African Scientific Reports
https://asr.nsps.org.ng/index.php/asr
<p><em>African Scientific Reports</em> is a peer reviewed, open access, inter- and multidisciplinary scientific journal that is dedicated to expanding access to African research, increasing intra-African scientific collaboration, and building academic research capacity in Africa. The journal aims to provide a modern, highly-visible platform for publishing pan-African research and welcomes submissions from all areas of the natural sciences, psychology, medicine and engineering. With the idea that making research openly available to the public promotes better global knowledge exchange, this journal offers direct open access to its contents, i.e., all the articles published in this journal are free to access immediately from the date of publication. ASR is available in print and online. The language used in this journal is English.</p> <p> </p>eneditor-in-chief@asr.nsps.org.ng (Tolulope Latunde (PhD))info@gpws.com.ng (Graxynet Portal and Web Solution (BN - 2699775), Ombi 1, Lafia, Nasarawa State. Home Page https://gpws.com.ng/)Thu, 01 Feb 2024 00:00:00 +0100Open Journal Systems 3.4.0.4http://blogs.law.harvard.edu/tech/rss60Numerical simulation of a nonlinear diffusion type equation in a two phase media with linear porosity and permeability model
https://asr.nsps.org.ng/index.php/asr/article/view/119
Section: Original Research<br />
Categories: PHYSICS<br />
Keywords: Permeability, Porosity, Nonlinear pressure diffusion equation, Numerical simulation<br />
Disciplines: physics, mathematics, computer sciences<br />
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<p>Predicting and understanding the behavior of pressure is important in reservoir maintenance and evaluation. This work studies the behavior of fluid pressure in a reservoir by numerical simulation of the pressure diffusion type equation in a two phase media with a linear porosity and permeability model. Because the porosity and permeability are pressure dependent, the resulting diffusion type equation is nonlinear and is solved using a backward-forward finite difference method. The simulation code was ran using a constant porosity and permeability model and a linear porosity and permeability model. The results from the linear porosity and permeability model was compared to that of the constant porosity and permeability model. In both cases the pressure gradient was greatest at the wellbore and decreases as the radial distances away from the wellbore increases. The pressure in both cases also decreased with time. However, at each location and time the pressure drop was lower in the linear porosity and permeability model than with the constant porosity and permeability. The backward-forward finite difference method proved to be useful in solving numerically the nonlinear diffusion type equation. This work can be applied in the oil and gas industry to predict pressure behavior in reservoirs and make investment decisions, production and maintenance decision.</p>
I. D. Dorothy, I. M. Echi, A. N. AmahOriginal ResearchPHYSICSPermeabilityPorosityNonlinear pressure diffusion equationNumerical simulationphysicsmathematicscomputer sciences
Copyright (c) 2024 I. D. Dorothy, I. M. Echi, A. N. Amah
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https://asr.nsps.org.ng/index.php/asr/article/view/119Thu, 01 Feb 2024 00:00:00 +0100Development of 3D flow diagnostic numerical simulator and rock property modelling for a homogeneous faulted reservoir
https://asr.nsps.org.ng/index.php/asr/article/view/167
Section: Original Research<br />
Categories: ENGINEERING<br />
Keywords: Faults, Flow diagnostics, Numerical modeling and simulation, Sweep efficiency, Reservoir<br />
Disciplines: Petroleum and Natural Gas Engineering <br />
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<p>Research has shown that faults, especially sealing faults, have become a barrier to flow. Flow diagnostics, on the other hand, are straightforward and controlled numerical flow experiments that are performed to examine a reservoir model, build links and offer rudimentary volume estimates as well as to quickly produce a qualitative representation of the reservoir’s flow patterns. To evaluate, assess, and validate reservoir models and production scenarios, the ’diagnostics’ module in the Matlab Reservoir Simulation Toolbox (MRST) provides a computationally less expensive alternative to running fully featured multiphase simulations. This is done to determine qualitatively regions for well placement to maximize hydrocarbon recovery. Monitoring flow fields, timelines, and tracers—neutral particles in the fluid that flow with the fluid—are all part of flow diagnostics. These techniques are used to determine volumetric communication between a pair of injector-producer wells, as well as flow patterns between injection-production wells and the arrival time between them. To create the grid, the simulation schedule, the wells, upscaling, arrival time computation, and flow diagnostics (drainage and sweep regions) were all done using the Matlab reservoir simulation toolbox (MRST) package by “Makemodel 3” on the data obtained from “SPE 10<em><sup>th </sup></em>comparative solution project” on the MRST package. This was done for a homogeneous anisotropic faulted porous medium. The simulation runs for about 473,739 milliseconds on a fine grid having 20040 active cells while in the coarse model with faster computational time of about 200 seconds, 112 milliseconds. At the early stages of the reservoir bottom-hole pressure for injector I1(about 7000psia) and three producers P1, P2 and P3 remains constant over time (about 3600psia) thanks to pressure support by I1. The extent of residence time after 10 years for the fine, coarse and more coarser model is that fluid element find it easier to transverse through the fault line from I1 to P1, P2 then P3 which takes lesser time than crossing across two intersecting faults, It can also be seen that the sweep efficiency of the fine grid is more effective than the coarse grid. Finally, it has been seen clearly that the fine grid model gives more accurate details but slower computational time while the coarse model which is less accurate but with faster computational time.</p>
Surajo Muhammed Gwio, Ibrahim Ayuba, Umar Faruk AminuaOriginal ResearchENGINEERINGFaultsFlow diagnosticsNumerical modeling and simulationSweep efficiency ReservoirPetroleum and Natural Gas Engineering
Copyright (c) 2024 Surajo Muhammed Gwio, Ibrahim Ayuba, Umar Faruk Aminua
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https://asr.nsps.org.ng/index.php/asr/article/view/167Thu, 01 Feb 2024 00:00:00 +0100Temperature-dependent viscometry of baobab pectin (Adansonia digitata L.)
https://asr.nsps.org.ng/index.php/asr/article/view/146
Section: Original Research<br />
Categories: MATHEMATICAL SCIENCES<br />
Keywords: Baobab pectin, Viscosity-temperature dependency, Arrhenius parameters, Thermodynamic parameters<br />
Disciplines: polymer chemistry, polysaccharides, thermodynamic properties<br />
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<p class="p1">This study uses the Arrhenius-type equation and the Frenkel-Eyring equation to evaluate the viscosity-temperature dependency of the baobab pectin (BoP) solution at 278.16-353.16 K. The viscosity parameters (apparent viscosity, η<span class="s1">A </span>and intrinsic viscosity, [η]) were analysed for polymeric systems of WEp (pectin extracted using water), AEp (pectin extracted using acid), and Cp (citrus pectin, a control). A Vibro-viscometer was used to measure η<span class="s1">A</span>, while [η] values were estimated from the Kuwara equation. The viscosity parameters decrease with an increase in temperature, though the effects were more pronounced in WEp than in AEp and Cp. Data from [η] indicated that activation energy E<span class="s1">a </span>was higher for AEp (12.24 kJ/mol) and lower for WEp (10.18 kJ/mol). In contrast, the η<span class="s1">A </span>data had a higher E<span class="s1">a </span>for WEp (21.38 kJ/mol) and a lower E<span class="s1">a </span>for Cp (16.49 kJ/mol). The η<span class="s1">A </span>data showed a non-linear viscosity-temperature relationship, and the Vogel-Fulcher-Tammann-Hesse equation was used instead to relate the temperature dependency of BoP. The flow patterns of all pectin solutions showed positive entropy (ΔS <span class="s1">+ </span><span class="s1">v </span>), positive enthalpy (ΔH<span class="s1">+ </span><span class="s1">v </span>), and negative Gibbs free energy (ΔG<span class="s1">−v </span>). This revealed that the flow was disordered, dependent on temperature, and spontaneous. Overall, the viscous flow of WEp was more sensitive and less dependent on temperature compared to AEp and Cp.</p>
Shadreck Muyambo, Jack A. UromboOriginal ResearchMATHEMATICAL SCIENCESBaobab pectin, Viscosity-temperature dependency, Arrhenius parameters, Thermodynamic parameterspolymer chemistrypolysaccharidesthermodynamic properties
Copyright (c) 2024 Shadreck Muyambo, Jack A. Urombo
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https://asr.nsps.org.ng/index.php/asr/article/view/146Thu, 08 Feb 2024 00:00:00 +0100Effect of hydrostatic pressure on opto-electronic, elastic and thermoelectric properties of the double perovskites Rb2SeX6(X=Cl,Br): a DFT study
https://asr.nsps.org.ng/index.php/asr/article/view/171
Section: Original Research<br />
Categories: PHYSICS<br />
Keywords: Hydrostatic Pressure, Density Functional Theory, Double perovskite, Opto-electronic property, Thermoelectric property<br />
Disciplines: Computational materials science<br />
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<p class="p1">Double perovskites find applications across a diverse range of situations and varying pressure conditions. In this work, Quantum ESPRESSO code with a plane wave basis set was used to study the opto-electronic, elastic, and thermoelectric properties of Rb<sub><span class="s1">2</span></sub>SeX<span class="s1"><sub>6</sub> </span>(X=Cl, Br) double perovskites under hydrostatic pressure (0 - 8 GPa). Perdew-Burke-Ernzerhof for Solids (PBESol) with generalized gradient approximation (GGA) was used as exchange-correlation functional. The band gap values of the materials decrease under hydrostatic pressure. Rb<sub><span class="s1">2</span></sub>SeCl<span class="s1"><sub>6</sub> </span>has a band gap value of 2.44 eV at 0 GPa, 2.21 eV at 2 GPa. Above 2 GPa, the material has a metallic nature. Rb<sub><span class="s1">2</span></sub>SeBr<span class="s1"><sub>6</sub> </span>has a band gap value of 1.56 eV at 0 GPa, but has a metallic nature under hydrostatic pressure (2 GPa to 8 GPa). The optical properties results indicate that the materials exhibit maximum absorption, high reflectivity, low optical loss in the visible and ultraviolet regions, good optical conductivity, and a refractive index suitable for use in opto-electronic applications. The materials are confirmed to be mechanically stable under all the hydrostatic pressure values studied. Electrical conductivity, thermal conductivity, and Seebeck coefficient (S ) values of the studied materials increase with an increase in hydrostatic pressure and temperature. The maximum value of S for Rb<sub><span class="s1">2</span></sub>SeBr<span class="s1"><sub>6</sub> </span>is 0.248 x 10<span class="s1"><sup>3</sup> </span>(m V/k), while for Rb<sub><span class="s1">2</span></sub>SeCl<sub><span class="s1">6</span></sub>, maximum S = 0.175 x 10<span class="s1"><sup>3</sup> </span>(m V/k). The positive values of S suggest that the predominant charge carriers of Rb<sub><span class="s1">2</span></sub>SeCl<sub><span class="s1">6</span></sub>/Br<span class="s1"><sub>6</sub> </span>are holes. Also, Rb<sub><span class="s1">2</span></sub>SeBr<span class="s1"><sub>6</sub> </span>has a figure of merit (ZT) value of 3.44, while for Rb<sub><span class="s1">2</span></sub>SeCl<sub><span class="s1">6</span></sub>, ZT = 1.07. Since the values of ZT are greater than unity, the two double perovskite materials have good ZT values for thermoelectric device engineering. The results also suggest that Rb<sub><span class="s1">2</span></sub>SeBr<span class="s1"><sub>6</sub> </span>is a better thermoelectric material than Rb<sub><span class="s1">2</span></sub>SeCl<sub><span class="s1">6</span></sub>.</p>
A. A. Yahaya, W. A. Yahya, I. A. RahmonOriginal ResearchPHYSICSHydrostatic PressureDensity Functional TheoryDouble perovskiteOpto-electronic propertyThermoelectric propertyComputational materials science
Copyright (c) 2024 A. A. Yahaya, W. A. Yahya, I. A. Rahmon
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https://asr.nsps.org.ng/index.php/asr/article/view/171Tue, 20 Feb 2024 00:00:00 +0100