scholarly journals 3D crustal stress state of Western Central Europe according to a data-calibrated geomechanical model – first results

2020 ◽  
Author(s):  
Steffen Ahlers ◽  
Andreas Henk ◽  
Tobias Hergert ◽  
Karsten Reiter ◽  
Birgit Müller ◽  
...  
Keyword(s):  
Stress State ◽  
Central Europe ◽  
Material Properties ◽  
Regional Scale ◽  
Horizontal Stress ◽  
Rock Properties ◽  
Upper Crust ◽  
Stress Regime ◽  
Crustal Stress ◽  
Lithostratigraphic Units

Abstract. The contemporary stress state in the upper crust is of great interest for geotechnical applications and basic research likewise. However, our knowledge of the crustal stress field from the data perspective is limited. For Western Central Europe basically two datasets are available: Orientations of the maximum horizontal stress (SHmax) and the stress regime as part of the World Stress Map (WSM) database (Heidbach et al., 2018) as well as a complementary compilation of stress magnitude data of Germany and adjacent regions (Morawietz et al., 2020). However, these datasets only provide pointwise, incomplete and heterogeneous information of the 3D stress tensor. Here, we present a geomechanical-numerical model that provides a continuous description of the contemporary 3D crustal stress state on a regional scale for Western Central Europe. The model covers an area of about 1000 × 1250 km2 and extends to a depth of 100 km containing seven lithostratigraphic units, with specific material properties (density and elastic rock properties) and laterally varying thicknesses: A sedimentary unit, four different units of the upper crust, the lower crust and the lithospheric mantle. The model is calibrated by the two datasets to achieve a best-fit regarding the SHmax orientations and the minimum horizontal stress magnitudes (Shmin). The modelled orientations of SHmax are almost entirely within the uncertainties of the WSM data used and the Shmin magnitudes fit to various datasets well. Only the SHmax magnitudes show locally significant deviations, primarily indicating too low values in the lower part of the model. The model is open for further refinements regarding model geometry, e.g., additional layers with laterally varying material properties, and incorporation of future stress measurements. In addition, it can provide the initial stress state for local geomechanical models with a higher resolution.

scholarly journals 3D crustal stress state of Germany according to a data-calibrated geomechanical model

Solid Earth ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1777-1799
Author(s):  
Steffen Ahlers ◽  
Andreas Henk ◽  
Tobias Hergert ◽  
Karsten Reiter ◽  
Birgit Müller ◽  
...  
Keyword(s):  
Stress State ◽  
Material Properties ◽  
Regional Scale ◽  
Basic Research ◽  
Horizontal Stress ◽  
Rock Properties ◽  
Upper Crust ◽  
Stress Regime ◽  
Initial Stress State ◽  
Crustal Stress

Abstract. The contemporary stress state in the upper crust is of great interest for geotechnical applications and basic research alike. However, our knowledge of the crustal stress field from the data perspective is limited. For Germany basically two datasets are available: orientations of the maximum horizontal stress (SHmax) and the stress regime as part of the World Stress Map (WSM) database as well as a complementary compilation of stress magnitude data of Germany and adjacent regions. However, these datasets only provide pointwise, incomplete and heterogeneous information of the 3D stress tensor. Here, we present a geomechanical–numerical model that provides a continuous description of the contemporary 3D crustal stress state on a regional scale for Germany. The model covers an area of about 1000×1250 km2 and extends to a depth of 100 km containing seven units, with specific material properties (density and elastic rock properties) and laterally varying thicknesses: a sedimentary unit, four different units of the upper crust, the lower crust and the lithospheric mantle. The model is calibrated by the two datasets to achieve a best-fit regarding the SHmax orientations and the minimum horizontal stress magnitudes (Shmin). The modeled orientations of SHmax are almost entirely within the uncertainties of the WSM data used and the Shmin magnitudes fit to various datasets well. Only the SHmax magnitudes show locally significant deviations, primarily indicating values that are too low in the lower part of the model. The model is open for further refinements regarding model geometry, e.g., additional layers with laterally varying material properties, and incorporation of future stress measurements. In addition, it can provide the initial stress state for local geomechanical models with a higher resolution.

Geomechanical Approach in Classification of Borehole Failures in Fractured Carbonates of Boca De Jaruco Field

2021 ◽  
Author(s):  
Anna Vladimirovna Norkina ◽  
Iaroslav Olegovich Simakov ◽  
Yuriy Anatoljevich Petrakov ◽  
Alexey Evgenjevich Sobolev ◽  
Oleg Vladimirovich Petrashov ◽  
...  
Keyword(s):  
Stress State ◽  
Horizontal Wells ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Vertical Wells ◽  
Stress Regime ◽  
Geophysical Information ◽  
The Republic ◽  
Maximum Horizontal Stress

Abstract This article is a continuation of the work on geomechanically calculations for optimizing the drilling of horizontal wells into the productive reservoir M at the Boca de Haruco field of the Republic of Cuba, presented in the article SPE-196897. As part of the work, an assessment of the stress state and direction was carried out using geological and geophysical information, an analysis of the pressure behavior during steam injections, cross-dipole acoustics, as well as oriented caliper data in vertical wells. After the completion of the first part of the work, the first horizontal wells were successfully drilled into the M formation. According to the recommendations, additional studies were carried out: core sampling and recording of micro-imager logging in the deviated sections. Presence of wellbore failures at the inclined sections allowed to use the method of inverse in-situ stress modeling based on image logs interpretation. The classification of wellbore failures by micro-imager logging: natural origin and violations of technogenic genesis is carried out. The type of breakout is defined. The result of the work was the determination of the stress state and horizontal stresses direction. In addition, the article is supplemented with the calculation of the maximum horizontal stress through the stress regime identifier factor.

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>

Lithological and structural control on the seismicity distribution in Central Italy

2020 ◽  
Author(s):  
Massimiliano R. Barchi ◽  
Lauro Chiaraluce ◽  
Cristiano Collettini
Keyword(s):  
Regional Scale ◽  
Central Italy ◽  
Shear Zones ◽  
Geological Structure ◽  
Rock Properties ◽  
Mountain Range ◽  
Upper Crust ◽  
Seismogenic Layer ◽  
Brittle Ductile Transition ◽  
Seismicity Distribution

<p>In the seismically active region of Central Italy, national (permanent) and local (not-permanent) seismic networks provided very accurate location of the seismicity recorded during the major seismic sequences occurred in the last 25 years (e.g. 1997-1998; 2009; 2016-2017), as well as of the background seismicity registered in the intervening periods.  In the same region, a network of seismic reflection profiles, originally acquired for oil exploration purposes, is also available, effectively imaging the geological structure at depth, to be compared with the seismicity distribution. </p><p>This comparison reveals that, if the position of the brittle/ductile transition exerts a role at regional scale for the occurrence of crustal seismicity, at a more local scale the depth and thickness of the seismogenic layer is mostly controlled by the contrasting rheological properties of the different lithological groups involved in the upper crust. </p><p>The upper crust stratigraphy, including the sedimentary cover and the uppermost part of the basement, consists of alternated strong (rigid, e.g. carbonates and dolostones) end weak (not-rigid, e.g. shales, sandstones, and phyllites) layers. This mechanically complex multilayer is involved in a belt of imbricated thrusts (Late Miocene-Early Pliocene), displaced by subsequent extensional (normal) faults (Late Pliocene-present), responsible for the observed regional seismicity. The top of the basement s.l. (composed of clastic sedimentary and slightly metamorphosed rocks) is involved in major thrusts.  For these different lithological units, combined field and lab studies of fault rock properties have documented localized and potentially unstable deformation occurring in granular mineral phases (carbonates) and distributed and stable slip within phyllosilicate-rich shear zones (shales and phyllites).</p><p>By comparing the geological structure with the seismicity distribution, we observed that:</p><p>-     The seismicity cut-off (i.e. the bottom of the seismogenic layer) is structurally (not thermally) controlled, and grossly corresponds to the top basement; the upper boundary of the seismogenic layer corresponds to the top of carbonates.</p><p>-     Most seismicity occurs within the rigid layers (carbonates and evaporites), and do not penetrate the turbidites and basements rocks.</p><p>-      Close to the axial region of the mountain range, where the larger amount of shortening is observed, the presence thrust sheets from the previous compressional phase, significantly affect the seismicity distribution and propagation.</p><p>-     Major east-dipping extensional detachments, recognized in the seismic profiles, are also marked by distinctive seismicity alignments.</p>

scholarly journals 20 July 2017 Bodrum-Kos Earthquake (Mw:6.6) in southwestern Anatolia, Turkey

2021 ◽  
Vol 25 (3) ◽  
pp. 309-321
Author(s):  
Semir Över ◽  
Süha Özden ◽  
Esra Kalkan Ertan ◽  
Fatih Turhan ◽  
Zeynep Coşkun ◽  
...  
Keyword(s):  
Fault Plane ◽  
Regional Scale ◽  
Aegean Sea ◽  
Horizontal Stress ◽  
Focal Mechanisms ◽  
Stress Axis ◽  
Small Scale ◽  
Normal Type ◽  
Fault Plane Solutions ◽  
Stress Regime

In the Aegean Sea, the western part of Gökova Gulf, Kos and Bodrum were struck by a 6.6 (Mw) earthquake on July 20, 2017. The fault plane solution for the main shock shows an E-W striking normal type fault with approximately N-S (N4°E) tensional axis (T-axis). Fault plane solutions of 33 aftershocks show two groups of normal type fault with E-W and NE-SW to ENE-WSW orientations. The inversion of the focal mechanisms of the aftershocks yields two different normal faulting stress regimes: one is characterized by an approximately N-S (N5°E) σ3 axis (minimum horizontal stress axis). This extension is obtained from 13 focal mechanisms of aftershocks with approximately E-W direction. The other is characterized by approximately NW-SE (N330°E) σ3 axis. The latter is calculated from 21 seismic faults of aftershocks with approximately NE-SW direction. These aftershocks occurred on relatively small-scale faults that were directed from NE-SW to ENE-WSW, and possibly contributed to expansion of the basin in the west. The 24 focal mechanisms of earthquakes which occurred since 1933 in and around Gökova Basin are introduced into the inversion analysis to obtain the stress state effective in a wider region. The inversion yields an extensional stress regime characterized by an approximately N-S (N355°E) σ3 axis. The E-W directional metric faults, measured in the central part of Gökova Fault Zone bordering the Gökova Gulf in the north, also indicate N-S extension. The NE-SW extension obtained from NE-SW aftershocks appears to be more local and is responsible for the expansion of the western part of the asymmetric Gökova Basin. This N-S extension which appears to act on a regional-scale may be attributed to the geodynamic effects related to the combined forces of the southwestward extrusion of Anatolia and the roll-back process of African subduction beneath Anatolia.

An integrated approach to the Surat Basin stratigraphy

2019 ◽  
Vol 59 (2) ◽  
pp. 940
Author(s):  
Mark Reilly ◽  
Suzanne Hurter ◽  
Zsolt Hamerli ◽  
Claudio L. de Andrade Vieira Filho ◽  
Andrew LaCroix ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Coal Seam ◽  
Methodological Approach ◽  
Regional Scale ◽  
Integrated Approach ◽  
Field Scale ◽  
Coal Seam Gas ◽  
Sequence Stratigraphic ◽  
Flow Models ◽  
Lithostratigraphic Units

The stratigraphy of the Surat Basin, Queensland, has historically been sub-divided by formation and unit nomenclature with a few attempts by other authors to apply sequence stratigraphy to existing formation boundaries. At a local- to field-scale, lithostratigraphy may be able to represent stratigraphy well, but at regional-scale, lithostratigraphic units are likely to be diachronous. To date, this lithology-driven framework does not accurately reflect time relationships in the sub-surface. An entirely new integrated methodological approach, involving well tied seismic data and sequence stratigraphic well-to-well correlations compared with published zircon age dates, has been applied to hundreds of deep wells and shallower coal seam gas wells. This method sub-divides the Surat Basin stratigraphy into defendable 2nd order to 3rd order sequence stratigraphic cycles and has required the use of an alpha-numeric sequence stratigraphic nomenclature to adequately and systematically label potential time equivalent surfaces basin-wide. Correlation of wells is the first step in building models of aquifers and coal seam gas fields for numerical simulation of fluid flow, which is necessary for responsible resource management. Lithostratigraphic correlations will overestimate the extent and hydraulic connectedness of the strata of interest. The result may be fluid flow models that do not represent a realistic pressure footprint of the flow. The present sequence stratigraphic method more accurately reflects the disconnectedness of sub-surface coals and sandstones (aquifers) on a field-to-field scale, adjacent field-scale, and basin-wide scale. It forms the basis for improved and more representative modelling of the sub-surface.

Defining structural permeability in Australian sedimentary basins

2015 ◽  
Vol 55 (1) ◽  
pp. 119 ◽  
Author(s):  
Adam Bailey ◽  
Rosalind King ◽  
Simon Holford ◽  
Joshua Sage ◽  
Martin Hand ◽  
...  
Keyword(s):  
Regional Scale ◽  
Sedimentary Basins ◽  
In Situ Stress ◽  
Natural Fracture ◽  
Enhanced Geothermal Systems ◽  
Structural Development ◽  
Geothermal Systems ◽  
Stress Regime ◽  
Orientation Data

Declining conventional hydrocarbon reserves have triggered exploration towards unconventional energy, such as CSG, shale gas and enhanced geothermal systems. Unconventional play viability is often heavily dependent on the presence of secondary permeability in the form of interconnected natural fracture networks that commonly exert a prime control over permeability due to low primary permeabiliy of in situ rock units. Structural permeability in the Northern Perth, SA Otway, and Northern Carnarvon basins is characterised using an integrated geophysical and geological approach combining wellbore logs, seismic attribute analysis and detailed structural geology. Integration of these methods allows for the identification of faults and fractures across a range of scales (millimetre to kilometre), providing crucial permeability information. New stress orientation data is also interpreted, allowing for stress-based predictions of fracture reactivation. Otway Basin core shows open fractures are rarer than image logs indicate; this is due to the presence of fracture-filling siderite, an electrically conductive cement that may cause fractures to appear hydraulically conductive in image logs. Although the majority of fractures detected are favourably oriented for reactivation under in situ stresses, fracture fill primarily controls which fractures are open, demonstrating that lithological data is often essential for understanding potential structural permeability networks. The Carnarvon Basin is shown to host distinct variations in fracture orientation attributable to the in situ stress regime, regional tectonic development and local structure. A detailed understanding of the structural development, from regional-scale (hundreds of kilometres) down to local-scale (kilometres), is demonstrated to be of importance when attempting to understand structural permeability.

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