Fault intersection and induced seismicity: the effects on the induced stress field and the dynamic rupture, and their implications

Intersecting faults are often ignored in the geomechanical simulation of induced seismicity. To investigate the effects of fault intersection and the resulting reservoir geometry on induced seismicity, caused, for instance, by gas extraction, we have developed 3D geomechanical models considering two intersecting normal faults and the...

Linking geomechanical simulation of induced seismicity to surface seismic observations: Simulated finite fault rupture to moment tensor inversion

Dynamic geomechanical modeling can generate the seismic wavefield caused by a fault rupture. In dynamic fault-rupture modeling, the source is considered to be finite, with a limited extent both in space and in time. This contrasts with the definition of a point source, which is generally assumed to explain the seismic wavefield caused by an...

Closing the performance gap between an iterative frequency-domain solver and an explicit time-domain scheme for 3D migration on parallel architectures

Three-dimensional reverse-time migration with the constant-density acoustic wave equation requires an efficient numerical scheme for the computation of wavefields. An explicit finite-difference scheme in the time domain is a common choice. However, it requires a significant amount of disk space for the imaging condition. The frequency-domain...

Multi-objective full waveform inversion in the absence of low frequencies

Least-squares inversion of seismic reflection waveforms can reconstruct remarkably detailed models of the Earth’s subsurface. However, the cycle-skipping associated with the highfrequency waveforms are responsible for spurious local minima in its objective function. Therefore, it is often difficult for descent methods to converge to the true...

Performance and scalability of finite-difference and finite-element wave-propagation modeling on Intel's Xeon Phi

With the rapid developments in parallel compute architectures, algorithms for seismic modeling and imaging need to be reconsidered in terms of parallelization. The aim of this paper is to compare scalability of seismic modeling algorithms: finite differences, continuous mass-lumped finite elements and discontinuous Galerkin finite elements. The...

Methods for source-independent Q estimation from microseismic and crosswell perforation shot data in a layered, isotropic viscoelastic medium

We consider the problem of anelastic full waveform inversion in a multi-layered, isotropic viscoelastic medium from microseismic and cross-hole perforation shots. Usually, the source wavelet is not well known, so we focus on Q estimation techniques that can handle this problem. We revisit the spectral ratio method (SRM) and discuss its domain of...

Decoupling of elastic parameters with iterative linearized inversion

Three model parameters as a function of position describe wave propagation in an isotropic elastic medium. Ideally, imaging of data for a point scatterer that consists of a perturbation in one of the elastic parameters should only provide a reconstruction of that perturbation, without cross-talk into the other parameters. This is not the case...

Local time stepping with the discontinuous Galerkin method for wave propagation in 3D heterogeneous media

Modeling and imaging techniques for geophysics are extremely demanding in terms of computational resources. Seismic data attempt to resolve smaller scales and deeper targets in increasingly more complex geologic settings. Finite elements enable accurate simulation of time-dependent wave propagation in heterogeneous media. They are more costly...

A new optimization approach for source-encoding full-waveform inversion

Waveform inversion is the method of choice for determining a highly heterogeneous subsurface structure. However, conventional waveform inversion requires that the wavefield for each source is computed separately. This makes it very expensive for realistic 3D seismic surveys. Source-encoding waveform inversion, in which the sources are modeled...

Quasi-analytical method for frequency-to-time conversion in CSEM applications

Frequency-to-time transformations are of interest to controlled-source electromagnetic methods when time-domain data are inverted for a subsurface resistivity model by numerical frequency-domain modeling at a selected, small number of frequencies whereas the data misfit is determined in the time domain. We propose an efficient, Prony-type method...

A new empirical complex electrical resistivity model

Macroscopic measurements of electrical resistivity require frequency-dependent effective models that honor the microscopic effects observable in macroscopic measurements. Effective models based on microscopic physics exist alongside with empirical models. We adopted an empirical model approach to modify an existing physical model. This provided...

Effects of the airwave in time-domain marine controlled-source electromagnetics

In marine time-domain controlled-source electromagnetics (CSEM), there are two different acquisition methods: with horizontal sources for fast and simple data acquisition or with vertical sources for minimizing the effects of the airwave. Illustrations of the electric field as a function of space and time for various source antenna orientations,...

Exploiting the airwave for time-lapse reservoir monitoring with CSEM on land

In the application of controlled source electromagnetics for reservoir monitoring on land, repeatability errors in the source will mask the time-lapse signal due to hydrocarbon production when recording surface data close to the source. We demonstrate that at larger distances, the airwave will still provide sufficient illumination of the target....

Near-surface attenuation estimation using wave-propagation modeling

The effect of the near surface on seismic land data can be so severe that static corrections are insufficient. Full-waveform inversion followed by redatuming may be an alternative, but inversion will work only if the starting model is sufficiently close to the true model. As a first step toward determining a viscoelastic near-surface model, we...

Time-domain modeling of electromagnetic diffusion with a frequency-domain code

We modeled time-domain EM measurements of induction currents for marine and land applications with a frequency-domain code. An analysis of the computational complexity of a number of numerical methods shows that frequency-domain modeling followed by a Fourier transform is an attractive choice if a sufficiently powerful solver is available. A...

A new iterative solver for the time-harmonic wave equation

The time-harmonic wave equation, also known as the Helmholtz equation, is obtained if the constant-density acoustic wave equation is transformed from the time domain to the frequency domain. Its discretization results in a large, sparse, linear system of equations. In two dimensions, this system can be solved efficiently by a direct method. In...