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76th EAGE Conference and Exhibition - Workshops
- Conference date: 16 Jun 2014 - 19 Jun 2014
- Location: Amsterdam, Netherlands
- ISBN: 978-90-73834-90-3
- Published: 16 June 2014
1 - 20 of 142 results
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Improving Subsalt Imaging by Image Conditioning and Enhancement with RTM Vector Image Partitions - A GoM Case Study
Authors C. Zhao, O. Zdraveva, A. Gonzalez, R. King, R. Gu and S. ChenSubsalt imaging remains challenging despite a growing need for more accurate subsalt characterization. Long offsets, wide-azimuth (WAZ), and full-azimuth (FAZ) acquisition technologies have provided step-change improvements in illumination, multiple attenuation and signal-to-noise ratio. Recently developed more advanced anisotropic velocity model building techniques, have also greatly enhanced our ability to build accurate salt models and reduce velocity error. Reverse-time Migration (RTM) has become the preferred imaging algorithm due to its superior tolerance for complex salt geometry compared with traditional ray-based Kirchhoff migration. However, even with these developments, subsalt imaging still remains a significant challenge. Recently, Vector Image Partitions (VIPs) from RTM have proven valuable for enhancing the image of challenging subsalt structures. In this paper, we present a new method for optimizing the final migrated image through enhancement of the consistent signal and suppression of noise among VIPs. We demonstrate the effectiveness of this method with a case study from the Gulf of Mexico. The result shows great improvements in the subsalt image quality in terms of signal to noise ratio, reflector continuity, and wavelet consistency along reflectors.
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Highly Detailed Reservoir Imaging by Using Sparse Layer Inversion in a Complex N.Sea Turbidite
Authors D.D. Mann, R.H. van Eykenhof, J.P. Castagna and C.P. AshtonSparse layer inversion (SLI), like sparse spike inversion (SSI), invokes a sparse reflectivity solution for the reconstruction of noisy seismic traces in the presence of a known, band-limited wavelet. However, solving for layers, i.e. dipoles, rather than individual interfaces, holds the potential for achieving increased detail and lateral stability over that usually achieved with SSI. In this paper, we present the method and show the application of SLI to a complex turbidite reservoir in the UK Central North Sea.
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Keynote Speech - Broadband Seismic - The Interpreters Dream Come True?
By J.E. LieBroadband seismic (BBS) has without doubt increased seismic resolution through a sharper wavelet with less side lobe artefacts. The low frequency richness of BBS has improved our estimation of rock properties through inversion. Full Waveform Inversion velocities derived from BBS data have improved both imaging and inversion results. This is all really sweet, but BBS data still contain noise, multiples and phase issues, and now they all come in broadband. In this talk we will be sharing some of our experiences with a variety of broadband seismic techniques and how Lundin Petroleum have dealt with whole new set of real world opportunities and problems that BBS has given
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Broadband Seismic - Uplift to the Interpreter
Authors N.A. O'Dowd and P.G. CarolanThe geophysical uplift of broadband data is widely reported as are the benefits it brings to reservoir characterisation. However there are also benefits to the qualitative interpreter which go beyond improved resolution and structural imaging. In addition to the benefits to efficiency and accuracy whilst auto-picking, the manual interpreter can gather more geological information from the texture within the data than just having improved confidence in the structural and stratigraphic image. The broad bandwidth of frequencies within the data produce a texture to the data which can highlight geological packages which may have been previously masked within conventional data. There is geological understanding and information which may be inferred and when accurately tied to well information can increase confidence in model building and help to focus further quantitative interpretation.
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Broadband - The Interpreter's Friend?
Authors M. Francis and C. CunnellThe positive impact of broadband acquisition and processing methods on the interpretation of seismic volumes has been well documented in recent years. While most gains have been achieved by extending low-frequency content, potential pitfalls exist for interpreters at both ends of the frequency spectrum, and care must be taken to understand the effective bandwidth of data. In addition, the handling of spatial frequencies (or wavenumbers) is as important as considerations for temporal aliasing. A complex earth creates a complex seismic wavefield in all directions, and so demands a revised definition of broadband with an emphasis on spatial resolution. We contend that the time has come to adopt the concept of effective spatial broadband based on high-resolution interpretation independent of orientation, and move towards the next level in geological understanding from our seismic volumes.
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Improvements to Frequency Decomposition Methodologies for Use with Broad Bandwidth Seismic Datasets
Authors J. Lowell, A. Eckersley, T. Kristensen, P. Szafian and N.J. McArdleBroadband technology, in its different guises has been developed to extend the spectral width of seismic data giving more sensitivity to the features imaged at high and low frequencies. This has lead to problems using existing frequency decomposition techniques with this data. We have adapted our existing code to meet these demands.
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Benefits of Broadband Seismic Data for Reservoir Characterization - Santos Basin, Brasil.
Authors E. Kneller, L. Zekian, T. Coleou, J.P. Coulon and Y. LafetQuantitative interpretation teams face two challenges when using model-based inversion: to extract meaningful wavelets and to build accurate low frequency models. The lack of low frequencies in conventional seismic data means that a low frequency model must be incorporated in the inversion process in order to recover absolute impedance values. Typically, low frequency models are obtained from low-pass filtered impedance logs. If well-logs are sparse and the geology complex, the well-derived low frequency model may be inaccurate and cause biased inversion results. One option to improve the low frequency model is to use seismic velocities. However, while seismic velocities provide information at very low frequencies (0-5 Hz), they are not usually suitable to provide information for the missing frequencies in the range from 5 to 10 Hz with conventional seismic data. Seismic data acquired using variable depth streamers are ideally suited for inversion as they provide directly these missing low frequencies, hence removing the need to build low frequency initial models from well data. In order to quantify the impact of the low frequency content on seismic inversion, comparative elastic inversion tests have been conducted using 3-D seismic data from conventionally towed Constant Depth Streamer (CDS) acquisition and broadband Variable Depth Streamer (VDS) acquisition. Both datasets from offshore Brasil, Santos Basin were acquired at different time. The CDS survey was acquired and processed in 2000, the VDS was acquired in 2012 and this paper uses fasttrack processing results. The VDS survey was acquired with streamer depth ranging from 10 to 50m.
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Fast Track Broadband Seismic Inversion Workflows
Authors A. Geisslinger and H.H. HamzahThis talk will focus on how Fast Track Reservoir Characterization approaches based on broadband data are being applied on a regional seismic data set of 7000km2 delivering Calibrated Impedance and Fluid Cubes for the entire regional volume, thus enabling Exploration and Development teams to readily harvest value of the improved rock property characterization through broadband seismic. 1 - Calibrated Impedance The much improved low frequency content of the broadband data together with higher frequency content of the velocity model generated by modern processing techniques allows us to close the conventional frequency gap at around 1-8 Hz. A seismic velocity model based low frequency P-Impedance model and reflectivity derived bandlimited impedance cube can be merged seamlessly into a calibrated impedance volume. 2 - Fluid Cube Using Broadband Seismic Data and an operator based Coloured Inversion workflow, followed by weighted stacking of the results, fluid cubes can be generated in a very efficient way. This allows their usage in prospect identification timely after end of a processing project and very early in the exploration interpretation workflows. Having fluid cubes early, is of particular value in the geology of Brunei Darussalam, where prospects are distributed over thousands of milliseconds of sand-shale sequences.
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Using Inversion to Estimate the Impact of Broadband Data on Elastic Property Uncertainties
Authors J.V.R. Townend and A.J. CherrettWe present a comparison of broadband and conventional data using joint elastic inversion to quantify posterior uncertainties. The uncertainty can be quantified at different scales, for example according to temporal frequency or layer thickness. Our observations confirm that enhancements to the usable bandwidth in extreme high and low seismic frequencies give rise to a quantifiable uplift in resolution across a full range of scale lengths.
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The Benefits of Broadband Seismic Data
By B. KrokanTo improve bandwidth and resolution in seismic data has been a priority since the early days of the seismic method. The last years the industry has made great strides forward in terms of providing techniques that contribute to enhanced seismic resolution, deeper penetration into the earth, more quantitative and reliable reservoir inversion, simplified interpretation and clearer facies discrimination. This presentation provides evidence for the improvements by case studies with recently acquired marine broadband data. It will also address a few R&D challenges.
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Addressing Obstacles to Adoption of Broadband Seismic by Asset Team Interpreters
Authors T. Bird, C. Reiser, E. Anderson and M. WhaleyBroadband seismic data is distinctively different from conventional ‘band-limited’ seismic data in appearance as a result of broader information content. Common reactions from interpreters encountering broadband seismic data for the first time are addressed. This paper illustrates these concerns and responds with suggestions to overcome these obstacles to broader adoption. Broadband has been promoted as a resolution solution, causing interpreters to anticipate higher frequencies at depth than is possible given the frequency-dependent attenuation of the earth. Broader frequencies result in a sharper wavelet with less side-lobe energy, causing some reflectors that were artifacts of side-lobe energy to disappear, radically changing the appearance but giving better ties to well data. The additional low frequencies of broadband data are crucial in delivering more stable and higher fidelity inversion results. Popular frequency-related seismic attributes such as ‘sweetness’ are also significantly improved by the additional low frequencies. Once seismic interpreters understand the reasons for the radically different appearance of broadband seismic data and start taking advantage of the additional information content and higher fidelity, it can be expected that this data will be demanded as standard.
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Reghosted 4D and 3D Reservoir Characterization Using a Broadband Monitor on a Deep Offshore Turbiditic Field
Authors C. Deplante, F. Jeanjean, V. Sebastiao and S. SagederOn a turbiditic deep offshore field covered by a recent yet conventional 4D baseline, a non-conventional route has been decided for the first monitor, to obtain seismic information related to dynamic heterogeneities but also better characterize reservoirs. The strategy decided for the first monitor (M1), one year after first oil, was to shoot broadband and process twice: - One 4D-dedicated processing mapped to conventional (with a Fast Track and a Full Processing phase) in order to match the baseline characteristics and obtain quality 4D signal to help understanding the early dynamic behaviour of the field. - One 3D broadband processing aiming to improve the existing seismic for reservoir characterization purposes. The superior resolution of the 4D signal over conventional data helps pushing the interpretation below the 3D resolution limits and has helped identifying sedimentary features which have confirmed the interpretation model but are also difficult to map accurately. Using the 3D broadband processing results, small scale geological details previously guessed from conventional data and locally underlined by 4D signal (but only at places impacted by changes in saturation and pressure), can now be seen more clearly: a more comparable resolution is achieved for 3D and 4D.
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Couy-1 Well, Paris Basin, France - An Open Window on the Toarcian Series for Organic Rich Shale Characterization
Authors C. Rigollet, D. Bonijoly, A. Hofmann, M. Power and M. SimpsonThe COUY-1 well (scientific well drilled in 1987, program “Géologie Profonde de la France”) presents a complete log data set, continuous cores and a well known geological context. Consequently, it is an appropriate case study to test the new technologies and workflows for organic rich shale characterization. This well is an open window on the Lower Toarcian shale: “Schistes Cartons” in France, lateral equivalent of the famous “Posidonia Shale”. The integration of various analyses from COUY-1 logs, cores and cuttings (geochemistry, mineralogy, geomechanic, logs...) led us to update the characterisation of the Lower Toarcian organic rich shales, despite the age of the dataset (almost 30 years). These new analytic approaches (QEMSCAN, CT-Scan, Nano-indentation...), coupled to common analysis in an optimized workflow, allow to consider larger studies with heterogeneous databases, long as geoscientists have access to cuttings. The main analysis recently performed from the COUY-1 dataset by SGS, with BRGM support, will be presented during the WS04 EAGE Workshop and compared with previous studies in Dutch North Sea and SW Algeria.
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How to Maximize Wellsite Information for Assessing Tight Hydrocarbon Opportunities
Authors M. Simpson, D. Bonijoly, M. Power and C. RigolletFor many years mud rich lithologies were largely ignored at the well site. Mud rich formations or shales, were simply the rock that had to be penetrated in order to reach the reservoir target. However mud rich rocks when examined properly at the wellsite are very important when investigating tight hydrocarbon domains. Mud rich formations can be characterized onsite to obtain quickly a first evaluation of the potential sweet spots. In further studies, these valuable first data accessible in the “mudlog”, must be systematically considered and integrated to the working dataset. The rate of penetration (ROP), Rotary torque, onsite analysis (methyl blue tests, calcimetry, fluorescence, isotopic analysis…), cuttings description (mineralogy, lithology, size, shape and morphology) and gas show bring enough information to make a first evaluation of the mud rich formation properties (rock strength, fracture presence, flow unit, TOC presence, maturity…) and hydrocarbon potential. The EAGE WS04 workshop will set out to look at the key characteristics of mud rich lithologies that can be identified at the well site and how some of these parameters can be determined. These parameters are integrated in a way that possible hydrocarbon potential can be identified so that follow up work can be initiated.
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Integrated Log-core Calibrated Approach for Petrophysical and Geomechanical Characterization of Source-rocks
Authors A. Di Matteo, D. Bonijoly, M. Power, C. Rigollet and M. SimpsonThe prediction of mineralogy, TOC, grain density, porosity and gas saturation in organic rich shale is a challenging process that needs to rely on the integration of several measurement methodologies usually performed at different scale and by different disciplines. LECO analysis data can be used to measure the TOC values on core scale. Such values can drive the logs in estimating the TOC on a well scale. QEMSCAN measurements on core and cuttings provide accurate information about the shale composition. This information can be used, along with the TOC content, routine core data and the petrophysical deterministic analysis, to solve a probabilistic petrophysical model that allows characterizing the mineralogy and the organic content of the shale of interest along the whole well path. Once estimated the rock composition, the Brittleness Index can be estimated by assuming a multi-variable dependence between BI and the shale mineral composition. The BI calculated from the mineral composition can be further calibrated by using site specific rock cuttings and by correlating the BI values based on mineral components with the geomechanical response based on nano-indentation measurements. This methodology will be illustrated during the EAGE WS04 workshop with the Toarcian shale (COUY-1 well, Paris Basin, France).
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The Role of Mineralogy (QEMSCAN) in the Facies Heterogeneity Characterization of Organic Rich Shale
Authors M. Power, D. Bonijoly, A. Hofmann, C. Rigollet and M. SimpsonDue to the increased complexity of unconventional plays, existing workflows, developed for more conventional reservoirs, are not always applicable. A better understanding of the rock matrix is critical for the development of improved models for the exploration and exploitation of these resources. As minerals control fundamental parameters such as grain density and directly or indirectly influence many of the wireline responses e.g. density, resistivity, spontaneous potential, gamma ray etc, accurate determination of the mineralogy is a vital input to petrophysical models. In addition, the composition and fabric of the reservoir rocks control geomechanical properties such as well bore stability and fracking potential. Therefore, accurate and reproducible quantification of the mineralogy and texture of the rock matrix is a particularly important factor in exploitation and development workflows for tight and / or unconventional resources. QEMSCAN analyses on the COUY-1 well cores and cuttings (Toarcian Shale, Paris Basin, France) provide quantitative mineralogical data, textural data and mineral maps of each cutting/core sample, thereby allowing for the detailed characterisation and determination of the nature and distribution of the inorganic sample components. The particles are lithotyped in order to quantify the variations between the samples and brittleness indices were calculated from the modal mineralogy.
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Shale Geomechanics - A Nano-indentation Application
Authors M. De Block, D. Bonijoly, A. Hofmann, M. Power, C. Rigollet and M. SimpsonNano-indentation is a technique developed to determine the mechanical properties of small samples. It is based on a hard tip, which is pressed into the surface of a rock sample. The ratio between the applied load and the displacement of the tip into the sample is used to calculate the hardness and Young’s modulus. Additionally, the load-displacement plot obtained from nano-indentation measurements can be used to define three areas which describe the plastic work done on the sample and the elastic work done on the sample. This work-of-indentation approach is a good predictor for the brittleness of shale formation. For the study, core samples were collected from the Toarcian shale formation of the Paris Basin (Couy-1 scientific well) and merged in epoxy resin blocks. First, mineralogical analysis was performed on each block (QEMSCAN analysis) and secondly blocks are used for nano-indentation measurements. Using nano-indentation, for each subsample the Young’s modulus and the hardness are determined. The work-of-indentation approach is utilized in order to predict the brittleness of the samples. Integrating the nano-indentation results with the QEMSCAN data the relation between the mineralogy and the mechanical properties is investigated. Results will presented in details and discussed during the EAGE WS04 workshop.
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Seismic Prospecting of Geothermal Reservoirs in Hard Rock Environment - General Concept and Field Study
Authors W. Rabbel and E. SzalaiovaWe are presenting an approach for finding realistic estimates of geothermal and hydraulic properties of deeply faulted and folded crystalline crust . The approach is based on 3D seismic reflection and geophysical borehole data. It is presented using the example of the 9.1 km deep Continental Deep Drillhole (KTB). This site contains all elements that make seismic prospecting in crystalline environ-ment often more difficult than in sedimentary units – basically complicated tectonics, spatially low-coherent strata, small scale fracturing, strong random component in the seismic velocity field, often rather scattering than reflected arrivals. Considered together these circumstances lead to a statistic approach in deriving underground models that have to be evaluated and calibrated by hydro-thermal modelling. In order to determine model uncertainties distribution functions need to be derived for all geophysical properties involved. The work concept followed during the geothermal potential assess-ment of the KTB site is applicable also for other reservoirs located in similar environment.
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3D Focused Seismic Imaging for Geothermal Reservoir Characterization in Crystalline Rock (Schneeberg, Germany)
Authors F. Hlousek, O. Hellwig and S. BuskeWe present the results of a high resolution 3D seismic survey acquired in the western Erzgebirge near the city of Schneeberg. The project aims at imaging a major fault zone in crystalline rock at a depth of 4-5 km with expected temperatures between 160 and 180°C, which is supposed to be used as a natural geothermal heat exchanger. We applied advanced imaging methods to the data set. 3D Kirchhoff prestack depth migration delivered a clear structural image of the various fault branches at depths of around 2-5 km. Furthermore we applied the focusing coherency migration method, which uses a coherency function of the data recorded at neighboring traces for imaging. This method even sharpened the image such that the 3D seismic result allows for a profound characterization of this potential geothermal reservoir in crystalline rock.
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3D Lithological and Structural Modeling of the Kevitsa 2D and 3D Reflection Seismic Data - A Case Study
Authors E. Koivisto, A. Malehmir, T. Voipio and C. WijnsThe Kevitsa mafic-ultramafic intrusion in northern Finland hosts a large, disseminated nickel-copper sulphide deposit. We present a 3D lithological and structural model of the Kevitsa area, obtained via modeling of 2D and 3D reflection seismic data from Kevitsa. The Kevitsa 3D model contains modeled surfaces of the contacts between the main lithological units and a model of the magmatic layering within the intrusion. The Kevitsa main mineralization is thought to be controlled by the lateral extents of this discontinuous, smaller-scale magmatic layering within the intrusion. An improved knowledge of the geometry of the intrusion, and in particular of the extent of the internal magmatic layering, provides a framework for near-mine and deep exploration in the area. Better control on the position of the basal contact of the intrusion provides an exploration target for the contact-type mineralization. The original purpose of the 3D seismic survey was to provide a structural framework for geotechnical planning of the mine, and accordingly the 3D seismic data were used to create a structural model of the 3D cube. The modeled structures reveal a complex pattern of fault and fracture zones, some of which will be important for slope stability and operational planning at the mine.
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