Download or read book Targeted Full waveform Inversion for Recovering Thin and Ultra thin layer Properties Using Radar and Seismic Reflection Methods written by Esther Babcock and published by . This book was released on 2014 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Ground penetrating radar (GPR) and seismic reflection methods are useful geophysical tools for near-surface characterization. Analysis of radar or seismic reflection data can combine velocity analysis with common physical transformations to provide subsurface physical properties such as subsurface porosity, density, and contaminant locations. However, reliable quantitative characterization of thin subsurface layers may be impossible using standard reflection data processing techniques, e.g. velocity analysis, if the layer thickness is below the conventional resolution limits of the data. The limiting layer thickness for layer resolution may be up to 1/2 or even 3/4 of the dominant wavelength ([lamda]) of the signal in the medium of interest. This limitation often depends on data noise levels and source characteristics. In many environmental problems, target layers may be below this layer thickness and accurate determination of layer properties becomes problematic. In order to reliably quantify thin-layer parameters in these cases, geophysical practitioners require additional tools such as attribute analyses and inversion methodologies. Full-waveform inversions may be able to quantify layer parameters even in the case of thin (

Download or read book Target oriented Elastic Full waveform Inversion written by Ettore Biondi and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Wave-equation-based parameter estimation techniques can retrieve accurate and high-resolution subsurface physical properties from seismic data acquired close to the surface of the Earth. In fact, multiple acoustic full-waveform inversion methods have been proposed over the years to retrieve the P-wave velocity of the subsurface. Moreover, researchers have extended full-waveform inversion approaches to estimate anisotropic and absorption parameters as well. Nowadays, some applications of elastic full-waveform inversion can also be found. However, given its prohibitive computational cost compared to the acoustic counterpart, elastic wave-equation inversion workflows still have limited applicability within seismic exploration datasets. To tackle this challenge, I propose a novel wave-equation-based elastic parameter estimation workflow based on wave-equation operators. I refer to the entire approach as target-oriented elastic full-waveform inversion. The method is composed of two steps. In the first one, I apply an extended linearized waveform inversion to the surface data. The obtained subsurface image is then employed to synthesize data as if they were acquired close to a target area. Finally, this dataset is inverted using an elastic full-waveform inversion workflow to estimate the subsurface elastic parameters. I demonstrate its efficacy on a 2D synthetic test and an ocean-bottom-node dataset acquired in the Gulf of Mexico, showing its ability to retrieve the elastic parameters of potential subsurface prospects. Compared to the elastic inversion of the surface dataset, the proposed method has a computational cost lower by two orders of magnitude.

Download or read book First Steps Towards a Full Waveform Inversion for Shear wave Velocity from Amplitude as a Function of Slowness written by Ingo A. Pecher and published by . This book was released on 2002 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Gas Charged Porous Media from Joint Inversion of P S Wave Attenuation Based on OBS And or Sonic Log Data written by Xiong Lei and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Attenuation refers to the exponential decay of wave amplitude with distance. It is caused by energy-conserved factors (scattering or geometric dispersion), and inelastic dissipation (intrinsic attenuation) where energy is converted into heat. The intrinsic attenuation is frequency dependent and of interest to exploration geophysics, including application in wave propagation forward modeling, signal filtering, gas detection, full waveform inversion, and, as focused on in this dissertation, reservoir property estimation. We characterize gas reservoir by intrinsic attenuation inversion. The advantages of seismic attenuation inversion are that attenuation has a stronger relationship to hydraulic properties than velocity, and gas has more pronounced effects in terms of attenuation. The proposed methodology is easily extendable to oil and other types of reservoirs. The foundation of seismic attenuation inversion is the measurement of quality factor, Q, which is inversely proportional to attenuation. However, it is difficult to estimate Q from reflection data due to the presence of noise intervention, which limits its application. Many methods have been proposed for Q estimation mainly for VSP (vertical seismic profile), crosswell, or transmitted data. With this study, we extend those approaches to reflection data. However, the specific techniques to cope with the corresponding issues, comparison of the efficacy for different approaches, and a clear recommendation on which methods are the best to use under which circumstances are rarely presented. The first part of this thesis is dedicated to resolve these issues using synthetic seismic data. We focus on three frequency-domain methods: spectral ratio method (SRM), centroid frequency shift method (CFS), and peak frequency shift method (PFS). They are less affected by scattering interference compared with time-domain methods. For the three frequency-domain methods, five kinds of pre-processing procedures paired with them are tested. We first determine the optimal length of the window function (for seismic signal frequency transformation). Secondly, we find that a traditional FFT coupled with either the SRM or CFS methods works the best and about equally well in terms of Q estimation error under various levels of noise. A close second is a technique that involves the extraction of wavelets from the signal and their subsequent frequency transformation, again coupled with either SRM or CFS. It is noted that this technique is superior when dealing with thin layers because of its stronger capability of wavelet restoration. Additionally, we find that Q tends to be more accurately estimated for layers with higher attenuation. Moreover, the effective-bandwidth coefficients, which control the length of the effective signal participating in the Q estimation, from 0.2 ~ 0.4 are good values. Then, I show that the joint inversion of P- and S-wave quality factor (Qp and Qs) is powerful in characterizing gas-bearing porous media. Compared to the inversion of Qp alone, where a rock physics model giving Qp as an output is inverted for its input parameters (rock and fluid properties), the joint inversion has one more dimension of information, increasing constraints on the model to suppress the occurrence of multiple solutions. Additionally, joint inversion improves the model sensitivity to the input parameters, enhancing its reliability. Moreover, besides porosity, it allows us to invert one more parameter, here gas saturation. In this section, we implement the inversion workflow on the ocean bottom seismometer (OBS) data from Finneidfjord, Norway, where the free-gas accumulation takes place in the sub-seabed. After sensitivity analysis, the efficacy of the inversion for gas saturation and porosity is verified. The nonsensitive parameters are eliminated from the inversion and set as constants, which reduces the complexity of the problem. By using Differential-Evolution MCMC scheme, we efficiently sample the joint posterior of the saturation and porosity. The estimated gas saturation and porosity (modes of the posteriors) agree with previous research in Finneidfjord. So far, we just discuss and invert the porosity and saturation. The next step would be to invert more solvable unknowns by introducing more information. In the final part of the research, we integrate multiple geophysical datasets (OBS and sonic logs) to realize a more advanced joint inversion. Usually, both the compressional and shear wave sonic waveform data has higher frequencies than seismic. At the two different frequencies, we can have two pairs of Qp, Qs. Adding two more dimensions to the inverse problem constrain the inversion even further, thus reducing uncertainty in estimates and improving the number of the solvable parameters. After establishing the workflow, we take the Hydrate Ridge, Oregon margin where there is free gas accompanied beneath the gas hydrate as a practical example to show the validity of a four-parameter inversion. The gas saturation, porosity, permeability, and characteristic (inclusion) size are simultaneously inverted and in good agreement with the literature about the Hydrate Ridge.

Download or read book Full waveform Inversion to 3D Seismic Land Data written by Ahmed Musallam Ali Al-Yaqoobi and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Full-waveform inversion (FWI) is a technique that seeks to find a high-resolution high-fidelity model of the Earth's subsurface that is capable of matching individual seismic waveforms, within an original raw field dataset, trace by trace. The method begins from a best-guess starting model, which is then iteratively improved using a sequence of linearized local inversions to solve a fully non-linear problem. In principle, FWI can be used to recover any physical property that has an influence upon the seismic wavefield, but in practice the technique has been used predominantly to recover P-wave velocity, and this is the route that is followed here. Full-waveform tomographic techniques seek to determine a highly resolved quantitative model of the sub-surface that will ultimately be able to explain the entire seismic wavefield including those phases that conventional processing and migration seek to remove such as refracted arrivals. Although the underlying theory of FWI is well established, its practical application to 3D land data, and especially to seismic data that have been acquired using vibrators, in a form that is effective and robust, is still a subject of intense research. In this study, 2D and 3D FWI techniques have been applied to a vibrator dataset from onshore Oman. Both the raw dataset and the subsurface model cause difficulties for FWI. In particular, the data are noisy, have weak early arrivals, are strongly elastic, and especially are lacking in low-frequency content. The Earth model appears to contain shallow low-velocity layers, and these compromise the use of first-arrival travel-time tomography for the generation of a starting velocity model. The 2D results show good recovery of the shallow part of the velocity models. The results show a low-velocity layer that extends across the velocity model, but lacking in a high-resolution image due to the absence of the third dimension. The seismograms of the final inversion models give a good comparison with the field data and produce a reasonably high correlation coefficient compared to the starting model. An inversion scheme has been developed in this study in which only data from the shorter offsets are initially inverted since these represent the subset of the data that is not cycle skipped. The offset range is then gradually extended as the model improves. The final 3D model contains a strongly developed low-velocity layer in the shallow section. The results from this inversion appear to match p-wave logs from a shallow drill hole, better flatten the gathers, and better stack and migrate the reflection data. The inversion scheme is generic, and should have applications to other similar difficult datasets.

Download or read book Full Waveform Inversion by Model Extension written by Guillaume Camille Michel Barnier and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic imaging is an effective method to produce accurate maps of the Earth's subsurface, and has been employed for decades in global seismology, hydrocarbon exploration, geothermal energy production, and more recently CO2 sequestration and monitoring. In complex geological settings, the quality of such maps highly depends on having a reliable seismic velocity model, which can be difficult to obtain. In this thesis, I develop a novel method, namely full waveform inversion by model extension (FWIME), designed to produce accurate acoustic velocity models of the subsurface from seismic recordings when conventional methods fail. I leverage the robust convergence properties of wave-equation migration velocity analysis (WEMVA) with the accuracy and high-resolution nature of acoustic full waveform inversion (FWI) by combining these techniques into a compact, mathematically consistent, and user-friendly workflow. By doing so, I mitigate the need for accurate initial models and the presence of coherent long-offset and/or low-frequency energy within the recorded data, which are difficult and costly to acquire but often necessary for conventional methods to succeed. The novelty of my method resides in the design of a custom loss function and the optimization strategy I develop to pair WEMVA with FWI, which is more efficient and powerful than applying each method separately or sequentially. I illustrate the potential of my proposed method by accurately inverting datasets generated by realistic 2D benchmark models which simulate complex and challenging geological scenarios encountered in field applications. In each scenario, the dataset lacks low-frequency energy and the initial velocity model is inaccurate, which prevents conventional methods from recovering useful solutions. In addition, I develop an efficient 3D numerical implementation of FWIME with the use of general-purpose graphics processing units (GPU) to handle 3D field datasets containing tens of terabytes of information, and to recover billions of unknown parameters. I successfully apply FWIME to a 3D ocean-bottom-node dataset acquired by Shell in the Gulf of Mexico. I show that my method outperforms conventional FWI and manages to improve the velocity model and the resulting subsurface image quality.

Download or read book Seismic Reflection Processing written by S.K. Upadhyay and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 641 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seismic Reflection Processing coherently presents the physical concepts, mathematical details and methodology for optimizing results of reservoir modelling, under conditions of isotropy and anisotropy. The most common form of anisotropy - transverse isotropy - is dealt with in detail. Besides, practical aspects in reservoir engineering - such as interval isotropic or anisotropic properties of layered media; identifying lithology, pore-fluid types and saturation; and determining crack/fracture-orientations and density - form the core of discussions. This book incorporates significant new developments in isotropic and anisotropic reflection processing, while organizing them to improve the interpretation of seismic reflection data and optimizing the modeling of hydrocarbon reservoirs. It is written primarily as a reference and tutorial for graduate/postgraduate students and research workers in geophysics.

Download or read book Analysis of Frequency Characteristics of Seismic Reflections with Attenuation in Thin Layer Zone written by Shenghong Tai and published by . This book was released on 2009 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Full Waveform Inversion of Reflection Seismic Data for Ocean Temperature Profiles written by and published by . This book was released on 2008 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We show that ocean temperature profiles can be accurately recovered using only acoustic methods employed at the sea surface. Using a towed air gun array and a hydrophone streamer, thermohaline boundaries are ensonified at a suite of frequencies and angles, yielding travel time trajectories and reflectivities. These data are inverted via full waveform inversion to estimate sound speed and, subsequently, a temperature profile. The high lateral data density of the seismic technique offers the potential of acoustically derived temperature profiles to be used to constrain models of ocean mixing and internal waves. Results on realistic synthetic data show that sound speed can be recovered with arbitrary accuracy when using broadband data, with known source function and recording geometry. Application to field seismic data (corroborated by expendable bathythermograph) shows that even with a seismic acquisition system not specifically calibrated for seismic oceanography, temperature contrasts within the ocean can be recovered to within one degree Celsius.

Download or read book Waveform Inversion of Seismic Reflection Data Through Local Optimisation Methods written by Jonas Lindgren and published by . This book was released on 1992-01-01 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 3D Elastic Full Waveform Inversion for Subsurface Characterization Study of a Shallow Seismic Multicomponent Field Data written by Theodosius Marwan Irnaka and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Full Waveform Inversion (FWI) is an iterative data fitting procedure between the observed data and the synthetic data. The synthetic data is calculated by solving the wave equation. FWI aims at reconstructing the detailed information of the subsurface physical properties. FWI has been rapidly developed in the past decades, thanks to the increase of the computational capability and the development of the acquisition technology. FWI also has been applied in a broad scales including the global, lithospheric, crustal, and near surface scale.In this manuscript, we investigate the inversion of a multicomponent source and receiver near-surface field dataset using a viscoelastic full waveform inversion algorithm for a shallow seismic target. The target is a trench line buried at approximately 1 m depth. We present the pre-processing of the data, including a matching filter correction to compensate for different source and receiver coupling conditions during the acquisition, as well as a dedicated multi-step workflow for the reconstruction of both P-wave and S-wave velocities. Our implementation is based on viscoelastic modeling using a spectral element discretization to accurately account for the wave propagation's complexity in this shallow region. We illustrate the inversion stability by starting from different initial models, either based on dispersion curve analysis or homogeneous models consistent with first arrivals. We recover similar results in both cases. We also illustrate the importance of taking into account the attenuation by comparing elastic and viscoelastic results. The 3D results make it possible to recover and locate precisely the trench line in terms of interpretation. They also exhibit another trench line structure, in a direction forming an angle at 45 degrees with the direction of the targeted trench line. This new structure had been previously interpreted as an artifact in former 2D inversion results. The archaeological interpretation of this new structure is still a matter of discussion.We also perform three different experiments to study the effect of multicomponent data on this FWI application. The first experiment is a sensitivity kernel analysis of several wave packets (P-wave, S-wave, and surface wave) on a simple 3D model based on a Cartesian based direction of source and receiver. The second experiment is 3D elastic inversion based on synthetic (using cartesian direction's source) and field data (using Galperin source) with various component combinations. Sixteen component combinations are analyzed for each case. In the third experiment, we perform the acquisition's decimation based on the second experiment. We demonstrate a significant benefit of multicomponent data FWI in terms of model and data misfit through those experiments. In a shallow seismic scale, the inversions with the horizontal components give a better depth reconstruction. Based on the acquisition's decimation, inversion using heavily decimated 9C seismic data still produce similar results compared to the inversion using 1C seismic of a dense acquisition.

Download or read book Seismic Full Waveform Inversion written by Dongzhuo Li and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: I present three topics in the area of theoretical development and application of Full Waveform Inversion (FWI). The first topic or contribution describes a learning-based adaptive and sparsity promoting regularization method to improve the accuracy of traditional FWI results with the prior knowledge of nonlocal similarity in geological structures. Such a priori is realized by multi-class orthogonal dictionary learning. The second topic extends the learning-based regularization to elastic waves and applies the approach to a field dataset to estimate P-wave and S-wave velocities. This topic highlights the importance of data pre-processing and modification of the FWI algorithm to accommodate field data issues such as radiation pattern estimation, wavelet estimation, and amplitude scaling. The aim of this part is high-resolution reservoir characterization, which is not only an extension of the technique in the first part but also serves as a preparation for the time-lapse inversion in the third part. In the third topic, I describe a framework for using FWI to estimate hidden parameters that are important to geophysical processes such as fluid flow in porous media. This framework extends the power of FWI beyond seismology to other geophysical problems such as reservoir engineering and hydrology by combining seismic observations, rock properties modeling, and flow modeling. This third topic represents a PDE-constrained inverse problem that I solve with an intelligent automatic differentiation method. The method provides three levels of user control with (1) built-in differentiable operators from modern deep-learning infrastructures, and customized operators that can either (2) encapsulate analytic adjoint gradient computation or (3) handle the forward simulation and compute the corresponding gradient for a single time step. This intelligent strategy strikes a good balance between computational efficiency and programming efficiency and would serve as a paradigm for a wide range of PDE-constrained geophysical inverse problems.

Download or read book Full waveform Inversion in the Time Domain with an Energy weighted Gradient written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: When applying full-waveform inversion to surface seismic reflection data, one difficulty is that the deep region of the model is usually not reconstructed as well as the shallow region. We develop an energy-weighted gradient method for the time-domain full-waveform inversion to accelerate the convergence rate and improve reconstruction of the entire model without increasing the computational cost. Three different methods can alleviate the problem of poor reconstruction in the deep region of the model: the layer stripping, depth-weighting and pseudo-Hessian schemes. The first two approaches need to subjectively choose stripping depths and weighting functions. The third one scales the gradient with only the forward propagation wavefields from sources. However, the Hessian depends on wavefields from both sources and receivers. Our new energy-weighted method makes use of the energies of both forward and backward propagated wavefields from sources and receivers as weights to compute the gradient. We compare the reconstruction of our new method with those of the conjugate gradient and pseudo-Hessian methods, and demonstrate that our new method significantly improves the reconstruction of both the shallow and deep regions of the model.

Download or read book Full Waveform Inversion of Walk away VSP Data written by Mark Alvin Roberts and published by . This book was released on 2007 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: Depletion of the earth's hydrocarbon reserves has led to exploration and production in increasingly complex environments. Imaging beneath allochthonous salt (e.g. salt domes) remains a challenging task for seismic techniques due to the large velocity contrast of the salt with neighbouring sediments and the very complex structures generated by salt movement. Extensive allochthonous salt sheets cover many potentially productive regions in the deep-water Gulf of Mexico. Drilling through the base of salt is an extremely challenging task due to widely varying pore-pressure found in the sediments beneath. Seismic methods to estimate the seismic velocity can be used in conjunction with empirical formula to predict the pore pressure. However, accurate measurements are often not possible from surface reflection seismic data, so walk-away Vertical Seismic Profile (VSP) data has been used. This involves repeatedly firing a seismic source at various distances from the borehole (usually an airgun array) while recording the velocities measured by geophones in the borehole placed at appropriate depths near the base of the salt. Before this thesis, the data had been processed using the amplitude versus angle information in a simple one-dimension approximation or using travel time information (also using a 1D assumption). In this thesis, I have used 2D full waveform inversion to tackle the problem of velocity estimation. This has the advantage of simultaneously inverting the whole dataset (including transmitted waves, reflected waves, converted waves) and the method includes traveltime and amplitude information. The inversion was performed using local inversion methods due to the size of the inverse problem and the cost of the forward problem. Concerns over large sensitivity variations, that are inherent in the data acquisition, have lead to an examination of the Gauss-Newton method and possible preconditioning matrices for the conjugate gradient method. Due to the poorly constrained nature of the inverse problem, a smoothness constraint has been applied with an innovative preconditioning method. The methodology has been applied to real data and the pore pressure has been predicted using the well established Eaton equation. In addition, the sub-salt structure was recovered, further demonstrating the value of this technique.

Download or read book Migration Imaging of the Transient Electromagnetic Method written by Xiu Li and published by Springer. This book was released on 2016-10-15 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is based on more than a decade of research the authors have pursued on the pseudo-seismic migration imaging of the transient electromagnetic method, and provides a series of important findings on the theory and applications in this area. It present and analyzes transforming principles, TEM wave field methods, characteristics of the TEM virtual wave field and studies on many significant related technologies. The coverage is supplemented by a wealth of 1-D, 2-D and 3-D figures to illustrate pseudo-seismic theory. The book offers a valuable resource for teachers, students, researchers and engineers in the fields of geophysics, earth exploration and information technology.

Download or read book Aspects of Seismic Reflection Data Processing written by R. Marschall and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Full 3D Seismic Waveform Inversion written by Po Chen and published by Springer. This book was released on 2016-10-29 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces a methodology for solving the seismic inverse problem using purely numerical solutions built on 3D wave equations and which is free of the approximations or simplifications that are common in classical seismic inversion methodologies and therefore applicable to arbitrary 3D geological media and seismic source models. Source codes provided allow readers to experiment with the calculations demonstrated and also explore their own applications.