scholarly journals Fluid pressure diffusion effects on the excess compliance matrix of porous rocks containing aligned fractures

2020 ◽  
Vol 222 (1) ◽  
pp. 715-733
Author(s):  
Gabriel A Castromán ◽  
Nicolás D Barbosa ◽  
J Germán Rubino ◽  
Fabio I Zyserman ◽  
Klaus Holliger
Keyword(s):  
Seismic Velocity ◽  
Fractured Rock ◽  
Finite Thickness ◽  
Practical Importance ◽  
Fluid Pressure ◽  
Porous Rocks ◽  
Compliance Matrix ◽  
Pressure Diffusion ◽  
Reservoir Permeability ◽  
Wide Range

SUMMARY The presence of sets of open fractures is common in most reservoirs, and they exert important controls on the reservoir permeability as fractures act as preferential pathways for fluid flow. Therefore, the correct characterization of fracture sets in fluid-saturated rocks is of great practical importance. In this context, the inversion of fracture characteristics from seismic data is promising since their signatures are sensitive to a wide range of pertinent fracture parameters, such as density, orientation and fluid infill. The most commonly used inversion schemes are based on the classical linear slip theory (LST), in which the effects of the fractures are represented by a real-valued diagonal excess compliance matrix. To account for the effects of wave-induced fluid pressure diffusion (FPD) between fractures and their embedding background, several authors have shown that this matrix should be complex-valued and frequency-dependent. However, these approaches neglect the effects of FPD on the coupling between orthogonal deformations of the rock. With this motivation, we considered a fracture model based on a sequence of alternating poroelastic layers of finite thickness representing the background and the fractures, and derived analytical expressions for the corresponding excess compliance matrix. We evaluated this matrix for a wide range of background parameters to quantify the magnitude of its coefficients not accounted for by the classical LST and to determine how they are affected by FPD. We estimated the relative errors in the computation of anisotropic seismic velocity and attenuation associated with the LST approach. Our analysis showed that, in some cases, considering the simplified excess compliance matrix may lead to an incorrect representation of the anisotropic response of the probed fractured rock.

scholarly journals Impact of fracture clustering on the seismic signatures of porous rocks containing aligned fractures

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. MR295-MR308 ◽  
Author(s):  
Nicolás D. Barbosa ◽  
J. Germán Rubino ◽  
Eva Caspari ◽  
Klaus Holliger
Keyword(s):  
Fractured Reservoirs ◽  
Fluid Pressure ◽  
Fracture Network ◽  
Analytical Models ◽  
Porous Rocks ◽  
Seismic Properties ◽  
Velocity Anisotropy ◽  
Pressure Diffusion ◽  
Dispersion Regime ◽  
Attenuation Anisotropy

The presence of fractures in a reservoir can have a significant impact on its effective mechanical and hydraulic properties. Many researchers have explored the seismic response of fluid-saturated porous rocks containing aligned planar fractures through the use of analytical models. However, these approaches are limited to the extreme cases of regular and uniform random distributions of fractures. The purpose of this work is to consider more realistic distributions of fractures and to analyze whether and how the frequency-dependent anisotropic seismic properties of the medium can provide information on the characteristics of the fracture network. Particular focus is given to fracture clustering effects resulting from commonly observed fracture distributions. To do so, we have developed a novel hybrid methodology combining the advantages of 1D numerical oscillatory tests, which allows us to consider arbitrary distributions of fractures, and an analytical solution that permits extending these results to account for the effective anisotropy of the medium. A corresponding numerical analysis indicates that the presence of clusters of fractures produces an additional attenuation and velocity dispersion regime compared with that predicted by analytical models. The reason for this is that a fracture cluster behaves as an effective layer and the contrast with respect to the unfractured background produces an additional fluid pressure diffusion length scale. The characteristic frequency of these effects depends on the size and spacing between clusters, the latter being much larger than the typical spacing between individual fractures. Moreover, we find that the effects of fracture clustering are more pronounced in attenuation anisotropy than velocity anisotropy data. Our results indicate that fracture clustering effects on fluid pressure diffusion can be described by two-layer models. This, in turn, provides the basis for extending current analytical models to account for these effects in inversion schemes designed to characterize fractured reservoirs from seismic data.

scholarly journals Fracture connectivity can reduce the velocity anisotropy of seismic waves

2017 ◽  
Vol 210 (1) ◽  
pp. 223-227 ◽  
Author(s):  
J. Germán Rubino ◽  
Eva Caspari ◽  
Tobias M. Müller ◽  
Klaus Holliger
Keyword(s):  
Hydraulic Properties ◽  
Seismic Waves ◽  
Fractured Rock ◽  
Fluid Pressure ◽  
Fracture Networks ◽  
Velocity Anisotropy ◽  
Rock Formations ◽  
Pressure Diffusion ◽  
Static Elasticity ◽  
Fracture Fluid

Abstract The degree of connectivity of fracture networks is a key parameter that controls the hydraulic properties of fractured rock formations. The current understanding is that this parameter does not alter the effective elastic properties of the probed medium and, hence, cannot be inferred from seismic data. However, this reasoning is based on static elasticity, which neglects dynamic effects related to wave-induced fluid pressure diffusion (FPD). Using a numerical upscaling procedure based on the theory of quasi-static poroelasticity, we provide the first evidence to suggest that fracture connectivity can reduce significantly velocity anisotropy in the seismic frequency band. Analyses of fluid pressure fields in response to the propagation of seismic waves demonstrate that this reduction of velocity anisotropy is not due to changes of the geometrical characteristics of the probed fracture networks, but rather related to variations of the stiffening effect of the fracture fluid in response to FPD. These results suggest that accounting for FPD effects may not only allow for improving estimations of geometrical and mechanical properties of fracture networks, but may also provide information with regard to the effective hydraulic properties.

Legal aspects of the brand protection in Ukraine and world

2020 ◽  
pp. 133-143
Author(s):  
Ivanna Babetska
Keyword(s):  
Public Relations ◽  
Practical Importance ◽  
Legal Protection ◽  
Legal Regulation ◽  
Legal Aspects ◽  
Scientific Article ◽  
Protection Mechanism ◽  
Brand Protection ◽  
Wide Range ◽  
International Regulations

Purpose. The purpose of the scientific article is to establish the ratio of the meanings of the concepts "trademark", "brand" and "well-known" trademark and then to characterize their common and distinctive features. Indicate the gaps in current legislation and the need to refine certain rules in this aspect to determine the aspects of protection and protection of the brand. Methodology. The methodology includes a comprehensive analysis and generalization of the available scientific and theoretical material and the formulation of appropriate conclusions and recommendations. During the research, the following methods of scientific knowledge were used: terminological, dialectical, logical-semantic, logical-normative, system-structural. Results: in the course of the conducted study, the main and optional components of the brand are determined, which make it possible to determine the features of its legal protection. It has been proved that despite a fairly wide range of domestic and international regulations, there are certain shortcomings of the brand protection mechanism. Originality. The study found that a trademark differs from a brand in that a trademark is a designation that is only the basis of the brand, as for the trademark are not essential such properties of the designation as a certain level of information among consumers and quality as a basis. gaining a reputation; the concept of "brand" is an evaluative, conditional concept, and therefore its consolidation at the regulatory level is impractical. It is sufficient to establish the factors on the basis of which the trademark can be considered "well known". A "well-known" trademark is a designation that is familiar to a wide range of consumers through its use to designate certain goods. Practical importance. The results of the study can be used in law-making activities for the purpose of legal regulation of public relations in the sphere of legal protection of the brand.

The use of «coasorption» concept while describing the effect of coagulants on the wastewater aqua systems

2021 ◽  
pp. 33-39
Author(s):  
Е.В. Алексеев
Keyword(s):  
Wastewater Treatment ◽  
Industrial Wastewater ◽  
Practical Importance ◽  
Quantitative Relationship ◽  
Synthetic Dyes ◽  
Pollutant Concentrations ◽  
Wide Range ◽  
Complex Chemical Composition ◽  
The One ◽  
Raw Wastewater

Широкое распространение реагентного коагулирования в технологии очистки природных и промышленных сточных вод обусловлено, с одной стороны, сложностью химического состава и фазово-дисперсного состояния их аквасистем, с другой – многофакторностью действия на них коагулянтов. Рассмотрены основные механизмы взаимодействия коагулянтов и загрязняющих веществ на примере очистки промышленных сточных вод, содержащих органические вещества (поверхностно-активные вещества и синтетические красители). Физико-химическое понятие «коагуляция» отражает только один из механизмов действия коагулянтов на загрязнители. Принятые в настоящее время технологические показатели «доза коагулянта» и «удельная доза коагулянта» также не отражают многообразие взаимодействий загрязняющих веществ с солями коагулянтов и не привязаны к результату коагулирования. Это обусловливает трудность описания совокупного действия физико-химических процессов при добавлении коагулянтов в очищаемые воды и его количественной оценки. Решение проблемы возможно введением понятия «коасорбция», определяющего многофакторность взаимодействия коагулянтов с загрязняющими веществами в процессах очистки сточных вод коагулированием, и технологического показателя «удельная коасорбция», устанавливающего количественную взаимосвязь между величинами загрязняющих веществ в исходной и очищенной воде с дозой коагулянта. Графически представлены функции удельной коасорбции в форме изотерм коасорбции для двух типов поверхностно-активных веществ и синтетических красителей. На основании результатов анализа особенностей изотерм показано, что они отражают разные механизмы взаимодействия коагулянтов и загрязняющих веществ. Использование коасорбции как технологического понятия способствует выявлению механизмов взаимодействия загрязняющих веществ с коагулянтом и созданию наилучших условий для осуществления процесса коагулирования. Функциональное описание изотерм коасорбции позволяет экстраполировать результаты пробного коагулирования в широком интервале концентраций загрязняющих веществ. Практическое значение изотерм удельной коасорбции состоит в возможности определения доз реагентов при коагулировании воды по начальному содержанию загрязняющих веществ и требуемому в очищенных водах. The widespread use of chemical coagulation in purification of natural water and industrial wastewater is due, on the one hand, to the complex chemical composition and phase-disperse state of their aqua systems, and on the other hand, to the multifactorial effect of coagulants on them. The main mechanisms of interaction between coagulants and pollutants are considered through the example of industrial wastewater treatment containing organic substances (surfactants and synthetic dyes). The physicochemical term «coagulation» reflects only one of the mechanisms of the effect of coagulants on pollutants. The currently accepted process parameters «dose of coagulant» and «specific dose of coagulant» do not reflect the variety of interactions of pollutants with coagulant salts either, and are not linked to the result of coagulation. This makes it difficult to describe the collective effect of physicochemical processes while adding coagulants to the treated water and to quantify it. The solution to the problem is possible introducing the concept of «coasorption» that determines the multifactorial origin of the interaction of coagulants and pollutants in the processes of wastewater treatment by coagulation; and the process parameter «specific coasorption» that establishes a quantitative relationship between the concentrations of pollutants in raw wastewater and effluent with a dose of coagulant. The specific coasorption functions are graphically presented in the form of coasorption isotherms for two types of surfactants and synthetic dyes. Based on the results of the analysis of the features of the isotherms, it is shown that they reflect different mechanisms of interaction between coagulants and pollutants. The use of coasorption as a technological concept provides for identifying the mechanisms of interaction of pollutants with a coagulant and establishing the best conditions for the coagulation process. The functional description of the coasorption isotherms allows extrapolating the results of trial coagulation in a wide range of pollutant concentrations. The practical importance of specific coasorption isotherms provides for determining the dosages of chemicals during coagulation of water based on the initial concentration of pollutants and effluent standard.

scholarly journals Thermo-hydro-mechanical processes in fractured rock formations during a glacial advance

2015 ◽  
Vol 8 (7) ◽  
pp. 2167-2185 ◽  
Author(s):  
A. P. S. Selvadurai ◽  
A. P. Suvorov ◽  
P. A. Selvadurai
Keyword(s):  
Rock Mass ◽  
Fractured Rock ◽  
Fluid Pressure ◽  
Computational Modelling ◽  
Fracture Zones ◽  
Saturated Rock ◽  
Rock Formations ◽  
Geological Formation ◽  
High Level Nuclear Waste ◽  
High Level

Abstract. The paper examines the coupled thermo-hydro-mechanical (THM) processes that develop in a fractured rock region within a fluid-saturated rock mass due to loads imposed by an advancing glacier. This scenario needs to be examined in order to assess the suitability of potential sites for the location of deep geologic repositories for the storage of high-level nuclear waste. The THM processes are examined using a computational multiphysics approach that takes into account thermo-poroelasticity of the intact geological formation and the presence of a system of sessile but hydraulically interacting fractures (fracture zones). The modelling considers coupled thermo-hydro-mechanical effects in both the intact rock and the fracture zones due to contact normal stresses and fluid pressure at the base of the advancing glacier. Computational modelling provides an assessment of the role of fractures in modifying the pore pressure generation within the entire rock mass.

A Simple Analytical Theory for Interpreting Measured Total Pressure in Multiphase Flows

1998 ◽  
Vol 120 (2) ◽  
pp. 385-389 ◽  
Author(s):  
Abhijit Guha
Keyword(s):  
Total Pressure ◽  
Multiphase Flows ◽  
Practical Importance ◽  
Present Theory ◽  
Vapour Phase ◽  
Solid Particles ◽  
Analytical Theory ◽  
Nonequilibrium Processes ◽  
Measuring Device ◽  
Wide Range

This paper presents a simple, analytical theory for determining total pressure in multiphase flows, a subject of theoretical interest as well as of practical importance. It is shown here that the nonequilibrium processes occurring in the vicinity of a measuring device have a significant influence on the magnitude of flow velocity inferred from Pitot measurements. The present theory predicts that, depending on the size of the particles or droplets, the total pressure varies monotonically between the two limiting values: the frozen total pressure (when there is no interphase mass, momentum, and energy transfer in the decelerating flow toward the stagnation point) and the equilibrium total pressure (when the dispersed phase, either liquid droplets, or solid particles, is always at inertial and thermodynamic equilibrium with the continuous vapour phase). The presented analytical theory is a relation between nondimensional total pressure and Stokes number, representing particle size or inertia, and specifies the total pressure under different nonequilibrium conditions. One simple equation applies to diverse multiphase mixtures, solid particle laden gas as well as vapour-droplet mixtures, and at a wide range of flow conditions, both subsonic and supersonic. The associated issue of interpreting total temperature, and the relation between measured total pressure and entropy production in multiphase flows have been discussed at length by Guha (1998).

scholarly journals Universities’ Intellectual Capital Report: The Formation Concept, Analytical Capabilities under Stakeholders Management Decisions-Making

2020 ◽  
Vol 7 (6) ◽  
pp. 40-54
Author(s):  
A. A. Vakhrushina ◽  
M. A. Vakhrushina
Keyword(s):  
Intellectual Capital ◽  
Practical Importance ◽  
Economic Life ◽  
Effective Management ◽  
Ministry Of Education ◽  
Systematic Analysis ◽  
Accounting Systems ◽  
Management Accounting Systems ◽  
Wide Range ◽  
Russian Universities

The modern trends in the socio-economic life, educational and research spheres lead to the increased attention of universities to the more effective management of available resources, as well as high-quality and relevant disclosure of information in their public reporting to the interested parties. Under the circumstances, the intellectual capital (IC) components become key objects in the management accounting systems, and the IC report may become one of the main engines to achieve the transparent information which can raise the interest of stakeholders. The analysis of this practice clarified the discussion points and helped to develop conceptual guidelines for the preparation of the IC report for Russian universities. There have been used the following methods to solve the problem, such as quantitative-systematic analysis, semantic grouping of results and logical relationships. The developed methodology for analyzing the report on IC universities has a certain practical importance. Such methodology also includes methods of financial and management analysis. The formulated recommendations are intended for a wide range of stakeholders, the leadership of the Russian Ministry of Education and Science and higher education institutions.

scholarly journals Including poroelastic effects in the linear slip theory

Geophysics ◽  
2015 ◽  
Vol 80 (2) ◽  
pp. A51-A56 ◽  
Author(s):  
J. Germán Rubino ◽  
Gabriel A. Castromán ◽  
Tobias M. Müller ◽  
Leonardo B. Monachesi ◽  
Fabio I. Zyserman ◽  
...  
Keyword(s):  
Viscous Friction ◽  
Seismic Wave Propagation ◽  
Seismic Attenuation ◽  
Porous Rocks ◽  
Compliance Matrix ◽  
Frequency Dependent ◽  
Attenuation Mechanism ◽  
Wave Induced ◽  
Complex Valued ◽  
Good Agreement

Numerical simulations of seismic wave propagation in fractured media are often performed in the framework of the linear slip theory (LST). Therein, fractures are represented as interfaces and their mechanical properties are characterized through a compliance matrix. This theory has been extended to account for energy dissipation due to viscous friction within fluid-filled fractures by using complex-valued frequency-dependent compliances. This is, however, not fully adequate for fractured porous rocks in which wave-induced fluid flow (WIFF) between fractures and host rock constitutes a predominant seismic attenuation mechanism. In this letter, we develop an approach to incorporate WIFF effects directly into the LST for a 1D system via a complex-valued, frequency-dependent fracture compliance. The methodology is validated for a medium permeated by regularly distributed planar fractures, for which an analytical expression for the complex-valued normal compliance is determined in the framework of quasistatic poroelasticity. There is good agreement between synthetic seismograms generated using the proposed recipe and those obtained from comprehensive, but computationally demanding, poroelastic simulations.

Seismic wave attenuation due to fluid pressure diffusion at the mesoscopic scale: an experimental and numerical study

2021 ◽  
Author(s):  
Samuel Chapman ◽  
Jan V. M. Borgomano ◽  
Beatriz Quintal ◽  
Sally M. Benson ◽  
Jerome Fortin
Keyword(s):  
Seismic Wave ◽  
Seismic Waves ◽  
Wave Attenuation ◽  
Fluid Pressure ◽  
Fluid Distribution ◽  
Mesoscopic Scale ◽  
Seismic Wave Attenuation ◽  
X Ray ◽  
Pressure Diffusion ◽  
Attenuation And Dispersion

<p>Monitoring of the subsurface with seismic methods can be improved by better understanding the attenuation of seismic waves due to fluid pressure diffusion (FPD). In porous rocks saturated with multiple fluid phases the attenuation of seismic waves by FPD is sensitive to the mesoscopic scale distribution of the respective fluids. The relationship between fluid distribution and seismic wave attenuation could be used, for example, to assess the effectiveness of residual trapping of carbon dioxide (CO2) in the subsurface. Determining such relationships requires validating models of FPD with accurate laboratory measurements of seismic wave attenuation and modulus dispersion over a broad frequency range, and, in addition, characterising the fluid distribution during experiments. To address this challenge, experiments were performed on a Berea sandstone sample in which the exsolution of CO2 from water in the pore space of the sample was induced by a reduction in pore pressure. The fluid distribution was determined with X-ray computed tomography (CT) in a first set of experiments. The CO2 exosolved predominantly near the outlet, resulting in a heterogeneous fluid distribution along the sample length. In a second set of experiments, at similar pressure and temperature conditions, the forced oscillation method was used to measure the attenuation and modulus dispersion in the partially saturated sample over a broad frequency range (0.1 - 1000 Hz). Significant P-wave attenuation and dispersion was observed, while S-wave attenuation and dispersion were negligible. These observations suggest that the dominant mechanism of attenuation and dispersion was FPD. The attenuation and dispersion by FPD was subsequently modelled by solving Biot’s quasi-static equations of poroelasticity with the finite element method. The fluid saturation distribution determined from the X-ray CT was used in combination with a Reuss average to define a single phase effective fluid bulk modulus. The numerical solutions agree well with the attenuation and modulus dispersion measured in the laboratory, supporting the interpretation that attenuation and dispersion was due to FPD occurring in the heterogenous distribution of the coexisting fluids. The numerical simulations have the advantage that the models can easily be improved by including sub-core scale porosity and permeability distributions, which can also be determined using X-ray CT. In the future this could allow for conducting experiments on heterogenous samples.</p>

scholarly journals Control of pre-existing fabric in fracture formation, reactivation and vein emplacement under variable fluid pressure conditions: An example from Archean Greenstone belt, India

2020 ◽  
Author(s):  
Sreyashi Bhowmick ◽  
Tridib Kumar Mondal
Keyword(s):  
Pressure Ratio ◽  
Fluid Pressure ◽  
Tectonic Stress ◽  
Fault Slip ◽  
Magnetic Fabric ◽  
Pressure Condition ◽  
Crustal Fluid ◽  
Wide Range ◽  
Riedel Shear ◽  
Archean Greenstone Belt

Abstract. Most of the upper crustal fluid flows are strongly influenced by the pre-existing fractures/foliations in the rocks under a certain state of tectonic stress and fluid pressure condition. In the present study, we analyze a wide range of crosscutting fractures that are filled with quartz veins of variable orientations and thicknesses, from the gold bearing massive metabasalts (supracrustal) of the Chitradurga Schist Belt adjacent to the Chitradurga Shear Zone (CSZ), western Dharwar craton, south India. The study involves the following steps: 1) analyzing the internal magnetic fabric using anisotropy of magnetic susceptibility (AMS) studies, and strength of the host metabasalts, 2) quantifying the fluid pressure condition through lower hemisphere equal area projection of pole to veins by determining the driving pressure ratio (R'), stress ratio (ϕ), and susceptibility to fracturing, and 3) deciphering the paleostress condition using fault slip analysis. We interpret that the NNW-SSE to NW-SE (mean 337°/69° NE) oriented magnetic fabric in the rocks of the region developed during regional D1/D2 deformation on account of NE-SW shortening. However, D3 deformation manifested by NW-SE to E-W shortening led to the sinistral movement along CSZ. As a consequence of this sinistral shearing, fractures with prominent orientations formed riedel shear components, with CSZ as the shear boundary. Subsequently, all the pre-existing fabrics along with the riedel shear components were reactivated and vein emplacement took place through episodic fluid pressure fluctuation from high to low Pf at shallow depth (~ 2.4 km). However, NNW-SSE orientations were susceptible for reactivation under both high and low Pf conditions leading to a much greater thickness along the same. The deduced paleostress from fault-slip analysis, along with the kinematics of the fractures and veins are in good agreement with the previously revealed regional tectonics. Thus, integrating multiple domains of studies, help in the logical interpretation of fluid flow condition and vein emplacement mechanism in the study area that has not been ventured before.

Sign in / Sign up

Export Citation Format

Share Document