Effect of Pore Fluids on the Elastic Properties of Sandstone PDF Download

Author: Robert Leo Mann
Publisher:
ISBN:
Category : Elastic solids
Languages : en
Pages : 128

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Author: Emmanuel Charles David
Publisher:
ISBN:
Category :
Languages : en
Pages :

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A model of elastic wave propagation in fluid-saturated sandstones is developed that takes into account pore fluid properties, and stress. It is based on the assumption that the pore space can be represented by a distribution of crack-like spheroidal pores having a distribution of aspect ratios, and a single family of non-closable spheroidal pores. The Eshelby-Wu formalism is used to find exact expressions for the bulk and shear compliances of the pores. Asymptotic analytical expressions are obtained for the compliances of both dry and fluid-saturated spheroidal pores that are crack-like, needle-like, or nearly spherical. These expressions are incorporated into two commonly used effective medium theories, the Mori-Tanaka and the Differential schemes, to obtain expressions for the effective elastic properties of dry and fluid-saturated rocks containing spheroids of a given aspect ratio, as a function of porosity or crack density. The stress dependence of the elastic velocities is modelled by considering that the elastic moduli vary with stress due to crack closure. This pore structure model is able to explain successfully the pressure dependence of ultrasonic dry velocities on many sets of laboratory data. Predictions of saturated velocities are made using either the Gassmann equation, or using an effective medium theory in conjunction with the aspect ratio distribution found from the dry data. For ultrasonic velocities obtained at high frequencies (MHz), the predictions of effective medium theories are more accurate than the Gassmann predictions. Low-frequency measurements (0.02 Hz) of the bulk modulus were obtained on Fontainebleau sandstone, under pressure, and with different pore fluids. For water and glycerin-saturated samples, both the 4% and 13% porosity rock specimens were more compliant at low frequencies than at high frequencies. Finally, a model is proposed for the frequency dependence of the wave velocities, assuming that at a given frequency, some pores obey the Gassmann equation, and others are isolated, with a critical aspect ratio demarcating the two families that depends on frequency and fluid viscosity.

Author: R.W. Zimmerman
Publisher: Elsevier
ISBN: 0080868878
Category : Technology & Engineering
Languages : en
Pages : 183

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This book is a comprehensive treatment of the elastic volumetric response of sandstones to variations in stress. The theory and data presented apply to the deformations that occur, for example, due to withdrawal of fluid from a reservoir, or due to the redistribution of stresses caused by the drilling of a borehole. Although the emphasis is on reservoir-type sandstones, results and methods discussed are also applicable to other porous rocks. Part One concerns the effect of stress on deformation and discusses porous rock compressibility coefficients. Elasticity theory is used to derive relationships between the porous rock compressibility coefficients, the porosity, and the mineral grain compressibility. Theoretical bounds on the compressibility coefficients are derived. The concept of effective stress coefficients is examined, as is the integrated form of the stress-strain relationships. Undrained compression and induced pore pressures are treated within the same general framework. Part One is concluded with a brief, elementary introduction to Biot's theory of poroelasticity. All the results in Part One are illustrated and verified with extensive references to published compressibility data. Part Two deals with the relationship between pore structure and compressibility, and presents methods that permit quantitative prediction of the compressibility coefficients. Two- and three-dimensional models of tubular pores, spheroidal pores, and crack-like "grain boundary" voids are analyzed. A critical review is made of various methods that have been proposed to relate the effective elastic moduli (bulk and shear) of a porous material to its pore structure. Methods for extracting pore aspect ratio distributions from stress-strain data or from acoustic measurements are presented, along with applications to actual sandstone data. Part Three is a brief summary of experimental techniques that are used to measure porous rock compressibilities in the laboratory. The information contained in this volume is of interest to petroleum engineers, specifically those involved with reservoir modeling, petroleum geologists, geotechnical engineers, hydrologists and geophysicists.

Author: Ekwere J. Peters
Publisher: Greenleaf Book Group
ISBN: 1936909448
Category : Nature
Languages : en
Pages : 239

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A practical, fast-paced approach to teaching the concepts and problems common in petroleum engineering that will appeal to a wide range of disciplines Petrophysics is the study of rock properties and their interactions with fluids, including gases, liquid hydrocarbons, and aqueous solutions. This three-volume series from distinguished University of Texas professor Dr. Ekwere J. Peters provides a basic understanding of the physical properties of permeable geologic rocks and the interactions of the various fluids with their interstitial surfaces, with special focus on the transport properties of rocks for single-phase and multiphase flow. Based on Dr. Peters's graduate course that has been taught internationally in corporations and classrooms, the series covers core topics and includes full-color CT and NMR images, graphs, and figures to illustrate practical application of the material. Subjects addressed in volume 1 (chapters 1-4) include - Geological concepts - Porosity and water saturation - Absolute permeability - Heterogeneity and geostatistics Advanced Petrophysics features over 140 exercises designed to strengthen learning and extend concepts into practice. Additional information in the appendices covers dimensional analysis and a series of real-world projects that enable the student to apply the principles presented in the text to build a petrophysical model using well logs and core data from a major petroleum-producing province.

Author: T. W. Thompson
Publisher:
ISBN:
Category : Sandstone
Languages : en
Pages :

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Author: Gary Mavko
Publisher: Cambridge University Press
ISBN: 1108420265
Category : Business & Economics
Languages : en
Pages : 741

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Brings together widely scattered theoretical and laboratory rock physics relations critical for modelling and interpretation of geophysical data.

Author: Francois Henri Cornet
Publisher:
ISBN:
Category : Rock mechanics
Languages : en
Pages : 576

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An investigation of the mechanical influence of interstitial fluids on the deformation process of saturated rocks has been conducted to determine the domain of validity of previously published theories. Equilibrium equations for fluid saturated materials in which the fluid is at rest or flows according to DARCY's law were derived. For this purpose, a new characterization of porosity has been proposed for analyzing porosity variation within a rock mass. This derivation indicates that the bulk material (solid plus fluid) can be represented by an equivalent homogeneous continuum for which the mass density and the stress tensor at any point depend upon average stresses and average densities of both the solid matrix and the saturating fluid as well as upon the surface and the volume porosity.

Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 1006

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Author: R. Worden
Publisher: John Wiley & Sons
ISBN: 1444304240
Category : Science
Languages : en
Pages : 352

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Quartz is the major porosity-reducing cement in many sandstonesequences. Therefore, Quartz cements represent a key source ofpetrographic and geochemical information about diagenetic history.They are also the major determinant of sandstone reservoirquality. While the ultimate goal of research in this area is to makerobust predictions about the amount and distribution of quartzcements in a wide variety of depositional and burial settings,there are nevertheless large areas of the subject that are poorlyunderstood and remain the subject of controversy. The aim of this Volume, which is based partly on paperssubmitted to a 1996 workshop in Belfast, and partly on invitedcontributions, is to bring together some of the main strands ofresearch into quartz cements and provide a focus for debate anddirection for future research. This book will be welcomed by sedimentologists, petrographersand geochemists involved in sandstone digenesis, as well as bypetroleum geologists seeking a deeper understanding of the factorsinfluencing reservoir porosity and permeability. Contributors from 11 countries and 4 continents. Represents the benchmark in quartz cement research. If you are a member of the International Association ofSedimentologists, for purchasing details, please see:http://www.iasnet.org/publications/details.asp?code=SP29

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 11

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A general analysis of poroelasticity for vertical transverse isotropy (VTI) shows that four eigenvectors are pure shear modes with no coupling to the pore-fluidmechanics. The remaining two eigenvectors are linear combinations of pure compression and uniaxial shear, both of which are coupled to the fluid mechanics. After reducing the problem to a 2x2 system, the analysis shows in a relatively elementary fashion how a poroelastic system with isotropic solid elastic frame, but with anisotropy introduced through the poroelastic coefficients, interacts with the mechanics of the pore fluid and produces shear dependence on fluid properties in the overall mechanical system. The analysis shows, for example, that this effect is always present (though sometimes small in magnitude) in the systems studied, and can be quite large (up to a definite maximum increase of 20 per cent) in some rocks--including Spirit River sandstone and Schuler-Cotton Valley sandstone.