Rus detachment in Dammam Dome, Eastern Saudi Arabia: a new soft-sediment structure as a ‘sensitive stress sensor’ for the Zagros collision

2021 ◽  
pp. 1-13
Author(s):  
Markos D. Tranos ◽  
Mutasim S. Osman
Keyword(s):  
Saudi Arabia ◽  
Fluid Pressure ◽  
Frictional Coefficient ◽  
Late Eocene ◽  
Soft Sediment ◽  
Stress Regime ◽  
Stress Sensor ◽  
Kinematic Indicators ◽  
Effective Principal ◽  
Displacement Zone

Abstract This paper describes in detail hydroplastic structures, which are ‘odd’ kinematic indicators in the basal part of the Eocene Middle Rus Formation. Such structures were previously ignored or falsely interpreted. These hydroplastic structures are found in the massive limestone exposures on the King Fahd University of Petroleum and Minerals (KFUPM) campus. They occur in relation to a principal displacement zone along the boundary/interface between the Lower/Middle Rus, which is referred to as the Rus soft-sediment detachment. The structures are fist-sized vugs associated with carrot- or comet-trail imprints (VCT structures) which were previously translated calcite geodes that have been weathered out. VCT structures show transport/slip towards the NNW (345°) and are found on flat to low-dipping surfaces classified as Y, R and P shears with respect to the orientation of the Rus detachment. Palaeostress analysis indicates an Andersonian transtension stress regime, though it does not facilitate the activation of the Rus soft-sediment detachment. Detachment activity occurred due to the negative effective principal stress σ3′ and the abnormally low frictional coefficient caused by fluid pressure. The soft-sediment Rus detachment can be considered a ‘sensitive stress sensor’ for the Zagros collision since it indicates the Arabian platform’s instability in the wider area of the Dammam Dome during the Late Eocene. This instability is attributed to the inception of the Zagros collision, which was previously considered to occur during the Oligocene based on the well-established pre-Neogene unconformity.

scholarly journals Soft-sediment deformation structures in cores from lacustrine slurry deposits of the Late Triassic Yanchang Fm. (central China)

Geologos ◽  
2016 ◽  
Vol 22 (3) ◽  
pp. 201-211 ◽  
Author(s):  
Renchao Yang ◽  
A.J. (Tom) van Loon ◽  
Wei Yin ◽  
Aiping Fan ◽  
Zuozhen Han
Keyword(s):  
Ordos Basin ◽  
Fluid Pressure ◽  
Volcanic Eruptions ◽  
Central China ◽  
Late Triassic ◽  
Soft Sediment ◽  
Deformation Structures ◽  
Sediment Deformation ◽  
Mass Flows ◽  
Soft Sediment Deformation

Abstract The fine-grained autochthonous sedimentation in the deep part of a Late Triassic lake was frequently interrupted by gravity-induced mass flows. Some of these mass flows were so rich in water that they must have represented slurries. This can be deduced from the soft-sediment deformation structures that abound in cores from these lacustrine deposits which constitute the Yanchang Fm., which is present in the Ordos Basin (central China). The flows and the resulting SSDS were probably triggered by earthquakes, volcanic eruptions, shear stress of gravity flows, and/or the sudden release of overburden-induced excess pore-fluid pressure. The tectonically active setting, the depositional slope and the high sedimentation rate facilitated the development of soft-sediment deformations, which consist mainly of load casts and associated structures such as pseudonodules and flame structures. Sediments with such deformations were occasionally eroded by slurries and became embedded in their deposits.

A General Formulation for Hydroforming of Arbitrarily-Shaped Boxes and Its Application to Hydroforming of an Elliptic-Circular Box

1998 ◽  
Vol 120 (3) ◽  
pp. 481-488 ◽  
Author(s):  
T. S. Noh ◽  
D. Y. Yang
Keyword(s):  
Velocity Field ◽  
Fluid Pressure ◽  
Frictional Coefficient ◽  
Total Power ◽  
Thickness Variation ◽  
Pressure Curve ◽  
Bound Solution ◽  
Total Power Consumption ◽  
Uniform Wall ◽  
Blank Size

A general kinematically admissible velocity field is suggested for the upper-bound solution of hydroforming of arbitrarily-shaped boxes. The suggested formulation is then applied to hydroforming of an elliptic-circular box. From the proposed velocity field, the fluid pressure vs. punch stroke relationship to render uniform thickness and the deformed configuration are determined by minimizing the total power consumption with respect to some chosen parameters. Experiments are carried out in the hydroforming press according to the computed pressure vs. punch stroke curve. The assumption of uniform wall thickness is confirmed by measuring the thickness variation. The effects of various process parameters including blank size, work-hardening exponent and frictional coefficient on the pressure curve are analyzed and discussed. It is thus shown that the proposed method of analysis in the present study can be effectively used for hydroforming of arbitrarily shaped boxes.

Assessing fault criticality using seismic monitoring and fluid pressure analysis

2020 ◽  
Author(s):  
Léa Perrochet ◽  
Giona Preisig ◽  
Benoît Valley
Keyword(s):  
Time Lag ◽  
Fluid Pressure ◽  
Back Analysis ◽  
Local Stress ◽  
Seismic Monitoring ◽  
Spring Discharge ◽  
Stress Regime ◽  
Groundwater Level Fluctuations ◽  
Area Of Interest ◽  
Discharge Rates

<p>The stability of a critically stressed fault depends on the surrounding stresses acting on it. Fluids, by reducing the effective normal stress, play a major role. It has been observed that in karstic regions, an increase in groundwater pressure following significant recharge (precipitations and/or seasonal snowmelt) can result in a fault re-activation, inducing microseismicity. This study combines the natural microseismicity and the groundwater level fluctuations observations to estimate the fault criticality. The research is carried out on two major strike-slip faults in the folded Jura in Switzerland – La Lance Fault and La Ferrière Fault – most likely critically stressed according to their position in the global stress-regime. Data acquisition mainly consists in hydrogeologic and seismic monitoring. The objectives are to have continuous discharge rates of the major karstic springs and to produce a seismic catalog for the area of interest. Combining both data sets will allow to determine relations between increasing spring discharge rates and low magnitude earthquakes and eventually to acquire a quantitative knowledge on what pressure change is affecting the fault’s stability. This knowledge will be used to develop a straighforward methodology to assess fault criticality.  In addition, the study of a possible time lag between aquifer response and fault activation, as well as back-analysis of seismic events can provide, respectively, important information about the deep-seated fluid circulation and the local stress-regime.</p>

3D numerical simulation of injection into a porous natural gas storage

2011 ◽  
Vol 51 (1) ◽  
pp. 653
Author(s):  
Amin Chamani ◽  
Vamegh Rasouli
Keyword(s):  
Natural Gas ◽  
Land Surface ◽  
Fluid Pressure ◽  
Fault Reactivation ◽  
Numerical Code ◽  
Displacement Fields ◽  
Stress Regime ◽  
Wellbore Instability ◽  
Increasing Demand ◽  
Rock Mechanical Properties

The increasing demand for the consumption of natural gas has attracted the interest to store natural gas in depleted reservoirs. Natural gas is injected into the depleted reservoir and then produced once needed to be supplied to the consumers through pipelines. Changes of reservoir fluid pressure due to injection/ depletion will result in the local changes of stress regime inside the reservoir as well as the surrounding rocks. These stress fluctuations will primarily lead to the deformations and changes of the loads exerted on the wellbore. This can potentially trigger hazardous events such as considerable land surface movements, wellbore instability and casing collapse, fault reactivation, and cap rock failure. Therefore a good knowledge of reservoir geomechanics is required when planning storage of natural gas in a depleted reservoir. In this paper the concept of effective stress and pore pressure will be reviewed. A 3D finite element (FE) numerical modelling technique is developed to investigate the changes in stresses and displacements either during the injection or the depletion in a complete isotropic elastic media. The numerical code is used to simulate the injection-induced stress and displacement fields at a field scale for a hypothetical model with an embedded porous formation. The effect of formation rock mechanical properties such as Young’s modulus is also investigated through a series of sensitivity analysis. The results are presented and interpreted and various conclusions are made.

Fault kinematic investigations along the Panchkula-Morni region, NW Himalaya, India

2020 ◽  
Author(s):  
Ajay Kumar ◽  
Soumyajit Mukherjee ◽  
Mohamedharoon A. Shaikh ◽  
Seema Singh
Keyword(s):  
Fault Plane ◽  
Regional Scale ◽  
Fault Slip ◽  
Fault System ◽  
Inversion Algorithm ◽  
Stress Regime ◽  
Kinematic Indicators ◽  
Kinematic Evolution ◽  
Slip Planes ◽  
Paleostress Inversion

<p>The Morni hills located in the north-western Himalaya in Panchkula district, Haryana has undergone poly-phase deformation owing to its complex tectonic history. In order to better understand the kinematic evolution of study area, detailed structural analyses of the fault system at regional-scale is carried out. We perform paleostress analyses on the collected fault-slip data to derive the paleostress tensors. The fault-slip data includes attitudes of fault planes and slickenside lineations, and the sense of slip along the fault plane determined by observing various kinematic indicators. The study area mainly exposes compacted, fine- to medium-grained calcareous sandstones belonging to the lower Siwalik formation in the Himalayan foreland basin. The exposed sandstones contain numerous striated slip planes of varying slip-sense. As the fault planes are intra-formational and exposed in uniform lithology, sense of slip cannot be determined through offset markers. In such cases, the sense of slip of the fault plane is determined solely by observing various slickenside kinematic indicators and fracture types developed on the faulted surface. The slickenside kinematic indicators e.g., calcite mineral steps were found useful in deciphering the sense of movement of each of the slip plane. The paleostress inversion of fault-slip data was carried out by applying the open source software T-Tecto studio X5 to obtain the reduced stress tensor. The Paleostress inversion algorithm called the Right Dihedral Method (RDM) is executed to estimate the principal stress axes orientations. Temporally, the slip planes may have reactivated multiple times preserving multiple slickenside orientations superimposing one another. Such fault-slip data are called heterogeneous and therefore, multiple stress states are deduced to explain the heterogeneous fault-slip data. The paleostress analysis results indicate stress regime index (R’) range 1.25–2.25 and 0.20–1.00 suggesting pure strike-slip to transpressive and pure extensive to transtensive stress regime respectively prevailing in the study area.</p>

Subsurface in situ stress magnitudes from oil-well drilling records: an example from the Venture area, offshore eastern Canada

1987 ◽  
Vol 24 (9) ◽  
pp. 1748-1759 ◽  
Author(s):  
W. B. Ervine ◽  
J. S. Bell
Keyword(s):  
Feed Rate ◽  
Fluid Pressure ◽  
Sedimentary Basins ◽  
In Situ Stress ◽  
Depth Interval ◽  
Principal Stresses ◽  
Eastern Canada ◽  
Stress Regime ◽  
Clastic Rocks

This report describes a method of obtaining information on in situ stress magnitudes at depth in sedimentary basins by using information gathered while drilling oil wells. If we assume that one of the principal stresses is vertical at a well site, principal stress magnitudes can be estimated in the following manner. Sv is equated with overburden load, which is obtained by integrating density log records. SHmin is equated with leak-off test pressures measured over short open-hole intervals and also from selected initial feed-rate pressures. SHmax is derived from the equation SHmax = 2P1 − P0, where P1 is the leak-off pressure or the initial feed-rate pressure, and P0 is the fluid pressure over a specified depth interval. This relationship is a simplified approximation of Hubbert and Willis' well-known equation Pb = T + 3SHmin − SHmax − P0, describing hydraulic fracturing around a borehole.Using this approach, stress magnitudes were estimated for 44 depth intervals in four wells drilled over the Venture structure on the Scotian Shelf, offshore eastern Canada. The information obtained between subsea depths of 815 and 5783 m provides a consistent record and points to a stress regime where SHmax > Sv > SHmin. At approximately 6000 m, Sv and SHmin may become equal. Inferred stress magnitudes in the upper 3000 m are comparable to those measured in clastic rocks in western Canada.

scholarly journals Correlation between tectonic stress regimes and methane seepage on the west-Svalbard margin

2018 ◽  
Author(s):  
Andreia Plaza-Faverola ◽  
Marie Keiding
Keyword(s):  
Fluid Pressure ◽  
Tectonic Stress ◽  
Temporal Variations ◽  
Passive Margin ◽  
Morphological Evidence ◽  
Glacial Cycles ◽  
The West ◽  
Stress Regime ◽  
Near Surface ◽  
Methane Seepage

Abstract. Methane seepage occurs across the west-Svalbard margin at water depths ranging from the upper shelf at  1000 m. The Vestnesa sedimentary ridge, located on oceanic crust between 1000–1700 m water depth, hosts a perennially stable gas hydrate system with evidence of both past and present-day seepage. On the ridge, an eastward transition from a zone with clear morphological evidence of past seepage to a zone of active present-day seepage coincides with a change in the faulting pattern of near-surface strata. We modelled the tectonic stress regime due to oblique spreading along the Molloy and Knipovich spreading ridges to investigate whether spatial and temporal variations in the regional stress field may explain patterns of seepage distribution. The model reveals a zone of tensile stress that extends northward from the Knipovich Ridge and encompasses a zone of active seepage and extensional faulting. A zone of past seepage is presently located in a strike-slip regime. Our modelling results suggest that seepage is promoted by opening of faults and fractures in a tensile regime. We develop a conceptual model to describe how seepage may be controlled by an interplay between tectonic stresses and pore fluid pressure within shallow gas reservoirs across the passive margin off west-Svalbard. Glacio-isostatic flexural stresses may have influenced fluid dynamics along the Vestnesa Ridge in the past, explaining the presence of dormant pockmarks outside the ridge segment that is under a tensile regime at present and reconciling formerly suggested models of seepage periodicity linked to glacial cycles.

Overburden characterization with formation pore pressure and anisotropic stress field estimation in the Athabasca Basin, Canada

2019 ◽  
Vol 7 (4) ◽  
pp. T761-T771
Author(s):  
Carmen C. Dumitrescu ◽  
Draga A. Talinga
Keyword(s):  
Pore Pressure ◽  
Elastic Stiffness ◽  
Seismic Inversion ◽  
Efficient Production ◽  
Oil Sand ◽  
Principal Stresses ◽  
Stress Regime ◽  
Athabasca Basin ◽  
Effective Principal ◽  
Formation Pore Pressure

One of the challenges encountered during the life cycle of an oil-sand thermal-production reservoir is the prediction of the formation pore pressure and in situ stress regime during the assessment phase of the reservoir development and, more importantly, during the development phase. We have investigated the state of formation pore pressure and stress in the overburden — represented by the Clearwater Formation, Grand Rapids Formation, and Colorado Group — of a preproduction oil-sands reservoir situated in the Athabasca Basin of Alberta, Canada. Our methodology integrates pressure data from piezometers, stress data from mini-frac (MF), dipole sonic logs, and elastic properties obtained from multicomponent 3D seismic inversion data. It combines the Terzaghi effective stresses with the Schoenberg and Sayers elastic stiffness matrix for horizontal transversely isotropic fractured materials. The total principal stresses (vertical, minimum, and maximum horizontal stresses) are expressed as functions of the normal fracture weakness (anisotropic correction factor), formation pore pressure, seismic data (Lamé constants), and the Biot-Willis coefficient. The effective principal stresses are estimated from the equivalent total principal stresses and the formation pore pressure multiplied by the Biot-Willis coefficient. On all three overburden intervals analysed, the relations between principal stresses indicate a normal stress regime. The estimated total minimum horizontal stress matches the MF values within 10%. The formation pore pressure, along with the 3D seismically derived estimates of the total and effective principal stresses, allows for better assessment of the caprock integrity and for operational savings based on a reduced number of MF tests. It can also be used for stress estimation within the formations hosting aquifers, which is so important for thermal production. Understanding the subsurface on the reservoir area is important for efficient production, but knowing the subsurface of the overburden is equally important for reducing potential issues due to production.

Vein geometry and hydrostatics during Yellowknife mineralisation

1978 ◽  
Vol 15 (10) ◽  
pp. 1653-1660 ◽  
Author(s):  
R. Kerrich ◽  
I. Allison
Keyword(s):  
Principal Stress ◽  
Shear Zone ◽  
Fluid Pressure ◽  
Shear Zones ◽  
Horizontal Stress ◽  
Maximum Principal Stress ◽  
Ambient Conditions ◽  
Stress Regime ◽  
Quartz Veins ◽  
Vertical Arrays

Three vein systems with distinct geometry and time relations are located within major ductile shear zones at Yellowknife. En échelon arrays of centimetre width quartz veins initiated at ~45° to the shear zone boundaries and normal to the schistosity during initial translation on the structures. These geometrical relations conform to the simple shear model of Ramsay and Graham. Orientation of the maximum principal stress was ~45° to the 70° dipping shear zone boundaries, implying that the horizontal stress in the crust was greater than the vertical stress.Gold-bearing quartz veins of metre dimensions are disposed parallel to the schistosity, cross cutting early veins. This geometry requires the stress regime to switch from the former orientation such that the maximum principal stress is parallel to the schistosity, and the effective stress normal to the schistosity is tensile. The change of stress orientation is attributed to transient high fluid pressure which generated hydraulic fracturing and correspondingly high values of permeability. Under these conditions the shear zones act as conduits for massive fluid discharge; quartz and gold were precipitated from solutions cooling along a temperature–pressure (TP) gradient. Crustal vertical stress was greater than horizontal stress.Late stage lenticular gold-bearing quartz veins of metre dimensions were emplaced as vertical arrays within the shear zones, oriented normal to schistosity. These tension fractures formed when the stress regime reverted to the ambient conditions for stage 1 veining during a second episode of displacement on the shear zones. Consideration of the kinetics of intergranular diffusion, with reference to the required transport distances of gold into a lode deposit, implies that long-range diffusive transport of gold into veins was not significant.

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