"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates"
"uuid:828be3c9-82fb-4ec3-b663-85d09d0a130f","http://resolver.tudelft.nl/uuid:828be3c9-82fb-4ec3-b663-85d09d0a130f","Application of the finite-difference contrast-source inversion algorithm to seismic full-waveform data","Abubakar, A.; Hu, W.; Habashy, T.M.; Van den Berg, P.M.","","2009","We have applied the finite-difference contrast-source inversion (FDCSI) method to seismic full-waveform inversion problems. The FDCSI method is an iterative nonlinear inversion algorithm. However, unlike the nonlinear conjugate gradient method and the Gauss-Newton method, FDCSI does not solve any full forward problem explicitly in each iterative step of the inversion process. This feature makes the method very efficient in solving large-scale computational problems. It is shown that FDCSI, with a significant lower computation cost, can produce inversion results comparable in quality to those produced by the Gauss-Newton method and better than those produced by the nonlinear conjugate gradient method. Another attractive feature of the FDCSI method is that it is capable of employing an inhomogeneous background medium without any extra or special effort. This feature is useful when dealing with time-lapse inversion problems where the objective is to reconstruct changes between the baseline and the monitor model. By using the baseline model as the background medium in crosswell seismic monitoring problems, high quality time-lapse inversion results are obtained.","finite difference methods; geophysical techniques; inverse problems; seismology","en","journal article","Society of Exploration Geophysicists","","","","","","","","Applied Sciences","IST/Imaging Science and Technology","","","",""
"uuid:1b484198-cf85-4350-8c30-6f271e6d9680","http://resolver.tudelft.nl/uuid:1b484198-cf85-4350-8c30-6f271e6d9680","Near-surface attenuation estimation using wave-propagation modeling","El Yadari, N.; Ernst, F.; Mulder, W.","","2008","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 assume that existing methods can provide a horizontally layered velocity and density model. Because near-surface attenuation is strongest, we propose a method to estimate the P-wave attenuation based on viscoacoustic finite-difference modeling. We compare energy decay along traveltime curves of reflection and refraction events in the modeled and observed seismic data for a range of attenuation parameters. The best match provides an estimate of the attenuation. First, we estimate only the attenuation of the top layer and study the sensitivity to depth and velocity perturbations. Then, we consider multiple layers. We apply the method to synthetic and real data and investigate the effect of source wavelet and topography. The method is robust against depth and velocity perturbations smaller than 10%. The results are sensitive to the source wavelet. Incorporating the surface topography in the computed traveltimes reduces the uncertainty of the attenuation estimates, especially for deeper layers.","finite difference methods; inverse problems; seismic waves; seismology; wavelet transforms","en","journal article","Society of Exploration Geophysicists","","","","","","","","Civil Engineering and Geosciences","Geotechnology","","","",""
"uuid:d318d898-7799-4c6a-b339-3fde71306c9e","http://resolver.tudelft.nl/uuid:d318d898-7799-4c6a-b339-3fde71306c9e","Application of a linear finite-frequency theory to time-lapse crosswell tomography in ultrasonic and numerical experiments","Spetzler, J.; Sijacic, D.; Wolf, K.H.A.A.","","2007","Time-lapse seismic monitoring is the geophysical discipline whereby multiple data sets recorded at the same location but at different times are used to locate and quantify temporal changes in the elastic parameters of the subsurface. We validate a time-lapse monitoring method by crosswell tomography using two types of wavefield-modeling experiments: (1) a 3D real ultrasonic waveform experiment and (2) 2D synthetic finite-difference wavefield simulations. For both wavefield experiments, a time-lapse structure simulating a fluid sweep in a reservoir layer is applied. The time-lapse tomographic monitoring approach is based on the standard ray theory and a finite-frequency wavefield theory, where the latter takes into account the finite-frequency properties of recorded wavefields. The inverted time-lapse models compiled with either the ray theory or the finite-frequency wavefield theory locate and correctly quantify the flooding zone in the simulated fluid sweep model. Both wavefield theories provide an adequate result because the flooding zone is comparable in size to the Fresnel volume.","finite difference methods; geophysical techniques; hydrocarbon reservoirs; seismic waves; seismology","en","journal article","Society of Exploration Geophysicists","","","","","","","","Civil Engineering and Geosciences","Geotechnology","","","",""
"uuid:78eea899-c7f4-4383-9eb8-9eac4bf7ec0e","http://resolver.tudelft.nl/uuid:78eea899-c7f4-4383-9eb8-9eac4bf7ec0e","Validation of first-order diffraction theory for the traveltimes and amplitudes of propagating waves","Jocker, J.; Spetzler, J.; Smeulders, D.M.J.; Trampert, J.","","2006","Ultrasonic measurements of acoustic wavefields scattered by single spheres placed in a homogenous background medium (water) are presented. The dimensions of the spheres are comparable to the wavelength and the wavelength and represent both positive (rubber) and negative (teflon) velocity anomalies with respect to the background medium. The sensitivity of the recorded wavefield to scattering in terms of traveltime delay and amplitude variation is investigated. The results validate a linear (first-order) diffraction theory for wavefields propagating in heterogeneous media with anomaly contrasts on the order of ±15%. The diffraction theory is compared further with the exact results known from literature for scattering from an elastic sphere, formulated in terms of Legendre polynomials. To investigate the 2D case, the first-order scattering theory is tested against 2D elastic finite-difference calculations. As the presented theory involves a volume integral, it is applicable to any geometric shape, and the scattering object does not need to be spherical or any other specific symmetrical shape. Furthermore, it can be implemented easily in seismic data inversion schemes, which is illustrated with examples from seismic crosswell tomography and a reflection experiment.","seismic waves; seismology; acoustic waves; rubber; finite difference methods","en","journal article","Society of Exploration Geophysicists","","","","","","","","Civil Engineering and Geosciences","Geotechnology","","","",""