Author: William C. Hunt
Publisher:
ISBN:
Category : Mechanical properties
Languages : en
Pages : 242

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Author: Johannes Herrmann
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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The thesis comprises three experimental studies, which were carried out to unravel the short- as well as the long-term mechanical properties of shale rocks. Short-term mechanical properties such as compressive strength and Young's modulus were taken from recorded stress-strain curves of constant strain rate tests. Long-term mechanical properties are represented by the time- dependent creep behavior of shales. This was obtained from constant stress experiments, where the test duration ranged from a couple minutes up to two weeks. A profound knowledge of the mechanical behavior of shales is crucial to reliably estimate the potential of a shale reservoir for an economical and sustainable extraction of hydrocarbons (HC). In addition, healing of clay-rich forming cap rocks involving creep and compaction is important for underground storage of carbon dioxide and nuclear waste. Chapter 1 introduces general aspects of the research topic at hand and highlights the motivation for conducting this study. At present, a shift from energy recovered...

Author: Yu Wang
Publisher: Scientific Research Publishing, Inc. USA
ISBN: 1618968963
Category : Art
Languages : en
Pages : 383

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This book is intended as a reference book for advanced graduate students and research engineers in shale gas development or rock mechanical engineering. Globally, there is widespread interest in exploiting shale gas resources to meet rising energy demands, maintain energy security and stability in supply and reduce dependence on higher carbon sources of energy, namely coal and oil. However, extracting shale gas is a resource intensive process and is dependent on the geological and geomechanical characteristics of the source rocks, making the development of certain formations uneconomic using current technologies. Therefore, evaluation of the physical and mechanical properties of shale, together with technological advancements, is critical in verifying the economic viability of such formation. Accurate geomechanical information about the rock and its variation through the shale is important since stresses along the wellbore can control fracture initiation and frac development. In addition, hydraulic fracturing has been widely employed to enhance the production of oil and gas from underground reservoirs. Hydraulic fracturing is a complex operation in which the fluid is pumped at a high pressure into a selected section of the wellbore. The interaction between the hydraulic fractures and natural fractures is the key to fracturing effectiveness prediction and high gas development. The development and growth of a hydraulic fracture through the natural fracture systems of shale is probably more complex than can be described here, but may be somewhat predictable if the fracture system and the development of stresses can be explained. As a result, comprehensive shale geomechanical experiments, physical modeling experiment and numerical investigations should be conducted to reveal the fracturing mechanical behaviors of shale.

Author: Hiroki Sone
Publisher:
ISBN:
Category :
Languages : en
Pages :

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The main focus of this thesis is to study the basic rock mechanical properties of shale gas reservoir rocks, the in-situ state of stress in shale gas reservoirs, and their inter-relation. Laboratory studies on the elastic and deformational mechanical properties of gas shales show that these rocks exhibit wide range of mechanical properties and significant anisotropy reflecting their wide range of material composition and fabric anisotropy. The elastic properties of these shale rocks are successfully described by tracking the relative amount soft components (clay and solid organic materials) in the rock and also acknowledging the anisotropic distribution of the soft components. Gas shales were also found to possess relatively stronger degree of anisotropy compared to other organic-rich shales studied in the literature, possibly due to the fact that these rocks come from peak-maturity source rocks. The deformational properties studied by observing the ductile creep behavior and brittle strengths were also found to be influenced by the amount of soft components in the rock and exhibited mechanical anisotropy. A strong correlation between the elastic properties and the deformational properties was also found through comparison of laboratory data. The relation between the elastic modulus and magnitude of ductile creep is investigated through differential effective medium (DEM) modeling of the shale elastic properties. The partitioning of the far-field stress between the stiff and soft components was calculated in the DEM modeling to forward model the ductile creep behavior of the shales. Results showed that the correlation between the elastic properties and magnitude of ductile creep arises because they are both influenced by the stress partitioning in the rocks. Examination of a FMI image log from a vertical well in Barnett shale showed that the in-situ state of stress fluctuates rapidly within the reservoir in terms of the orientation and magnitude of the principal stress. The appearance and disappearance of drilling-induced tensile fractures roughly correlated with the variation in the clay and organic content in the formation, suggesting that there is a fluctuation in the magnitude of the horizontal stress difference, on the order of 10 MPa, that may be controlled by the mechanical heterogeneity of the formations. In order to explain the linkage between the observed stress variation and formation heterogeneity, we focused on the variation of ductile creep behavior exhibited by the gas shale rocks observed in the laboratory. The laboratory creep data was analyzed under the framework of viscoelastic theory to quantify its behavior and allow the calculation of the stress carrying capacity of the rocks. The viscoelastic behavior of the gas shales were found to be best approximated by a power-law function of time and the accumulation of differential stress over geological time in these rocks were calculated according to this constitutive description. Stress analysis assuming a simple constant strain rate tectonic loading history over 150 Ma shows that the horizontal stress difference on the order of 10 MPa observed in the Barnett shale can be explained by the variation in viscoelastic properties within the Barnett shale. Our results highlight the importance of acknowledging viscous deformation of shale gas reservoir rocks to understand the current in-situ state of stress in these reservoirs. A study of frictional properties of a saponite-rich fault gouge from a serpentinite-bearing fault in central Japan is also presented in this thesis. Field characterization of the internal structure of a fault juxtaposing serpentinites and Cretaceous sedimentary rocks show that hydrothermal metasomatic reactions took place at the fault interface which produced peculiar mineral assemblages along the fault plane. The saponite-rich fault gouge resulting from the metasomatic reaction exhibits extremely low coefficient of friction, ~0.1, at wet conditions and strong velocity-strengthening characteristics. The study highlights the importance of geochemical reactions along fault planes which may ultimately control the overall mechanical behavior of major fault zones.

Author: A. Evangelista
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: G.E. Andreev
Publisher: CRC Press
ISBN: 9789054106029
Category : Technology & Engineering
Languages : en
Pages : 464

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This text comprises different basic aspects of brittle failure for rocks. It considers classical and contemporary models, as well as failure patterns under different loading schemes.

Author: Bernard Amadei
Publisher: Springer Science & Business Media
ISBN: 3642820409
Category : Technology & Engineering
Languages : en
Pages : 498

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Book Description
Any undisturbed rock mass is subject to natural stresses inclu ding gravitational stresses due to the mass of the overburden and possibly tectonic stresses due to the straining of the earth's crust and remanent stresses due to past tectonism. Knowledge of the in situ stress field must be integrated into any rock engineering design along with general rock mass characteristics such as de for mability, strength, permeability and time dependent behavior. For example, the choice of optimum orientation and shape of deep underground caverns or complex underground works will be controlled by the orientation and the magnitude of the in situ stress @ield if it is necessary to minimize stress concentration problems. Long term variation of the in situ stress field may also help to evaluate the potential hazard of earthquake occurences. The magnitude and orientation of the stress field ata point within a rock mass can be measured but there is no known method by which the state of stress at a point can be accurately determined by instruments located remotely. In general, measurements are made inside boreholes, on outcrops or on the internal surfaces of under ground cavities. Most of the measuring techniques intentionally disturb the state of stress in the rock and then measure consequent strains and displacements. Measured strains or displacements are then related to the stresses through assumptions of material behavior. A common procedure is to assume that the rock mass is linearly elastic, isotropic, continuous and homogeneous.

Author: Erling Fjær
Publisher: Elsevier
ISBN: 0080557090
Category : Science
Languages : en
Pages : 515

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Engineers and geologists in the petroleum industry will find Petroleum Related Rock Mechanics, 2e, a powerful resource in providing a basis of rock mechanical knowledge - a knowledge which can greatly assist in the understanding of field behavior, design of test programs and the design of field operations. Not only does this text give an introduction to applications of rock mechanics within the petroleum industry, it has a strong focus on basics, drilling, production and reservoir engineering. Assessment of rock mechanical parameters is covered in depth, as is acoustic wave propagation in rocks, with possible link to 4D seismics as well as log interpretation. Learn the basic principles behind rock mechanics from leading academic and industry experts Quick reference and guide for engineers and geologists working in the field Keep informed and up to date on all the latest methods and fundamental concepts

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Author: Z. T. Bieniawski
Publisher:
ISBN:
Category : Brittleness
Languages : en
Pages : 486

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