FORMATION VELOCITY AND DENSITY—THE DIAGNOSTIC BASICS FOR STRATIGRAPHIC TRAPS

Geophysics ◽  
1974 ◽  
Vol 39 (6) ◽  
pp. 770-780 ◽  
Author(s):  
G. H. F. Gardner ◽  
L. W. Gardner ◽  
A. R. Gregory
Keyword(s):  
Mineral Composition ◽  
Chemical Interaction ◽  
Sedimentary Rocks ◽  
Fluid Pressure ◽  
P Wave ◽  
Elastic Behavior ◽  
Reflection Coefficients ◽  
Porous Rocks ◽  
The Difference ◽  
Recent Sediments

A multiplicity of factors influence seismic reflection coefficients and the observed gravity of typical sedimentary rocks. Rock velocity and density depend upon the mineral composition and the granular nature of the rock matrix, cementation, porosity, fluid content, and environmental pressure. Depth of burial and geologic age also have an effect. Lithology and porosity can be related empirically to velocity by the time‐average equation. This equation is most reliable when the rock is under substantial pressure, is saturated with brine, and contains well‐cemented grains. For very low porosity rocks under large pressures, the mineral composition can be related to velocity by the theories of Voigt and Reuss. One effect of pressure variation on velocity results from the opening or closing of microcracks. For porous sedimentary rocks, only the difference between overburden and fluid pressure affects the microcrack system. Existing theory does not take into account the effect of microcrack closure on the elastic behavior of rocks under pressure or the chemical interaction between water and clay particles. The theory of Gassmann can be used to calculate the effect of different saturating fluids on the P-wave velocity of porous rocks. The effect may be large enough in shallow, recent sediments to permit gas sands to be distinguished from water sands on seismic records. At depths greater than about 6000 ft, however, the reflection coefficient becomes essentially independent of the nature of the fluid. Data show the systematic relationship between velocity and density in sedimentary rocks. As a result, reflection coefficients can often be estimated satisfactorily from velocity information alone.

Incorporating mechanisms of fluid pressure relaxation into inclusion‐based models of elastic wave velocities

Geophysics ◽  
2003 ◽  
Vol 68 (4) ◽  
pp. 1173-1181 ◽  
Author(s):  
S. Richard Taylor ◽  
Rosemary J. Knight
Keyword(s):  
Elastic Wave ◽  
Water Saturation ◽  
Laboratory Data ◽  
Fluid Pressure ◽  
P Wave ◽  
Porous Rocks ◽  
Low Frequencies ◽  
Wave Velocities ◽  
Exact Agreement ◽  
Flow Through

Our new method incorporates fluid pressure communication into inclusion‐based models of elastic wave velocities in porous rocks by defining effective elastic moduli for fluid‐filled inclusions. We illustrate this approach with two models: (1) flow between nearest‐neighbor pairs of inclusions and (2) flow through a network of inclusions that communicates fluid pressure throughout a rock sample. In both models, we assume that pore pressure gradients induce laminar flow through narrow ducts, and we give expressions for the effective bulk moduli of inclusions. We compute P‐wave velocities and attenuation in a model sandstone and illustrate that the dependence on frequency and water‐saturation agrees qualitatively with laboratory data. We consider levels of water saturation from 0 to 100% and all wavelengths much larger than the scale of material heterogeneity, obtaining near‐exact agreement with Gassmann theory at low frequencies and exact agreement with inclusion‐based models at high frequencies.

Anisotropic P-SV-wave dispersion and attenuation due to inter-layer flow in thinly layered porous rocks

Geophysics ◽  
2011 ◽  
Vol 76 (3) ◽  
pp. WA135-WA145 ◽  
Author(s):  
Fabian Krzikalla ◽  
Tobias M. Müller
Keyword(s):  
Wave Attenuation ◽  
Fluid Pressure ◽  
Pore Fluid ◽  
P Wave ◽  
Angle Of Incidence ◽  
Porous Rocks ◽  
Frequency Dependent ◽  
Symmetry Properties ◽  
Wave Induced ◽  
Attenuation And Dispersion

Elastic upscaling of thinly layered rocks typically is performed using the established Backus averaging technique. Its poroelastic extension applies to thinly layered fluid-saturated porous rocks and enables the use of anisotropic effective medium models that are valid in the low- and high-frequency limits for relaxed and unrelaxed pore-fluid pressures, respectively. At intermediate frequencies, wave-induced interlayer flow causes attenuation and dispersion beyond that described by Biot’s global flow and microscopic squirt flow. Several models quantify frequency-dependent, normal-incidence P-wave propagation in layered poroelastic media but yield no prediction for arbitrary angles of incidence, or for S-wave-induced interlayer flow. It is shown that generalized models for P-SV-wave attenuation and dispersion as a result of interlayer flow can be constructed by unifying the anisotropic Backus limits with existing P-wave frequency-dependent interlayer flow models. The construction principle is exact and is based on the symmetry properties of the effective elastic relaxation tensor governing the pore-fluid pressure diffusion. These new theories quantify anisotropic P- and SV-wave attenuation and velocity dispersion. The maximum SV-wave attenuation is of the same order of magnitude as the maximum P-wave attenuation and occurs prominently around an angle of incidence of [Formula: see text]. For the particular case of a periodically layered medium, the theoretical predictions are confirmed through numerical simulations.

Incorporating pore geometry and fluid pressure communication into modeling the elastic behavior of porous rocks

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 106-117 ◽  
Author(s):  
Anthony L. Endres ◽  
Rosemary J. Knight
Keyword(s):  
Closed System ◽  
Elastic Moduli ◽  
Pore Space ◽  
Fluid Pressure ◽  
Continuous Distribution ◽  
Elastic Behavior ◽  
Pore Geometry ◽  
Porous Rocks ◽  
Low Frequencies ◽  
Poroelastic Theory

Inclusion‐based formulations allow an explicit description of pore geometry by viewing porous rocks as a solid matrix with embedded inclusions representing individual pores. The assumption commonly used in these formulations that there is no fluid pressure communication between pores is reasonable for liquid‐filled rocks measured at high frequencies; however, complete fluid pressure communication should occur throughout the pore space at low frequencies. A generalized framework is presented for incorporating complete fluid pressure communication into inclusion‐based formulations, permitting elastic behavior of porous rocks at high and low frequencies to be described in terms of a single model. This study extends previous work by describing the pore space in terms of a continuous distribution of shapes and allowing different forms of inclusion interactions to be specified. The effects of fluid pressure communication on the elastic moduli of porous media are explored by using simple models and are found to consist of two fundamental elements. One is associated with the cubical dilatation and governs the effective bulk modulus. Its magnitude is a function of the range of pore shapes present. The other is due to the extensional part of the deviatoric strain components and affects the effective shear modulus. This element is dependent on pore orientation, as well as pore shape. Using sandstone and granite models, an inclusion‐based formulation shows that large differences between high‐ and low‐frequency elastic moduli can occur for porous rocks. An analysis of experimental elastic wave velocity data reveals behavior similar to that predicted by the models. Quantities analogous to the open and closed system moduli of Gassmann‐Biot poroelastic theory are defined in terms of inclusion‐based formulations that incorporate complete fluid pressure communication. It was found that the poroelastic relationships between the open and closed system moduli are replicated by a large class of inclusion‐based formulations. This connection permits explicit incorporation of pore geometry information into the otherwise empirically determined macroscopic parameters of the Gassmann‐Biot poroelastic theory.

Simplified anisotropy parameters for transversely isotropic sedimentary rocks

Geophysics ◽  
1995 ◽  
Vol 60 (6) ◽  
pp. 1933-1935 ◽  
Author(s):  
Colin M. Sayers
Keyword(s):  
Elastic Constants ◽  
Sedimentary Rocks ◽  
Anisotropy Parameter ◽  
Transversely Isotropic ◽  
P Wave ◽  
Time Migration ◽  
Vsp Data ◽  
Walkaway Vsp ◽  
Anisotropy Parameters ◽  
The Difference

Sedimentary rocks frequently possess an anisotropic structure resulting, for example, from fine scale layering, the presence of oriented microcracks or fractures, or the preferred orientation of nonspherical grains or anisotropic minerals. For many rocks the anisotropy may be described, to a good approximation, as being transversely isotropic. The purpose of this note is to present simplified anisotropy parameters for these rocks that are valid when the P‐wave normal moveout (NMO) and vertical velocities differ by less than 25%. This condition appears reasonable since depths calculated from P‐wave stacking velocities are often within 10% of actual depths (Winterstein, 1986). It is found that when this condition is satisfied the elastic constants [Formula: see text] and [Formula: see text] affect the P‐wave NMO velocity and anellipticity only through the combination [Formula: see text], a combination of elastic constants that can be determined using walkaway VSP data (Miller et al., 1993). The anellipticity quantifies the deviation of the P‐phase slowness from an ellipse and also determines the difference between the vertical and NMO velocities for SV‐waves. Helbig (1983) has shown that a time‐migrated section for which elliptical anisotropy has been taken into account is identical to one that has been determined under the assumption of isotropy. The anellipticity is therefore the important anisotropy parameter for anisotropic time migration. The results given are of interest for anisotropic velocity analysis, time migration, and time‐to‐depth conversion.

An exact anelastic model for the free-surface relfection of P and S-I waves

1989 ◽  
Vol 79 (3) ◽  
pp. 842-859
Author(s):  
R. D. Borcherdt ◽  
G. Glassmoyer
Keyword(s):  
Free Surface ◽  
Volumetric Strain ◽  
Major Axis ◽  
P Wave ◽  
Reflection Coefficients ◽  
S Wave ◽  
Low Loss ◽  
Surface Reflection ◽  
Pierre Shale ◽  
Homogeneous Wave

Abstract Exact anelastic solutions incorporating inhomogeneous waves are used to model numerically S-I and P waves incident on the free surface of a low-loss anelastic half-space. Anelastic free-surface reflection coefficients are computed for the volumetric strain and displacement components of inhomogeneous wave fields. For the problem of an incident homogeneous S-I wave in Pierre shale, the largest strain and displacement amplitudes for the reflected P wave occur at angles of incidence for which the particle motion for the reflected inhomogeneous P wave is elliptical (minor/major axis = 0.6), the specific absorption (QP−1) is greater (300 per cent) and the velocity is less (25 per cent) than those for a corresponding homogeneous P wave, the direction of phase propagation is not parallel to the free surface, and the amplitude of the wave shows a significant increase with depth (6 per cent in one wavelength). Energy reflection coefficients computed for this low-loss anelastic model show that energy flow due to interaction of the incident and reflected waves reach maxima (30 per cent of the incident energy) near large but nongrazing angles of incidence. For the problem of an incident homogeneous P wave in Pierre shale, the inhomogeneity of the reflected S wave is shown not to contribute to significant variations in wave field characteristics over those that would be expected for a homogeneous wave.

The Effect of Total Precipitation of Various Periods to Flow Regimes in Mountainous Catchments in Japan : Considering the Geological Characteristics of Catchments

2021 ◽  
Author(s):  
Yuka Muto ◽  
Takeyoshi Chibana ◽  
Masafumi Yamada
Keyword(s):  
Sedimentary Rocks ◽  
Correlation Coefficients ◽  
Flow Regimes ◽  
Rate Of Change ◽  
Total Precipitation ◽  
Lower Type ◽  
Geological Characteristics ◽  
Mountainous Catchments ◽  
Geological Conditions ◽  
The Difference

<p>In order to conduct an appropriate management in each catchment, it is important to understand how the difference in geological conditions affect the relationship between precipitation and flow regimes.</p><p>Considering the differences in geological characteristics of catchments, this study aims 1)to clarify the period for calculating the total precipitation that is most influential to several levels of daily flow respectively and 2)to clarify the contribution of the change in the total precipitation of ‘the most influential period’ to the change in flow.</p><p>In this study, 63 mountainous catchments (dam catchments) within the Japanese Archipelago were selected as target areas. First, the 63 catchments were divided into 4 groups according to their geological characteristics. Second, from the observed data of daily flow lasting 26 years (from 1993 to 2018), 6 types of daily flow which represent flow of different scales within a year (1, 10, 25, 50, 75, 95 percentiles of daily flow within a year) were searched. In each geological classification, correlation coefficients between each 6 type of flow and total precipitation of various periods (from 2 days to 365 days) were calculated. Finally, for each geological classification and each type of flow, single regression analyses were conducted, setting the rate of change in flow amount as the objective variable, and the rate of change in total precipitation amount of the appropriate period as the explanatory variable.</p><p>As a result, in the analysis of correlation coefficients, significant differences among different geological classifications were seen for lower type of flows but not for higher type of flows. For catchments of volcanic rocks in the Quaternary period, total precipitation of 365 days before the flow occurrence had the highest correlation coefficient with lower type of flows. On the other hand, for catchments of sedimentary rocks in the Mesozoic or Paleozoic era, the most influential period was approximately 45 days, which was the shortest.</p><p>Also, increasing trends in flow (i.e. the rate of change in flow > 1.0) during the target period were seen regardless of the geological classification or the type of flow. However, from the simple regression analysis, the significant effect of the change in precipitation to the change in flow was only seen for annual maximum flow of catchments of sedimentary rocks from the Mesozoic or Paleozoic era. Except this specific geological characteristic and flow type, there is a possibility that other conditions of the catchments (e.g. change in land use) have larger effect to the change in flow compared to the change in precipitation.</p><p>In the analyses mentioned above, the effect of snowfall is not considered. Therefore, in the presentation, the difference between snow covered regions and others are compared in addition.</p>

Abstract 15414: Diagnostic Performance of Deep Learning on 12-lead Electrocardiography to Distinguish Takotsubo Syndrome and Acute Anterior Myocardial Infarction

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Masato Shimizu ◽  
shummo cho ◽  
Yoshiki Misu ◽  
Mari Ohmori ◽  
Ryo Tateishi ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Deep Learning ◽  
Diagnostic Performance ◽  
P Wave ◽  
Takotsubo Syndrome ◽  
Anterior Myocardial Infarction ◽  
Color Mapping ◽  
Lead Avr ◽  
The Difference ◽  
And Gender

Introduction: Takotsubo syndrome (TTS) and acute anterior myocardial infarction (ant-AMI) show very similar 12-lead electrocardiography (ECG) featured at onset, and it is often difficult to distinguish them without cardiac catheterization. The difference of ECG between them was studied, but the diagnostic performance of machine learning (deep learning) for them had not been investigated. Hypothesis: Deep learning on 12-leads ECG has high diagnostic performance to diagnose TTS and ant-AMI at onset. Methods: Consecutive 50 patients of TTS were one-to-one matched to ant-AMI randomly by their age and gender, and total 100 patients were enrolled. No sinus rhythm patients were excluded. All ECGs were divided into each 12-lead, and 5 heart beats from one lead were extracted. For each lead, 250 ECG waves of TTS/AMI were sampled as 24bit bitmap image, and prediction model construction by convolutional neural network (CNN: transfer learning, using VGG16 architecture) underwent to distinguish the two diseases in each lead. Next, gradient weighted class activation color mapping (GradCam) was performed to detect the degree and position of convolutional importance in the leads. Results: Lead aVR (mean accuracy 0.748), I (0.733), and V1 (0.678) were the top 3 leads with high accuracy. In aVR lead, GradCam showed strong convolution of negative T wave in TTS, and sharp R wave in ant-AMI. In I lead, it spotlighted several parts of ECG wave in ant-AMI. However in TTS, whole shape of the wave, P wave onset, and negative T were invertedly convoluted in TTS. Conclusions: Deep learning was a powerful tool to distinguish TTS and ant-AMI at onset, and GradCam method gave us new insight of the difference on ECG between the two diseases.

scholarly journals On a new approach to assessing the energy characteristics of substances

2019 ◽  
Vol 124 ◽  
pp. 01017
Author(s):  
O. S. Sirotkin ◽  
A. M. Pavlova ◽  
R. O. Sirotkin ◽  
A. E. Buntin
Keyword(s):  
Energy Production ◽  
Chemical Interaction ◽  
Heat Of Formation ◽  
Redox Properties ◽  
Chemical Components ◽  
Reaction Products ◽  
Energy Characteristics ◽  
New Approach ◽  
Production Technologies ◽  
The Difference

Within the unified model of chemical bonding and methods of quantitative assessment of components of mixed chemical interaction between the elements in compounds, developed by the authors, a new approach was developed to assess the structural and energy characteristics of substances and fuels. It comprises establishing a correlation between the difference of bonds’ chemical components of reactants and end products. Changes in the chemical bond components affect such characteristics of chemical reactions as the heat of formation of the reaction products, their redox properties, whether reaction is endoor exothermic, as well as the heat of fuel combustion reactions. This approach is an additional reserve for improving the methods for assessing the energy characteristics of fuels and increasing the efficiency of energy production technologies.

Enrichment of chalcophile elements in seawater accompanying the end-Cretaceous impact event

2020 ◽  
Vol 132 (9-10) ◽  
pp. 2055-2066
Author(s):  
Teruyuki Maruoka ◽  
Yoshiro Nishio ◽  
Tetsu Kogiso ◽  
Katsuhiko Suzuki ◽  
Takahito Osawa ◽  
...  
Keyword(s):  
Organic Matter ◽  
Iron Oxides ◽  
Sedimentary Rocks ◽  
Reductive Dissolution ◽  
X Ray ◽  
Asteroid Impact ◽  
Chalcophile Elements ◽  
The Difference ◽  
Impact Heating ◽  
Fe Ions

Abstract Chalcophile elements are enriched in the Cretaceous–Paleogene (KPg) boundary clays from Stevns Klint, Denmark. As the concentrations of Cu, Ag, and Pb among several chalcophile elements such as Cu, Zn, Ga, As, Ag, and Pb are correlated with those of Ir, we suggest that these elements were supplied to the oceans by processes related to the end-Cretaceous asteroid impact. Synchrotron X-ray fluorescence images revealed that Cu and Ag exist as trace elements in pyrite grains or as 1–10-µm-sized discrete phases specifically enriched in Cu or Ag. The difference in carrier phases might depend on the materials that transported these elements to the seafloor. Based on their affinities with Cu, Ag, and Ir, iron oxides/hydroxides and organic matter were identified as the potential carrier phases that supplied these elements to the seafloor. Chalcophile elements adsorbed on iron oxides/hydroxides might have been released during reductive dissolution of iron oxides/hydroxides and incorporated into the pyrite produced simultaneously with the reductive dissolution of iron oxides/hydroxides. Both iron oxides/hydroxides and chalcophile elements were possibly released from the KPg target rocks (i.e., sedimentary rocks and/or basement crystalline rocks) by impact heating. Elements with a high affinity to organic matter would have been released upon its degradation and then converted into discrete minerals because of the deficiency in Fe ions. As such discrete minerals include the elements that form acid soluble sulfides such as Cu, Ag, and Pb, enrichment of these elements might have been induced by the intense acid rain just after the end-Cretaceous asteroid impact.

Toward phenomenological universality of the mechanical behavior of arbitrarily anisotropic porous rocks

Geophysics ◽  
2011 ◽  
Vol 76 (3) ◽  
pp. WA167-WA183 ◽  
Author(s):  
Patrick N. J. Rasolofosaon
Keyword(s):  
Mechanical Behavior ◽  
Empirical Relation ◽  
Fluid Pressure ◽  
Porous Rocks ◽  
Porous Network ◽  
Hooke’S Law ◽  
Fluid Content ◽  
Elastic Hysteresis ◽  
Hydraulic Hysteresis ◽  
Hooke's Law

The great diversity of the microstructures of rocks impedes the use of a universal rock physics model with idealized geometry to correctly describe the mechanical behavior of rocks. In this quest for universality, by ignoring the detailed description of the causes of the observed phenomenon and only focusing on the empirical relation between the cause (applied stress) and the effect (resulting strain), phenomenological models such as the linear elastic Hooke’s law roughly describe the mechanical behavior of rocks of contrasted microstructures. However, in detail, numerous laboratory experiments covering broad frequency and strain ranges (both typically more than eight orders of magnitude) on various types of rocks have also shown deviations from Hooke’s law due to anisotropy, frequency dependence, nonlinearity, possibly with the presence of hysteresis, and poroelasticity. A phenomenological model has been recently proposed that synthesizes all these behaviors in a single model, but unfortunately does not integrate the porous nature of rocks. The new model is based on a reformulation in modified spectral decomposition of the previous work using the 7D poroelastic tensor linking the dynamic parameters (i.e., the six stress components and fluid pressure) and the kinematic parameters (i.e., the six strain components and the local increase of fluid content ζ). In addition to the elastic hysteresis of the stress-strain curves, the model also predicts the existence of a second hysteresis, or hydraulic hysteresis, of the curve fluid pressure p versus fluid content ζ, qualitatively similar to the first one. Indeed, the elastic hysteresis is due to the opening and the closure of some compliant pores at different stress levels. These pores represent possible access radii for the saturating fluid; the hysteresis in the geometry of the porous network also induces the hydraulic hysteresis in the p-ζ curves.

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