Ground-penetrating radar imaging of Albian rudist buildups, central Texas

2015 ◽  
Vol 3 (3) ◽  
pp. SY67-SY81 ◽  
Author(s):  
Xavier Janson ◽  
Keumsuk Lee ◽  
Chris Zahm ◽  
Charles Kerans
Keyword(s):  
Middle East ◽  
Ground Penetrating Radar ◽  
Reservoir Modeling ◽  
Size Difference ◽  
Seismic Resolution ◽  
Stratigraphic Architecture ◽  
Order Of Magnitude ◽  
Central Texas ◽  
Ground Penetrating ◽  
Subsurface Reservoir

Rudist buildups are important reservoirs in many Cretaceous fields in the Middle East, but they are generally near or below seismic resolution. The dimension, shape, and architecture of rudist buildups can be assessed using outcrop, although only partly so because of pseudo-2D observations of geobodies intersecting with the outcrop. We used ground-penetrating radar to enhance our understanding of the shape, dimension, and architecture of Albian rudist buildups in two outcrops in Texas. In the Lake Georgetown spillway, caprinid rudist buildups are 10–30 m wide and 2–7 m high. They are elliptical with an aspect ratio of as much as 1.7. They show no or very little flank development. The older buildup exposed in the Red Bluff Creek area displays 10- to 25-m-wide and 5- to 10-m-high in situ caprinid rudist mound core accumulations with as much as 100-m-wide reworked flanks in the shallower part of the depositional profile. Downdip along the depositional profile, caprinid buildups are 5–20 m wide and 3–7 m high with no flank debris. The buildups in the Lake Georgetown area have similar architecture and comparable size with the downdip buildups exposed in Red Bluff Creek. These buildups were compared with other outcropping Albian buildups in Texas that have different sizes, shapes, and stratigraphic architecture to provide dimensional data that could be used in subsurface reservoir modeling, either for calibrating variogram ranges or to build training images. The rudist buildups exposed in Texas are an order of magnitude smaller than those present in the subsurface in the Middle East, but they have comparable stratigraphic architecture. The size difference might be the result of subsurface buildups being mapped using well-log or core correlations or seismic extractions that cannot resolved at that scale of heterogeneity.

Combining Ground-Penetrating Radar profiles with geomechanical and petrophysical in situ measurements to characterize sub-seismic resolution structural and diagenetic heterogeneities in porous sandstones (Northern Apennines, Italy)

2020 ◽  
Author(s):  
Leonardo Del Sole ◽  
Antonino Calafato ◽  
Marco Antonellini
Keyword(s):  
Ground Penetrating Radar ◽  
Host Rock ◽  
Northern Apennines ◽  
Reservoir Rock ◽  
Small Scale ◽  
Strengthening Effect ◽  
Deformation Bands ◽  
Geomechanical Properties ◽  
Seismic Resolution ◽  
Ground Penetrating

<p>Deformation bands and structurally-related diagenetic heterogeneities, here named Structural Diagenetic Heterogeneities (SDH), have been recognized to affect subsurface fluid flow on a range of scales and potentially promoting reservoir compartmentalization, altering flow paths, influencing flow buffering, and sealing during production. Their impact on reservoir hydraulic properties depends on many factors, such as their permeability contrast with respect to the undeformed reservoir rock, their anisotropy, thickness, geometry as well as their physical connectivity and arrangement in the subsurface. Deformation bands offsets (from a few mm to 20-40 mm) and diagenetic heterogeneities (carbonate nodules) dimensions (from 0.2 to 15 m in length; from 0.1 to 1.0 m in thickness) make them SDH below seismic resolution.</p><p>We used Ground Penetrating Radar (GPR) for detection and analysis of the assemblage “deformation bands - carbonate nodules”, in high-porosity arkose sandstone of the Northern Apennines (Italy). Petrophysical (air-permeability) and mechanical (uniaxial compressive strength) properties of host rock, deformation bands, and calcite-cement nodules were evaluated along a 30-meters thick stratigraphic log to characterize the permeability and strength variations of those features. 2D GPR surveys allowed the description of the SDH spatial organization, geometry, and continuity in the subsurface. The assemblage “deformation bands – nodules” decreases porosity and permeability and produces a strengthening effect of the rock volume, inducing a strong mechanical and petrophysical heterogeneity to the pristine rock. Different textural, petrophysical, and geomechanical properties of deformation bands, nodules, and host rock result in different GPR response (dielectric permittivity; instantaneous attributes). We show that GPR can be useful to characterize variations in petrophysical and geomechanical properties other than characterize the geometry and spatial distribution of flow baffles and small-scale flow barriers in the subsurface such as deformation bands and cement-nodules. GPR showed its worth as a high-resolution and non-invasive tool to extend outcrop information (petrophysical and geomechanical data) to 3D subsurface volumes in a way to reconstruct realistic and detailed outcrop analogues. Such potential could be critical in assisting and improving the characterization of SDH networks in the study of faulted aquifers and reservoirs in porous sandstones.</p>

Ground penetrating radar imaging of a collapsed paleocave system in the Ellenburger dolomite, central Texas

1998 ◽  
Vol 39 (1) ◽  
pp. 1-10 ◽  
Author(s):  
George A McMechan ◽  
Robert G Loucks ◽  
Xiaoxian Zeng ◽  
Paul Mescher
Keyword(s):  
Ground Penetrating Radar ◽  
Radar Imaging ◽  
Central Texas ◽  
Ground Penetrating

scholarly journals Comparison of modelled and observed responses of a glacier snowpack to ground-penetrating radar

2003 ◽  
Vol 37 ◽  
pp. 293-297 ◽  
Author(s):  
Jack Kohler ◽  
John C. Moore ◽  
Elisabeth Isaksson
Keyword(s):  
High Resolution ◽  
Time Domain ◽  
Ground Penetrating Radar ◽  
Ice Core ◽  
Reflection Coefficients ◽  
Order Of Magnitude ◽  
The Time Domain ◽  
Ground Penetrating ◽  
Physical And Chemical ◽  
Firn Core

AbstractThe upper 10 m of the firn of a Svalbard glacier is imaged along the centre line using a 500 MHz ground-penetrating radar, and a 10 m firn core taken along the profile. Complex reflection coefficients are calculated from the high-resolution capacitance and conductance measurements made on the snow core. The reflection coefficient depth series is converted to the time domain and convolved with model radar monopulses to synthesize traces that compare well with radar traces recorded near the ice core. Differences are probably due to cm-scale physical and chemical inhomogeneities that are smoothed when imaged by the radar beam, which integrates information over areas that are of the same order of magnitude as the depth to the layer.

Utility of Ground-Penetrating Radar in Near-Surface, High-Resolution Imaging of Lansing-Kansas City (Pennsylvanian) Limestone Reservoir Analogs

1998 ◽  
pp. 43-59
Author(s):  
Alex Martinez ◽  
Joseph M. Kruger ◽  
Evan K. Franseen
Keyword(s):  
High Resolution ◽  
Ground Penetrating Radar ◽  
Kansas City ◽  
Reservoir Modeling ◽  
Near Surface ◽  
Well Control ◽  
Imaging Tool ◽  
Velocity Information ◽  
Ground Penetrating ◽  
Bounding Surfaces

High-resolution ground-penetrating radar (GPR) is a subsurface imaging tool that can extend results gained from studies of reservoir-analog outcrops and add detailed information about reservoir analogs that is unavailable from either seismic data or well control alone. Integration of GPR-reflection information and outcrop photomosaics allowed detailed study of subtle changes in lithology and bedding surfaces by comparing lateral and vertical changes in GPR-reflection character with outcrop features. Outcrops are valuable for confirming interpretations of reflections and providing velocity information for the GPR data. Outcrops of two Lansing-Kansas City Group limestone units, the Captain Creek Limestone and the Plattsburg Limestone, were used as test sites to determine the vertical imaging resolution, penetration depth, and reflection character of high-frequency (500 MHz) GPR in interbedded carbonate and shale units, where the carbonate units contained thin interbeds of shale. Features as small as 0.1-0.2 m (0.3-0.7 ft)--including major architectural elements (such as major and minor bounding surfaces) and internal features (such as fractures, internal bedding, and crossbedding)--were successfully imaged and confirmed by outcrop data. Variations in GPR-reflection character between geologic units allowed recognition of argillaceous limestone units in the subsurface. Although shale and soil at the surface generally impeded GPR signal penetration, thin shale layers and shale at bounding surfaces actually enhanced reflectivity and aided in interpretation. Our results indicate that GPR can be successfully used as an aid in outcrop studies to provide quantitative data for use in reservoir modeling.

Genesis of giant, bouldery bars in a Miocene gravel-bed river: Insights from outcrop sedimentology, UAS-SfM photogrammetry, and GPR

2020 ◽  
Vol 90 (1) ◽  
pp. 27-47 ◽  
Author(s):  
Jesse T. Korus ◽  
R. Matthew Joeckel ◽  
Shane T. Tucker
Keyword(s):  
Ground Penetrating Radar ◽  
Unmanned Aircraft ◽  
Coarse Grained ◽  
Aircraft Structure ◽  
Valley Slope ◽  
Fluvial Transport ◽  
Bed Erosion ◽  
Stratigraphic Architecture ◽  
Valley Side ◽  
Ground Penetrating

ABSTRACT Bedsets of bouldery intraformational conglomerate partly fill a narrow, 40-m-deep paleovalley in the Arikaree Group (lower Miocene) in Nebraska, USA. Entire bar successions are exposed in 3D, offering an opportunity to improve upon sedimentological models for coarse-grained fluvial deposits. Using unmanned aircraft, structure-from-motion photogrammetry, and ground-penetrating radar, we offer the first comprehensive assessment of the lithofacies and stratigraphic architecture of this regionally unique fluvial conglomerate. We interpret three lithofacies associations: (1) beds of chaotic breccias lining the exhumed valley wall (colluvium), (2) < 5-m-thick units dominated by horizontal to gently inclined (2–3°) beds of granule to pebble conglomerates, and (3) 10–24-m-thick units of steeply inclined (∼ 30°) beds of bouldery conglomerates, which dominate the channel fill. The deposit comprises at least four stories, but its thickest part is a deep scour filled by a single story of steeply inclined bouldery deposits. The direction of accretion of the giant bars was toward the paleovalley wall, where contemporaneous valley-side colluvium and bar deposits are juxtaposed. We propose that increased discharge in a high-order trunk stream rapidly eroded the friable sandstone of the underlying Monroe Creek–Harrison formations, amassing resistant, large concretions that were subject to valley-slope mass movements and fluvial transport (subaqueous traction, grainflow, and debris flow). Giant accretion surfaces formed as fluvial bars migrated over the edges of deep scours. Thus, the funneling of increased discharges through a confined paleovalley amplified the magnitudes of valley and bed erosion, water depth, stream competence, and bar thickness, preserving an exceptionally thick, coarse-grained deposit.

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