First-Time Insights into Hydraulic Fracturing of Unconsolidated Sands from Novel Laboratory Experiments with in-situ CT-Scanning

2021 ◽  
Author(s):  
Karin de Borst ◽  
Chee Phuat Tan ◽  
M. Faizzudin Mat Piah ◽  
Jeroen Groenenboom
Keyword(s):  
Large Scale ◽  
Shear Failure ◽  
Ct Scanning ◽  
Core Material ◽  
Cavity Formation ◽  
Initiation Mechanism ◽  
Unconsolidated Sands ◽  
Sand Control ◽  
First Time

Abstract Waterflooding in unconsolidated sands has been observed to frequently result in injectivity decline of injectors when operated under ‘fractured’ conditions, resulting in reduction of waterflooding value creation and potential premature injector failure. Optimization of injector design and operation is currently limited by an insufficient understanding of the mechanics of ‘fracture’ and its associated mechanisms in unconsolidated sands, and the lack of adequate quantitative tools to predict injection performance. Utilizing in-situ CT scanning during large-scale laboratory injection experiments delivered novel insights into generation, closure and re-opening of ‘fractures’ in sand packs built from synthetic sands and highly unconsolidated downhole core material. Cavity formation was identified as main ‘fracturing’ mechanism. The cavities opened at injection pressures exceeding the confining stress and subsequently enlarged against a very low cohesive strength for the downhole core sands. This suggests material fluidization rather than shear failure as the immediate cavity initiation mechanism. Injectivity was found to be controlled by the interplay of fines transportation away from the injection region, resulting in injectivity increase, and the permanent compaction of the sand around the cavity, resulting in injectivity decrease. These first-time insights challenge the current understanding of matrix vs ‘fractured’ injection in unconsolidated sand reservoirs and highlight the role of sand fluidization and cavity formation. Furthermore, the injectivity behaviour is dependent on the combined effects of the sand material, the presence of fines, and the injection flow regime. The knowledge of the sand destabilization and mobilization processes enable design and operation optimizationof water injectors with implications on sand control strategies and remediation measures.

scholarly journals Spatial scales of temperature and salinity variability estimated from Argo observations

2015 ◽  
Vol 12 (4) ◽  
pp. 1793-1814
Author(s):  
F. Ninove ◽  
P. Y. Le Traon ◽  
E. Remy ◽  
S. Guinehut
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Deep Ocean ◽  
General Tendency ◽  
Zero Crossing ◽  
Tropical Regions ◽  
Covariance Functions ◽  
Salinity Variability ◽  
First Time

Abstract. Argo observations from 2005 to 2013 are used to characterize spatial scales temperature and salinity variations from the surface down to 1500 m. Simulations are first performed to analyze the sensitivity of results to Argo sampling; they show that several years of Argo observations are required to estimate the spatial scales of ocean variability over 20° × 20° boxes. Spatial scales are then computed over several large scale areas. Zonal and meridional spatial scales (Lx and Ly which are also zero crossing of covariance functions) vary as expected with latitudes. Scales are of about 100 km at high latitudes and more of 700 km in the Indian and Pacific equatorial/tropical regions. Zonal and meridional scales are similar: except in these tropical/equatorial regions where zonal scales are much larger (by a factor of 2 to 3) than meridional scales. Spatial scales are the largest close to the surface and have a general tendency for temperature to increase in deeper layers. There are significant differences between temperature and salinity scales, in particular, in the deep ocean. Results are consistent with previous studies based on sparse in-situ observations or satellite altimetry. They provide, however, for the first time a global description of temperature and salinity scales of variability and a characterization of their variations according to depths.

Online in situ prediction of 3-D flame evolution from its history 2-D projections via deep learning

2019 ◽  
Vol 875 ◽  
Author(s):  
Jianqing Huang ◽  
Hecong Liu ◽  
Weiwei Cai
Keyword(s):  
Deep Learning ◽  
Large Scale ◽  
Proof Of Concept ◽  
Time Resolved ◽  
Computational Costs ◽  
Rapid Prediction ◽  
Computational Fluid Dynamics Cfd ◽  
In Situ Prediction ◽  
First Time

Online in situ prediction of 3-D flame evolution has been long desired and is considered to be the Holy Grail for the combustion community. Recent advances in computational power have facilitated the development of computational fluid dynamics (CFD), which can be used to predict flame behaviours. However, the most advanced CFD techniques are still incapable of realizing online in situ prediction of practical flames due to the enormous computational costs involved. In this work, we aim to combine the state-of-the-art experimental technique (that is, time-resolved volumetric tomography) with deep learning algorithms for rapid prediction of 3-D flame evolution. Proof-of-concept experiments conducted suggest that the evolution of both a laminar diffusion flame and a typical non-premixed turbulent swirl-stabilized flame can be predicted faithfully in a time scale on the order of milliseconds, which can be further reduced by simply using a few more GPUs. We believe this is the first time that online in situ prediction of 3-D flame evolution has become feasible, and we expect this method to be extremely useful, as for most application scenarios the online in situ prediction of even the large-scale flame features are already useful for an effective flame control.

scholarly journals Magnetic reconnection driven by filament eruption in the 7 June 2011 event

2013 ◽  
Vol 8 (S300) ◽  
pp. 502-503
Author(s):  
L. van Driel-Gesztelyi ◽  
D. Baker ◽  
T. Török ◽  
E. Pariat ◽  
L. M. Green ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Filament Eruption ◽  
Mhd Simulations ◽  
Reconnection Region ◽  
Solar Eruptions ◽  
Magnetic Modelling ◽  
First Time

AbstractDuring an unusually massive filament eruption on 7 June 2011, SDO/AIA imaged for the first time significant EUV emission around a magnetic reconnection region in the solar corona. The reconnection occurred between magnetic fields of the laterally expanding CME and a neighbouring active region. A pre-existing quasi-separatrix layer was activated in the process. This scenario is supported by data-constrained numerical simulations of the eruption. Observations show that dense cool filament plasma was re-directed and heated in situ, producing coronal-temperature emission around the reconnection region. These results provide the first direct observational evidence, supported by MHD simulations and magnetic modelling, that a large-scale re-configuration of the coronal magnetic field takes place during solar eruptions via the process of magnetic reconnection.

scholarly journals Spatial scales of temperature and salinity variability estimated from Argo observations

Ocean Science ◽  
2016 ◽  
Vol 12 (1) ◽  
pp. 1-7 ◽  
Author(s):  
F. Ninove ◽  
P.-Y. Le Traon ◽  
E. Remy ◽  
S. Guinehut
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Deep Ocean ◽  
General Tendency ◽  
Zero Crossing ◽  
Tropical Regions ◽  
Covariance Functions ◽  
Salinity Variability ◽  
First Time

Abstract. Argo observations from 2005 to 2013 are used to characterize spatial scales of temperature and salinity variations from the surface down to 1300 m. Simulations are first performed to analyze the sensitivity of results to Argo sampling; they show that several years of Argo observations are required to estimate spatial scales of ocean variability over 20°  ×  20° boxes. Spatial scales are then computed over several large-scale areas. Zonal and meridional spatial scales (Lx and Ly which are zero crossing of covariance functions) vary as expected with latitudes. Scales are of about 100 km at high latitudes and more of 700 km in the Indian and Pacific equatorial–tropical regions. Zonal and meridional scales are similar except in tropical–equatorial regions where zonal scales are much larger (by a factor of 2 to 3) than meridional scales. Spatial scales are the largest close to the surface and have a general tendency for temperature to increase in deeper layers. There are significant differences between temperature and salinity scales, in particular, in the deep ocean. Results are consistent with previous studies based on sparse in situ observations or satellite altimetry. They provide, however, for the first time a global description of temperature and salinity scales of variability and a characterization of their variations according to depths.

High-Resolution Dynamic Analysis of the Phase Transformation in Ge2Sb2Te5 Alloy

2007 ◽  
Vol 26-28 ◽  
pp. 1199-1202
Author(s):  
Se Ahn Song ◽  
Wei Zhang ◽  
Hong Sik Jeong ◽  
Jin Gyu Kim ◽  
Youn Joong Kim
Keyword(s):  
Phase Transformation ◽  
Crystal Growth ◽  
High Resolution ◽  
Large Scale ◽  
Voltage Electron ◽  
Transmission Electron ◽  
In Situ Heating ◽  
First Time ◽  
Crystal Growth Behavior

Phase transformation and crystal growth behavior of Ge2Sb2Te5 were investigated systematically by means of in situ heating (from room temperature to 500 oC) of amorphous Ge2Sb2Te5 alloy in a high voltage electron microscope with real-time monitoring. Large-scale crystallization occurred to amorphous Ge2Sb2Te5 around 200 oC. Large crystal growth developed on heating from 200 oC to 400 oC, and single crystalline grains grew up to 150 nm. Eventually the onset of partial melting of thin Ge2Sb2Te5 foil was at 500 oC and liquid Ge2Sb2Te5 was observed for the first time by high-resolution transmission electron microscopy. Hexagonal Ge2Sb2Te5 phase remains after a subsequent cooling.

scholarly journals An Analytical Framework for Stress Shadow Analysis During Hydraulic Fracturing – Applied to the Bakken Formation, Saskatchewan, Canada

2021 ◽  
Author(s):  
Mostafa Gorjian ◽  
Sepidehalsadat Hendi ◽  
Christopher D. Hawkes
Keyword(s):  
Hydraulic Fracturing ◽  
Large Scale ◽  
Shear Failure ◽  
Microseismic Monitoring ◽  
Natural Fracture ◽  
Hydraulic Fractures ◽  
Natural Fractures ◽  
Bakken Formation ◽  
Stress Shadow

Abstract. This paper presents selected results of a broader research project pertaining to the hydraulic fracturing of oil reservoirs hosted in the siltstones and fine grained sandstones of the Bakken Formation in southeast Saskatchewan, Canada. The Bakken Formation contains significant volumes of hydrocarbon, but large-scale hydraulic fracturing is required to achieve economic production rates. The performance of hydraulic fractures is strongly dependent on fracture attributes such as length and width, which in turn are dependent on in-situ stresses. This paper reviews methods for estimating changes to the in-situ stress field (stress shadow) resulting from mechanical effects (fracture opening), poro-elastic effects, and thermo-elastic effects associated with fluid injection for hydraulic fracturing. The application of this method is illustrated for a multi-stage hydraulic fracturing operation, to predict principal horizontal stress magnitudes and orientations at each stage. A methodology is also presented for using stress shadow models to assess the potential for inducing shear failure on natural fractures. The results obtained in this work suggest that thermo and poro-elastic stresses are negligible for hydraulic fracturing in the Bakken Formation of southeast Saskatchewan, hence a mechanical stress shadow formulation is used for analyzing multistage hydraulic fracture treatments. This formulation (and a simplified version of the formulation) predicts an increase in instantaneous shut-in pressure (ISIP) that is consistent with field observations (i.e., ISIP increasing from roughly 21.6 MPa to values slightly greater than 26 MPa) for a 30-stage fracture treatment. The size of predicted zones of shear failure on natural fractures are comparable with the event clouds observed in microseismic monitoring when assumed values of 115°/65° are used for natural fracture strike/dip; however, more data on natural fracture attributes and more microseismic monitoring data for the area are required before rigorous assessment of the model is possible.

scholarly journals Optical Spectral Tools for Diagnosing Water Media Quality: A Case Study on the Angara/Yenisey River System in the Siberian Region

Land ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 342
Author(s):  
Costas A. Varotsos ◽  
Vladimir F. Krapivin ◽  
Ferdenant A. Mkrtchyan ◽  
Yong Xue
Keyword(s):  
Simulation Model ◽  
Large Scale ◽  
River System ◽  
In Situ Measurements ◽  
Optical Measurements ◽  
Yenisei River ◽  
Oil Hydrocarbons ◽  
Water Media ◽  
First Time

This paper presents the results of spectral optical measurements of hydrochemical characteristics in the Angara/Yenisei river system (AYRS) extending from Lake Baikal to the estuary of the Yenisei River. For the first time, such large-scale observations were made as part of a joint American-Russian expedition in July and August of 1995, when concentrations of radionuclides, heavy metals, and oil hydrocarbons were assessed. The results of this study were obtained as part of the Russian hydrochemical expedition in July and August, 2019. For in situ measurements and sampling at 14 sampling sites, three optical spectral instruments and appropriate software were used, including big data processing algorithms and an AYRS simulation model. The results show that the water quality in AYRS has improved slightly due to the reasonably reduced anthropogenic industrial impact. Chemical concentrations in water have been found to vary along the Angara River depending on the location of the dams. The results of in situ measurements and modeling evaluations are given. To overcome the uncertainties in the data caused by the large monitoring area, it is recommended to use the combined AYRS simulation model and the universal 8-channel spectrophotometer installed on a fixed platform for continuous monitoring.

Scheming

2018 ◽  
Author(s):  
Seán Damer
Keyword(s):  
Social Class ◽  
Housing Policy ◽  
Large Scale ◽  
Class Structure ◽  
Local Council ◽  
Housing Scheme ◽  
Post War ◽  
First Time ◽  
The Voice ◽  
House Building

This book seeks to explain how the Corporation of Glasgow, in its large-scale council house-building programme in the inter- and post-war years, came to reproduce a hierarchical Victorian class structure. The three tiers of housing scheme which it constructed – Ordinary, Intermediate, and Slum-Clearance – effectively signified First, Second and Third Class. This came about because the Corporation uncritically reproduced the offensive and patriarchal attitudes of the Victorian bourgeoisie towards the working-class. The book shows how this worked out on the ground in Glasgow, and describes the attitudes of both authoritarian housing officials, and council tenants. This is the first time the voice of Glasgow’s council tenants has been heard. The conclusion is that local council housing policy was driven by unapologetic considerations of social class.

Probing the Dynamic Self-Assembly Behaviour of Photoswitchable Wormlike Micelles in Real Time

2018 ◽  
Author(s):  
Elaine A. Kelly ◽  
Judith E. Houston ◽  
Rachel Evans
Keyword(s):  
Real Time ◽  
Absorption Spectroscopy ◽  
Self Assembly ◽  
Uv Light ◽  
Wormlike Micelles ◽  
Tetraethylene Glycol ◽  
Light Illumination ◽  
First Time ◽  
Dependent Processes

Understanding the dynamic self-assembly behaviour of azobenzene photosurfactants (AzoPS) is crucial to advance their use in controlled release applications such as<i></i>drug delivery and micellar catalysis. Currently, their behaviour in the equilibrium <i>cis-</i>and <i>trans</i>-photostationary states is more widely understood than during the photoisomerisation process itself. Here, we investigate the time-dependent self-assembly of the different photoisomers of a model neutral AzoPS, <a>tetraethylene glycol mono(4′,4-octyloxy,octyl-azobenzene) </a>(C<sub>8</sub>AzoOC<sub>8</sub>E<sub>4</sub>) using small-angle neutron scattering (SANS). We show that the incorporation of <i>in-situ</i>UV-Vis absorption spectroscopy with SANS allows the scattering profile, and hence micelle shape, to be correlated with the extent of photoisomerisation in real-time. It was observed that C<sub>8</sub>AzoOC<sub>8</sub>E<sub>4</sub>could switch between wormlike micelles (<i>trans</i>native state) and fractal aggregates (under UV light), with changes in the self-assembled structure arising concurrently with changes in the absorption spectrum. Wormlike micelles could be recovered within 60 seconds of blue light illumination. To the best of our knowledge, this is the first time the degree of AzoPS photoisomerisation has been tracked <i>in</i><i>-situ</i>through combined UV-Vis absorption spectroscopy-SANS measurements. This technique could be widely used to gain mechanistic and kinetic insights into light-dependent processes that are reliant on self-assembly.

The Total Synthesis of Rhabdastrellic Acid A

2018 ◽  
Author(s):  
Yaroslav Boyko ◽  
Christopher Huck ◽  
David Sarlah
Keyword(s):  
Total Synthesis ◽  
Late Stage ◽  
Cross Coupling ◽  
Side Chains ◽  
General Strategy ◽  
Modular Approach ◽  
Linear Sequence ◽  
Generating Sequence ◽  
First Time

<div>The first total synthesis of rhabdastrellic acid A, a highly cytotoxic isomalabaricane triterpenoid, has been accomplished in a linear sequence of 14 steps from commercial geranylacetone. The prominently strained <i>trans-syn-trans</i>-perhydrobenz[<i>e</i>]indene core characteristic of the isomalabaricanes is efficiently accessed in a selective manner for the first time through a rapid, complexity-generating sequence incorporating a reductive radical polyene cyclization, an unprecedented oxidative Rautenstrauch cycloisomerization, and umpolung 𝛼-substitution of a <i>p</i>-toluenesulfonylhydrazone with in situ reductive transposition. A late-stage cross-coupling in concert with a modular approach to polyunsaturated side chains renders this a general strategy for the synthesis of numerous family members of these synthetically challenging and hitherto inaccessible marine triterpenoids.</div>

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