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This paper aims to review the quad-porosity shale system from a production standpoint. Understanding the complex but coupled flow mechanisms in such reservoirs is essential to design appropriate completions and further, optimally produce them. Dual-porosity and dual permeability models are most commonly used to describe a typical shale gas reservoir.

Characterization of such reservoirs with extremely low permeability does not aptly capture the physics and complexities of gas storage and flow through their existing nanopores. This paper reviews the methods and experimental studies used to describe the flow mechanisms of gas through such systems, and critically recommends the direction in which this work could be extended. A quad-porosity shale system is defined not just as porosity in the matrix and fracture, but as a combination of multiple porosity values.

It has been observed from studies conducted that shale gas production modeled with conventional simulator/model is seen to be much lower than actually observed in field data. This paper reviews the various flow mechanisms in shale nanopores by capturing the physics behind the actual process. The contribution of Knudson diffusion and gas slippage, gas desorption and gas diffusion from Kerogen to total production is studied in detail.

The results observed from experimental studies and simulation runs indicate that the above effects should be considered while modeling and making production forecast for such reservoirs.

Optimized three-dimensional (3D) fracture networks are crucial for multistage hydrofracturing. To better understand the mechanisms controlling potential disasters as well as to predict them in 3D multistage hydrofracturing, some governing factors, such as fluid injection-induced stratal movement, compression between multiple hydraulic fractures, fracturing fluid flow, fracturing-induced microseismic damaged and contact slip events, must be properly simulated via numerical models. This study aims to analyze the stratal movement and microseismic behaviours induced by multistage propagation of 3D multiple hydraulic fractures.

Adaptive finite element–discrete element method was used to overcome the limitations of conventional finite element methods in simulating 3D fracture propagation. This new approach uses a local remeshing and coarsening strategy to ensure the accuracy of solutions, reliability of fracture propagation path and computational efficiency. Engineering-scale numerical models were proposed that account for the hydro-mechanical coupling and fracturing fluid leak-off, to simulate multistage propagation of 3D multiple hydraulic fractures, by which the evolution of the displacement, porosity and fracture fields, as well as the fracturing-induced microseismic events were computed.

Stratal movement and compression between 3D multiple hydraulic fractures intensify with increasing proximity to the propagating fractures. When the perforation cluster spaces are very narrow, alternate fracturing can improve fracturing effects over those achieved via sequential or simultaneous fracturing. Furthermore, the number and magnitude of microseismic events are directly proportional to the stratal movement and compression induced by multistage propagation of fracturing fracture networks.

Microseismic events induced by multistage propagation of 3D multiple hydraulic fractures and perforation cluster spaces and fracturing scenarios that impact the deformation and compression among fractures in porous rock matrices are well predicted and analyzed.

The purpose of this study is to calibrate a microstructure-based fatigue model for its use in predicting fatigue life of additively manufactured (AM) Ti-6Al-4V. Fatigue models that are capable of better predicting the fatigue behavior of AM metals is required to further the adoption of such metals by various industries. The trustworthiness of AM metallic material is not well characterized, and fatigue models that consider unique microstructure and porosity inherent to AM parts are needed.

Various Ti-6Al-4V samples were additively manufactured using Laser Engineered Net Shaping (LENS), a direct laser deposition method. The porosity within the LENS samples, as well as their subsequent heat treatment, was varied to determine the effects of microstructure and defects on fatigue life. The as-built and heat-treated LENS samples, together with wrought Ti-6Al-4V samples, underwent fatigue testing and microstructure and fractographic inspection. The collected microstructure/defect statistics were used for calibrating a microstructure-sensitive fatigue model.

Fatigue lives of the LENS Ti-6Al-4V samples were found to be consistently less than those of the wrought Ti-6Al-4V samples, and this is attributed to the presence of pores/defects within the LENS material. Results further indicate that LENS Ti-6Al-4V fatigue lives, as predicted by the used microstructure-sensitive fatigue model, are in close agreement with experimental results. The used model could predict upper and lower prediction bounds based on defect statistics. All the fatigue data were found to be within the bounds predicted by the microstructure-sensitive fatigue model.

To further test the utility of microstructure-sensitive fatigue models for predicting fatigue life of AM samples, future studies on additional material types, additive manufacturing processes and heat treatments should be conducted.

This study shows the utility of a microstructure-sensitive fatigue model for use in predicting the fatigue life of LENS Ti-6Al-4V with various levels of porosity and while in a heat-treated condition.

The evolution in developed countries has taken a role in global warming and natural disasters such as flash flood, El-Nino, earthquake and groundwater contamination. The underground storage tank leakage problems and spillage of hydrocarbon liquid leading to the contamination of non-aqueous phase liquids (NAPLs) into the groundwater could reduce the quality of groundwater. This chapter is intended to investigate the behaviour and the pattern of NAPL migrations in double-porosity soil under vibration and intact conditions. The experimental model is developed by using kaolin soil type S300 and toluene as NAPLs. The kaolin soil was mixed with 25% of moisture content to produce kaolin granules in the soil column and vibrate under 0.98 Hz of frequency within 60 seconds. As a result, both specimen liquids completely migrated to the bottom of soil column: sample 1 has higher permeability compared to sample 2. This is due to the fracture in double-porosity soil under vibration effect and loosened the soil structure in sample 1 compared to good intact soil sample 2 with stronger and compact soil structure. In conclusion, this study proves that the dangerous hydrocarbon NAPL migration in fractured double-porosity soil has very harmful effect on the environment and groundwater resources.

The impact of climate change towards water surface resources is crucial, particularly in developing and non-developing countries. Groundwater as a main water resource is thus an essential. However, contamination due to hydrocarbon spills affects the groundwater as a water resource, especially as a main source of drinking water. This chapter investigates the light non-aqueous phase liquid (LNAPL) penetrations in double-porosity soil with different moisture contents and with or without vibration impact. It also explains the LNAPL penetration phenomena by employing image analysis. The physical laboratory experiments were implemented using an acrylic cylinder, a mirror, toluene and a Nikon D90 DSLR digital camera. Prepared soil was poured in an acrylic cylinder and compressed with compressor until it became 10 cm in height. LNAPL was then poured instantaneously onto the acrylic cylinder that was filled with soil sample. The LNAPL penetration patterns were recorded and monitored using a Nikon D90 DSLR digital camera. The processing technique was conducted at predetermined time intervals using Surfer software and Matlab routine to plot the LNAPL pattern. The results showed that a higher penetration rate of LNAPL occurred with higher moisture content and without vibration impact. The penetration time for LNAPL to reach the bottom of the soil sample was found to be longer for the soil that had low moisture content and with vibration impact.

The purpose of this paper to construct the fundamental solution of partial differential equations in the generalized theory of thermoelastic diffusion materials with double porosity.

The paper deals with the study of pseudo oscillations in the generalized theory of thermoelastic diffusion materials with double porosity.

The paper finds the fundamental solution of partial differential equations in terms of elementary functions.

Assuming the displacement vector, volume fraction fields, temperature change and chemical potential functions in terms of oscillation frequency in the governing equations, pseudo oscillations have been studied and finally the fundamental solution of partial differential equations in case of pseudo oscillations in terms of elementary functions has been constructed.

Selective laser melting (SLM) is an additive manufacturing technology that is gaining industrial and research interest as it can directly fabricate near full density metallic components. The paper aims to identify suitable process parameters for SLM of processing of pure nickel powder and to study the microstructure of such products. The study also aims to characterize the microhardness and tensile properties of pure nickel produced by SLM.

A 2⁴ factorial design experiment was carried out to identify the most significant factors on the resultant porosity of nickel parts. A subsequent experiment was carried out with a laser power of 350 W. The scanning speeds and hatch spacings were varied.

Scanning speed and hatch spacing have significant effects on the porosity of SLM components. A high relative density of 98.9 per cent was achieved, and microhardness of 140 to 160 Hv was obtained from these samples. A tensile strength 452 MPa was obtained.

As the energy input levels were made in steps of 20 J/mm³ for the optimization study, the true optimal combination of parameters may have been missed. Therefore, researchers are encouraged to test the parameters with smaller variations in energy levels.

The paper provides a set of optimized parameters for the SLM of pure nickel. This study enables the three-dimensional (3D) printing of objects with nickel, which has applications in chemical catalyses and in microelectromechanical systems with its magnetostrictive properties.

This research is the first in direct processing of pure nickel using SLM, with the identification of suitable process parameters. The study also provides an understanding of the porosity, microhardness, strength and microstructure of SLM produced nickel parts. This work paves the way for standardization of 3D printed nickel components and enables the applications of pure nickel via SLM.

The purpose of this work is the study of the steady free convection in a square differentially heated cavity filled by a Brinkman bidisperse porous medium. An appropriate mathematical model considering the Brinkman, momentum and energy interphase terms is proposed. The dependence of the stream functions, isotherms and of the Nusselt numbers on the governing parameters is analysed.

The both phases of flow and heat transfer are solved numerically using a modified finite difference technique. The algebraic system obtained after discretization is solved using the SOR method. The results are found to be in a significant agreement with the ones presented by the literature for a Darcy bidisperse porous medium and a Brinkman monodisperse porous medium.

The effects of the governing parameters on stream functions, isotherms and Nusselt numbers are discussed. It has been found that in the case of the Brinkman bidisperse model, the Nusselt numbers decrease compared to the Darcy model, and this behaviour is significant in comparison to the Brinkman monodisperse case.

A mathematical model for the free convection inside a cavity filled by a non-Darcy bidisperse porous medium, based on the Brinkman equation, is used. The effect of Darcy number, Rayleigh number, modified inter-phase heat transfer parameter, modified thermal conductivity ratio and the inertial parameters is studied. To the best of the authors’ knowledge, this problem has not been studied before, and the results are new and original.

The purpose of this paper is to report on software development in which mathematical algorithms apply geometric transformations to digitised images in preparation for layer manufacturing by printing a binder onto a rotating powder substrate.

Spiral growth manufacturing (SGM) is a high‐speed rapid manufacturing technique in which objects are built up, layer by layer, by simultaneously depositing, levelling and selectively consolidating thin powder layers onto a rotating build platform. Consolidation occurs by infiltrating the powder layer with a binding agent deposited in droplet form using inkjet technology. During each rotation, the build platform falls away from a stationary doctor blade and print head assembly. This gives a continuous spiralled layer of powder with a constant layer pitch. To faithfully print digitised images onto a rotating substrate, polar and linear transformations have to be applied.

In support of this work, dimensional accuracy measurements of transformed printed images are reported and the measured results were found to be within ±0.2 mm of their predicted size. The experimental work is briefly extended to the printing of transformed images, using an aqueous binder, onto plaster powder to demonstrate the build speed capabilities of SGM. Primitive multiple layer parts built at speeds of 10 layers/min are reported.

From a practical standpoint, SGM has the potential to increase build speed by an order of magnitude over existing commercial rapid prototyping/manufacturing systems.

There is no commercial system available that allows high‐speed simultaneous deposition and processing of powder material and so this method could have implications in large batch manufacture.

The durability of concrete containing recycled aggregates, sourced from concrete specimens that have been tested in laboratory testing facilities, remains understudied. This paper aims to present the results of experiments investigating the effect of incorporating such type of concrete waste on the strength and durability-related properties of concrete.

A total of 77 concrete cylinders sized Ø100 × 200 mm with varying amount of recycled concrete aggregate (RCA) (0%–100% by volume, at 25% increments) and maximum aggregate size (12.5, 19.0 and 25.0 mm) were fabricated and tested for slump, compressive strength, sorptivity and electrical resistivity. Disk-shaped specimens, 50-mm thick, were cut from the original cylinders for sorptivity and resistivity tests. Analysis of variance and post hoc test were conducted to detect statistical variability among the data.

Compared to regular concrete, a reduction of slump (by 18.6%), strength (15.1%), secondary sorptivity (31.5%) and resistivity (17.0%) were observed from concrete containing 100% RCA. Statistical analyses indicate that these differences are significant. In general, an aggregate size of 19 mm was found to produce the optimum value of slump, compressive strength and sorptivity in regular and RCA-added concrete.

The results of this study suggest that comparable properties of normal concrete were still achieved by replacing 25% of coarse aggregate volume with 19-mm RCA, which was processed from laboratory-tested concrete samples. Therefore, such material can be considered as a potential and sustainable alternative to crushed gravel for use in light or nonstructural concrete construction.