- Home
- Conferences
- Conference Proceedings
- Conferences
80th EAGE Conference and Exhibition 2018
- Conference date: June 11-14, 2018
- Location: Copenhagen, Denmark
- Published: 11 June 2018
1 - 20 of 1073 results
-
-
3D Seismic Forward Modeling from the Multi-Physical Reservoir Model at the Ketzin CO2 Storage Site
Authors Y. Zheng, B.U. Wiese, S. Lüth, R. Zeng and Y. WangSummaryAbout 67 kt of CO2 have been injected into the deep saline formation at the Ketzin pilot CO2 storage site from June 2008 to August 2013. During the injection, 3D seismic survey has been performed and repeated to monitor the migration of sequestered CO2. The results of seismic monitoring are limited by the acquisition and signal-to-noise ratio of the data. Reservoir simulation can provide information on the CO2 fluid behavior and the approximated model should be calibrated with the monitor results. In this work, the property models are delivered from the multi-physical model at the time of 3D repeated seismic survey. Seismic data modeled based on the models are compared with the real data and the results validate the effectiveness of the multi-physical inversion method. Time-lapse analysis shows the trend of the CO2 migration during and after the injection.
-
-
-
Diffraction Imaging in 3D via Image Spectral Decomposition of Partial Images
Authors M. Protasov, K. Gadylshin, V. Tchevreda, A. Pravduhin and N. IsakovSummaryThe paper presents 3D diffraction imaging based on spectral decomposition of the different combination of selective or partial images. These images are got by the pre-stack asymmetric migration procedure which is weighted data summation. Spectral decomposition is done in Fourier domain with respect to spatial dip and azimuth angles. Numerical examples with application of different workflows for the synthetic and real data examples demonstrate detailed reliable reconstruction of the fractured zones and reliable reconstruction of fracture orientation on synthetic and real 3D data examples.
-
-
-
Diffraction Modeling and Imaging of Sand Injectites
Authors M.A. Pelissier, D. Brethaut, R.L. Hartstra, M. Jaya and T.J. MoserSummaryIn this paper we use a conceptual model to investigate the diffraction response of sand injectites. Unlike conventional seismic attributes derived from a migrated image using a local averaging process, the diffraction image provides the full resolution of the wavefield. We model a dike representing a typical injectite wing. This is of particular interest due to the advantage in illumination provided by diffraction over reflection for the steep flanks of the dike. We show that the model produces three type of diffraction response. These are associated with the host rock reflector terminations, with discontinuities in reflectivity along the flanks of the dike due to layering of the host rock, and with the pinchout of the dike. In each case the diffraction response is the resultant of a pair of edge diffractors, and the interference of the imaged diffractors depends on the geometry of the injectite. These results illustrate the potential for diffraction imaging to provide additional resolution of injectite geometries.
-
-
-
Application of Deep Learning Along Directional Image Gathers for High-Definition Classification of Subsurface Features
Authors Y. Serfaty, L. Itan, R. Levy and Z. KorenSummaryWe present a novel method for decomposing different geometrical characteristics of imaged seismic data. The automation of procedures for enhancing interpreted/classified image data is achieved by applying principle component analysis (PCA) to directional (dip/azimuth) gathers, followed by deep learning (convolutional neural network) classification. The subsurface geometrical objects to be classified are reflectors (continuous structural surfaces) and different types of diffractors (discontinuous objects such as small-scale fractures and faults). This approach shows great promise in identifying subsurface structural features with high accuracy, low cost (no processing preparation is needed) and simple yet scalable implementation. Our preliminary results show superiority over other methods involved in geometrical transformation (e.g., Radon) and specular/diffraction weighted stacks.
-
-
-
An Outlook on Seismic Diffraction Imaging Using Pattern Recognition
Authors B. Lowney, I. Lokmer, C.J. Bean, G.S. O’Brien and M. IgoeSummaryA seismic image is formed by interactions of the seismic wavefield with geological interfaces, in the form of reflections, diffractions, and other coherent noise. While in conventional processing workflows reflections are favoured over diffractions, this is only beneficial in areas with uniform stratigraphy. Diffractions form as interactions of the wavefield with discontinuities and therefore can be used to image them. However, to image diffractions, they must first be separated from the seismic wavefield. Here we propose a pattern recognition approach for separation, employing image segmentation. We then compare this to two existing diffraction imaging methods, plane-wave destruction and f-k filtering.
Image segmentation can be used to divide the image into pixels which share certain criteria. Here, we have separated the image first by amplitude using a histogram-based segmentation method, followed by edge detection with a Sobel operator to locate the hyperbola.
The image segmentation method successfully locates diffraction hyperbola which can then be separated and migrated for diffraction imaging. When compared with plane-wave destruction and f-k filtering, the image segmentation method proves beneficial as it allows for identification of the hyperbolae without noise. However, the method can fail to identify hyperbolae in noisier environments and when hyperbolae overlap.
-
-
-
Advanced PP and PS Model Building — An Offshore Mexico Example
Summary“Model building and depth imaging with PS converted-wave data is more complicated than with P-wave data alone. We must determine appropriate compressional and shear velocities such that PP and PS sections match, and accuracy of anisotropic parameters is crucial to minimize residual moveout on both data types. Fortunately, recent technological developments, notably joint PP-PS tomography, allow us to produce excellent PS depth-imaged results with reasonable turnaround time.
In this case study we describe the application of PP-PS model building and depth imaging to an OBC seismic survey. The area is characterized by complex structure combined with large velocity contrasts, both of which cause problems for PS model building. A state-of-the-art workflow was applied that included joint PP-PS tomography, maximum use of well data, and minimal interpretation. High-quality PP and PS results were produced in a reasonable timeframe.”
-
-
-
Automated and Semi-Automated Depth Registration of PP and PS Images
Authors C. Bagaini, Y. Elmosharaf, A. Dhara, J. Mathewson and M. Acosta PerezSummaryThe registration of PP to PS images is an essential step of iterative model building of multicomponent data. Depending on the quality of the data and the accuracy of the initial model of the earth’s interior, this operation may or may not require identifying corresponding geological boundaries. We developed a method for PP to PS registration that operates directly on images defined in the depth domain. This method can use horizons (either manually or automatically interpreted) or perform this operation in a data driven (automated mode) without interpreter input using only PP and PS seismic images. The application to synthetic and real data demonstrates the value of this method.
-
-
-
New Model-Based PS Deghosting Boost Data Quality at Grane PRM
Authors S. Ostmo, H. Westerdahl, H. Mehdi Zadeh, M.S. Guttormsen, B. King and L.J. TveitoSummaryIn permanent reservoir monitoring (PRM) PS data, acquired with buried receivers, we have observed a number of notches in the spectra. These notches were not present in the spectra of receivers on the seafloor. To restore the PRM PS data quality, a model-based PS deghosting method for buried receivers is proposed and tested on real data, assuming that the variation in spectra is created by strong contrasts in the shear wave velocity in the very near surface. Only predominantly vertically travelling SS-reflections and transmissions are considered, including important contribution from internal multiples. A shallow layered model is inverted for using picked notches on receiver spectra. Inverse filters, one per receiver, is constructed from the model response and applied to receiver gathers. The method was tested within a complete processing sequence and applied to PRM data from the Grane field in the North Sea. Results indicated very low S-velocities close to the seabed, in the order of 20–40 m/s. The deghosting clearly improved the continuity and resolution in the final image.
-
-
-
An Elastic Reverse Time Migration Method Based on the S-Wave Quasi-Tensor
More LessSummaryIn this manuscript, an alternative converted-wave image with elastic reverse-time migration is proposed. In the proposed method, PS image is generated by applying the imaging condition to the P- and S-wave stress wavefields. In decoupled wave equation, which is used to separate wavefields, we can obtain the P- and S-wave particle-velocity (or displacement) wavefields and P-wave stress, however we cannot obtain the pure S-wave stress. To fully excavate potential of using stress to produce converted-wave image, we construct a quasi S-wave stress from S-wave particle-velocity wavefield using the so called ‘acoustic shear wave equation’. We illustrate such S-wave stress can provide polarity-consistent converted-wave image theoretically and numerically.
-
-
-
PZ Processing of a Signal-Apparition Triple-Source Field Test in the North Sea
SummaryWe present results from a triple-source signal apparition-style field test carried out over a PRM array in the North Sea during the summer of 2017. In addition to the triple-source line, two reference lines were acquired firing the central source only.
Assessing the quality of acoustic and elastic P/Z combination confirms high fidelity data quality throughout the bandwidth of the data. Comparing prestack migrated images of elastic P/Z combination against Amundsen demultiple images shows that multiples are a significant challenge in the area and that removing all surface related multiples as done in the Amundsen demultiple method is critical for unambiguous interpretation.
Amundsen demultiple requires the deconvolution of the downgoing wavefield from the upgoing wavefield. Thus, the process relies on excellent data fidelity in separated wavefield constituents. We find that comparisons of reference line on reference line display a similar level of residual as the reference line compared to the isolated source result corresponding to the same source location. The reference line compared to the decoded source result corresponding to the other offset source locations display a larger residual. Our results thus confirm that triple-source signal apparition-style acquisition enables highly productive acquisition of seismic data without compromising on data quality.
-
-
-
Time Delays in Simultaneous-Source Acquisition and Its Impact on Low Frequencies
Authors K.E. Haavik, Å.S. Pedersen and M. ThompsonSummarySimultaneous-source acquisition enables more efficient and/or denser seismic data acquisition. While acquiring simultaneous source data is a relatively simple extension of conventional operations, separating the signal from the different sources is a more involved process. Modern simultaneous source acquisition is enabled by applying time delays to one or more of the sources in order for the separation process to work. Here we present a theoretical study on the effect of this time delay on the emitted signal from the simultaneous sources. Our findings suggests that small time delays are preferable over larger time delays when considering the amplitude and radiation pattern for low-frequencies (<15 Hz).
-
-
-
A Seismic Apparition Experiment on Towed Streamer Seismic Data
More LessSummaryThis paper discusses a field test of seismic apparition, a simultaneous source technique for marine airgun sources that uses modulation to facilitate source separation. The first part of the paper focuses on the design of the modulation codes. The second part introduces a field test where a single line of 3D data was acquired using three two-string sources. This field test provides real data for testing current and future implementations of the seismic apparition method. In this paper we present initial separation results obtained after minimal pre-processing of the recorded data. Conclusions are drawn on the challenges and opportunities of towed-streamer seismic apparition for multi-source surveys.
-
-
-
High-Multiplicity Simultaneous Sources and Marine Vibrator Acquisition Effects
Authors D. Halliday, R. Laws, A. Özbek and J. HopperstadSummaryHigh-fidelity marine seismic vibrators allow control of the phase of the emitted seismic wavefield. Phase control of the seismic source can allow new simultaneous-source encoding techniques. These techniques may allow highly efficient seismic acquisition without sacrificing data quality. One approach that uses phase control is phase sequencing, where the emitted source wavefield phase is changed in a non-random way from shot-to-shot, allowing manipulation of data in the frequency-wavenumber domain. Combined with wavefield reconstruction, phase sequencing allows separation of simultaneous sources with minimal residual crosstalk. An important consideration when evaluating such techniques is that marine seismic vibrator deployment and utilization will be different from an air-gun source. For example, a marine vibrator source array is likely to move while emitting energy, it may have different array elements distributed at different depths, it will emit swept rather than impulsive waveforms, and it may behave differently in the presence of a rough sea. We demonstrate the separation of high-multiplicity simultaneous sources using phase sequencing, before discussing marine-vibrator specific acquisition effects. The impact of these acquisition effects will be demonstrated in future publications.
-
-
-
Compressed Sensing Based Land Simultaneous Acquisition Using Encoded Sweeps
Authors R. Kumar, S. Sharan, N. Moldoveanu and F. J. HerrmannSummarySimultaneous shooting methods using encoded sweeps can enhance the productivity of land acquisition in situations where deployment of many vibrators and larger receiver spread is not possible in the field due to obstructions or permit limitations. However, the existing framework requires shooting the full sequence of encoded sweeps on each shot point to reconstruct the complete frequency bandwidth Green’s function. Although this simultaneous shooting method reduces the sweeping time vs conventional sequential shooting, the gain in efficiency is limited. To further reduce the sweeping time, we propose to acquire randomly selected subsets of the encoded sweeps sequences followed by a rank-minimization based joint source separation and spectral interpolation framework to reconstruct the full bandwidth deblended Green’s function. We demonstrate the advantages of proposed sampling and reconstruction framework using a synthetic seismic line simulated using SEG-SEAM Phase II land velocity and density model.
-
-
-
Survey Designing for Blended Acquisition with Irregularly Sub-Sampled Geometries
Authors S. Nakayama, G. Blacquière, T. Ishiyama and S. IshikawaSummaryWe introduce a workflow to derive survey parameters responsible for source blending as well as spatial sampling of detectors and sources. The proposed workflow iteratively performs the following three steps. The first step is application of blending and sub-sampling to an unblended and well-sampled data. We then apply a closed-loop deblending and data reconstruction enabling a robust estimate of a deblended and reconstructed data. The residue for a given design from this step is evaluated, and subsequently used by genetic algorithms (GAs) to simultaneously update the survey parameters related to both blending and spatial sampling. The updated parameters are fed into a next iteration till they satisfy given stopping criteria. We also propose repeated encoding sequence (RES) used to form a parameter sequence in GAs, making the proposed designing workflow computationally affordable. We demonstrate the results of the workflow using numerically simulated examples that represent blended dispersed source array data. Difference attributable only to a way to design parameters is easily recognizable. The optimized parameters yield clear improvement of deblending and data reconstruction quality and subsequently provide optimal acquisition scenarios. Additionally, comparison among different optimization schemes illustrates ability of GAs along with RES to efficiently find better solutions.
-
-
-
Blended Noise Suppression Using a Hybrid Median Filter, Normal Moveout and Complex Curvelet Transform Approach
Authors L.Q. Dong, M.G. Zhang, C.H. Wang, Y.M. Zhang and Y. ZhuSummaryThe high density acquisition way can uplift the subsurface imaging accuracy, whereas the high cost limits the widely application in practice. Blending acquisition way has emerged as a promising way of significantly increasing the efficiency of seismic acquisition. However, there will exist a large challenge of severe interference noise and decrease S/N ratio. Therefore, with recent processing practices, the success of blending acquisition relies heavily on the effectiveness of de-blending to separate signals from simultaneous sources. In the paper, we proposed a blended noise suppression approach using a hybrid median filter, normal moveout (NMO) and complex curvelet transform (CCT) approach. Firstly, the large step median filter is applied to the initial data after NMO correction. Next, we continue to extract the residual energy to get the de-blended result by the CCT-based threshold method. Then, re-iterate the difference data by subtracting the original pseudo de-blended data and the pseudo de-blended data of the de-blended result from each iteration as the above processing flow. Finally, the final de-blended data is derived by adding the remained energy of each iteration until the S/N ratio satisfies the desired one. We demonstrate through a simulated field data the effectiveness of the approach.
-
-
-
Triple Source Isolation: Results from a North Sea Field Test
Authors J.O.A. Robertsson, F. Andersson, D.J. van Manen, K. Eggenberger, R. Walker, C.R. Berg, J. Gateman and I. GimseSummarySeabed seismic data have proven critical for addressing long-standing challenges in seismic imaging both for exploration and reservoir development and management. Significant advances have been made to bring down the cost and increase efficiency for deploying and retrieving ocean bottom nodes, such that the efficiency on the source side increasingly becomes the bottleneck for efficient operations.
We present results from a recent field test in the North Sea where three source lines were acquired simultaneously from a single vessel without compromising inline sampling such that the fold is doubled compared to conventional flip-flop acquisition. The acquisition and processing technology is partially based on the science of signal apparition that allows for an optimally large part of the data corresponding to the individual sources to be exactly recovered while accurately reconstructing the full bandwidth beyond the region in frequency-wavenumber space of exact reconstruction. For the triple source field test presented here, the productivity increases 50% compared to conventional flip-flop acquisition or three-fold compared to conventional single-source full-fold acquisition suitable for reservoir development and management applications.
-
-
-
Incorporating Stationary-Phase Implementation into QPSTM and Application in Daqing Oilfield
More LessSummaryWe have improved the so-called QPSTM by introducing a dip-angle domain stationary-phase implementation. QPSTM compensates absorption and dispersion via an actual wave propagation path using effective Q parameters. However, this strongly degrades the resolution gained by the compensation and requires more computational effort than conventional PSTM. Our stationary-phase implementation improves QPSTM through the determination of an optimal migration aperture based on an estimate of the Fresnel zone. This significantly attenuates the noises and reduces the computational cost of 3D QPSTM. We have estimated the 2D Fresnel zone in terms of two dip angles through building a pair of 1D migrated dip angle gathers using PSTM. Our stationary-phase QPSTM was implemented as a two-stage process. First, we used conventional PSTM to obtain the Fresnel zones. Then, we performed QPSTM with the Fresnel-zone-based optimized migration aperture. We apply the QPSTM to the actual 3D seismic data, obtain higher resolution imaging results, and verify the practicability of the method.
-
-
-
Visco-Acoustic Reverse-Time Migration based on the Stereo-Modeling Operator
More LessSummaryViscous effects causes seismic energy attenuation and waveform distortion. Conventional acoustic migration cannot account for this effect, which may produce images with poor illumination, reduced resolution, and wrong placement of reflectors. Reverse time migration (RTM) based on the visco-acoustic wave equation is an effective way to image subsurface media. Solving the wave equation accurately and efficiently affects the RTM results. Stereo-modeling methods have great ability in suppressing numerical dispersion, thus can improve computational efficiency with coarse grids. Based on the stereo-modeling operator, we derive a nearly-analytic central difference (NACD) method (4th-order accuracy in both time and space) to solve the visco-acoustic wave equation. The efficiency test shows it can suppress the numerical dispersion effectively and is more efficient compared with Lax-Wendroff correction (LWC) method with the same accuracy. The acoustic and visco-acoustic RTM based on NACD is performed on the fault and Marmousi models. The results show that the application of NACD in RTM improves the accuracy and the resolution of images. Moreover, the images obtained by visco-acoustic RTM are clearer and have higher resolution compared with images obtained by acoustic RTM because the viscous effects are considered and compensated.
-
-
-
Angle Gathers from a Kirchhoff Pre-Stack Depth Migration using a Space-Lag Extended Imaging Condition
Authors G. O’Brien, S. Delaney and M. IgoeSummaryTraditional Kirchhoff pre-stack depth migration methods output surface offset common image gathers (CIG) but exploration workflows require subsurface reflection angle CIGs to extract accurate angle versus amplitude measurements. Providing any incremental uplift to the amplitude versus angle (AVA) attributes and the associated seismic inversions can significantly impact exploration and development success. Several high-end imaging techniques exist to extract subsurface angles directly, notably reverse time migration methods and common reflection angle migrations. Here, we explore the ability of the relatively cheap well-used Kirchhoff pre-stack depth migration to output subsurface reflection angle common image gathers via a local space-shift extended imaging condition. A layered synthetic model and a complex 2-D synthetic model are used to assess the space-shift image gathers output from such a migration scheme and to evaluate the seismic attributes relative to the traditional surface offset CIGs. The synthetic results show that the extended imaging condition clearly provides an uplift in the measured AVA over the surface offset migration. Finally, we show an example of a 3D space-lag gather from deep marine data and compare the resultant angle gathers with those generated from an offset migration and a time-shift imaging condition Kirchhoff migration.
-