Diffraction imaging using a mathematical morphological filter with a time-varying structuring element

Geophysics ◽  
2021 ◽  
pp. 1-51
Author(s):  
Chuangjian Li ◽  
Jingtao Zhao ◽  
Suping Peng ◽  
Yanxin Zhou
Keyword(s):  
High Resolution ◽  
Stationary Point ◽  
Energy Band ◽  
Field Experiments ◽  
Small Scale ◽  
Imaging Method ◽  
Morphological Filter ◽  
Time Varying ◽  
Structuring Element ◽  
Diffraction Imaging

Diffraction imaging is an important technique for high-resolution imaging because of the close relationship between diffractions and small-scale discontinuities. Therefore, we propose a diffraction imaging method using a mathematical morphological filter (MMF). In a common-image gather (CIG), reflections have an evident energy band associated with the Fresnel zone and stationary point, whereas diffractions can be observed in a wide illumination direction and therefore has no energy band. Based on these phenomena, we analyze the amplitude distributions of the diffractions and reflections, and propose a time-varying structuring element (SE) in the MMF. Based on the time-varying SE, the proposed method can effectively suppress reflections and has the advantage of automatically preserving the diffractions energy near the stationary point. Numerical and field experiments demonstrate the efficient performance of the proposed method in imaging diffractions and obtaining high-resolution information.

Diffraction imaging method by Mahalanobis-based amplitude damping

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. S399-S408 ◽  
Author(s):  
Jingtao Zhao ◽  
Suping Peng ◽  
Wenfeng Du ◽  
Xiaoting Li
Keyword(s):  
High Resolution ◽  
Velocity Model ◽  
Migration Velocity ◽  
Field Application ◽  
Small Scale ◽  
Imaging Method ◽  
High Resolution Imaging ◽  
Reflected Waves ◽  
Diffraction Imaging ◽  
Resolution Imaging

Clarifying and locating small-scale discontinuities or inhomogeneities in the subsurface, such as faults and collapsed columns, plays a vital role in safe coal mining because these discontinuities or inhomogeneities may destroy the continuity of layers and result in dangerous mining accidents. Diffractions carry key information from these objects and therefore can be used for high-resolution imaging. However, diffracted/scattered waves are much weaker than reflected waves and consequently require separation before being imaged. We have developed a Mahalanobis-based diffraction imaging method by modifying the classic Kirchhoff formula with an exponential function to account for the dynamic differences between reflections and diffractions in the shot domain. The imaging method can automatically account for destroying of reflected waves, constructive stacking of diffracted waves, and strengthening of scattered waves. The method can overcome the difficulties in handling Fresnel apertures, and it is suitable for high-resolution imaging because of the consistency of the waveforms in the shot domain. Although the proposed method in principle requires a good migration velocity model for calculating elementary diffraction traveltimes, it is robust to an inaccurate migration velocity model. Two numerical experiments demonstrate the feasibility of the proposed method in removing reflections and highlighting diffractions, and one field application further confirms its efficiency in resolving masked faults and collapsed columns.

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.

Diffractivity — Another attribute for the interpretation of seismic data in hard rock environment, a case study

2016 ◽  
Vol 4 (4) ◽  
pp. B23-B32 ◽  
Author(s):  
Mohammad Javad Khoshnavaz ◽  
Andrej Bóna ◽  
Muhammad Shahadat Hossain ◽  
Milovan Urosevic ◽  
Kit Chambers
Keyword(s):  
Seismic Data ◽  
Hard Rock ◽  
Shear Zones ◽  
Primary Objective ◽  
Seismic Exploration ◽  
Image Point ◽  
Small Scale ◽  
Imaging Method ◽  
Data Set ◽  
Diffraction Imaging

The primary objective of seismic exploration in a hard rock environment is the detection of heterogeneities such as fracture zones, small-scale geobodies, intrusions, and steeply dipping structures that are often associated with mineral deposits. Prospecting in such environments using seismic-reflection methods is more challenging than in sedimentary settings due to lack of continuous reflector beds and predominance of steeply dipping hard rock formations. The heterogeneities and “fractal” aspect of hard rock geologic environment produce considerable scattering of the seismic energy in the form of diffracted waves. These scatterers can be traced back to irregular and often “sharp-shaped” mineral bodies, magmatic intrusions, faults, and complex and heterogeneous shear zones. Due to the natural lack of reflectors and abundant number of diffractors, there are only a few case studies of diffraction imaging in hard rock environments. There are almost no theoretical models or field examples of diffraction imaging in prestack domain. We have filled this gap by applying a 3D prestack diffraction imaging method to image point diffractors. We calculated the diffractivity by computing the semblance of seismic data along diffraction traveltime curves in the prestack domain. The performance of the method is evaluated on a synthetic case and a field seismic data set collected over the Kevitsa mineral deposit in northern Finland. The high-resolution results obtained by the application of prestack diffraction imaging suggest that diffractivity is a robust attribute that can be used in addition to other seismic attributes for the interpretation of seismic data in hard rock environment.

3D diffraction imaging with Kirchhoff time migration using vertical traveltime difference gathers

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. S555-S566 ◽  
Author(s):  
Zhengwei Li ◽  
Jianfeng Zhang
Keyword(s):  
Fresnel Zone ◽  
Lateral Position ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Small Scale ◽  
Imaging Method ◽  
Time Migration ◽  
Diffraction Imaging ◽  
Dip Angle ◽  
Angle Gather

We have built a vertical traveltime difference (VTD) gather to image diffractions in the 3D time domain. This significantly improves detection of small-scale faults and heterogeneities in 3D seismic data. The VTD gather is obtained using 3D Kirchhoff prestack time migration based on the traveltime-related inline and crossline dip angles, which is closely related to the 2D dip-angle gather. In VTD gathers, diffraction events exhibit flattening, whereas reflection events have convex upward-sloping shapes. Different from the 2D dip-angle gather, Fresnel zone-related specular reflections are precisely focused on the given regions over all offsets and azimuths, thus leaving more diffraction energy after muting. To image linear diffractors, such as faults in three dimensions, the VTD gather can be extended into two dimensions by adding a dip-azimuth dimension. This makes it possible to correct phases of edge diffractions and detect the orientations of the linear diffractors. The memory requirement of the VTD or VTD plus azimuth gathers is much less than that of the 2D dip-angle gathers. We can store the gathers at each lateral position and then correct the phase and enhance the weak diffractions in 3D cases. Synthetic and field data tests demonstrate the effectiveness of our 3D diffraction imaging method.

Accurate diffraction imaging for detecting small-scale geologic discontinuities

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. S447-S457 ◽  
Author(s):  
Peng Lin ◽  
Suping Peng ◽  
Jingtao Zhao ◽  
Xiaoqin Cui ◽  
Wenfeng Du
Keyword(s):  
Signal To Noise Ratio ◽  
Migration Velocity ◽  
Minimum Variance ◽  
Seismic Interpretation ◽  
Small Scale ◽  
Imaging Method ◽  
Velocity Analysis ◽  
Diffraction Imaging ◽  
Correlation Properties ◽  
Beamforming Technique

Seismic diffractions contain valuable information regarding small-scale inhomogeneities or discontinuities, and therefore they can be used for seismic interpretation in the exploitation of hydrocarbon reservoirs. Velocity analysis is a necessary step for accurate imaging of these diffractions. A new method for diffraction velocity analysis and imaging is proposed that uses an improved adaptive minimum variance beamforming technique. This method incorporates the minimum variance, coherence factor, and correlation properties to improve the signal-to-noise ratio and enhance correlations. Our method can make seismic diffractions become better focused in semblance panels, allowing for the optimal migration velocity for diffractions to be accurately picked. Synthetic and field examples demonstrate that the migration velocity for the diffractions can differ from that for the reflections. The results suggest that the diffraction velocity analysis and imaging method is feasible for accurately locating and identifying small-scale discontinuities, which leads to the possibility of using this approach for practical application and seismic interpretation.

High Resolution Diffraction Imaging of Small Scale Fractures Fields in Uconventional Shale Plays

2013 ◽  
Author(s):  
Alexander Mihai Popovici ◽  
Ioan Sturzu ◽  
Iulian Musat ◽  
Nick Tanushev ◽  
Tijmen Moser ◽  
...  
Keyword(s):  
High Resolution ◽  
Small Scale ◽  
Diffraction Imaging
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