractions with and without phase-reversal. Moreover, the weak diffractions tangent to reflections can be clearly imaged. Diffraction PSTM can update migration velocities according to behaviors of reflection and diffraction events in the migrated gathers by scanning, thus overcoming a crucial problem in diffraction imaging. The reflector dips used in diffraction PSTM are obtained by picking the angles related to reflections in the shot and opening-angle gathers for a partial migration. Synthetic and field data tests demonstrate the validity of diffraction PSTM.

scholarly journals Land Subsidence Estimation for Aquifer Drainage Induced by Underground Mining

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4658
Author(s):  
Artur Guzy ◽  
Wojciech T. Witkowski
Keyword(s):  
Environmental Impact ◽  
Land Subsidence ◽  
Field Data ◽  
Underground Mining ◽  
Small Scale ◽  
Aquifer System ◽  
Maximum Value ◽  
The Impact ◽  
Method Model ◽  
Impact Of Mining

Land subsidence caused by groundwater withdrawal induced by mining is a relatively unknown phenomenon. This is primarily due to the small scale of such movements compared to the land subsidence caused by deposit extraction. Nonetheless, the environmental impact of drainage-related land subsidence remains underestimated. The research was carried out in the “Bogdanka” coal mine in Poland. First, the historical impact of mining on land subsidence and groundwater head changes was investigated. The outcomes of these studies were used to construct the influence method model. With field data, our model was successfully calibrated and validated. Finally, it was used for land subsidence estimation for 2030. As per the findings, the field of mining exploitation has the greatest land subsidence. In 2014, the maximum value of the phenomenon was 0.313 cm. However, this value will reach 0.364 m by 2030. The spatial extent of land subsidence caused by mining-induced drainage extends up to 20 km beyond the mining area’s boundaries. The presented model provided land subsidence patterns without the need for a complex numerical subsidence model. As a result, the method presented can be effectively used for land subsidence regulation plans considering the impact of mining on the aquifer system.

scholarly journals Small-scale characterization of vine plant root water uptake via 3-D electrical resistivity tomography and mise-à-la-masse method

2018 ◽  
Vol 22 (10) ◽  
pp. 5427-5444 ◽  
Author(s):  
Benjamin Mary ◽  
Luca Peruzzo ◽  
Jacopo Boaga ◽  
Myriam Schmutz ◽  
Yuxin Wu ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Root System ◽  
Field Data ◽  
Electrical Resistivity Tomography ◽  
Root Zone ◽  
Plant Root ◽  
Root Water Uptake ◽  
Small Scale ◽  
Noninvasive Methods ◽  
Resistivity Tomography

Abstract. The investigation of plant roots is inherently difficult and often neglected. Being out of sight, roots are often out of mind. Nevertheless, roots play a key role in the exchange of mass and energy between soil and the atmosphere, in addition to the many practical applications in agriculture. In this paper, we propose a method for roots imaging based on the joint use of two electrical noninvasive methods: electrical resistivity tomography (ERT) and mise-à-la-masse (MALM). The approach is based on the key assumption that the plant root system acts as an electrically conductive body, so that injecting electrical current into the plant stem will ultimately result in the injection of current into the subsoil through the root system, and particularly through the root terminations via hair roots. Evidence from field data, showing that voltage distribution is very different whether current is injected into the tree stem or in the ground, strongly supports this hypothesis. The proposed procedure involves a stepwise inversion of both ERT and MALM data that ultimately leads to the identification of electrical resistivity (ER) distribution and of the current injection root distribution in the three-dimensional soil space. This, in turn, is a proxy to the active (hair) root density in the ground. We tested the proposed procedure on synthetic data and, more importantly, on field data collected in a vineyard, where the estimated depth of the root zone proved to be in agreement with literature on similar crops. The proposed noninvasive approach is a step forward towards a better quantification of root structure and functioning.

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