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75th EAGE Conference & Exhibition - Workshops
- Conference date: 10 Jun 2013 - 13 Jun 2013
- Location: London, UK
- ISBN: 978-90-73834-49-1
- Published: 10 June 2013
61 - 80 of 138 results
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About ADCIG Residual Moveout
Authors J.-P. Montel and G. LambaréThe increasing usage of wave equation and reverse time migration has motivated investigations about new types of common images gathers. Several types of angle domain common image gathers have then been proposed. While they should have the same aspect (up to specific artefacts) when the exact velocity model is used it appears that they exhibit significant differences in curvature when the velocity model is erroneous. This observation is analysed here by a theoretical analysis in the frame of high frequency asymptotics. This analysis is performed for several types of angle domain common image gathers revealing much more complexity than expected. It demonstrates that some well admitted statements such as the validity of Snell Descartes law for tomographic rays or the idea that the tomographic ray tracing could be limited to lower layers may not be satisfied for all type of angle gathers.
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The Challenge of Short-wavelength, High-contrast Velocity Anomalies
By J. EtgenConventional velocity estimation, based on post migration residual moveout, works very well when the velocity structure of the Earth is smooth enough in the lateral directions. This is true even when the initial velocity model is far from correct. Stated another way, long wavelength lateral velocity errors are not a significant challenge anymore. However, once the velocity varies significantly in the lateral directions at scales approaching or less than a few wavelengths, residual moveout estimation plus reflection tomography will often fail to improve velocity models.
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Unmanned Aircraft Systems for Rapid Near Surface Geophysical Measurements
More LessThis paper looks at some of the unmanned aircraft systems (UAS) options and deals with a magnetometer sensor system which might be of interest in conducting rapid near surface geophysical measurements. Few of the traditional airborne geophysical sensors are now capable of being miniaturized to sizes and payload within mini UAS limits (e.g. airborne magnetics, gamma ray spectrometer). Here the deployment of a fluxgate magnetometer mounted on an UAS is presented demonstrating its capability of detecting metallic materials that are buried in the soil. The effectiveness in finding ferrous objects (e.g. UXO, landslides) is demonstrated in a case study.
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Successful Execution of Remotely Piloted Ocean Vehicles to Conduct METOC and Turbidity Pre-site Survey
More LessThis is to present case studies conducted for Chevron’s Environmental Technology Unit off the coast of North West Australia. Two sorties, first a METOC survey followed by a detailed Turbidity study was conducted over 2 months (Dec 2012 and Jan 2013) to collect baseline data as pre-site survey prior to the start of a full scale dredging operation to lay a pipeline.
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Analysis and Separation of Surface and Body Waves in Onshore-seismic Dual Fields
Authors F. Poletto, A. Schleifer, B. Farina and L. PetronioDual-field seismic data are achieved recording particle velocity and pressure/stress at a same receiver-device location. The dual-field method makes it possible to separate different components of the propagating wavefields activated by a single source. We analyze the results of an onshore seismic application using dual-field measurements in the shallow ground. We acquired the seismic data by reciprocal source-receiver geometry that makes it possible to limit the number of dual-receivers installations and to record dual-field data by a source activated along a seismic line. The data obtained by shallow stress sensors buried in the ground and surface geophone are studied for the characterization of vertically propagating body waves, and of surface waves propagating in the horizontal direction with amplitude decaying in depth. The analysis shows that the surface and body waves can be separated combining the dual signals without needing of multi-dimensional processing. This technique may represent a new approach useful for wavefield analysis in near-surface applications, and not only, easily achievable with reciprocal geometry in shallow seismic acquisition surveys.
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Fusing Multi Source Remote Sensing Data – Selected Aspects on Geometric and Thematic Accuracy
Authors M. Pregesbauer, R. Michel and A. AltenbergerRemote Sensing data is widely used in geosciences for all kind of applications. The user thereby relies on, for his purposes, sufficient accuracy and well calibrated data. Beside standard processing methods geometric accuracy and radiometric calibration can be increased with the aim to enhance the thematic accuracy. With the focus on airborne remote sensing, different strategies for laserscanning and hyperspectral data processing with the focus on the subsequent analysis and interpretation are going to be discussed and an assessment on the possible accuracy is given.
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Seabed Sampling for Stratigraphy and Seep Studies Offshore Greenland and Norway
Authors S. Polteau, S. Planke, R. Myklebust and G. HickmanGravity coring and dredging has been used to obtain extensive seabed sampling of escarpments and potential hydrocarbon seep sites offshore Greenland in the northeast Atlantic. Sampling of sub cropping strata and thin overburden sediments provide consistent information on ages of the strata and the nature of potential active hydrocarbon systems. Our results are the first to document active hydrocarbon systems in the Baffin Bay, the northeast Greenland shelf, and on the southern Jan Mayen Ridge.
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Mapping Palaeorivers from Satellite Radar and Surface-wave Velocities
Authors A. Laake and C. StrobbiaSatellite radar data have revealed the existence of extensive palaeodrainage patterns below sand dunes in the eastern Sahara. So far, studies have focused mainly on the lateral mapping of these so-called radar rivers. We use seismic surface-wave data to estimate the penetration of satellite radar into the ground on a regional scale. We developed a scheme for the classification of radar backscatter intensity that allows the discrimination of direct surface backscatter in areas with hard rock at the surface from areas where the radar data penetrate the surface and provide information about palaeorivers in the subsurface. The estimated radar penetration depth is calibrated with seismic surface-wave velocity profiles. Corendering both data sets in 3D shows the high degree of correlation. The method is demonstrated on an area of about 200 x 200 km in the hyperarid desert of southwest Egypt. A 200-km high-resolution seismic section provides the shallow seismic data. The seismic surface waves confirm the existence of two phases of palaeovalleys in the area: wide valleys of several km in width from the Tertiary and Pleistocene rivers, the channels of which are mapped by the satellite radar data.
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Surface Deformation Monitoring with InSAR Data for Oil & Gas Applications
Authors A. Rucci, A. Ferretti and F. RoccaApart from the environmental impact of subsidence and uplift phenomena induced by fluid injection and/or extraction, recent reservoir optimization techniques ask for timely information about many geophysical parameters, both downhole and on the surface. In particular, surface deformation measurements are lately gaining increasing attention within the reservoir engineer community, which is searching for new monitoring tools to complement seismic surveys. In the last decade, a new remote-sensing technology called PSInSAR™- based on the use of satellite radar data - is receiving an increasing attention, thanks to its capability to provide accurate, large-scale surface deformation measurements. The main advantages of PSInSAR™ data, compared to conventional geodetic networks, are essentially related to the spatial density of measurement points, the temporal frequency of the observations, the precision and the limited cost, at least for the monitoring of large areas. Since the number of radar-mounted satellite platforms is increasing, as well as the accuracy of radar measurements, this source of information will probably become more and more common in projects related to reservoir monitoring and optimization. More in detail, ground deformation measurement can provide valuable information to better understand the fluid/gas flow in the subsurface or to calibrate the geomechanical model of the reservoir/overburden, if properly interpreted and integrated with more conventional data.
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Outcrop Structural Mapping from Hi-res DEM and Worldview Satellite Imagery
Authors B. Baugh and K. NavulurRecent trends in commercial remote sensing imagery point to increased spatial, spectral resolution, and agility of satellites. Satellites are now planned at 1foot pixel resolution allowing for new applications. The global capacity of satellites at these high spatial resolutions has signalled a new market for geological applications. Similarly, the number of spectral bands is evolving from traditional bands to specialized bands designed for specific applications. DigitalGlobe has recently announced that Worldview-3, the next generation satellite, will have 17 bands ranging from VNIR to SWIR region of the spectrum that are suited of variety of geological applications. These spectral bands can detect specific phenomenology of outcrops that are indicators of subsurface minerals. The advent of CMG’s allow for backward and forward scanning, allowing for unprecedented agility for collection of stereo imagery that can be used for creating elevation models. Several research papers show accuracy of DEM’s derived from satellite imagery are around 2 meters LE90. Combing the spectral capabilities of Worldview satellites with elevation models, can be indicators of outcrops for geological mapping. This papers talks about specific phenomenology that can be exploited for outcrop structural mapping from hi-res DEM and Worldview satellite imagery.
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Geoid Determination in the Western Part of Egypt from Gravity Data and Gps/Leveling
By A. RadwanPrecise geoid determination is one of the main current geodetic interests in Egypt. The method of Least-squares collocation (LSC) is used in this research for the computation of geoid in Egypt, combining a geopotentail model complete to degree and order 360 in addition to gravity and GPS/leveling data. No topographic information was taken into account on the area under study.
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Reactive Transport in Carbonate Reservoirs: Seismic and Transport Properties
Authors J.P. Nunes, L.G. Rodrigues and R.R. GuérillotThe recent surge in CO2 rich gas injection activities for both Capture Carbon and Sequestration (CCS) and Enhanced Oil Recovery (EOR) projects have led the oil industry and the academia to explore the implications of rock-fluid interactions at full scale development projects. Some of the main questions are: Do reactions occur? Are they relevant for CO2 capture and/or oil recovery? How to monitor them? To illustrate some of the ways the industry may tackle these questions reactive transport simulations have been made to evaluate the impact of rock-fluid interactions in the seismic, mechanical and flow properties in an outcrop based 3D geocellular model. Changes in elastic properties are evaluated using a flow coupled petroelastic model based on an effective medium approach. Current challenges to develop pore-to-reservoir reactive models will also be addressed.
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Dual Mineral Matrix and Organic Pore Textures in Mature Niobrara Formation, Rocky Mountains, USA – Implications for Tight-Oil Carbonate Reservoir Modeling
Authors C. Laughrey and R. RubleProspective tight-oil reservoirs in the Upper Cretaceous Niobrara Formation B Chalk in the northern Denver basin include elements of hybrid/interbedded and porous mudstone fine-grained systems. We recognize three reservoir/source rock lithologies: 1) argillaceous, organic-rich, pelletal impure chalk; 2) organic-rich pelletal chalk; and, 3) highly organic-rich pelletal impure chalk. Geochemical parameters indicate the rocks belong to Organic Facies B (oil-prone), and are thermally mature with respect to oil generation. We recognize both mineral matrix pores and organic-matter pores in the Niobrara reservoirs. Mineral matrix pores include interparticle and intraparticle voids. Intraparticle pores dominate storage capacity in the rocks and consist of nano- to micro-scale fabric-selective and not-fabric-selective carbonate pore textures preserved within compacted pelletal allochems. Organic porosity is well developed in alginite and liptodetrinite, but is absent in bituminite, and thus may be related to the original kerogen structure. Complex intraparticle pore geometry is readily modeled by 3D FIB/SEM segmentation. Laboratory NMR measurements of the modeled samples appear to discriminate discrete pore and fluid distributions in the tight reservoirs.
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Bi-Directional Interactions between Fluids and Geomechanics in Fractured Reservoirs
By G. CouplesPopular ideas used to explain geomechanical-fluid interactions in fractured reservoirs are inadequate, or wrong, as they are based on assumptions that are incorrect. Poro-elasticity considerations show that predicted aperture effects are highly sensitive to the local boundary conditions, which themselves may change during reservoir operation. The more-general approach is to consider fully-coupled systems of matrix blocks bounded by fractures, and the porefluids. Simulations based on such systems reveal significant insights, as well as surprising outcomes, with effective permeabilities that can vary by more than 1000x due to small changes in conditions. Application of these concepts within reservoir models can be used to improve the results of reservoir flow simulation.
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Carbonate Rock-typing – Diagenesis and Multi-scale Heterogeneity
Authors C. van der Land and Z. JiangCarbonate rock typing methods aim to associate texture with petrophysically similar rocks. Here, we use 2D thin sections of carbonate reservoir rocks to create 3D statistical pore-size distributions and extract pore network models from these to obtain multiphase flow properties. This novel rocktyping method is applied to synthetic depositional rock textures which are progressively altered by a succession of typical diagenetic processes. For each stage in the paragenetic sequence, flow properties were calculated. Secondly, by comparing experimental results with our modelled predictions, we validate our methodology of pore reconstruction, network extraction, stochastic network generation and creation of multi-scale networks.
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Calculating Vertical Stress in Chalk
More LessWhen effective stress is calculated with reference to the grain cross sectional area as defined from Biot’s coefficient, it is simple to illustrate zones of chalk where the stress on the mineral grains is high, and pore collapse would be a challenge during production of hydrocarbons.
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Quantification of Depositional and Diagenetic Geobody Geometries for Reservoir Modelling, Hammam Fauran Fault Block, Sinai Peninsula, Egypt
Authors C. Hollis, H. Corlett, J. Hirani, D. Hodgetts, R. Gawthorpe, A. Rotevatn and E. BastesenOutcrop data has traditionally been used to constrain conceptual models during subsurface reservoir characterisation and geocellular modeling, but published data of depositional and diagenetic geobodies in carbonate systems is lacking. Furthermore, few studies address how these diagenetic bodies, which often cross-cut sedimentary bedding, can be captured in reservoir models, even though diagenetic modification is likely to impart a significant influence on flow behaviour. This paper presents a case study from the differentially dolomitised pre-rift Eocene Thebes Formation on the Sinai Peninsula. It documents the size of depositional and diagenetic geobodies and demonstrates how these data have been incorporated into a 3D geocellular model. The results can be used as input parameters or templates for reservoirs in which fault/fracture controlled dolomite bodies have been described, whilst the workflow could have broader applications to other carbonate reservoirs.
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Modeling and Validation of Fluid Flow-Geomechanics of Mauddud Reservoir in Sabriya Field
More LessIntegrating fluid flow and geomechanics is becoming increasingly important in the oil and gas industry to improve production history matching and forecasting. This is especially the case in carbonate reservoirs due to the heterogeneous nature of the rock and flow properties within the pores and sometimes fractures. During production, carbonate reservoirs are subject to mechanical, hydraulic, and, in some cases, thermal processes. Coupled modeling between these processes helps to better understand the behavior of a carbonate field. When hydrocarbon is produced, the pore-pressure change within the reservoir gives rise to accompanying stress changes, which cause rock deformation that will either reduce or enhance permeability and porosity. A multidisciplinary approach is necessary to integrate geology, petrophysics, fluid flow, and geomechanics within a coupled reservoir simulation. 3D fluid-flow geomechanical modeling was conducted for a carbonate field in order to improve the history match of a reservoir model, and we examined the impact of permeability change and enhancement on well performance. The results showed significant improvement of the reservoir production history matching by including coupled reservoir simulations. The geomechanical changes brought on by production will influence other field-development operations such as in-fill drilling. Geomechanical modeling of the reservoir can be extended to optimize wellbore stability through a 3D mud-weight cube for field-scale in-fill drilling optimization.
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Challenges in Brazilian Pre-Salt Reservoirs Geophysical Characterization
By P. JohannThis paper focuses on the impact that reservoir geophysics has had on the production development of the Brazilian marine carbonate pre-salt fields starting from the first oil discovery in 2005 to 2011. The evolution of three main knowledge areas of reservoir geophysics technology will be detailed, namely: acquisition, processing and interpretation, all oriented towards reservoir characterization and monitoring. Seismic acquisition technology has experienced an increase in “information density” (seismic traces per square kilometer). In the seismic processing domain, the improvement of seismic algorithms and methodologies has allowed for better seismic data quality, resolution and imaging. In particular, the algorithms/techniques of 3-D multiple suppression and 3-D depth migration have significantly evolved in recent years. In the seismic interpretation area, geological context-oriented seismic attributes algorithms/methodologies have made possible better reservoir characterization in the deep and ultra deep-water Brazilian offshore basins. No extended abstract available.
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Land Vibroseis Source Advances towards Low Frequencies
Authors Z. Wei and T.F. PhillipsExtending the frequency bandwidth towards low frequencies using the Vibroseis method has gained a lot of attenation recently. The source (vibrators) becomes one of the obtacles in the success of recording low frequency seismic signals. How do we increase the vibrator ground force at low frequencies (< 10 Hz)? Can the vibrator control electronics effectively supress harmonic distortion at low frequencies? This paper attempts to provide a fresh look at these questions.
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