**Source**

**Conference**

**Theme**

**Author**

**Concept Tag**

- acoustic-poroelastic interface (1)
- algorithm (1)
- Alkhalifah (2)
- America (1)
- anelliptic approximation (3)
- anisotropic media (4)
- anisotropic parameterization (1)
- anisotropy (4)
- anisotropy continuation (1)
- annual international meeting (2)
- annual meeting (3)
- aperture (1)
- approximation (4)
- artifact (1)
- Artificial Intelligence (3)
- assumption (1)
- blue line (1)
- bulk modulus (1)
- Bulletin (1)
- Cartesian (1)
- coefficient (2)
- continuity (1)
- critical angle (1)
- Curvilinear (1)
- decomposition (1)
- depth-imaging domain (2)
- Directional Drilling (1)
- directionality (1)
- discontinuity (1)
- displacement (1)
- drilling operation (1)
- elastic wave (2)
- elastic-poroelastic interface (1)
- exploration (1)
- fast time-to-depth (1)
- Fomel (1)
- forward modeling (1)
- frequency (1)
- generalized nonhyperboloidal moveout approximation (1)
- geophysical journal international (2)
- geophysics (7)
- homogeneous vti (1)
- hyperbola traveltime approximation (1)
- image ray (2)
- incidence angle (1)
- interface (1)
- international exposition (1)
- intersection singularity (1)
- Interval velocity estimation (1)
- inversion (1)
- isotropic media (1)
- lateral heterogeneity (1)
- layered media (1)
- lowrank approximation (1)
- machine learning (1)
- Marchenko (2)
- Marchenko equation (1)
- Marchenko method (2)
- media (6)
- null null null null (1)
- nullnull (1)
- orthorhombic media (4)
- phase direction (1)
- phase velocity (1)
- plane-wave analysis (1)
- point singularity (1)
- polarization vector (1)
- porous media (1)
- Psencik (1)
- qp -velocity (1)
- qP velocity (3)
- radiation direction (1)
- reciprocity theorem (1)
- recursive integral time extrapolation (1)
- reference list (4)
- reflection coefficient (1)
- Reflection Traveltime (1)
- relative misfit (1)
- Reservoir Characterization (12)
- SEG (1)
- seg denver 2014 (3)
- seismic anisotropy (2)
- seismic ray (1)
- seismological society (1)
- sensitivity (1)
- separation (1)
- singularity (1)
- subsurface (2)
- subsurface position (1)
- surface aperture (1)
- symmetry plane (1)
- th annual international (1)
- time-to-depth conversion (2)
- transversely isotropic (3)
- traveltime (3)
- Tsvankin (3)
- Upstream Oil & Gas (14)
- Van der Neut (1)
- VTI model (1)
- Wapenaar (2)

**File Type**

A focusing function is a specially constructed field that will come into focus at a specified subsurface position upon back propagation (injection) into the medium. The concept of focusing functions is a key ingredient in the Marchenko method and its applications such as retrieving Green’s function, redatuming, imaging with multiples, and creating virtual sources/receivers. In this study, we show how the focusing function and its corresponding focused response at a specified subsurface position are heavily influenced by the data aperture at the surface. Such effects can be explained by considering focusing function in the context of time-domain imaging and its usual assumptions. In particular, we show that the focused response in the time-imaging domain radiates in the direction perpendicular to the line drawn from the center of the surface data aperture to the focused position. The corresponding direction in the Cartesian domain is simply then a combination of the time-domain direction and the directional change due to time-to-depth conversion. Therefore, the result from this study provides insights towards a better understanding of focusing function and may have meaningful implications in applications such as the construction of virtual subsurface source, where the directionality of the focused response is important.

Presentation Date: Tuesday, October 16, 2018

Start Time: 1:50:00 PM

Location: Poster Station 12

Presentation Type: Poster

SPE Disciplines: Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)

The Marchenko method represents a constructive technique toobtain Green�s functions between the acquisition surface andany arbitrary point in the medium. The process generally involvessolving an inversion starting with a direct-wave Green's function from the desired subsurface position, which is typicallyobtained using an approximate velocity model. In thisstudy, we first propose to formulate the Marchenko method inthe time-imaging domain. We recognize that the traveltimeof the direct-wave Green�s function is related to the Cheop�straveltime pyramid commonly used in time-domain processingand can be readily obtained from the local slopes of thecommon-midpoint (CMP) gathers. This observation allowsus to substitute the need for a prior velocity model with thedata-driven slope estimation process. Moreover, we show thatworking in the time-imaging domain allows for the specificationof the desired subsurface position in terms of vertical time,which is connected to the Cartesian depth position via the timeto-depth conversion. Our results suggest that the prior velocitymodel is only required when specifying the position in depthbut this requirement can be circumvented by making use of thetime-imaging domain and its usual assumptions. Provided thatthose assumptions are satisfied, the estimated Green�s functionsfrom the proposed method have comparable quality tothose obtained with the knowledge of a prior velocity model.

Presentation Date: Wednesday, October 17, 2018

Start Time: 1:50:00 PM

Location: 211A (Anaheim Convention Center)

Presentation Type: Oral

SPE Disciplines: Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)

The Biot theory provides a general framework for describing the seismic response of porous media. Proper boundary conditions must be specified for the following three cases: the elastic-poroelastic interface, the acoustic-poroelastic interface and the poroelastic-poroelastic interface for accurate modeling and inversion of seismic data. In this study, we first review the expressions for reflection coefficients for all three cases from plane-wave analysis. We subsequently benchmark the first two cases against spectral element method (SEM) forward modeling to verify and ensure consistency between finite-frequency wavelets. We show with numerical examples, that both methods lead to comparable results within frequency range between 5Hz and 80Hz, which is of relevance to exploration seismology.

Presentation Date: Monday, October 15, 2018

Start Time: 1:50:00 PM

Location: Poster Station 15

Presentation Type: Poster

acoustic-poroelastic interface, bulk modulus, coefficient, continuity, critical angle, displacement, elastic-poroelastic interface, forward modeling, frequency, incidence angle, interface, plane-wave analysis, porous media, reflection coefficient, relative misfit, Reservoir Characterization, Upstream Oil & Gas

SPE Disciplines: Reservoir Description and Dynamics > Reservoir Characterization > Seismic processing and interpretation (1.00)

Shibo Xu and Alexey Stovas, Norwegian University of Science and Technology Yanadet Sripanich, the University of Texas at Austin Summary We propose an anelliptic approximation for the relative geometrical spreading of P -wave in a homogeneous transversely isotropic medium with vertical symmetry axis (VTI) and an orthorhombic medium (ORT). The coefficients in the proposed approximation are only defined within the symmetry planes. From our numerical examples, we show that for a homogeneous VTI model, the anelliptic approximation is more accurate than the gene ralized nonhyperbolic moveout approximation (GMA) form approximation for larger offset. For a homogeneous ORT model, the proposed anelliptic approximation is more accurate than the indirect approximation. The geometrical spreading needs to be considered for prestack Kirchhoff migration, amplitude versus offset (AVO) analysis and other seismic data processing methods that require the true amplitude processing.

We develop a general framework for computing reflection traveltime derivatives with respect to offset in layered anisotropic media with weak lateral heterogeneities from curved interfaces and smoothly variable velocities. We specify the expression for the second-order derivative related to normal moveout (NMO) velocity and show that it is influenced by both types of heterogeneities. In general layered media, the effects get accumulated along the raypath from the source to the receiver and can be computed using the proposed recursive relationship. Numerical examples show that taking into account heterogeneities can lead to more accurate moveout approximations and therefore, aid in analysis of estimated NMO velocities in practice.

Presentation Date: Monday, September 25, 2017

Start Time: 2:40 PM

Location: Exhibit Hall C/D

Presentation Type: POSTER

We propose a method for time-to-depth conversion and interval velocity estimation in the presence of weak lateral velocity variations. By considering only first-order perturbative effects from lateral variations, the exact system of partial differential equations (PDEs) required to accomplish the exact conversion is reduced to a simpler system that can be solved efficiently in a layer-stripping fashion. Numerical examples show that the proposed method can achieve reasonable accuracy and is significantly more efficient with a speedup by a factor of 10 than previously proposed methods that are based on the numerical solution of the original system of PDEs.

Presentation Date: Wednesday, September 27, 2017

Start Time: 10:10 AM

Location: 371A

Presentation Type: ORAL

Velocity continuation is a process of continuous image propagation in velocity. It allows one to generate an image corresponding to a certain migration velocity without returning to the original data. We extend the theory of velocity continuation to account for non-hyperbolic shape of travel-time curves in anisotropic media using shifted-hyperbola approximation. Corresponding image propagation process becomes two-dimensional, where propagation parameters are the normal moveout velocity and the anisotropy parameter. Continuity of image transformation with respect to migration parameters leads to superior computational efficiency of the proposed approach with respect to conventional migration velocity analysis techniques in anisotropic media. Synthetic data examples demonstrate the validity of the method.

Presentation Date: Tuesday, September 26, 2017

Start Time: 3:05 PM

Location: Exhibit Hall C/D

Presentation Type: POSTER

Conventional solutions of elastic wave equations rely on inaccurate finite-difference approximations of the time derivative, which result in strict dispersion and stability conditions and limitations. In this work, we derive a general solution to the elastic anisotropic wave equation, in the form of a Fourier Integral Operator (FIO). The proposed method is a generalization of the previously developed recursive integral time extrapolation operators from acoustic to elastic media, and can accurately propagate waves in time using the form of the analytical solution in homogeneous media. The formulation is closely connected to elastic wave mode decomposition, and can be applied to the most general anisotropic medium. The numerical calculation of the FIO makes use of lowrank approximation to enable highly accurate and stable wave extrapolations. Numerical examples include wave propagation in 3D heterogeneous orthorhombic and triclinic models.

Presentation Date: Monday, October 17, 2016

Start Time: 1:00:00 PM

Location: 171/173

Presentation Type: ORAL

Good choices of anisotropic parameters allow complex formulas for wave attributes to be expressed in a concise manner with the complexity hidden inside the notation. Other important features of good parameterizations include simple reduction to pseudoacoustic approximations for qP waves and relative independence (orthogonality) for parameter estimation. We compare four parameterization schemes for TI and orthorhombic anisotropy by analyzing the sensitivity of the qP-wave phase and group velocities to different parameters. We quantify the parameter sensitivity using a generic resolution matrix when both the full parameterization and pseudoacoustic approximation are considered separately. Our results indicate that the Muir-Dellinger and Chapman-Miller-Fowler parameterizations represent better behaved schemes to characterize qP-wave kinematics.

Presentation Date: Wednesday, October 19, 2016

Start Time: 3:35:00 PM

Location: Lobby D/C

Presentation Type: POSTER

Alkhalifah, anisotropic media, anisotropic parameterization, anisotropy, approximation, Artificial Intelligence, elastic wave, geophysical journal international, geophysics, machine learning, media, orthorhombic media, Psencik, qP velocity, reference list, Reservoir Characterization, sensitivity, transversely isotropic, Tsvankin, Upstream Oil & Gas, weakly anisotropic

**Summary**

The task of wave-vector decomposition is to separate wave modes in the wavenumber domain. We consider an analytical decomposition operator and extend it to orthorhombic media. We define the two qS-wave modes by sorting them according to phase velocity, which leads to dividing the qS-wave phaseslowness surfaces along the point singularity. The point singularity is located using an analytical condition derived from the exact phase-velocity expressions for qS waves. This condition defines an area in which we apply a smoothing operator to reduce the planar artifacts caused by the local discontinuity of polarization vectors at the singularity. The proposed method provides an effective decomposition of the two qS-wave modes in orthorhombic media.

**Introduction**

In seismic imaging, seismic wave modes generally need to be decoupled. Wave-mode separation in isotropic media is relatively simple by means of the divergence and curl operators (Aki and Richards, 2002). Dellinger and Etgen (1990) extended this concept to 2D anisotropic media and projected the vector wavefield onto the mode polarization vectors found by solving the Christoffel equation. Yan and Sava (2008) applied wave-mode separation for elastic RTM (reverse-time migration) in isotropic media. Yan and Sava (2009) addressed wave-mode separation in the space domain via the use of nonstationary spatial filters. This method was later extended to the tilted transversely isotropic (TTI) media (Yan and Sava, 2012) and improved by frequency-domain phase-shift plus interpolation (PSPI) technique, which increases its performance (Yan and Sava, 2011).

Alternatively, Zhang and McMechan (2010) proposed a vector decomposition method, which was based on the principle of projecting wavefield onto polarization vectors, and successfully applied this method to vertical transversely isotropic (VTI) media. In both wave-mode separation and vector decomposition, computational cost presents a primary challenge because of the need to solve the Christoffel equation in all phase directions for a given set of stiffness tensor coefficients at each spatial location in the medium. Cheng and Fomel (2014) proposed to reformulate the separation and decomposition operators as Fourier Integral Operators (FIOs) and apply the low-rank approximation (Fomel et al., 2013) for computing FIOs, which significantly improved computational efficiency. In a different approach, partial mode separation during extrapolation using the pseudo-pure-mode wave equations also improves the efficiency and produces satisfactory results (Cheng and Kang, 2014; Kang and Cheng, 2012).

anisotropic media, artifact, Artificial Intelligence, decomposition, discontinuity, geophysics, intersection singularity, media, orthorhombic media, phase direction, phase velocity, point singularity, polarization vector, Reservoir Characterization, separation, singularity, Upstream Oil & Gas, vector, wave-mode separation, wave-vector decomposition, wavefield

Thank you!