scholarly journals Stress rotation – The impact and interaction of rock stiffness and faults

2020 ◽  
Author(s):  
Karsten Reiter
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Active Faults ◽  
Horizontal Stress ◽  
Stress Pattern ◽  
Upper Crust ◽  
Low Friction ◽  
Stress Rotation ◽  
Stress Orientation ◽  
Order Stress

Abstract. It has been assumed, that the maximum compressive horizontal stress (SHmax) orientation in the upper crust is governed on a regional scale by the same forces that drive plate motion. However, several regions are identified, where stress orientation deviates from the expected orientation due to plate boundary forces (first order stress sources), or the plate wide pattern. In some of this regions a gradual rotation of the SHmax orientation has been observed. Several second and third order stress sources have been identified, which may explain stress rotation in the upper crust. For example lateral heterogeneities in the crust, such as density, petrophysical or petrothermal properties and discontinuities, like faults are identified as potential candidates to cause lateral stress rotations. To investigate several of the candidates, generic geomechanical numerical models are utilized. These models consist of up to five different units, oriented by an angle of 60° to the direction of contraction. These units have variable elastic material properties, such as Young's modulus, Poisson ratio and density. Furthermore, the units can be separated by contact surfaces that allow them so slide along these faults, depending on a selected coefficient of friction. The model results indicate, that a density contrast or the variation of the Poisson's ratio alone sparsely rotates the horizontal stress orientation (≦ 17°). Conversely, a contrast of the Young's modulus allows significant stress rotations in the order of up to 78°; not only areas in the vicinity of the material transition are affected by that stress rotation. Stress rotation clearly decreases for the same stiffness contrast, when the units are separated by low friction discontinuities (19°). Low friction discontinuities in homogeneous models do not change the stress pattern at all, away from the fault; the stress pattern is nearly identical to a model without any active faults. This indicates that material contrasts are capable of producing significant stress rotation for larger areas in the crust. Active faults that separates such material contrasts have the opposite effect, they rather compensate stress rotations.

scholarly journals Stress rotation – impact and interaction of rock stiffness and faults

Solid Earth ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 1287-1307
Author(s):  
Karsten Reiter
Keyword(s):  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Active Faults ◽  
Stress Pattern ◽  
Poisson's Ratio ◽  
Upper Crust ◽  
Low Friction ◽  
Stress Rotation ◽  
Order Stress

Abstract. It has been assumed that the orientation of the maximum horizontal compressive stress (SHmax) in the upper crust is governed on a regional scale by the same forces that drive plate motion. However, several regions are identified where stress orientation deviates from the expected orientation due to plate boundary forces (first-order stress sources), or the plate wide pattern. In some of these regions, a gradual rotation of the SHmax orientation has been observed. Several second- and third-order stress sources have been identified in the past, which may explain stress rotation in the upper crust. For example, lateral heterogeneities in the crust, such as density and petrophysical properties, and discontinuities, such as faults, are identified as potential candidates to cause lateral stress rotations. To investigate several of these candidates, generic geomechanical numerical models are set up with up to five different units, oriented by an angle of 60∘ to the direction of shortening. These units have variable (elastic) material properties, such as Young's modulus, Poisson's ratio and density. In addition, the units can be separated by contact surfaces that allow them to slide along these vertical faults, depending on a chosen coefficient of friction. The model results indicate that a density contrast or the variation of Poisson's ratio alone hardly rotates the horizontal stress (≦17∘). Conversely, a contrast of Young's modulus allows significant stress rotations of up to 78∘, even beyond the vicinity of the material transition (>10 km). Stress rotation clearly decreases for the same stiffness contrast, when the units are separated by low-friction discontinuities (only 19∘ in contrast to 78∘). Low-friction discontinuities in homogeneous models do not change the stress pattern at all away from the fault (>10 km); the stress pattern is nearly identical to a model without any active faults. This indicates that material contrasts are capable of producing significant stress rotation for larger areas in the crust. Active faults that separate such material contrasts have the opposite effect – they tend to compensate for stress rotations.

Impact of elastic material properties and discontinuities on the stress orientation

2020 ◽  
Author(s):  
Karsten Reiter
Keyword(s):  
Elastic Material ◽  
Material Properties ◽  
Horizontal Stress ◽  
Upper Crust ◽  
Third Order ◽  
Orientation Data ◽  
Stress Rotation ◽  
Stress Orientation ◽  
The World ◽  
Order Stress

<p>The in-situ stress state in the upper crust is an important issue for diverse economic purposes and scientific questions as well. Several methods have been established in the last decades to estimate the present-day orientation of the maximum compressive horizontal stress (S<sub>Hmax</sub>) in the crust. It has been assumed, that the S<sub>Hmax</sub> orientation on a regional scale is governed by the same forces that drive plate motion too. The S<sub>Hmax</sub> orientation data, compiled by the World Stress Map (WSM) project, confirmed that for many regions in the world. Due to the increasing amount of data, it is now possible to identify several areas in the world, where stress orientation deviates from the expected orientation due to plate boundary forces (first order stress sources), or the plate wide pattern. In some of this regions a gradual rotation of the S<sub>Hmax</sub> orientation is observed.</p><p>Several second and third order stress sources have been identified which may explain stress rotation in the upper crust. For example, lateral heterogeneities in the crust, such as density, petrophysical or petrothermal properties and discontinuities, like faults are identified. Apparently, there are just a few studies, that deal with the potential extend of stress rotation as a function of second and third order stress sources. For that reason, generic geomechanical numerical models have been developed, consisting of up to five different units oriented at an angle of 60 degrees to the direction of contraction. These units have variable elastic material properties, such as Young’s modulus, Poisson ratio and density. In addition, an identical model geometry allows the units to be separated by contact surfaces that allow them so slide along the faults, depending on a selected coefficient of friction.</p><p>The model results indicate, that a density contrast or the variation of the Poisson’s ratio alone sparsely rotates the horizontal stress orientation. Conversely, a contrast of the Young’s modulus allows significant stress rotations. Not only areas in the vicinity of the material transition are affected by the stress rotation, but the entire blocks. Low friction discontinuities do not change the stress pattern when viewed over a wide area in homogeneous models. This also applies to models with alternating stiff and soft blocks - the stress orientation is determined solely by the boundary conditions, not the material transitions. This indicates that material contrasts are capable of producing significant stress rotation for larger areas in the crust. Active faults that separates such material contrasts have the opposite effect, they compensate for stress rotations.</p>

scholarly journals Determination of the mud weight window, optimum drilling trajectory, and wellbore stability using geomechanical parameters in one of the Iranian hydrocarbon reservoirs

2021 ◽  
Author(s):  
Masoud Hoseinpour ◽  
Mohammad Ali Riahi
Keyword(s):  
Young’S Modulus ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Horizontal Stress ◽  
Wellbore Stability ◽  
Poisson's Ratio ◽  
Drilling Mud ◽  
Geomechanical Parameters ◽  
Weight Window ◽  
Gurpi Formation

AbstractThe challenges behind this research were encountered while drilling into the Ilam, Mauddud, Gurpi, and Mishrif Formations, where severe drilling instability-related issues were observed across the weaker formations above the reservoir intervals. In this paper, geomechanical parameters were carried out to determine optimum mud weight windows and safe drilling deviation trajectories using the geomechanical parameters. We propose a workflow to determine the equivalent mud window (EMW) that resulted in 11.18–12.61 ppg which is suitable for Gurpi formation and 9.36–13.13 ppg for Ilam and Mishrif Formations, respectively. To estimate safe drilling trajectories, the Poisson’s ratio, Young’s modulus, and unconfined compressive strength (UCS) parameters were determined. These parameters illustrate an optimum drilling trajectory angle of 45° (Azimuth 277°) for the Ilam to Mauddud Formations and less than 35° for the Gurpi Formation. Our analysis reveals that maximum horizontal stress and Poisson’s ratio have the most impact on determining the optimum drilling mud weight windows and safe drilling deviation trajectories. On the contrary, vertical stress and Young’s modulus have minimum impact on drilling mud weight windows and safe drilling deviation trajectories. This study can be used as a reference for the optimal mud weight window to overcome drilling instability issues in future wellbore planning in the study.

scholarly journals Effect of Mineral Processes and Deformation on the Petrophysical Properties of Soft Rocks during Active Faulting

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 444
Author(s):  
Anita Torabi ◽  
Juan Jiménez-Millán ◽  
Rosario Jiménez-Espinosa ◽  
Francisco Juan García-Tortosa ◽  
Isabel Abad ◽  
...  
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Damage Zone ◽  
Active Faults ◽  
Soft Rock ◽  
Microstructural Characterization ◽  
Rock Properties ◽  
Deformation Bands ◽  
Carbonate Cement ◽  
Granada Basin

We have studied damage zones of two active faults, Baza and Padul faults in Guadix-Baza and Granada basins, respectively, in South Spain. Mineral and microstructural characterization by X-ray diffraction and field emission electron microscopy studies have been combined with structural fieldwork and in situ measurements of rock properties (permeability and Young’s modulus) to find out the relation between deformation behavior, mineral processes, and changes in the soft rock and sediment properties produced by fluid flow during seismic cycles. Our results show that microsealing produced by precipitation of dolomite and aragonite along fractures in the damage zone of Baza Fault reduces the permeability and increases the Young’s modulus. In addition, deformation bands formed in sediments richer in detrital silicates involved cataclasis as deformation mechanism, which hamper permeability of the sediments. In the Granada Basin, the calcarenitic rocks rich in calcite and clays in the damage zone of faults associated to the Padul Fault are characterized by the presence of stylolites without any carbonate cement. On the other hand, marly lithofacies affected by faults are characterized by the presence of disaggregation bands that involve cracking and granular flow, as well as clay smear. The presence of stylolites and deformation bands in these rocks reduces permeability.

Characterization of elastic mechanical properties of Tuscaloosa Marine Shale from well logs using the vertical transversely isotropic model

2020 ◽  
Vol 8 (4) ◽  
pp. T1023-T1036
Author(s):  
Cristina Mariana Ruse ◽  
Mehdi Mokhtari
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Hydraulic Fracture ◽  
Poisson’S Ratio ◽  
Young's Modulus ◽  
Horizontal Stress ◽  
Poisson's Ratio ◽  
Isotropic Solution ◽  
Marine Shale ◽  
Minimum Horizontal Stress

To avoid steep declines in the Tuscaloosa Marine Shale (TMS) production, wells are fracture-stimulated to release the hydrocarbons trapped in the matrix of the formation. An accurate estimation of Young’s modulus and Poisson’s ratio is essential for hydraulic fracture propagation. In addition, ignoring the highly heterogeneous and anisotropic character of TMS can lead to erroneous stress values, which subsequently affect hydraulic fracture width estimates and the overall hydraulic fracturing process. We have developed an empirical 1D geomechanical model that takes into account VTI anisotropy, and it is used to characterize the elastic mechanical properties of TMS in two wells. In the analyzed formation, the vertical Poisson’s ratio is less than the horizontal Poisson’s ratio, which suggests the necessity of an alternative to the ANNIE equations. The stiffness coefficients [Formula: see text] and [Formula: see text] were estimated using the relationships developed from the ultrasonic core data available for the two TMS. Further, correlations between the static and dynamic properties from laboratory tests were used to improve the minimum horizontal stress calculation. We compare VTI Young’s moduli, Poisson’s ratios, and minimum horizontal stress with the isotropic solution. VTI modeling improves the estimation of the elastic mechanical properties. The isotropic solution underestimates the minimum horizontal stress in the formation. Moreover, it was shown that the 20 ft shale interval below the TMS base is characterized by a low Young’s modulus (the vertical Young’s modulus is equal to 20 GPa, whereas the horizontal Young’s modulus is equal to 40 GPa) and may be a frac barrier.

Evaluation of geotechnical property variability

1999 ◽  
Vol 36 (4) ◽  
pp. 625-639 ◽  
Author(s):  
Kok-Kwang Phoon ◽  
Fred H Kulhawy
Keyword(s):  
Shear Strength ◽  
Measurement Error ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Friction Angle ◽  
Horizontal Stress ◽  
Undrained Shear Strength ◽  
Stress Coefficient ◽  
Undrained Shear

To evaluate geotechnical variability on a general basis that will facilitate the use of reliability-based design procedures, it is necessary to assess inherent soil variability, measurement error, and transformation uncertainty separately. The inherent variability and measurement error are addressed in a companion paper, and transformation uncertainty is addressed herein. A second-moment probabilistic approach is applied to combine these uncertainties consistently based on the manner in which the design soil property is derived. The design properties considered in this paper are undrained shear strength, effective stress friction angle, in situ horizontal stress coefficient, and Young's modulus. This paper concludes with specific guidelines on the typical coefficients of variation for these common design soil properties as a function of the test type and the type of correlation used.Key words: transformation uncertainty, undrained shear strength, friction angle, in situ horizontal stress coefficient, Young's modulus, geotechnical variability.

High hardness, low Young's modulus and low friction of nanocrystalline ZrW2 Laves phase and Zr1−xWx thin films

2012 ◽  
Vol 73 (4) ◽  
pp. 554-558 ◽  
Author(s):  
D. Horwat ◽  
E. Jimenez-Pique ◽  
J.F. Pierson ◽  
S. Migot ◽  
M. Dehmas ◽  
...  
Keyword(s):  
Thin Films ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
High Hardness ◽  
Laves Phase ◽  
Low Friction

Mechanical properties of FeAlSi powders prepared by mechanical alloying from different initial feedstock materials

2019 ◽  
Vol 107 (2) ◽  
pp. 207 ◽  
Author(s):  
Jaroslav Čech ◽  
Petr Haušild ◽  
Miroslav Karlík ◽  
Veronika Kadlecová ◽  
Jiří Čapek ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Alloying ◽  
Young’S Modulus ◽  
Milling Time ◽  
Young's Modulus ◽  
Element Model ◽  
X Ray Diffraction ◽  
X Ray ◽  
Powder Particles ◽  
Complete Homogenization

FeAl20Si20 (wt.%) powders prepared by mechanical alloying from different initial feedstock materials (Fe, Al, Si, FeAl27) were investigated in this study. Scanning electron microscopy, X-ray diffraction and nanoindentation techniques were used to analyze microstructure, phase composition and mechanical properties (hardness and Young’s modulus). Finite element model was developed to account for the decrease in measured values of mechanical properties of powder particles with increasing penetration depth caused by surrounding soft resin used for embedding powder particles. Progressive homogenization of the powders’ microstructure and an increase of hardness and Young’s modulus with milling time were observed and the time for complete homogenization was estimated.

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