Refined karst feature and fault identification through integrated wave field separation and imaging of Diffraction energy

2021 ◽  
Author(s):  
R. Alay
Keyword(s):  
Wave Field ◽  
Water Environment ◽  
Fault Identification ◽  
Small Scale ◽  
Advantages And Disadvantages ◽  
Specular Reflections ◽  
Total Wave ◽  
Karst Feature ◽  
Wave Field Separation ◽  
Field Separation

In this abstract, a case study from offshore Indonesia is showcased with examples emphasizing integrated wave field separation methods with the objective of diffraction imaging towards refined karst feature and fault identification. For imaging optimally all diffraction energy, pre-migration and post-migration methods have been integrated. The dataset and examples in this abstract are in a complex geological setting in a very shallow water environment, with a subsurface that is characterized by large carbonate pinnacles containing large amount of karst features with thinning and thickening carbonate layers. For the purpose of refined imaging of diffraction energy only, the total wave field has been separated into specular reflections and diffractions prior to migration and these have been integrated with existing post-migration wave field separation methods. Both the pre-migration and post-migration wave field separation methods have their advantages and disadvantages and is discussed later in this abstract. Diffraction energy, in general is much lower in amplitude than the specular reflections and separately imaging these, unveils higher resolution small scale geological features such as karst features and faults complementing the total wave field PSDM data. With existing industry available methods applying wave field separation in either pre-migration or post-migration stage, limitations have been observed, and therefore we propose in this abstract to integrate both methods and take advantage of the improvements showcased with examples throughout the abstract.

Processing of a nine‐component near‐offset VSP for seismic anisotropy

Geophysics ◽  
1997 ◽  
Vol 62 (2) ◽  
pp. 676-689 ◽  
Author(s):  
Colin MacBeth ◽  
Xiang‐Yang Li ◽  
Xinwu Zeng ◽  
Dale Cox ◽  
John Queen
Keyword(s):  
Wave Field ◽  
Seismic Anisotropy ◽  
Similarity Transformation ◽  
Seismic Profile ◽  
Test Facility ◽  
Near Surface ◽  
Common Reference ◽  
Wave Field Separation ◽  
Matrix Operators ◽  
Field Separation

A convolutional sequence of matrix operators is offered as a convenient deterministic scheme for processing a multicomponent vertical seismic profile (VSP). This sequence is applied to a nine‐component near‐offset VSP recorded at the Conoco borehole test facility, Kay County, Oklahoma. These data are corrected for tool spin and near‐surface anisotropy together with source coupling or imbalance. After wave‐field separation using a standard f‐k filter, each source and receiver pair for the upgoing waves is adjusted to a common reference depth using a matrix operator based on the downgoing wave‐field. The up‐ and downgoing waves are then processed for anisotropy by a similarity transformation, to separate the [Formula: see text] and [Formula: see text] waves, from which the anisotropic properties are estimated. These estimates reveal a strong (apparent) vertical birefringence in the near‐surface, but weak or moderate values for the majority of the subsurface. The target zone consists of a thin sandstone and deeper shale layer, both of which possess a strong vertical birefringence. The sandstone corresponds to a zone of known fluid flow. An observed [Formula: see text] attenuation and polarization change in the shale suggest it contains large fractures.

scholarly journals Coherent diffraction imaging for enhanced fault and fracture network characterization

Solid Earth ◽  
2020 ◽  
Vol 11 (5) ◽  
pp. 1891-1907
Author(s):  
Benjamin Schwarz ◽  
Charlotte M. Krawczyk
Keyword(s):  
Wave Field ◽  
Fracture Network ◽  
Small Scale ◽  
Fracture Networks ◽  
Systematic Assessment ◽  
Advantages And Disadvantages ◽  
Coherent Diffraction Imaging ◽  
Diffraction Imaging ◽  
Geophysical Imaging ◽  
Data Coherence

Abstract. Faults and fractures represent unique features of the solid Earth and are especially pervasive in the shallow crust. Aside from directly relating to crustal dynamics and the systematic assessment of associated risk, fault and fracture networks enable the efficient migration of fluids and therefore have a direct impact on concrete topics relevant to society, including climate-change-mitigating measures like CO2 sequestration or geothermal exploration and production. Due to their small-scale complexity, fault zones and fracture networks are typically poorly resolved, and their presence can often only be inferred indirectly in seismic and ground-penetrating radar (GPR) subsurface reconstructions. We suggest a largely data-driven framework for the direct imaging of these features by making use of the faint and still often underexplored diffracted portion of the wave field. Finding inspiration in the fields of optics and visual perception, we introduce two different conceptual pathways for coherent diffraction imaging and discuss respective advantages and disadvantages in different contexts of application. At the heart of both of these strategies lies the assessment of data coherence, for which a range of quantitative measures is introduced. To illustrate the versatility and effectiveness of the approach for high-resolution geophysical imaging, several seismic and GPR field data examples are presented, in which the diffracted wave field sheds new light on crustal features like fluvial channels, erosional surfaces, and intricate fault and fracture networks on land and in the marine environment.

Expanding boundaries in search for small size features – towards an integrated wave field separation approach

2020 ◽  
Author(s):  
Riaz Alai ◽  
Afiq Mokhtar ◽  
Christopher Lee Slind ◽  
Yonghe Guo ◽  
Jun Wang ◽  
...  
Keyword(s):  
Wave Field ◽  
Wave Field Separation ◽  
Field Separation
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