scholarly journals Influence of fluid pressure changes on the reactivation potential of pre-existing fractures: a case study in the Archaean metavolcanics of the Chitradurga region, India

2021 ◽  
pp. 1-15
Author(s):  
Sreyashi Bhowmick ◽  
Tridib Kumar Mondal
Keyword(s):  
Deformation Behaviour ◽  
Fluid Pressure ◽  
Pressure Variation ◽  
Magnetic Fabric ◽  
Opening Angle ◽  
Fracture Planes ◽  
Fracture Reactivation ◽  
Multiple Cycles ◽  
Pressure Changes

Abstract The metavolcanics of Chitradurga region host numerous shallow crustal veins and fractures and faults of multiple orientations. Several high and low Pf cycles have been recorded in the region, leading to the reactivation of most of the pre-existing fractures for high Pf and selective reactivation of some well-oriented fractures under low Pf conditions. The pre-existing anisotropy (magnetic fabric) in the metavolcanics acted as the most prominent planar fabric for fracture propagation and vein emplacement under both conditions, thereby attaining maximum vein thickness. In this study, we emphasize the reactivation propensity of these pre-existing fracture planes under conditions of fluid pressure variation, related to the high and low Pf cycles. Multiple cycles of fluid-induced fracture reactivation make it difficult to quantify the maximum/minimum fluid pressure magnitudes. However, in this study we use the most appropriate fluid pressure magnitudes mathematically feasible for a shallow crustal depth of ∼2.4 km. We determine the changes in the reactivation potential with states of stress for the respective fracture orientations under both high and low Pf conditions. Dependence of fluid pressure variation on the opening angle of the fractures is also monitored. Finally, we comment on the failure mode and deformation behaviour of the fractures within the prevailing stress field inducing volumetric changes at the time of deformation. We find that deformation behaviour is directly related to the dip of the fracture planes.

Fluid Pressure Variation in a Sedimentary Geothermal Reservoir in the North German Basin: Case Study Groß Schönebeck

2006 ◽  
Vol 163 (10) ◽  
pp. 2141-2152 ◽  
Author(s):  
Ernst Huenges ◽  
Ute Trautwein ◽  
Björn Legarth ◽  
Günter Zimmermann
Keyword(s):  
Fluid Pressure ◽  
Pressure Variation ◽  
Geothermal Reservoir ◽  
North German Basin ◽  
The North ◽  
German Basin

Pressure variation in a fluid at rest (hydrostatics)

2018 ◽  
Author(s):  
Marcel Escudier
Keyword(s):  
Equation Of State ◽  
Static Pressure ◽  
Applied Pressure ◽  
Pressure Variation ◽  
Constant Density ◽  
Fluid Temperature ◽  
Earth’S Atmosphere ◽  
Hydrostatic Equation ◽  
Depth Increase ◽  
Pressure Changes

The three fundamental principles for the variation of static pressure p throughout a body of fluid at rest are (a) the pressure at a point is the same in all directions (Pascal’s law), (b) the pressure is the same at all points on the same horizontal level, and (c) the pressure increases with depth z according to the hydrostatic equation. dp/dz= ρ‎g For a fluid with constant density ρ‎, the increase in pressure over a depth increase h is ρ‎gh, a result which can be used to analyse the response of simple barometers and manometers to applied pressure changes and differences. In situations where very large changes in pressure occur an equation of state may be required to relate pressure and density together with an assumption about the fluid temperature. The hydrostatic equation is still valid but more difficult to integrate, as illustrated by consideration of the earth’s atmosphere.

The role of geomechanical modeling in the measurement and understanding of geophysical data collected during carbon sequestration

2021 ◽  
Vol 40 (6) ◽  
pp. 413-417
Author(s):  
Chunfang Meng ◽  
Michael Fehler
Keyword(s):  
Pore Pressure ◽  
Fault Location ◽  
Mechanical Response ◽  
Fluid Pressure ◽  
Geophysical Data ◽  
Fluid Injection ◽  
Coupled Flow ◽  
Cap Rock ◽  
Stress And Deformation ◽  
Pressure Changes

As fluids are injected into a reservoir, the pore fluid pressure changes in space and time. These changes induce a mechanical response to the reservoir fractures, which in turn induces changes in stress and deformation to the surrounding rock. The changes in stress and associated deformation comprise the geomechanical response of the reservoir to the injection. This response can result in slip along faults and potentially the loss of fluid containment within a reservoir as a result of cap-rock failure. It is important to recognize that the slip along faults does not occur only due to the changes in pore pressure at the fault location; it can also be a response to poroelastic changes in stress located away from the region where pore pressure itself changes. Our goal here is to briefly describe some of the concepts of geomechanics and the coupled flow-geomechanical response of the reservoir to fluid injection. We will illustrate some of the concepts with modeling examples that help build our intuition for understanding and predicting possible responses of reservoirs to injection. It is essential to understand and apply these concepts to properly use geomechanical modeling to design geophysical acquisition geometries and to properly interpret the geophysical data acquired during fluid injection.

scholarly journals Control of pre-existing fabric in fracture formation, reactivation and vein emplacement under variable fluid pressure conditions: An example from Archean Greenstone belt, India

2020 ◽  
Author(s):  
Sreyashi Bhowmick ◽  
Tridib Kumar Mondal
Keyword(s):  
Pressure Ratio ◽  
Fluid Pressure ◽  
Tectonic Stress ◽  
Fault Slip ◽  
Magnetic Fabric ◽  
Pressure Condition ◽  
Crustal Fluid ◽  
Wide Range ◽  
Riedel Shear ◽  
Archean Greenstone Belt

Abstract. Most of the upper crustal fluid flows are strongly influenced by the pre-existing fractures/foliations in the rocks under a certain state of tectonic stress and fluid pressure condition. In the present study, we analyze a wide range of crosscutting fractures that are filled with quartz veins of variable orientations and thicknesses, from the gold bearing massive metabasalts (supracrustal) of the Chitradurga Schist Belt adjacent to the Chitradurga Shear Zone (CSZ), western Dharwar craton, south India. The study involves the following steps: 1) analyzing the internal magnetic fabric using anisotropy of magnetic susceptibility (AMS) studies, and strength of the host metabasalts, 2) quantifying the fluid pressure condition through lower hemisphere equal area projection of pole to veins by determining the driving pressure ratio (R'), stress ratio (ϕ), and susceptibility to fracturing, and 3) deciphering the paleostress condition using fault slip analysis. We interpret that the NNW-SSE to NW-SE (mean 337°/69° NE) oriented magnetic fabric in the rocks of the region developed during regional D1/D2 deformation on account of NE-SW shortening. However, D3 deformation manifested by NW-SE to E-W shortening led to the sinistral movement along CSZ. As a consequence of this sinistral shearing, fractures with prominent orientations formed riedel shear components, with CSZ as the shear boundary. Subsequently, all the pre-existing fabrics along with the riedel shear components were reactivated and vein emplacement took place through episodic fluid pressure fluctuation from high to low Pf at shallow depth (~ 2.4 km). However, NNW-SSE orientations were susceptible for reactivation under both high and low Pf conditions leading to a much greater thickness along the same. The deduced paleostress from fault-slip analysis, along with the kinematics of the fractures and veins are in good agreement with the previously revealed regional tectonics. Thus, integrating multiple domains of studies, help in the logical interpretation of fluid flow condition and vein emplacement mechanism in the study area that has not been ventured before.

Osmoregulation and interstitial fluid pressure changes in humans during water immersion

1981 ◽  
Vol 51 (3) ◽  
pp. 686-692 ◽  
Author(s):  
S. S. Khosla ◽  
A. B. DuBois
Keyword(s):  
Interstitial Fluid ◽  
Water Immersion ◽  
Plasma Concentrations ◽  
Fluid Pressure ◽  
Interstitial Fluid Pressure ◽  
Sodium Potassium ◽  
Maximum Decrease ◽  
Blood And Urine Samples ◽  
Pressure Changes ◽  
Male Subjects

The aim of the present study was to determine the magnitude and direction of the shift of body fluids during water immersion of humans to the neck. Five healthy male subjects were studied lying in air for 1.5 h, sitting in 34 degrees C water to the neck for 1 h, and again lying in air for 1.5 h in two sets of experiments. For the first set, vasopressin (0.75 IU, sc) was injected before immersion. Blood and urine samples were drawn every 30 min in air and every 20 min in water. Urinary sodium, potassium, and osmolal clearances were significantly increased during immersion. When the mean maximum change during immersion was calculated for five subjects hematocrit fell by 1.1 U, plasma concentrations of sodium by 3.9 meq/l, chloride by 3.5 meq/l, potassium by 0.2 meq/l, osmolality by 7.9 mosmol/kg H2O, and proteins by 0.25 g/100 ml, whereas total plasma CO2 content increased by 1.33 mmol/l, threonine by 11.6%, proline by 9.0%, methionine by 14.0%, and alanine by 29%. Plasma volume increased 6.1%, and red blood cell volume calculated from hematocrit and hemoglobin increased 3.5%. In the second set of immersion experiments, without vasopressin injection, interstitial fluid pressures were measured with a cotton wick in PE-50 tubing inserted subcutaneously. A mean interstitial fluid pressure of -0.5 cmH2O was observed when the subjects were lying in air. Interstitial fluid pressure had started to decrease by 20 min of immersion, with a maximum decrease during immersion averaging 2.10 cmH2O. We conclude that hyposmotic fluid is mobilized into the blood from interstitial and other extravascular spaces during immersion.

scholarly journals CASE STUDY EXEMPLAR OF DETECTING SEVERE DIASTOLIC DYSFUNCTION USING BALLISTOCARDIOGRAM

2019 ◽  
Vol 3 (Supplement_1) ◽  
pp. S88-S89
Author(s):  
Laurel A Despins ◽  
Giovanna Guidoboni ◽  
Marjorie Skubic ◽  
Lorenzo Sala ◽  
Moein Enayati ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Diastolic Function ◽  
Hospital Readmissions ◽  
Clinical Problem ◽  
Physiological Model ◽  
Function Data ◽  
Great Vessels ◽  
New Diagnosis ◽  
Pressure Changes

Abstract The specific aim of this case study was to describe how monitoring ballistocardiogram (BCG) waveforms can detect early heart failure (HF) changes. HF significantly impairs quality of life and is the principal cause for hospital readmissions in older adults. HF prevalence in American adults aged 65 years and older is expected to increase over 70% by 2030. Detecting worsening HF is challenging. Invasive arterial waveforms display blood pressure changes with each heartbeat; BCG waveforms display repetitive body motions resulting from ejection of blood into the great vessels. BCG waveforms change as cardiac function changes. Currently, BCG signals can be captured non-invasively using sensors placed under a bed mattress and provide heart and respiratory rates. We have developed a new way to analyze the BCG waveform using an innovative closed-loop physiological model of the cardiovascular system. The subject, a 94-year old female with hypertension, presented to her physician with symptoms associated with a new diagnosis of acute mixed congestive HF. Mean heart and respiratory rate trends obtained from her bed sensor in the prior two months did not indicate HF. We simulated cardiac cycles using normal cardiac function data, mildly impaired diastolic function data, and the subject’s echocardiography data. The results demonstrated BCG waveform changes that correlated with decreasing cardiac output related to worsening diastolic function. New methods for clinically interpreting BCG waveforms present a significant opportunity for improving early HF detection and improving outcomes. Working on a clinical problem from an engineering perspective merges two disciplines, creating a new methodology.

Electrode design and insertional depth-dependent intra-cochlear pressure changes: a model experiment

2017 ◽  
Vol 132 (3) ◽  
pp. 224-229 ◽  
Author(s):  
P Mittmann ◽  
A Ernst ◽  
I Todt
Keyword(s):  
Cochlear Implant ◽  
Fluid Pressure ◽  
Electrode Array ◽  
Lateral Wall ◽  
Peak Frequency ◽  
Peak Amplitude ◽  
Residual Hearing ◽  
Electrode Arrays ◽  
Pressure Peak ◽  
Pressure Changes

AbstractBackground:Preservation of residual hearing is one of the major goals in modern cochlear implant surgery. Intra-cochlear fluid pressure changes influence residual hearing, and should be kept low before, during and after cochlear implant insertion.Methods:Experiments were performed in an artificial cochlear model. A pressure sensor was inserted in the apical part. Five insertions were performed on two electrode arrays. Each insertion was divided into three parts, and statistically evaluated in terms of pressure peak frequency and pressure peak amplitude.Results:The peak frequency over each third part of the electrode increased in both electrode arrays. A slight increase was seen in peak amplitude in the lateral wall electrode array, but not in the midscalar electrode array. Significant differences were found in the first third of both electrode arrays.Conclusion:The midscalar and lateral wall electrode arrays have different intra-cochlear fluid pressure changes associated with intra-cochlear placement, electrode characteristics and insertion.

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