scholarly journals Comparing organic-hosted and intergranular pore networks: topography and topology in grains, gaps and bubbles

2018 ◽  
Vol 484 (1) ◽  
pp. 241-253 ◽  
Author(s):  
Matthew Andrew
Keyword(s):  
Coordination Number ◽  
Positive Curvature ◽  
Network Connectivity ◽  
Pore Network ◽  
Pore Shape ◽  
Pore Networks ◽  
Geological Processes ◽  
Shale Reservoirs ◽  
Curvature Distribution ◽  
The Impact

AbstractThe relationship between pore structures was examined using a combination of normalized topographical and topological measurements in two qualitatively different pore systems: organic-hosted porosity, common in unconventional shale reservoirs; and intergranular porosity, common in conventional siliciclastic reservoirs. The organic-hosted pore network was found to be less well connected than the intergranular pore network, with volume-weighted coordination numbers of 1.16 and 8.14 for organic-hosted and intergranular pore systems, respectively. This disparity in coordination number was explained by differences in the pore shapes that are caused by variations in the geological processes associated with the generation of the pore network. Measurements of pore shape showed that the pores in the organic-hosted network were both significantly more spherical and had a more positive curvature distribution than the pores present within the intergranular network. The impact of such changes in pore shape on pore-network connectivity was examined by creating a suite of synthetic pore geometries using both erosion/dilation of the existing network and image-guided object-based methods. Coordination number, Euler characteristic and aggregate porosity analyses performed on these synthetic networks showed that organic-type pore networks become connected at much higher aggregate porosities (35–50%) than intergranular-type pore networks (5–10%).

scholarly journals A Novel Modeling Approach to Stochastically Evaluate the Impact of Pore Network Geometry, Chemistry and Topology on Fluid Transport

2020 ◽  
Author(s):  
Maria Apostolopoulou ◽  
Michail Stamatakis ◽  
Alberto Striolo ◽  
Ron Dusterhoft ◽  
Rob Hull ◽  
...  
Keyword(s):  
Transport Properties ◽  
Fluid Transport ◽  
Pore Network ◽  
Gas Production ◽  
Systematic Evaluation ◽  
Pore Throat ◽  
Pore Networks ◽  
Throat Width ◽  
Width Distribution ◽  
The Impact

AbstractFine-grained sandstones, siltstones, and shales have become increasingly important to satisfy the ever-growing global energy demands. Of particular current interest are shale rocks, which are mudstones made up of organic and inorganic constituents of varying pore sizes. These materials exhibit high heterogeneity, low porosity, varying chemical composition and low pore connectivity. Due to the complexity and the importance of such materials, many experimental, theoretical and computational efforts have attempted to quantify the impact of rock features on fluids diffusivity and ultimately on permeability. In this study, we introduce a stochastic kinetic Monte Carlo approach developed to simulate fluid transport. The features of this approach allow us to discuss the applicability of 2D vs 3D models for the calculation of transport properties. It is found that a successful model should consider realistic 3D pore networks consisting of pore bodies that communicate via pore throats, which however requires a prohibitive amount of computational resources. To overcome current limitations, we present a rigorous protocol to stochastically generate synthetic 3D pore networks in which pore features can be isolated and varied systematically and individually. These synthetic networks do not correspond to real sample scenarios but are crucial to achieve a systematic evaluation of the pore features on the transport properties. Using this protocol, we quantify the contribution of the pore network’s connectivity, porosity, mineralogy, and pore throat width distribution on the diffusivity of supercritical methane. A sensitivity analysis is conducted to rank the significance of the various network features on methane diffusivity. Connectivity is found to be the most important descriptor, followed by pore throat width distribution and porosity. Based on such insights, recommendations are provided on possible technological approaches to enhance fluid transport through shale rocks and equally complex pore networks. The purpose of this work is to identify the significance of various pore network characteristics using a stochastic KMC algorithm to simulate the transport of fluids. Our findings could be relevant for applications that make use of porous media, ranging from catalysis to radioactive waste management, and from environmental remediation to shale gas production.

Linking pore network structure derived by microfocus X-ray CT to mass transport parameters in differently compacted loamy soils

Soil Research ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 642
Author(s):  
Arjun Baniya ◽  
Ken Kawamoto ◽  
Shoichiro Hamamoto ◽  
Toshihiro Sakaki ◽  
Takeshi Saito ◽  
...  
Keyword(s):  
Mass Transport ◽  
Coordination Number ◽  
Structural Parameters ◽  
Network Connectivity ◽  
Pore Network ◽  
Gas Diffusion ◽  
Transport Parameters ◽  
X Ray ◽  
Surface Areas ◽  
X Ray Computed

Mass transport in soil occurs through the soil pore network, which is highly influenced by pore structural parameters such as pore-size distribution, porosity, pore tortuosity, and coordination number. In this study, we visualised the networks of meso- and macro-pores (typical pore radius r ≥ 10 μm) using microfocus X-ray computed tomography (MFXCT) and evaluated pore structural parameters of two loamy soils from Japan and New Zealand packed at different degrees of compaction. The effect of compaction on pore structural parameters and relationships between pore structural parameters and measured mass transport parameters were examined. Results showed a clear influence of compaction on pore structural parameters, with the MFXCT-derived mean pore radii and pore tortuosities decreasing and the mean pore coordination number increasing with increasing dry bulk density. Especially, pores with r > 80 µm became finer or were not well formed due to compaction. The MFXCT-derived pore structural parameters were not well correlated with the equivalent pore radii from measured water retention curves. However, volumetric surface areas and pore-network connectivity-tortuosity factors derived from MFXCT allowed a fair prediction of several important mass transport parameters such as saturated hydraulic conductivities, soil-gas diffusion coefficients, and soil-air permeabilities. Further studies are needed to link micro-pores with radii smaller than the X-ray CT resolution to meso- and macro-pores visualised by X-ray CT to improve the prediction of mass transport parameters in soil.

scholarly journals Nonuniform Collective Dissolution of Bubbles in Regular Pore Networks

2022 ◽  
Author(s):  
Nerine Joewondo ◽  
Valeria Garbin ◽  
Ronny Pini
Keyword(s):  
Concentration Field ◽  
Network Connectivity ◽  
Solute Concentration ◽  
Pore Network ◽  
Collective Effects ◽  
Dissolution Time ◽  
Concentration Gradients ◽  
Pore Networks ◽  
Spherical Bubbles ◽  
Power Law Function

AbstractUnderstanding the evolution of solute concentration gradients underpins the prediction of porous media processes limited by mass transfer. Here, we present the development of a mathematical model that describes the dissolution of spherical bubbles in two-dimensional regular pore networks. The model is solved numerically for lattices with up to 169 bubbles by evaluating the role of pore network connectivity, vacant lattice sites and the initial bubble size distribution. In dense lattices, diffusive shielding prolongs the average dissolution time of the lattice, and the strength of the phenomenon depends on the network connectivity. The extension of the final dissolution time relative to the unbounded (bulk) case follows the power-law function, $${B^k/\ell }$$ B k / ℓ , where the constant $$\ell$$ ℓ is the inter-bubble spacing, B is the number of bubbles, and the exponent k depends on the network connectivity. The solute concentration field is both the consequence and a factor affecting bubble dissolution or growth. The geometry of the pore network perturbs the inward propagation of the dissolution front and can generate vacant sites within the bubble lattice. This effect is enhanced by increasing the lattice size and decreasing the network connectivity, yielding strongly nonuniform solute concentration fields. Sparse bubble lattices experience decreased collective effects, but they feature a more complex evolution, because the solute concentration field is nonuniform from the outset.

Earth's energy “Golden Zone”: a synthesis from mineralogical research

Clay Minerals ◽  
2011 ◽  
Vol 46 (1) ◽  
pp. 1-24 ◽  
Author(s):  
P. H. Nadeau
Keyword(s):  
Oil And Gas ◽  
Gulf Coast ◽  
Clay Mineralogy ◽  
Sedimentary Basins ◽  
Entrapment Efficiency ◽  
Permeability Evolution ◽  
Reservoir Temperature ◽  
Fundamental Particle ◽  
Geological Processes ◽  
The Impact

AbstractThe impact of diagenetic processes on petroleum entrapment and recovery efficiency has focused the vast majority of the world's conventional oil and gas resources into relatively narrow thermal intervals, which we call Earth's energy “Golden Zone”. Two key mineralogical research breakthroughs, mainly from the North Sea, underpinned this discovery. The first is the fundamental particle theory of clay mineralogy, which showed the importance of dissolution/precipitation mechanisms in the formation of diagenetic illitic clays with increasing depth and temperature. The second is the surface area precipitation-rate-controlled models for the formation of diagenetic cements, primarily quartz, in reservoirs. Understanding the impacts of these geological processes on permeability evolution, porosity loss, overpressure development, and fluid migration in the subsurface, lead to the realization that exploration and production risks are exponential functions of reservoir temperature. Global compilations of oil/gas reserves relative to reservoir temperature, including the US Gulf Coast, have verified the “Golden Zone” concept, as well as stimulated further research to determine in greater detail the geological/mineralogical controls on petroleum migration and entrapment efficiency within the Earth's sedimentary basins.

The impact of porosity on organic matter cycling in a two-dimensional porous medium 

2021 ◽  
Author(s):  
Hanbang Zou ◽  
Pelle Ohlsson ◽  
Edith Hammer
Keyword(s):  
Porous Medium ◽  
Organic Matter ◽  
Carbon Sequestration ◽  
Soil Carbon ◽  
Pore Network ◽  
Pore Scale ◽  
Decomposition Of Organic Matter ◽  
Organic Matter Cycling ◽  
The Impact

<p>Carbon sequestration has been a popular research topic in recent years as the rapid elevation of carbon emission has significantly impacted our climate. Apart from carbon capture and storage in e.g. oil reservoirs, soil carbon sequestration offers a long term and safe solution for the environment and human beings. The net soil carbon budget is determined by the balance between terrestrial ecosystem sink and sources of respiration to atmospheric carbon dioxide. Carbon can be long term stored as organic matters in the soil whereas it can be released from the decomposition of organic matter. The complex pore networks in the soil are believed to be able to "protect" microbial-derived organic matter from decomposition. Therefore, it is important to understand how soil structure impacts organic matter cycling at the pore scale. However, there are limited experimental studies on understanding the mechanism of physical stabilization of organic matter. Hence, my project plan is to create a heterogeneous microfluidic porous microenvironment to mimic the complex soil pore network which allows us to investigate the ability of organisms to access spaces starting from an initial ecophysiological precondition to changes of spatial accessibility mediated by interactions with the microbial community.</p><p>Microfluidics is a powerful tool that enables studies of fundamental physics, rapid measurements and real-time visualisation in a complex spatial microstructure that can be designed and controlled. Many complex processes can now be visualized enabled by the development of microfluidics and photolithography, such as microbial dynamics in pore-scale soil systems and pore network modification mimicking different soil environments – earlier considered impossible to achieve experimentally. The microfluidic channel used in this project contains a random distribution of cylindrical pillars of different sizes so as to mimic the variations found in real soil. The randomness in the design creates various spatial availability for microbes (preferential flow paths with dead-end or continuous flow) as an invasion of liquids proceeds into the pore with the lowest capillary entry pressure. In order to study the impact of different porosity in isolation of varying heterogeneity of the porous medium, different pore size chips that use the same randomly generated pore network is created. Those chips have the same location of the pillars, but the relative size of each pillar is scaled. The experiments will be carried out using sterile cultures of fluorescent bacteria, fungi and protists, synthetic communities of combinations of these, or a whole soil community inoculum. We will quantify the consumption of organic matter from the different areas via fluorescent substrates, and the bio-/necromass produced. We hypothesise that lower porosity will reduce the net decomposition of organic matter as the narrower pore throat limits the access, and that net decomposition rate at the main preferential path will be higher than inside branches</p>

scholarly journals A New Analysis Model for Potential Contamination of a Shallow Aquifer from a Hydraulically-Fractured Shale

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3010
Author(s):  
Weihong Peng ◽  
Menglin Du ◽  
Feng Gao ◽  
Xuan Dong ◽  
Hongmei Cheng
Keyword(s):  
Migration Time ◽  
Shallow Aquifer ◽  
Contaminant Migration ◽  
Analysis Model ◽  
Shallow Aquifers ◽  
Shale Formations ◽  
Migration Mechanism ◽  
Shale Reservoirs ◽  
Time Required ◽  
The Impact

Hydraulic fracturing (HF) is widely used in shale gas development, which may cause some heavy metals release from shale formations. These contaminants could transport from the fractured shale reservoirs to shallow aquifers. Thus, it is necessary to assess the impact of pollution in shallow aquifers. In this paper, a new analysis model, considering geological distributions, discrete natural fractures (NFs) and faults, is developed to analyze the migration mechanism of contaminants. Furthermore, the alkali erosion of rock caused by high-pH drilling of fluids, is considered in this paper. The numerical results suggest that both NFs and alkali erosion could reduce the time required for contaminants migrating to aquifers. When NFs and alkali erosion are both considered, the migration time will be shortened by 51 years. Alkali erosion makes the impact of NFs, on the contaminant migration, more significant. The migration time decreases with increasing pH values, while the accumulation is on the opposite side. Compared with pH 12.0, the migration time would be increased by 45 years and 29 years for pH 11.0 and 11.5, respectively. However, the migration time for pH 12.5 and 13.0 were found to be decreased by 82 years and 180 years, respectively. Alkali erosion could increase the rock permeability, and the elevated permeability would further enhance the migration velocity of the contaminants, which might play a major role in assessing the potential contamination of shallow aquifers.

scholarly journals MPA network design based on graph theory and emergent properties of larval dispersal

2020 ◽  
Vol 650 ◽  
pp. 309-326
Author(s):  
A Ospina-Alvarez ◽  
S de Juan ◽  
J Alós ◽  
G Basterretxea ◽  
A Alonso-Fernández ◽  
...  
Keyword(s):  
Graph Theory ◽  
Network Design ◽  
Early Life ◽  
Larval Dispersal ◽  
Network Connectivity ◽  
Life Stages ◽  
Early Life Stages ◽  
Larval Connectivity ◽  
The Impact ◽  
Mpa Network

Despite the recognised effectiveness of networks of marine protected areas (MPAs) as a biodiversity conservation instrument, MPA network design frequently disregards the importance of connectivity patterns. In the case of sedentary marine populations, connectivity stems not only from the stochastic nature of the physical environment that affects dispersal of early life stages, but also from the spawning stock attributes that affect reproductive output (e.g. passive eggs and larvae) and survivorship. Early life stages are virtually impossible to track in the ocean. Therefore, numerical ocean current simulations coupled with egg and larval Lagrangian transport models remain the most common approach for the assessment of marine larval connectivity. Inferred larval connectivity may differ depending on the type of connectivity considered; consequently, the prioritisation of sites for the conservation of marine populations might also differ. Here, we introduce a framework for evaluating and designing MPA networks based on the identification of connectivity hotspots using graph theoretic analysis. As a case study, we used a network of open-access areas and MPAs off Mallorca Island (Spain), and tested its effectiveness for the protection of the painted comber Serranus scriba. Outputs from network analysis were used to (1) identify critical areas for improving overall larval connectivity, (2) assess the impact of species’ biological parameters in network connectivity and (3) explore alternative MPA configurations to improve average network connectivity. Results demonstrate the potential of graph theory to identify non-trivial egg/larval dispersal patterns and emerging collective properties of the MPA network, which are relevant for increasing protection efficiency.

scholarly journals Antiepileptic Efficacy and Network Connectivity Modulation of Repetitive Transcranial Magnetic Stimulation by Vertex Suppression

2021 ◽  
Vol 15 ◽  
Author(s):  
Cong Fu ◽  
Aikedan Aisikaer ◽  
Zhijuan Chen ◽  
Qing Yu ◽  
Jianzhong Yin ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Seizure Frequency ◽  
Magnetic Stimulation ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Reduction Rate ◽  
Network Connectivity ◽  
Hamilton Depression Scale ◽  
Depression And Anxiety ◽  
Epileptiform Discharges ◽  
The Impact

A core feature of drug-resistant epilepsy is hyperexcitability in the motor cortex, and low-frequency repetitive transcranial magnetic stimulation (rTMS) is a suitable treatment for seizures. However, the antiepileptic effect causing network reorganization has rarely been studied. Here, we assessed the impact of rTMS on functional network connectivity (FNC) in resting functional networks (RSNs) and their relation to treatment response. Fourteen patients with medically intractable epilepsy received inhibitive rTMS with a figure-of-eight coil over the vertex for 10 days spread across two weeks. We designed a 6-week follow-up phase divided into four time points to investigate FNC and rTMS-induced timing-dependent plasticity, such as seizure frequency and abnormal interictal discharges on electroencephalography (EEG). For psychiatric comorbidities, the Hamilton Depression Scale (HAM-D) and the Hamilton Anxiety Scale (HAM-A) were applied to measure depression and anxiety before and after rTMS. FNC was also compared to that of a cohort of 17 healthy control subjects. The after-effects of rTMS included all subjects that achieved the significant decrease rate of more than 50% in interictal epileptiform discharges and seizure frequency, 12 (14) patients with the reduction rate above 50% compared to the baseline, as well as emotional improvements in depression and anxiety (p < 0.05). In the analysis of RSNs, we found a higher synchronization between the sensorimotor network (SMN) and posterior default-mode network (pDMN) in epileptic patients than in healthy controls. In contrast to pre-rTMS, the results demonstrated a weaker FNC between the anterior DMN (aDMN) and SMN after rTMS, while the FNC between the aDMN and dorsal attention network (DAN) was greater (p < 0.05, FDR corrected). Importantly, the depressive score was anticorrelated with the FNC of the aDMN-SMN (r = −0.67, p = 0.0022), which was markedly different in the good and bad response groups treated with rTMS (p = 0.0115). Based on the vertex suppression by rTMS, it is possible to achieve temporary clinical efficacy by modulating network reorganization in the DMN and SMN for patients with refractory epilepsy.

Testing the Impact of Road Network Connectivity on Criminal Lethality

2018 ◽  
Vol 22 (3) ◽  
pp. 277-295 ◽  
Author(s):  
Aaron C. Poole ◽  
James C. McCutcheon ◽  
Kayla Toohy ◽  
Bert Burraston
Keyword(s):  
Road Network ◽  
Reporting System ◽  
Explanatory Variable ◽  
Network Connectivity ◽  
Google Earth ◽  
Community Survey ◽  
Data Sources ◽  
American Community Survey ◽  
Positive Outcomes ◽  
The Impact

Increased road network connectivity has been linked to more positive outcomes among all health outcomes. Road network connectivity has yet to be tested in association with specifically criminal lethality. The current study looks to incorporate road network connectivity as an explanatory variable for criminal lethality. Data on Road Network Connectivity and Criminal Lethality are gathered for 190 cities. Data sources include the National Incident-Based Reporting System (NIBRS), 2010 Census, 2010 American Community Survey, Google Earth, and Census Topologically Integrated Geographic Encoding and Referencing (TIGER) files. The data demonstrate that a city’s road network connectivity is related to decreases in the rates of lethality among assaults. Implications of this finding are discussed.

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