Characterization of a coalesced, collapsed paleocave reservoir analog using GPR and well‐core data

Geophysics ◽  
2002 ◽  
Vol 67 (4) ◽  
pp. 1148-1158 ◽  
Author(s):  
George A. McMechan ◽  
Robert G. Loucks ◽  
Paul Mescher ◽  
Xiaoxian Zeng
Keyword(s):  
Host Rock ◽  
Three Dimensional ◽  
Near Surface ◽  
Lower Ordovician ◽  
Central Texas ◽  
Integrated Interpretation ◽  
Core Descriptions ◽  
Ground Penetrating ◽  
The City

The three‐dimensional architecture, spatial complexity, and pore‐type distribution are mapped in a near‐surface analog of a coalesced, collapsed paleocave system in the Lower Ordovician Ellenburger Group near the city of Marble Falls in central Texas. The surface area of the site has dimensions of about 350 × 1000 m. The data collected include about 12 km of 50‐MHz ground‐penetrating radar (GPR) data arranged in a grid of orthogonal lines, 29 cores of about 15‐m length, and detailed facies maps of an adjacent quarry face. Electrical property measurements along with detailed core descriptions were the basis of integrated interpretation of the GPR data. Three main GPR facies are defined on the basis of degree of brecciation in the corresponding cores: undisturbed host rock, disturbed host rock, and paleocave breccia. This GPR facies division defined the major paleocave trends and the distribution of porosity types, which correlate with reservoir quality. Highly brecciated zones are separated by disturbed and undisturbed host rock. The breccia bodies that outline the trend of collapsed cave passages are up to 300 m wide; the intervening intact areas between breccias are up to 200 m wide. Understanding the breccia distribution in a reservoir analog will help in defining strategies for efficient development of coalesced, collapsed paleocave reservoirs.

Three-dimensional architecture of a coalesced, collapsed-paleocave system in the Lower Ordovician Ellenburger Group, central Texas

AAPG Bulletin ◽  
2004 ◽  
Vol 88 (5) ◽  
pp. 545-564 ◽  
Author(s):  
Robert G. Loucks ◽  
Paul K. Mescher ◽  
George A. McMechan
Keyword(s):  
Three Dimensional ◽  
Lower Ordovician ◽  
Central Texas

scholarly journals Recording and Reconstructing the Sacred Landscapes of Sicilian Naxos

2019 ◽  
Vol 5 (1) ◽  
pp. 416-433 ◽  
Author(s):  
Jari Pakkanen ◽  
Maria Costanza Lentini ◽  
Apostolos Sarris ◽  
Esko Tikkala ◽  
Meropi Manataki
Keyword(s):  
Urban Landscape ◽  
Line Drawing ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Sacred Landscape ◽  
Sacred Landscapes ◽  
Architectural Features ◽  
Starting Point ◽  
Ground Penetrating ◽  
The City

AbstractIn recent years, an on-going project investigating the urban landscape of Naxos has surveyed and produced several new digital reconstructions of the settlement’s simple non-peripteral temples, most with highly decorative roofs. Three Archaic sacred buildings of Sicilian Naxos are used to demonstrate different approaches to recording the remains and reconstructing their architectural features. This work reflects changes in digital strategies over the past ten years. Tempietto H is a small shrine located outside the city’s boundaries and the site is currently inaccessible, so its reconstruction is based on excavation documentation and roof terracottas. The visible half of Tempietto C was documented using three-dimensional line-drawing with total stations and photogrammetry; the back-filled south-western part was surveyed with ground penetrating radar. Temple B is the largest sacred structure in Naxos. A geophysical survey gives new data on the eastern extent of the sanctuary. The area has been recorded with handheld and aerial photography to create a three-dimensional model of the sanctuary. A new orthogonal grid of the city was established circa 470 BCE and a rectangular base was placed in the south-east corner of every crossroad. These bases were the starting point for the plan, and their interpretation as altars converts the entire urban plan into a sacred landscape.

Tire Contact Stresses and Their Effects on Instability Rutting of Asphalt Mixture Pavements: Three-Dimensional Finite Element Analysis

2003 ◽  
Vol 1853 (1) ◽  
pp. 150-156 ◽  
Author(s):  
Marc Novak ◽  
Bjorn Birgisson ◽  
Reynaldo Roque
Keyword(s):  
Asphalt Mixture ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Shear Stresses ◽  
Element Analysis ◽  
Surface Shear ◽  
Near Surface ◽  
Vertical Loading ◽  
Stress States

Instability rutting generally occurs within the top 2 in. of the asphalt layer when the structural properties of the asphalt concrete are inadequate to resist the stresses imposed on it. Several researchers have presented observations in attempts to explain instability rutting, but a clear identification of the mechanism does not exist. Stresses in the asphalt layer caused by measured tire interface stresses were analyzed in three dimensions by using finite elements to identify possible mechanisms for instability rutting. The analysis showed that radial tires produce high near-surface shear stresses at low confinements, which are not predicted with traditional uniform vertical loading conditions, in the region where instability rutting is known to occur. The resulting shear stresses tend to be shallower than for the uniformly loaded case, and they are focused in areas where instability rutting has been observed. The observed stress states imply that the characterization of instability rutting requires testing at these low confinement (and sometimes tensile) stress states, rather than at the higher stress states typically used in the strength characterization of mixtures.

Application of ground-penetrating radar imagery for three-dimensional visualisation of near-surface structures in ice-rich permafrost, Barrow, Alaska

2007 ◽  
Vol 18 (4) ◽  
pp. 309-321 ◽  
Author(s):  
Jeffrey S. Munroe ◽  
Jim A. Doolittle ◽  
Mikhail Z. Kanevskiy ◽  
Kenneth M. Hinkel ◽  
Frederick E. Nelson ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Three Dimensional ◽  
Surface Structures ◽  
Near Surface ◽  
Radar Imagery ◽  
Ground Penetrating

Geoelectrical Characterization of the Al-Kawamil New Settlement, Sohag, Egypt

2019 ◽  
Vol 24 (2) ◽  
pp. 327-332
Author(s):  
Mohammed A. Mohammed ◽  
Abdelbaset M. Abudeif
Keyword(s):  
Electrical Resistivity ◽  
Geophysical Methods ◽  
Three Dimensional ◽  
Site Investigation ◽  
University Campus ◽  
Clayey Sand ◽  
Near Surface ◽  
Drilling Site ◽  
The University

Electrical resistivity tomography (ERT) is one of the most effective geophysical methods used to acquire detailed pictures of subsurface conditions without drilling. Site investigation using two- and three-dimensional electrical resistivity imaging is now a fundamental step before the design and construction of campus buildings at the University of Sohag in Egypt. In this study, an ERT survey was implemented at two pre-defined sites with the aim of selecting the most favorable location for construction of a new educational building on the university campus. The resistivity results were confirmed with boreholes drilled at both sites. RES2DINV and RES3DINV software were used for data processing and interpretation. The results show that the near surface sedimentary succession beneath both sites consists of four geoelectrical and lithological units. From the surface to a depth of 20 m, these layers are: unit 1) unconsolidated boulders and gravels intercalated with percentages of sand and reddish clay; unit 2) fine crushed calcareous gravels and sands with clays intercalations; unit 3) dry sand and clayey sand; and unit 4) shale, at the base. According to an evaluation of the presence and abundance of shale and sand contents cracks, fissures and faults, the second site is identified as more suitable for construction.

Modeling 3D porosity and permeability from GPR data in the Ellenburger Dolomite, central Texas

Geophysics ◽  
2011 ◽  
Vol 76 (6) ◽  
pp. J35-J46 ◽  
Author(s):  
Hussein Harbi ◽  
George A. McMechan
Keyword(s):  
Signal To Noise Ratio ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Carbonate Reservoir ◽  
Horizontal Orientation ◽  
Air Interface ◽  
Porosity And Permeability ◽  
Central Texas ◽  
Ground Penetrating ◽  
Velocity Tomography

Three-dimensional porosity and permeability were modeled in an Ellenburger carbonate reservoir analog from 2D crosshole and 3D surface survey ground-penetrating radar (GPR) data. Two-dimensional GPR crosshole velocity tomography, 3D migration of the GPR surface data, and porosity and permeability calibration to GPR attributes results in 3D porosity and permeability predictions that provide a consistent model of the paleocave structures and facies distributions. Picking the maximum instantaneous amplitude of the direct arrival wavelet for velocity tomography reduces uncertainties caused by a low signal-to-noise ratio, uncorrelated noise, and the interference between reflections and critical refractions at the earth/air interface. The GPR velocity is anisotropic with an average vertical to horizontal velocity ratio of 0.93, which is attributed to the dominance of the relatively horizontal orientation of the maximum porosity and permeability. Porosity and permeability trends are influenced by regional northeast-southwest and northwest-southeast striking conjugate fractures associated with the Pennsylvanian Ouachita orogeny and breccia facies generated by three episodes of burial and the resulting paleocave collapses. At depths [Formula: see text] from the present surface, large brecciated dolomite and limestone blocks have low porosity and low permeability. Between a depth of [Formula: see text] and [Formula: see text] irregular fracture orientations and distributions associated with collapse breccias have a higher average porosity and permeability. A deeper zone ([Formula: see text] to [Formula: see text] in depth), has intermediate permeability and porosity. Porosity and permeability could not be calibrated in open voids. Thus, the predictions are applicable to the core-scale to which they were calibrated, but are lower bounds for the whole volume, which contains breccias, karst, and fractures that increase both porosity and permeability at larger scales.

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