scholarly journals The coupling of dehydration and deformation results in localised fluid flow in the accretionary wedge – a novel study of calcite veins

2020 ◽  
Author(s):  
Ismay Vénice Akker ◽  
Christoph E. Schrank ◽  
Michael W.M. Jones ◽  
Cameron M. Kewish ◽  
Alfons Berger ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Fluid Transport ◽  
Mechanical Stability ◽  
Fluid Pressure ◽  
Ductile Deformation ◽  
Accretionary Wedge ◽  
Seismic Zone ◽  
Calcite Veins ◽  
Deformation Features ◽  
Long Time

<p>In plate-convergent settings, fluid-saturated sediments dehydrate during subduction. The sediments are subsequently accreted to the upper plate. Along their dehydration-deformation path, the initial unconsolidated soft marine sediments become thick, foliated, impermeable meta-sedimentary sequences. Fluid flow through such ‘non’-porous low-permeability rocks is concentrated in fracture networks, ranging from the mm- to the km-scale. We study the interplay between ductile and brittle deformation processes and fluid flow by investigating calcite veins in slates from the exhumed European Alpine accretionary wedge across scales (µm to km). These slates experienced peak metamorphic temperatures between 200°C and 330°C and represent the transition between the upper aseismic and seismic zone. With the use of Synchrotron X-ray Fluorescence Microscopy (SXFM), we investigate the slates by visualizing trace-element distributions. This technique shows that alternating cycles of slow pressure-dissolution processes and brittle fracturing persist over long time scales. At the micron-scale, pressure solution of the initial carbonate-rich slates is indicated by an enrichment of newly recrystallized phyllosilicates on cleavage planes and in pressure shadows. These ductile deformation features are mutually overprinted by calcite veins (aperture 10 µm), which are nicely visualized with Sr-SXFM maps. Increasing compaction and recrystallization in the slate-rich matrix leads to progressed dehydration resulting in an increased pore fluid pressure and subsequent hydrofracturing. The micron-sized fractures are immediately filled in with minerals, which are oversaturated at that time in the fluid, resulting in the formation of (i) micron-veinlets. Micron-veinlets collect (ii) into mm-cm sized veins, which themselves form (iii) vein arrays and (iv) mega-arrays, respectively at the 50-100 m and 300-400 m scale. This upscaling of fluid pathways indicates a localised fluid transport through the accretionary wedge, which has important implications for the understanding of the mechanical stability of the accretionary wedge and related seismic activity.</p>

scholarly journals Focused fluid seepage related to variations in accretionary wedge structure, Hikurangi margin, New Zealand

Geology ◽  
2019 ◽  
Vol 48 (1) ◽  
pp. 56-61 ◽  
Author(s):  
Sally J. Watson ◽  
Joshu J. Mountjoy ◽  
Philip M. Barnes ◽  
Gareth J. Crutchley ◽  
Geoffroy Lamarche ◽  
...  
Keyword(s):  
Fluid Flow ◽  
New Zealand ◽  
Fluid Pressure ◽  
Data Sets ◽  
Accretionary Wedge ◽  
Fault Mechanics ◽  
Spatial Coverage ◽  
Fluid Seepage ◽  
Pressure Regime ◽  
Subduction Setting

Abstract Hydrogeological processes influence the morphology, mechanical behavior, and evolution of subduction margins. Fluid supply, release, migration, and drainage control fluid pressure and collectively govern the stress state, which varies between accretionary and nonaccretionary systems. We compiled over a decade of published and unpublished acoustic data sets and seafloor observations to analyze the distribution of focused fluid expulsion along the Hikurangi margin, New Zealand. The spatial coverage and quality of our data are exceptional for subduction margins globally. We found that focused fluid seepage is widespread and varies south to north with changes in subduction setting, including: wedge morphology, convergence rate, seafloor roughness, and sediment thickness on the incoming Pacific plate. Overall, focused seepage manifests most commonly above the deforming backstop, is common on thrust ridges, and is largely absent from the frontal wedge despite ubiquitous hydrate occurrences. Focused seepage distribution may reflect spatial differences in shallow permeability architecture, while diffusive fluid flow and seepage at scales below detection limits are also likely. From the spatial coincidence of fluids with major thrust faults that disrupt gas hydrate stability, we surmise that focused seepage distribution may also reflect deeper drainage of the forearc, with implications for pore-pressure regime, fault mechanics, and critical wedge stability and morphology. Because a range of subduction styles is represented by 800 km of along-strike variability, our results may have implications for understanding subduction fluid flow and seepage globally.

scholarly journals Numerical modeling of porosity waves as a mechanism for rapid fluid transport in elastic porous media

2015 ◽  
Author(s):  
◽  
Ajit Joshi
Keyword(s):  
Porous Media ◽  
Fluid Transport ◽  
Fluid Pressure ◽  
Source Rocks ◽  
Lithostatic Pressure ◽  
Accretionary Wedge ◽  
The World ◽  
Porosity And Permeability ◽  
High Fluid ◽  
High Fluid Pressure

The rapid ascent of fluids through kilometer-scale thicknesses of low permeability sediments at rates much faster than predicted Darcy fluxes has been observed in numerous locations around the world. A consistently observed condition associated with this anomalously rapid fluid flow is high fluid pressure approaching lithostatic pressure. This high fluid pressure can be produced by a number of geologic processes, including the production of hydrocarbon fluids by maturation of organic matter, the production of water through dehydration reactions of hydrous minerals, compaction disequilibrium during the deposition and burial of sediments, and earthquakes. As fluid pressure increases in a deformable porous medium, the pore spaces in the medium expand, increasing porosity and permeability. This zone of increased fluid pressure, porosity, and permeability, termed a porosity wave, may travel much faster than fluids flowing at Darcy fluxes in the surroundings, provided that permeability is a sensitive function of fluid pressure or effective stress. In addition, because porosity waves have higher porosity than their surroundings, they can serve as a mechanism for enhance fluid transport. The main goal of the present study was to evaluate the formation and fluid transport capabilities of porosity waves in elastic rocks. The study was performed using a numerical solution to a mass conservation equation for fluids in porous media and Darcy's law. Results of the study show that rates of fluid pressure generation by sediment compaction disequilibrium and hydrocarbon formation in porous media saturated with dense and viscous fluids like oil or water can generally only form porosity waves at depths below ~4 km, and are unable to form porosity waves in porous media saturated with low density and viscosity fluids like methane. In order to form porosity waves in methane-saturated porous media, geologically instantaneous rates of fluid pressure generation are needed, which may be possible from earthquakes. Once formed, methane-saturated porosity waves may travel at speeds of ~10's of m per year for distances of 1-2 km under geological conditions similar to those of the Eugene Island hydrocarbon field in the Gulf of Mexico basin, one of the focus areas of the present study. However, porosity waves are unlikely to have played a major role in transporting methane to shallow reservoirs at Eugene Island. This is in part because Eugene Island appears to have been seismically quiescent throughout its geological history and because most of the reservoirs are separated by more than two kilometers from the hydrocarbon source rocks. In the Nankai accretionary wedge, another focus area of the present study, results show that porosity waves formed at a depth of ~2 km can ascend along the decollement at the minimum 1's of km per day velocities needed to cause aseismic slip, provided that fluid pressures in porosity source region either exceed lithostatic pressure or are slightly below lithostatic pressure but other hydrogeologic parameters are near the limits of their geologically reasonable ranges. Though the present study was focused on two specific field sites, the results have implications for rapid fluid transport in other geologically similar environments in other locations around the world.

What slates can tell us about strain localisation and fluid flow in accretionary wedges: a microstructural analysis of deforming foreland basin sediments

2021 ◽  
Author(s):  
Ismay Vénice Akker ◽  
Christoph E. Schrank ◽  
Michael W.M. Jones ◽  
Cameron M. Kewish ◽  
Alfons Berger ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Microstructural Evolution ◽  
Microstructural Analysis ◽  
Foreland Basin ◽  
Intensity Increase ◽  
Accretionary Wedge ◽  
European Alps ◽  
Strain Localisation ◽  
Calcite Veins ◽  
Metamorphic Gradient

<p>During the accretion of foreland basin sediments into an accretionary or orogenic wedge, the sediments dehydrate and deform. Both dehydration and deformation intensity increase from the outer to the inner wedge and are a function of metamorphic processes and strain. Here, we study the microstructural evolution of slates from the exhumed Flysch units making up a paleo accretionary wedge in the European Alps. With classic SEM imaging and synchrotron X-ray fluorescence microscopy, we document the evolution of slate fabrics and calcite veins and aim at understanding the role of the evolving slate fabrics for strain localisation and fluid flow at the micro-scale.</p><p>The investigated slate samples are from a NW-SE transect covering the outer and inner wedge from 200 to 330 °C. The metamorphic gradient directly correlates with an increasing background strain gradient. With the use of the autocorrelation function, we quantify the evolution of the microfabrics along the metamorphic gradient and document deformation stages from a weakly deformed slate without foliation in the outer wedge to a strongly deformed slate with a dense spaced foliation in the inner wedge. The foliation mainly forms by dissolution-precipitation processes, which increase with increasing metamorphic gradient.</p><p>The slate matrix reveals two main sets of veins. The first vein set includes micron-scaled calcite veinlets with very high spatial densities. The second vein set includes layer parallel calcite veins that form vein-arrays (couple of metres thick) in the inner wedge. Both vein sets could have moved large amounts of fluids through the wedge. The spatial distribution of the micron-veinlets reveals that fluids were moved pervasively. In the case of the layer parallel veins forming vein-arrays, fluid flow was localized, supported by the dense spaced foliation formed in the slate matrix in the inner wedge. This way we now establish a direct link between the microstructural evolution in the slate matrix and associated dehydration, where fluids become increasingly channelled towards the inner wedge. Knowing that the vein-arrays have length dimensions in the order or hundreds of metres to kilometres, these structures are important for larger-scale fluid flow, the feeding of fluids into megathrusts and for related seismic activity in the wedge.</p>

scholarly journals Fluid pressure evolution during the earthquake cycle controlled by fluid flow and pressure solution crack sealing

2002 ◽  
Vol 54 (11) ◽  
pp. 1139-1146 ◽  
Author(s):  
Jean-Pierre Gratier ◽  
Pascal Favreau ◽  
François Renard ◽  
Eric Pili
Keyword(s):  
Fluid Flow ◽  
Fluid Pressure ◽  
Pressure Solution ◽  
Earthquake Cycle ◽  
Crack Sealing ◽  
Pressure Evolution

Dynamics of Interstitial Fluid Pressure in Extracellular Matrix Hydrogels in Microfluidic Devices

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Joe Tien ◽  
Le Li ◽  
Ozgur Ozsun ◽  
Kamil L. Ekinci
Keyword(s):  
Extracellular Matrix ◽  
Pressure Distribution ◽  
Interstitial Fluid ◽  
Scaling Laws ◽  
Fluid Pressure ◽  
Interstitial Fluid Pressure ◽  
External Loading ◽  
Interstitial Pressure ◽  
Time Resolved ◽  
Long Time

In order to understand how interstitial fluid pressure and flow affect cell behavior, many studies use microfluidic approaches to apply externally controlled pressures to the boundary of a cell-containing gel. It is generally assumed that the resulting interstitial pressure distribution quickly reaches a steady-state, but this assumption has not been rigorously tested. Here, we demonstrate experimentally and computationally that the interstitial fluid pressure within an extracellular matrix gel in a microfluidic device can, in some cases, react with a long time delay to external loading. Remarkably, the source of this delay is the slight (∼100 nm in the cases examined here) distension of the walls of the device under pressure. Finite-element models show that the dynamics of interstitial pressure can be described as an instantaneous jump, followed by axial and transverse diffusion, until the steady pressure distribution is reached. The dynamics follow scaling laws that enable estimation of a gel's poroelastic constants from time-resolved measurements of interstitial fluid pressure.

A Unique Approach in Modelling Flow in Tight Oil Unconventional Reservoirs With Viscous, Inertial and Diffusion Forces Contributions

2021 ◽  
Author(s):  
Mohammed Aldhuhoori ◽  
Hadi Belhaj ◽  
Bisweswar Ghosh ◽  
Ryan Fernandes ◽  
Hamda Alkuwaiti ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Fluid Transport ◽  
Synthetic Data ◽  
Diffusion Term ◽  
Flowing Fluid ◽  
New Model ◽  
Forchheimer’S Equation ◽  
Low Viscosity ◽  
Flow Parameters ◽  
Unique Approach

Abstract A model for single-phase fluid flow in tight UCRs was previously produced by modifying the flow Forchheimer’s equation. The new modification addresses the fluid transport phenomena into three scales incorporating a diffusion term. In this study, a new liner model, numerically solved, has been developed and deployed for a gas huff and puff project. The new model has been numerically validated and verified using synthetic data and huff and puff case study. Ideally, the new model suits fluid flow in tight UCRs. The modified Forchheimer’s model presented is solved using the MATLAB numerical method for linear multiphase flow. For the huff & puff case, very simple profiles and flow dynamics of the main flow parameters have been established and a thorough parametric analysis and verifications were performed. It has been observed that the diffusion system becomes more prominent in regulating flow velocity with low permeability of the formation rock and low viscosity of the flowing fluid. The findings indicate a behavioral alignment with a previous hypothesis that matches actual reservoir behavior.

Time Constraints on Seepage Through Fractured Regions on the Vestnesa Ridge off the W-Svalbard Coast

2021 ◽  
Author(s):  
Hariharan Ramachandran ◽  
Andreia Plaza-Faverola ◽  
Hugh Daigle ◽  
Stefan Buenz
Keyword(s):  
Fluid Flow ◽  
Effective Stress ◽  
Gas Hydrate ◽  
Fluid Pressure ◽  
Fracture Network ◽  
The Arctic ◽  
Stability Zone ◽  
Methane Seepage ◽  
Carbonate Formation ◽  
Hydrate Stability

<p>Evidences of subsurface fluid flow-driven fractures (from seismic interpretation) are quite common at Vestnesa Ridge (around 79ºN in the Arctic Ocean), W-Svalbard margin. Ultimately, the fractured systems have led to the formation of pockmarks on the seafloor. At present day, the eastern segment of the ridge has active pockmarks with continuous methane seep observations in sonar data. The pockmarks in the western segment are considered inactive or to seep at a rate that is harder to identify. The ridge is at ~1200m water depth with the base of the gas hydrate stability zone (GHSZ) at ~200m below the seafloor. Considerable free gas zone is present below the hydrates. Besides the obvious concern of amount and rates of historic methane seeping into the ocean biosphere and its associated effects, significant gaps exist in the ability to model the processes of flow of methane through this faulted and fractured region. Our aim is to highlight the interactions between physical flow, geomechanics and geological control processes that govern the rates and timing of methane seepage.</p><p>For this purpose, we performed numerical fluid flow simulations. We integrate fundamental mass and component conservation equations with a phase equilibrium approach accounting for hydrate phase boundary effects to simulate the transport of gas from the base of the GHSZ through rock matrix and interconnected fractures until the seafloor. The relation between effective stress and fluid pressure is considered and fractures are activated once the effective stress exceeds the tensile limit. We use field data (seismic, oedometer tests on calypso cores, pore fluid pressure and temperature) to constrain the range of validity of various flow and geomechanical parameters in the simulation (such as vertical stress, porosity, permeability, saturations).</p><p>Preliminary results indicate fluid overpressure greater than 1.5 MPa is required to initiate fractures at the base of the gas hydrate stability zone for the investigated system. Focused fluid flow occurs through the narrow fracture networks and the gas reaches the seafloor within 1 day. The surrounding regions near the fracture network exhibit slower seepage towards the seafloor, but over a wider area. Advective flux through the less fractured surrounding regions, reaches the seafloor within 15 years and a diffusive flux reaches within 1200 years. These times are controlled by the permeability of the sediments and are retarded further due to considerable hydrate/carbonate formation during vertical migration. Next course of action includes constraining the methane availability at the base of the GHSZ and estimating its impact on seepage behavior.</p>

scholarly journals Development and analytical validation of a finite element model of fluid transport through osteochondral tissue

2020 ◽  
Author(s):  
Brady D. Hislop ◽  
Chelsea M. Heveran ◽  
Ronald K. June
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Fluid Transport ◽  
Fluid Pressure ◽  
Viscoelastic Model ◽  
Element Model ◽  
Pressure Gradients ◽  
Superficial Zone ◽  
Bone Interface ◽  
Osteochondral Tissue

AbstractFluid transport between cartilage and bone is critical to joint health. The objective of this study was to develop and analytically validate a finite element model of osteochondral tissue capable of modeling cartilage-bone fluid transport. A biphasic viscoelastic model using an ellipsoidal fiber distribution was created with three distinct layers of cartilage (superficial zone, middle zone, and deep zone) along with a layer of subchondral bone. For stress-relaxation in unconfined compression, our results for compressive stress, radial stress, effective fluid pressure, and elastic recoil were compared with established biphasic analytical solutions. Our model also shows the development of fluid pressure gradients at the cartilage-bone interface during loading. Fluid pressure gradients developed at the cartilage-bone interface with consistently higher pressures in cartilage following initial loading to 10% strain, followed by convergence towards equal pressures in cartilage and bone during the 400s relaxation period. These results provide additional evidence that fluid is transported between cartilage and bone during loading and improves upon estimates of the magnitude of this effect through incorporating a realistic distribution and estimate of the collagen ultrastructure. Understanding fluid transport between cartilage and bone may be key to new insights about the mechanical and biological environment of both tissues in health and disease.

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