The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
J A Munoz - One of the best experts on this subject based on the ideXlab platform.
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Studying monogenetic volcanoes with a terrestrial laser scanner: case study at Croscat volcano (Garrotxa Volcanic Field, Spain)
Bulletin of Volcanology, 2015Co-Authors: A. Geyer, D. García-sellés, D. Pedrazzi, S. Barde-cabusson, J. Marti, J A MunozAbstract:Erosional processes (natural or anthropogenic) may partly destroy the relatively small-sized volcanic edifices characteristic of monogenetic volcanic zones, leaving their internal structure well exposed. Nevertheless, the study of these Outcrops may be extremely challenging due to restricted accessibility or safety issues. Digital representations of the Outcrop surface have been lately used to overcome such difficulties. Data acquired with terrestrial laser scanning instruments using Light Detection and Ranging technology enables the construction of such digital Outcrops. The obtained high-precision 3-D terrain models are of greater coverage and accuracy than conventional methods and, when taken at different times, allow description of geological processes in time and space. Despite its intrinsic advantages and the proven satisfactory results, this technique has been little applied in volcanology-related studies. Here, we want to introduce it to the volcanological community together with a new and user-friendly digital Outcrop analysis methodology for inexperienced users. This tool may be useful, not only for volcano monitoring purposes, but also to describe the internal structure of exposed volcanic edifices or to estimate Outcrop erosion rates that may be helpful in terms of hazard assessment or preservation of volcanic landscapes. We apply it to the Croscat volcano, a monogenetic cone in the La Garrotxa Volcanic Field (Catalan Volcanic Zone, NE Spain), quarrying of which leads to a perfect view of its interior but restricts access to its uppermost parts. Croscat is additionally one of the most emblematic symbols of the La Garrotxa Volcanic Field Natural Park, and its preservation is a main target of the park administration.
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supervised identification and reconstruction of near planar geological surfaces from terrestrial laser scanning
Computers & Geosciences, 2011Co-Authors: D Garciaselles, Pau Arbués, Stefano Tavani, O Falivene, Oscar Gratacos, J A MunozAbstract:Terrestrial laser scanning is an effective method for digitally capturing Outcrops, enabling them to be visualized, analyzed, and revisited in an office environment without the limitations of fieldwork (such as time constraints, weather conditions, Outcrop accessibility, repeatability, and poor resolution of measurements). It is common practice in geological interpretation of digital Outcrops to use visual identification and manual digitization of pointsets or polylines in order to characterise geological features using 3D CAD-like modules. Other recent and less generic approaches have focused on automated extraction of geological features by using segmentation methods, mostly based on geometric parameters derived from the point cloud, but also aided by attributes captured from the Outcrop (intensity, RGB). This paper presents a workflow for the supervised and automated identification and reconstruction of near-planar geological surfaces that have a three-dimensional exposure in the Outcrop (typically bedding, fractures, or faults enhanced by differential erosion). The original point cloud is used without modifications, and thus no decimation, smoothing, intermediate triangulation, or gridding are required. The workflow is based on planar regressions carried out for each point in the point cloud, enabling subsequent filtering and classification to be based on orientation, quality of fit, and relative locations of points. A coarse grid preprocessing strategy is implemented to speed up the search for neighboring points, permitting analysis of multimillion point clouds. The surfaces identified are organized into classes according to their orientations and regression quality parameters. These can then be used as seeds for building Outcrop reconstructions or further analyzed to investigate their characteristics (geometry, morphology, spacing, dimensions, intersections, etc.). The workflow is illustrated here using a synthetic example and a natural example from a limestone Outcrop, in which surfaces corresponding to bedding and three fault orientations were reconstructed.
Okke Batelaan - One of the best experts on this subject based on the ideXlab platform.
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the usefulness of Outcrop analogue air permeameter measurements for analyzing aquifer heterogeneity quantifying Outcrop hydraulic conductivity and its spatial variability
Hydrological Processes, 2014Co-Authors: Bart Rogiers, Koen Beerten, Tuur Smeekens, Matej Gedeon, Marijke Huysmans, Okke Batelaan, Dirk MallantsAbstract:Saturated hydraulic conductivity (K) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Although several well-established laboratory methods exist for determining K, in situ measurements of this parameter remain very complex and scale dependent. Often, the limited accessibility of subsurface sediments for sampling means an additional impediment to our ability to quantify subsurface K heterogeneity. One potential solution is the use of Outcrops as analogues for subsurface sediments. This paper investigates the use of air permeameter measurements on Outcrops of unconsolidated sediments to quantify K and its spatial heterogeneity on a broad range of sediment types. The Neogene aquifer in northern Belgium is used as a case study for this purpose. To characterize the variability in K, 511 small-scale air permeability measurements were performed on Outcrop sediments representative over five of the aquifer's lithostratigraphic units. From these measurements, Outcrop-scale equivalent K tensors were calculated using numerical upscaling techniques. Validation of the air permeameter-based K values by comparison with laboratory constant head K measurements reveals a correlation of 0.93. Overall, the results indicate that hand-held air permeameters are very efficient and accurate tools to characterize saturated K, as well as its small-scale variability and anisotropy on a broad range of unconsolidated sediments. The studied Outcrops further provided a qualitative understanding of aquifer hydrostratigraphy and quantitative estimates about K variability at the centimetre-scale to metre-scale. Copyright © 2013 John Wiley & Sons, Ltd.
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The usefulness of Outcrop analogue air permeameter measurements for analysing aquifer heterogeneity: testing Outcrop hydrogeological parameters with independent borehole data
2013Co-Authors: Bart Rogiers, Koen Beerten, Tuur Smeekens, Matej Gedeon, Marijke Huysmans, Okke Batelaan, Dirk Mallants, A. DassarguesAbstract:Abstract. Outcropping sediments can be used as easily accessible analogues for studying subsurface sediments, especially to determine the small-scale spatial variability of hydrogeological parameters. The use of cost-effective in situ measurement techniques potentially makes the study of Outcrop sediments even more attractive. We investigate to what degree air permeameter measurements on Outcrops of unconsolidated sediments can be a proxy for aquifer saturated hydraulic conductivity (K) heterogeneity. The Neogene aquifer in northern Belgium, known as a major groundwater resource, is used as case study. K and grain size data obtained from different Outcropping sediments are compared with K and grain size data from aquifer sediments obtained either via laboratory analyses on undisturbed borehole cores (K and grain size) or via large-scale pumping tests (K only). This comparison shows a pronounced and systematic difference between Outcrop and aquifer sediments. Part of this difference is attributed to grain size variations and earth surface processes specific to Outcrop environments, including root growth, bioturbation, and weathering. Moreover, palaeoenvironmental conditions such as freezing-drying cycles and differential compaction histories will further alter the initial hydrogeological properties of the Outcrop sediments. A linear correction is developed for rescaling the Outcrop data to the subsurface data. The spatial structure pertaining to Outcrops complements that obtained from the borehole cores in several cases. The higher spatial resolution of the Outcrop measurements identifies small-scale spatial structures that remain undetected in the lower resolution borehole data. Insights in stratigraphic and K heterogeneity obtained from Outcrop sediments improve developing conceptual models of groundwater flow and transport.
Robert Wilson - One of the best experts on this subject based on the ideXlab platform.
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Mapping and analysing virtual Outcrops
Visual Geosciences, 2005Co-Authors: Immo Trinks, Nick Holliman, Jonny Imber, Steve Waggott, Bob Holdsworth, Ken Mccaffrey, Richard Hobbs, Richard Jones, Phillip Clegg, Robert WilsonAbstract:Laser scanning is a very efficient way to generate realistic, high-resolution\ndigital models of 3-D geological Outcrops. This paper discusses the\nmethodologies involved in the creation and analysis of virtual Outcrops,\nbased on laser scanner data. The visualisation of the laser scanner\ndata as a photorealistic 3-D object is described. Geological features\npicked out on the virtual Outcrop (e.g. fractures, faults or bedding\nplanes) can be extrapolated outward, into space, and inward, into\nthe subsurface, using tension surfaces.
Roger M Slatt - One of the best experts on this subject based on the ideXlab platform.
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lithology stratigraphy chemostratigraphy and depositional environment of the mississippian sycamore rock in the scoop and stack area oklahoma usa field lab and machine learning studies on Outcrops and subsurface wells
Marine and Petroleum Geology, 2020Co-Authors: Benmadi Milad, Roger M Slatt, Zou FugeAbstract:Abstract This paper presents an interpreted depositional environment, developed 2nd order sequence stratigraphy framework, and detailed lithofacies identification from two Mississippian Sycamore Outcrops (I-35 Sycamore and Speake Ranch) and subsurface wells in the SCOOP (South Central Oklahoma Oil Province). Then these rocks calibrate the rock properties with wireline log responses to identify the best landing zones. Qualitative and quantitative techniques of field, laboratory, and machine learning studies were conducted. For the field studies, we measured the complete 450 ft of the Outcrop stratigraphic section, another separate 50 ft Outcrop, examined the underlying Woodford Shale and overlying Caney Shale boundary contacts, documented sedimentary structures, constructed an Outcrop gamma-ray profile, and developed a sequence stratigraphic framework. Laboratory studies included petrographic analyses, detailed X-ray Fluorescence (XRF), Scanning Electron Microscopy (SEM), and X-ray Diffraction (XRD). For machine learning studies, a principal component analysis (PCA), elbow method, and self-organizing map (SOM) were used to analyze the electrofacies and chemofacies from the Outcrop and a subsurface uncored well. The Outcrop hand-held gamma ray profile was obtained and correlated with subsurface wells. Five major Outcrop lithofacies and chemofacies, within six stratigraphic units of alternating siltstone and shale strata, were identified from the wireline logs. A Maximum Flooding Surface (MFS), and two major 2nd order Sequence Boundaries (SB) were recognized at the Outcrop and a nearby subsurface well. Bouma sequences and repetitive cycles of sedimentary structures indicated sediment gravity flow deposition on a marine slope setting. This study provides geologic insights to better understanding the depositional environment and the lithology of the Sycamore rocks. The bioturbated siliceous shale and/or the sandy siltstone can be potential target zones due to their reservoir quality, lithology, bed continuity, and brittleness. This information can be of direct benefit to the exploration and development programs of many companies in the SCOOP area, particularly in the Anadarko and Ardmore basins in Oklahoma.
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Chapter 13: Outcrop Gamma-Ray Logging Applied to Subsurface Petroleum Geology
2011Co-Authors: Roger M Slatt, James M. Borer, Brian W. Horn, Hisham A. Al-siyabi, Sarah R. PietraszekAbstract:Abstract Developing a gamma-ray log profile of an Outcrop with a hand-held scintillometer has many applications to subsurface petroleum geology. The Outcrop gamma-ray log provides a readily understandable bridge between what is observed in Outcrop and what is to be interpreted on well logs and seismic records. Several examples are presented in this paper that demonstrate major applications. An Outcrop from the Cretaceous Mesaverde Group in Colorado provides an excellent example of the use of Outcrop gamma-ray logs to better visualize spatial variability of depositional settings for improved well log correlations. Outcrops from the Cretaceous Almond Formation, Niobrara Formation, and Graneros Shale in Colorado serve as examples of Outcrop gamma-ray logging used to correlate Outcrops with their subsurface equivalents for improved lithologic and stratigraphic interpretation of well logs. Outcrops of the Cretaceous Sharon Springs Member of the Pierre Shale in Colorado and the Eocene Green River Formation in Wyoming provide examples of the application of Outcrop-gamma ray logging to identify and characterize organic-rich shales in Outcrops and on well logs. Outcrops of the Pennsylvanian Jackfork Formation in Arkansas demonstrate the use of Outcrop logging to yield improved interpretation of reservoir quality on well logs and for one- and two-dimensional seismic modeling. An Outcrop of Precambrian and Cambro-Ordovician rocks from Algeria provides an example of Outcrop logging to recognize unconformities and other major surfaces on well logs. An Outcrop of the Niobrara Formation in Colorado is used as an example for improved understanding of horizontal gamma-ray log response. The example logs presented are all derived with a hand-held scintillometer. This technique is simple, quick, and relatively inexpensive, so is recommended for any Outcrop work that is intended to be applied to subsurface well logs or seismic interpretation.
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application of ground penetrating radar imaging to deepwater turbidite Outcrops
Marine and Petroleum Geology, 2003Co-Authors: Roger A Young, Roger M Slatt, J G StaggsAbstract:Ground Penetrating Radar (GPR) provides a high resolution image of bed-scale features within the interior of an Outcrop. This geophysical technique has been used successfully in fluvial-deltaic sequences, but its successful use in deepwater deposits is less documented. The present paper demonstrates the ability of GPR to define the nature of channel margins and to distinguish internal channel facies at turbidite Outcrops in Wyoming (Cretaceous Lewis Shale), USA. Profiles obtained behind the Lewis Shale Outcrops show channel-fills having complex, slumped margins between channel sandstones and adjacent levee thin-beds, as well as onlap of sandstone beds onto the channel margins. Within the channel-fill, facies distinguished by GPR vary from interbedded debris flows and turbidites on one side of a channel to cross-bedded sandstones on the other side. Lateral accretion surfaces and onlap features, which cannot be observed at the Outcrop scale, are present on GPR profiles. They may represent cross-channel sediment transport and deposition within a sinuous channel. These examples suggest that, when used together with geologic mapping, photomosaics, and available behind-Outcrop drilling and logging, GPR surveys spanning large Outcrops may provide valuable sub-seismic scale architectural information for building more robust 3-D models of deepwater reservoirs. q 2003 Elsevier Ltd. All rights reserved.
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Imaging of Turbidite Outcrop Analogs Using Ground Penetrating Radar
SEG Technical Program Expanded Abstracts 1999, 1999Co-Authors: Roger A Young, Ben Peterson, Roger M SlattAbstract:High-resolution Outcrop stratigraphic analysis is becoming increasingly utilized to build detailed, quantitative reservoir architectural models. With suitably long Outcrops, preferably in three dimensions, this analysis can provide the best method of developing reservoir models which include hard data on continuity and connectivity of different bed types. The addition of geophysical logs and cores taken immediately behind Outcrop faces provides a valuable means for geological correlation in the plane of the Outcrop.
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Outcrop gamma-ray logging applied to subsurface petroleum geology
The mountain Geologist, 1995Co-Authors: Roger M Slatt, James M. Borer, Brian W. Horn, Hisham A. Al-sitabi, Sarah R. PietraszekAbstract:Developing a gamma-ray log profile of an Outcrop with a hand-held scintillometer has many applications to subsurface petroleum geology. The Outcrop gamma-ray log provides a readily understandable bridge between what is observed in Outcrop and what is to be interpreted on well logs and seismic records. Several examples are presented in this paper that demonstrate major applications. An Outcrop from the Cretaceous Mesaverde Group in Colorado provides an excellent example of the use of Outcrop gamma-ray logs to better visualize spatial variability of depositional settings for improved well log correlations. Out crops from the Cretaceous Almond Formation, Niobrara Formation, and Graneros Shale in Colorado serve as examples of Outcrop gamma-ray logging used to correlate Outcrops with their subsurface equivalents for improved lithologic and stratigraphic interpretation of well logs. Outcrops of the Cretaceous Sharon Springs Member of the Pierre Shale in Colorado and the Eocene Green River Formation in Wyoming provide examples of the application of Outcrop-gamma ray logging to identify and characterize organic-rich shales in Outcrops and on well logs. Outcrops of the Pennsylvanian Jackfork Formation in Arkansas demonstrate the use of Outcrop logging to yield improved interpretation of reservoir quality on well logs and for one- and two-dimensional seismicmore » modeling. An Outcrop of Precambrian and Cambro-Ordovician rocks from Algeria provides an example of Outcrop logging to recognize unconformities and other major surfaces on well logs. An Outcrop of the Niobrara Formation in Colorado is used as an example for improved understanding of horizontal gamma-ray log response. The example logs presented are all drived with a hand-held scintillometer. This technique is simple, quick, and relatively inexpensive, so is recommended for any Outcrop work that is intended to be applied t;o subsurface well logs or seismic interpretation.« less
G Bertotti - One of the best experts on this subject based on the ideXlab platform.
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an integrated workflow for stress and flow modelling using Outcrop derived discrete fracture networks
Computers & Geosciences, 2017Co-Authors: K Bisdom, Hamidreza M Nick, G BertottiAbstract:Fluid flow in naturally fractured reservoirs is often controlled by subseismic-scale fracture networks. Although the fracture network can be partly sampled in the direct vicinity of wells, the inter-well scale network is poorly constrained in fractured reservoir models. Outcrop analogues can provide data for populating domains of the reservoir model where no direct measurements are available. However, extracting relevant statistics from large Outcrops representative of inter-well scale fracture networks remains challenging. Recent advances in Outcrop imaging provide high-resolution datasets that can cover areas of several hundred by several hundred meters, i.e. the domain between adjacent wells, but even then, data from the high-resolution models is often upscaled to reservoir flow grids, resulting in loss of accuracy. We present a workflow that uses photorealistic georeferenced Outcrop models to construct geomechanical and fluid flow models containing thousands of discrete fractures covering sufficiently large areas, that does not require upscaling to model permeability. This workflow seamlessly integrates geomechanical Finite Element models with flow models that take into account stress-sensitive fracture permeability and matrix flow to determine the full permeability tensor. The applicability of this workflow is illustrated using an Outcropping carbonate pavement in the Potiguar basin in Brazil, from which 1082 fractures are digitised. The permeability tensor for a range of matrix permeabilities shows that conventional upscaling to effective grid properties leads to potential underestimation of the true permeability and the orientation of principal permeabilities. The presented workflow yields the full permeability tensor model of discrete fracture networks with stress-induced apertures, instead of relying on effective properties as most conventional flow models do. Display Omitted A new workflow for realistic discrete fracture-matrix flow models is proposed.Realistic fracture geometries are obtained from Outcrops using photogrammetry.Aperture and permeability are calculated from geomechanical Finite Element models.The result is a permeability tensor for large-scale discrete fracture-matrix models.
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toward a quantitative definition of mechanical units new techniques and results from an Outcropping deep water turbidite succession tanqua karoo basin south africa
AAPG Bulletin, 2007Co-Authors: G Bertotti, N Hardebol, Taalvan J Koppen, Stefan M LuthiAbstract:The physical properties of reservoirs are strongly influenced by distributed fracture fields. Outcrop studies are commonly used to determine them but have provided unsatisfactory results because the definition of mechanical units, i.e., (groups of) layers displaying homogeneous fracture patterns, is difficult and typically conducted in a qualitative manner. We have developed a systematic methodology to acquire and process fracture patterns in Outcrops and to define their relation with stratigraphy. We dedicate particular attention to the vertical distribution of fractures in a sedimentary succession, commonly composed of layers of different thicknesses and compositions. The method makes full use of geographic information system technologies and allows for direct digital acquisition in the field leading to time-efficient acquisition. Data are processed with a newly developed routine that permits an objective description of the changes of fracture characteristics along the stratigraphy of the Outcrop. The operator is then able to define the most suitable fracture stratigraphy. The integration of results from different Outcrops is thought to provide a tool for predicting fracture distributions in subsurface target areas.
