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This letter generalizes Pentland's result about the fractal dimension of the optical image of rough natural surfaces, without imposing his requirement that the reflection is Lambertian. Instead, it is assumed that the reflectance coefficient is proportional to the focusing/defocusing due to local surface curvature. It will be proved for this case that the density distribution across the optical image inherits the fractal dimension of the mapped surface. 相似文献
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Gabor Korvin Klavdia Oleschko Abdulazeez Abdulraheem 《Arabian Journal of Geosciences》2014,7(3):1127-1138
A simple rock model is presented which reproduces the measured hydraulic and electric transport properties of sedimentary rocks and connects these properties with each other, as well as with the acoustic propagation velocities and elastic moduli. The model has four geometric parameters (average coordination number Z of the pores, average pore radius r, average distance between nearest pores d, and average throat radius δ) which can be directly determined from the measured porosity Φ, hydraulic permeability k, and cementation exponent m of the rock via simple analytic expressions. Inversion examples are presented for published sandstone data, and for cores taken from Saudi Arabian, Upper Jurassic and Permian carbonate reservoirs. For sandstone, the inversion works perfectly; for carbonates, the derived rock model shows order-of-magnitude agreement with the structure seen in thin sections. Inverting the equations, we express the transfer properties Φ, k, and m as functions of r, d, δ, and Z. Formulae are derived for the bulk density D b, formation factor F, and P-wave velocity in terms of the proposed geometrical parameters. 相似文献
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Jarrah Mohammed Ahmed Babiker Mustafa Mohammed Hariri Osman Abdullatif Gabor Korvin 《Arabian Journal of Geosciences》2017,10(6):146
This study evaluates the Late Ordovician glaciofluvial deposits of the Sarah Formation and equivalent outcroppings in north, central, and southwestern Saudi Arabia. The Sarah Formation also covers a wide area in the subsurface and is considered as an important target for unconventional tight gas reservoir. Defining the fracture types, nature, and distribution in outcrop scale might help to establish a successful fracture simulation model and behavior for the Sarah tight gas reservoir in the subsurface. This study investigates fracture characteristics for the Sarah Formation at Sarah paleochannel outcrops. The study revealed three sets of fractures, which have EW, NS, and SE-NW directions, and these fractures vary from open, resistive, and filled to resistive fractures. The closed fractures are filled with ferruginated iron oxides and gypsum. The filled fractures (the thrust boundary) are found in the study area at the SE-NW strike fracture set, while open and resistive fractures are found mainly at S-N and E-W fracture sets, respectively. The syn-depositional filled fractures (iron oxides) are considered as the younger fracture sets while the open and resistive fractures are post-depositional fractures which may have resulted from uplift or tectonic movement. A general model representing the fracture pattern and the thrusting boundaries due to glacial movement was constructed. It has been noticed that the systematic occurrence of filled fractures (thrust boundaries) described the boundaries between different glacial events, which act as a fluid barrier (filled fractures) and decrease the reservoir quality. The finding of this study might be utilized as a guide and lead for exploration in the subsurface Sarah glacial deposits. It will also help to understand and speculate the nature pattern and distribution of fractures with the Sarah Formation. 相似文献
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The Late Ordovician glacio-fluvial Sarah Formation is an important tight gas reservoir target in Saudi Arabia. This study uses statistical methods to characterize the petrophysical heterogeneity of the paleovalleys of the Sarah Formation that crop out in central Saudi Arabia. Four paleovalleys were studied: Bukayriyah, Hanadir, Sarah, and Khanasir Sarah. Several lithofacies were identified in each that vary in texture, porosity, permeability, and facies abundance that reflect periods of ice advance and retreat. The heterogeneity analysis is based on three statistical measures, namely, the coefficient of variation, the Dykstra-Parsons coefficient, and the Lorenz coefficient. The coefficient of variation values is in the 0.62–1.94 range, indicating an extremely heterogeneous distribution. The Dykstra-Parsons coefficient values are in the 0.56–0.88 range, suggesting very high to extremely high heterogeneity in the reservoirs. The Lorenz coefficient correlates well with the Dykstra-Parsons coefficient for paleovalleys of the Sarah Formation. The heterogeneity parameters studied here indicate that the outcrops of Sarah Formation paleovalleys represent heterogeneous to very heterogeneous reservoirs, which may be attributed to complex depositional and diagenetic variations that have affected the porosity and permeability distribution. 相似文献
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Gabor Korvin 《Pure and Applied Geophysics》1989,131(1-2):289-305
Recent geophysical studies revealed that the Palaeozoic basement of the Gulf of Suez consists of an enormous number of fault blocks whose network qualitavely resembles the contraction-crack polygons which can be found in nature in a wide variety of materials and on all scales (mud cracks, hardening concrete, age cracking in paintings,etc.). The fault network of the Gulf of Suez basement forms a rather uniformly spaced polygonal pattern, most of the blocks are four-sided, the lengths of block sides parallel with the Gulf of Suez axis are exponentially distributed. The power-law size distribution associated with the fractal (scale-free) fragmentation can be possibly ruled out.The paper calls attention to the necessity of calssifying the physical processes leading to fragmentations with exponential-, lognormal-, and power-law size distributions, respectively. 相似文献
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A. F.?Nieto-SamaniegoEmail author S. A.?Alaniz-Alvarez G.?Tolson K.?Oleschko G.?Korvin S. S.?Xu J. A.?Pérez-Venzor 《Pure and Applied Geophysics》2005,162(5):805-826
We present a case of detailed analysis of fracture arrays spanning four orders of magnitude in length; all of them measured at a single natural site by acquiring images at progressively larger scales. There is a high dispersion of cumulative-length exponents, box dimensions and fracture densities. However, the fractal analysis supports the fractal nature of fracture arrays. Our data indicate the existence of an upper limit for the density parameters, as similarly reported by other authors. We prove that box dimension is in inverse relation with fracture concentration and in direct relation with fracture density. These relations are also observed in our data and additionally there is an upper limit for the box dimensions. We interpret the dispersion in our results as more fundamental than methodological problems. It represents a truncation in the complete evolution of the fracture systems because in natural cases strain initiates overprinting of previous fracture arrays. Considering that larger fractures accommodate strain more efficiently than small fractures, the generation of small fractures is inhibited in the presence of pre-existing larger fractures. Maximum values of fracture density prevent accommodating an excess of strain in a single or restricted range of scales; we claim this condition produces migration of fracturing to larger scales originating fracture scaling. 相似文献
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