- Home
- Conferences
- Conference Proceedings
- Conferences
79th EAGE Conference and Exhibition 2017
- Conference date: June 12-15, 2017
- Location: Paris, France
- Published: 12 June 2017
41 - 60 of 1073 results
-
-
Calibration of Frequency Decomposition Colour Blends Using Forward Modelling - Examples from the Scarborough Gas Field
Authors C. Han and P. SzafianSummaryThis study investigates using a combination of seismic forward modelling with frequency decomposition (FD) and colour blending analysis with the aim of better understanding what the major controlling factors on the frequency response are and how this impacts the spectral interference colour patterns observed in FD colour blends. Examples are provided using data from the Scarborough giant gas accumulation, offshore Northwest Australia. Forward modelling of reflectivity is common practice in the oil and gas industry, generally used to provide information on amplitude and phase changes which may occur in response to changes in a model. By incorporating frequency decomposition and red-green-blue (RGB) colour blending into the workflow there may be potential to detect subtle changes within the data, since the interplay between three band-restricted frequency volumes produces a colour blend which is extremely sensitive to frequency change and can often highlight features or trends not seen in full frequency or bandpass volumes. Increasing understanding of FD colour blends may aid in supporting or disproving interpretations made using other lines of evidence, as well as potentially allowing additional geological insights to be made, such as identification of facies, fluids, thicknesses and other changes in reservoir characteristics based on frequency response.
-
-
-
Augmented Full Wavefield Modeling: An Iterative Directional Modeling Scheme for Inhomogeneous Media
Authors H.I. Hammad and D.J. VerschuurSummaryWe derive a representation theorem for modeling directional wavefields using reciprocity theorem of the convolution-type. A Neumann series expansion of the representation yields a series that is similar to that of Bremmer. A generalized Neumann series is also derived similar to that used for solving the non-directional Lippmann-Schwinger representation. An example shows how the series can model each scattering order separately for inhomogeneous media. This could potentially be useful in imaging and inverse problems.
-
-
-
High-Order Leapfrog and Rapid Expansion Time Integrations On Staggered Finite Difference Wave Simulations
Authors O.J. Rojas, C. Spa and J. de la PuenteSummaryThis work is an exploratory study of coupling high-order time integrations to a finite-difference (FD) spatial discretization of the 1-D wave equation that combines eigth-order differencing at grid interior, with lateral formulas of order sixth and fourthat boundary neighborhood. This reduction of spatial accuracy at the grid vecinity of free surfaces is a known stability limitation of FD methods, when coupled to the two-step Leap-frog (LF) time stepping, which is widely used on seismic modeling. We first implement LF time integrations with an arbitrary accuracy order, as given from a standard Lax-Wendroff procedure, and compare results from the fourth-, sixth-, and twelfth order schemes, against the popular second-order LF. Our emphirical analyses establish the CFL stability constraints for propagation on an homogeneous medium, as first results, and then consider velocity heterogeneities when assessing dispersion and dissipation anomalies. Finally, we use a rapid expansion method (REM) to approximate the exponential of the semidiscrete FD discretization operator by a truncated Chebyshev matrix expansion. Althougth, REM has been previouslly applied to peudospectral (PS) wave simulations, this REM-FD scheme is the first reported in the technical literature according to our knowledge.
-
-
-
Modelling of Time-varying Rough Sea Surface Ghosts and Source Deghosting by Integral Inversion
Authors E. Cecconello, E.G. Asgedom, O.C. Orji and W. SöllnerSummaryA major impediment to the full understanding of the data acquired in marine seismic is the restricting assumption of a flat and stationary sea surface used in certain pre-processing tools. A first step towards removing this assumption is to accurately account for the sea state (time varying free surface) in the deghosting process. On the receiver side, this is handled properly by using dual-sensor streamer. In this work, we present an integral approach to model the source side ghost effects from time-varying rough sea surfaces and show that the interaction with time-varying sea surfaces affect the subsurface reflections and may have a significant impact on seismic repeatability. We then continue with a theoretical derivation where we develop deghosting operator based on an integral inversion of the modeling operator. This formulation for source deghosting can account for the time-variation of rough sea surfaces.
-
-
-
2D Wideline Feasibility Study — A Synthetic Example in Foothills
Authors J.M. Mougenot, A. Lafram, S. Tlalka, M. Appe and H. PuntousSummaryElastic feasibility study was performed on a foothills synthetic model. A special focus was put on signal to noise ratio of the modelled data to mimic real shots as much as possible. Blind processing sequence was performed leading to PSTM sections. True velocity model was used for PSDM imaging. Results show gain for wider and denser acquisition patterns. The replacement of dense crossline sampling by CRS seams questionable.
-
-
-
Performance and Convergence of the Non-Periodic Homogenization for the 3D Elastic Wave Equation
Authors P. Cupillard and Y. CapdevilleSummarySeismic waves propagating in the Earth are affected by different sizes of heterogeneities. When modelling these waves using numerical methods, taking into account small heterogeneities is a challenge because it often requires important meshing efforts and leads to high, sometimes prohibitive, numerical costs. In the recent years, this problem has been overcome by applying the so-called homogenization technique to the elastic wave equation in non-periodic media. This technique allows to upscale the small heterogeneities and yields a smooth effective medium. In the present paper, we describe a 3D implementation of the method and we show that it can handle large and highly heterogeneous models with an acceptable speed and a good accuracy. This development opens the path to the correct account of the effect of small scale structures on the seismic wave propagation in complex 3D models of the subsurface.
-
-
-
Directional Full-Wave Scatter Source Modelling and Dip-Sensitive Target-Oriented RTM
Authors M. Verschuren and M. Araya-PoloSummaryReverse Time Migration is now the dominant method to image complex geology. Nevertheless, illumination studies are still mostly done with ray-based methods, because wave-equation methods generally do not generate directional information, or only at considerable computational cost.
We introduce a simple way to numerically restrict the directional aperture of a full-wave source without distortion of the resulting wave front. At the location of the scatter source, a damping mask with chosen angular aperture, such as critical reflection angle, and direction, such as normal to structural dip, is applied in forward modelling time following a sine function that peaks at a small number of periods of the source wavelet.
The resulting scatter energy measured at the acquisition surface may be used in the same way as ray counts in myriad applications, such as in directional illumination or visibility analysis for survey design, and in target-oriented RTM shot selection. The main advantages of the proposed method are: implementation simplicity, computing efficiency, fidelity to the physics of wave propagation in complex geology, and stability across rugose velocity contrasts.
-
-
-
Innovative and Interactive Methods Emphasizing Geological Events through Spectral Decomposition New Zealand Case Study
Authors B. Durot, M.M. Mangue, B.L. Luquet, J.P.A. Adam and N.D. DaynacSummaryThis paper presents how an interactive method in spectral decomposition can facilitate and improve processes in exploration. This study focuses on the Maui field, located offshore New Zealand, in the Taranaki basin. Its aim is to emphasize specific geological features by interactively performing spectral decomposition at different locations on surfaces generated from a Relative Geological Time (RGT) model. This model is obtained thanks to seismic interpretation based on horizon auto-tracking trough a grid (Pauget et al., 2009) and its refinement. It provides a new way to achieve a strata-slicing into the seismic data and allowing a quick and interactive navigation throughout the surfaces. By combining this workflow with the analysis of frequency variations along geological events, it is possible to get an enhanced spectral decomposition of geological features from their averaged spectral signature (low, medium and high frequencies). Each one of these key frequencies was mapped on surfaces and blended into a Red-Green-Blue (RGB) viewer. Such a technique allows the interpreter to better highlight turbidite channels which were then extracted as geobodies with a high rate of confidence.
-
-
-
Seismic Spectral Decomposition for Reservoir Prediction In Glaciogenic Reservoirs
Authors F.J. Bataller Torre, A. Moscariello and N. McDougallSummaryThe present paper will focus on how to use Seismic Spectral Decomposition and RGB blending applied to a glaciogenic reservoir in Norht Africa aimed to obtain reservoir de-risking maps by calibrating and performing supervised classifications to Spectral Decomp outputs in order to be able to reduce uncertainties regarding the prediction of reservoir lithology, specifically in the case of non-reservoir, sub-seismic formations, which are not easy to predict.
-
-
-
Interpretational Aspects of Multispectral Coherence
By K.J. MarfurtSummarySeismic coherence volumes are routinely used to delineate geologic features that might otherwise be overlooked on conventional amplitude volumes. In general, the quality of a coherence image is a direct function of the quality of the input seismic amplitude data. However, even after careful processing, certain spectral components will better illuminate a given feature than others. For this reason, one may wish to not only examine coherence computed from different filter banks, but somehow combine them into a single composite image. I do so by summing structure-oriented covariance matrices computed from spectral voices prior to computing coherence. I show that multispectral coherence images are superior to traditional broadband coherence images, even if the seismic amplitude data have been previously spectrally balanced. While much of this improvement can also be found in RGB blended volumes, multispectral coherence provides several advantages: (1) one can combine the information content of more than three coherence volumes, (2) there is only one rather than three volumes to be loaded into the workstation, and (3) the resulting grey-scale images can be co-rendered with other attributes of interest plotted against a polychromatic colour bar, such as P-impedance vs. Poisson’s ratio or SOM cluster results.
-
-
-
Using Wigner-Ville Distribution Properties for Thin Bed Identification
By C.J. StotterSummaryIn the search for ever more subtle reservoirs we often deal with hydrocarbon deposits, where the thickness of individual layers is below the seismic tuning thickness. Several methods were developed in the time and frequency domain to circumvent or go below this fundamental limitation of the seismic method. In this paper we investigate properties of the Wigner-Ville (WVD) time-frequency distribution, and especially of the cross-terms. We start with the mathematical definition of the WVD and investigate cross-term properties for two Gaussian time signals. We then examine the WVD of a wedge model and find that the cross-term shows variations even if the wedge thickness is below the tuning limit. We concentrate on the time location of the first-order minimum of the WVD cross-term which indicates the centre of the wedge even below the tuning thickness. Subsequently we apply this property for thin layer identification in a real seismic example. We conclude that tracking the location of the first-order minimum of the WVD cross-term can indicate the existence of layers below the tuning thickness in seismic data, and locate the mid-point between the top and base of the tuned layer.
-
-
-
Multiscale Fusion for Improved Instantaneous Attribute Analysis
Authors M. Alfarraj, H. Di and G. AlRegibSummaryIn this abstract, we propose a multiscale approach for enhancing the resolution of instantaneous attributes, such as cosine of phase and phase dip, both of which tend to be highly sensitive to noise in seismic data. In particular, we use a multiscale representation, namely the Gaussian pyramid, to exploit seismic features at different resolutions followed by multiscale fusion to enhance both the quality and reduce noise sensitivity of these attributes. The value of the proposed technique is demonstrated through application on the Netherlands offshore F3 block, indicating its potential for improving more seismic attributes, such as coherence and curvature.
-
-
-
Two Improved RGB Blend Methods Based on PCA and Brovey Transform
More LessSummaryWith the characteristics of effectively improving the limitations of single attribute analysis and making the results of reservoir description more reliable, seismic attribute fusion technology has been widely used in attribute analysis for years. RGB blend method fits well with the attribute interpretation and reservoir identification for combining various information of different frequency together. In this paper, we introduce two methods to improve the visual effect of the RGB attribute with the purpose of analyzing the attribute better and identifying the reservoir more easily. The two methods are both based on the RGB attribute, but better than it in effect, which is proved by the real data. The participation of full-frequency attribute and the intensity compensation in HSI colour space may be the main reasons.
-
-
-
Generalized Spectral Decomposition and Its Use in Spectral Balancing
Authors W. Weinzierl, V. Aarre and S. CourtadeSummaryA new spectral balancing method based on a continuous wavelet transform is introduced. A hybrid spectral decomposition method, customizable to behave either as a short time Fourier or continuous wavelet transform, is used to decompose the input into its constituent frequencies. Anelastic attenuation processes are accounted for by construction of mother wavelets, being scaled and dilated. This new method is true-amplitude, lifting weaker amplitude frequencies to the same level as the amplitude of the strongest frequency band. The improvements within an interpretation context are evident when comparing the input and spectrally enhanced output. We test the new spectral balancing method on a 3D onshore survey acquired across the Teapot Dome structure, Wyoming. Previously unresolved features in the original amplitude are resolved on the spectrally balanced output. Spectral balancing provides additional information which often is obscured or masked by the limited bandwidth in conventional post-stack data.
-
-
-
Continuous Coverage of Recent High Resolution Seismic and Magnetic Data gives New Insight into the Early Development of the Gulf of Mexico
Authors I. Deighton and F. WinterSummaryExtensive coverage of the entire Mexican Gulf of Mexico (MGoM) by long offset 2D marine seismic data, processed in time and depth, along with gravity and magnetic shipborne data were acquired on an evenly space survey grid during 2015–16 and enable a better understanding of the deep structure of the entire GoM. A correction of the GoM oceanic spreading transform fault locations, previously only diffusely identifiable on a Vertical Derivative version of the Sandwell Free Air Anomaly Map was carried out and a refinement of existing models of the extinct Jurassic-Early Cretaceous GoM spreading ridge locations was undertaken by coupling the above with gravity and magnetic grids and profile plots of seismic depth of top oceanic crust vs. distance. Due to thick sediment (up to 13 km) overlying the oceanic crust in the GoM, the magnetic anomaly signal and, therefore, the spreading anomaly pattern are more difficult to identify than those in younger and wider oceanic basins. Nonetheless, the location of the magnetic isochrons are readily identifiable by forward modelling of transform parallel transects within each spreading segment, and we are able to review existing models of oceanic opening time, rotation poles and spreading rates.
-
-
-
Research of Seismoelectrical Effect
Authors S. Riabova and A.A. SpivakSummaryResearch of electric field variations in the propagation of seismic waves is of considerable interest for development of new techniques and methods to describe the structure of the crust and diagnosis of its geodynamic state. The intensity of the energy transformation of medium fluctuations in the electric field energy is largely determined by the properties of the environment and characteristics of its stress-strain state. It means that the response of environment on seismic influence as induced electrical signals contains information about the properties of the medium, stress operating in medium, and origin of its strains. We carried out a comparative analysis of amplitude variations in the field of seismic oscillations (waves of earthquakes, different types of local events, etc.) and synchronous with them variations in the electric field. The data analysis show the presence of seismoelectric effect in times of the seismic waves, which is well recorded in the absence of strong disturbances induced by other sources (the passage of atmospheric fronts, thunderstorms, strong winds, etc.). For the first time we obtained a quantitative relationship between the amplitude of the seismic and induced electric signal in certain conditions.
-
-
-
Kinematics of a Silica Particle in the Deposition to Piping of Geothermal Power Plant
By M. IwataSummaryThe buildup of silica scale inside geothermal pipes and wells has serious impacts on the power generation efficiency in geothermal systems. There have been a large number of studies on controlling silica scale. However, silica deposition estimated by simple chemical kinetics cannot give a rational explanation of the complicated features empirically observed in laboratory and field experiments. The aim of this research is to investigate physical effects on silica particles and calculate scale precipitation rate quantitatively with a method of numerical simulation. We regarded silica scale as colloidal particles and analyzed the particle behavior by solving the motion equation of a particle. In this process, we computed the time required for the particle diffusion to the vicinity of wall surface by considering various physical reactions including hydrodynamic process, Brownian motion, particle-wall interaction, particle size, etc. In addition, we calculated the probability of particle re-entrainment from wall surface, which can be applied to CFD (Computational Fluid Dynamics). Our simulation results showed good agreement with an experimental data. Concerning the quantitative prediction of silica deposition, we emphasize the importance of physical effects on silica scaling.
-
-
-
Appraising Structural Interpretations Using Seismic Data Misfit Functionals
Authors M. Irakarama, P. Cupillard, G. Caumon and P. SavaSummaryStructural interpretation can be challenging because of complex wave interactions and limited seismic bandwidth. A single seismic image can lead to multiple structural interpretations, reflecting structural interpretation uncertainties. Typically, this uncertainty is captured by generating several possible structural geometries. However, a quantitative assessment of the different possible structural interpretations is often difficult. In this paper we propose a methodology for assessing structural interpretations using seismic data misfit functions. We first develop a conceptual framework for solving such a problem before applying the method to a carefully designed synthetic study. Our results suggest that it is possible to appraise structural interpretation using seismic data if an appropriate misfit function is used.
-
-
-
Estimating Detectability of Microseismicity with a Surface Monitoring Array Using Downhole Monitoring Array
Authors P. Wandycz, E. Święch, L. Eisner, D. Anikiev, A. Pasternacki and T. MaćkowskiSummaryWe analyze detectability of microseismic events by surface array using simultaneously deployed downhole array. We show that the detectability of the perforation shots on surface array can be assessed by the observations of the signals on the downhole array. Furthermore, we show that microseismic events weaker than the two detected perforation shots were not detected by the surface monitoring array and we show that later and stronger events would be potentially detectable if the surface array was not dismantled. This analysis allows us to determine the parameters of the surface array needed to carry out microseismic monitoring in this area of Poland.
-
-
-
Non-double Couple Microseismic Events - Evidence from the Laboratory
Authors I.A. Vera Rodriguez and S. StanchitsSummarySource mechanism is an attribute of interest in acoustic emission (AE) analysis which has been used to determine the nature of failure during laboratory experiments. In this abstract, we present the results of the moment tensor inversion of AEs recorded during the hydraulic fracturing of a Colton sandstone block at triaxial stress conditions. The source geometries given by the biaxial decomposition of the moment tensor solutions contain a family of auxiliary planes lying parallel to the orientation of the main hydraulic fracture’s plane. During fracture propagation, most AEs were concentrated near the edge of the fracture, reflecting a tensile stress regime with opening angles mostly around 30 degrees. After breakdown, the pumps were reversed to withdraw fluid from the borehole. At this point, the stress field became compressive with AEs distributed across the complete face of the hydraulic fracture showing source mechanisms that reflected the closing of the fracture’s plane. Closing angles were in general lower in magnitude than opening angles.
-