A Modified Model for Predicting Permeability Damage due to Oilfield Scale Deposition

Abstract

Scaling is a major problem in water flooding caused by the mixing of incompatible injected and formation waters. The phenomenon results in precipitation and accumulation of oilfield scale around the well bore after water breakthrough at reduced reservoir pressure. This results in formation damage, which may influence reservoir well bore performance and success of water flood project. This article presents a modified model for predicting permeability damage due to oilfield scale precipitation at different operational and reservoir/brine parameters. The key operational and reservoir parameters that influence the magnitude of flow impairment by scale deposition are identified through the modification.     

Functionalization of powdered walnut shell with orthophosphoric acid for Congo red dye removal

This study investigates the adsorption of Congo red dye on walnut shell powder based activated carbon in batch process (WNAA). Walnut shell powder was carbonized by treating with phosphoric acid (H₃PO₄), and the adsorbent was characterized using Fourier Transform-Infrared spectrophotometer (FT-IR), Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDX), and pH point of zero charge (pH_pzc), respectively. Operational parameters such as contact time, initial dye concentration, and pH were investigated using batch-adsorption techniques. The adsorption uptake was found to increase with increase in initial dye concentration and contact time. The optimum CR dye uptake was observed at pH 3.12 corresponding to 94.53% removal. Pseudo-first-order, pseudo-second-order, Elovich, and Intraparticle diffusion kinetic models were used to test the adsorption data. The pseudo-second order exhibited the best fit out of the four kinetic models used. Equilibrium data were fitted to the Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. Langmuir model fitted the adsorption data most with maximum monolayer coverage of 40?mg/g. Thermodynamic parameters such as Gibbs free energy, enthalpy, entropy, and the activation energy were determined. It was found that Congo red dye adsorption was spontaneous and endothermic. 0.02M Hydrochloric acid was used to regenerate the adsorbent prepared, and the regenerated adsorbent was used for dye adsorption. Congo red dye adsorption capacity ranged from 90% to 93% at three consecutive times. This study has shown that walnut shell is a good adsorbent in the treatment of Congo red dye from aqueous solutions.     

Asynchronous interconnection of large-scale photovoltaic plants: site selection considerations

Large-scale penetration of photovoltaic (PV) energy in a distribution network requires careful planning of its location on the distribution network since it evidently demands large space, flexible maintenance access and exposure to driving energy sources such as sunlight for PV plants. Besides that, the technical aspects of the design should consider possible constraints that may introduce inefficiency in the generation or simply unexpected loss in the distribution. This paper addresses the decentralisation requirement for large-scale deployment of PV power sources as it resists the intermittency of the PV output naturally. In this study, a Monte Carlo method was used to justify the validity of this implication. A modified Gaussian distribution function was used to model the random fluctuations of the PV source and was used in the Monte Carlo simulation. The result shows considerable boost in the average power level and suppression of the fluctuation rate while the interconnected sources are uncorrelated.     

Harnessing information and communication technologies (ICTs) to address urban poverty: Emerging open policy lessons for the open knowledge economy

Urban poverty is a complex socio-economic problem. The expected doubling of the urban population relative to rural areas by 2050 without a corresponding economic and infrastructure growth will worsen the problem, especially in emerging economies. Poor urban residents face rising unemployment and underemployment, constrained access to financial services, market exploitation, poor housing, crime, unsatisfactory health services and scant education opportunities. Several players have attempted to address these problems through information and communication technologies. This paper isolated a few of these to determine critical success factors on the economic empowerment front.     

SMALL SCALE MASHING EXPERIMENTS WITH GRISTS CONTAINING HIGH PROPORTIONS OF RAW SORGHUM

Small scale mashes (50 g total grist) with grists containing high proportions of raw sorghum (50%–80% malt replacement) showed high values of extract recovery and produced worts of lower total nitrogen, free amino nitrogen, viscosity and colour but higher values of pH compared to worts produced from all malt mashes. Increasing the proportion of raw sorghum in the grist relative to malt resulted in a decline in extract recovery, wort total nitrogen, free amino nitrogen and an increase in wort pH. Addition of industrial enzyme preparations to mashes containing raw sorghum resulted in higher values of extract recovery (enzyme preparations containing α amylase and β glucanase), higher values of wort total nitrogen and free amino nitrogen (enzyme preparations containing a neutral proteinase) and decreased wort viscosity (enzyme preparations containing β glucanase or cellulases) compared to worts produced from untreated mashes. Worts and beers were produced on a pilot brewery scale from 50% malt and 50% polished (whole) sorghum (single decoction mashing regime) and 20% malt and 80% raw sorghum supplemented with an industrial enzyme preparation (double mashing regime). Mashes comprising 50% malt and 50% polished sorghum showed comparable wort filtration behaviour (lautering) to that of control mashes (70% malt and 30% maize grists) whereas wort produced from 20% malt and 80% raw sorghum filtered slowly. Worts produced from grists containing sorghum were of high fermentability and showed lower levels of total nitrogen and free amino nitrogen compared to control worts. Analysis of worts produced from small scale mashes containing raw sorghum and a pilot brewery scale mash comprising 20% malt and 80% raw sorghum demonstrated that the levels of total nitrogen and free amino nitrogen were higher than expected from the reduction in the malt content of the mash, consistent with the release of nitrogenous components (polypeptides, peptides and amino acids) derived from sorghum into the wort. Beers produced from 50% malt and 50% polished sorghum and 20% malt and 80% raw sorghum were filtered without difficulty and were of sound flavour. Beers produced from 50% malt and 50% polished sorghum contained lower levels of isobutanol, 2-methylbutanol, dimethylsulphide and higher levels of n propanol and diacetyl compared to control beers.     

Experimental study on the discharge characteristics of two eutectic solder packed bed latent heat storage systems

Metallic solder based PCMs possess higher thermal conductivities, larger storage masses and exhibit lower subcooling effects compared to their organic or inorganic counterparts. It is thus justified to investigate their potential usage for medium temperature applications. These solders are relatively expensive and can be combined with cheaper PCMs in cascaded storage systems which are more thermodynamically efficient compared to single PCM systems as reported recently. The aim of the research is thus to compare two packed bed storage systems during discharging cycles using eutectic solder (Sn63/Pb37), that is widely available worldwide. The single PCM system (40 capsules) consists of encapsulated spheres of eutectic solder, whereas the second cascaded system consists of encapsulated spheres of eutectic solder and erythritol in an equal storage ratio in the tank. For the cascaded system, the eutectic solder capsules are placed at the top and erythritol at the bottom of the storage tank (20 capsules at the top and 20 at the bottom). The effect of the discharging flow-rates of 4 mL/s, 6 mL/s and 8 mL/s is investigated in relation to the temperature profiles, energy rates and exergy rates. Increasing the flow-rate, increases heat transfer rate thus shortening the discharging time as well as increasing thermal profile reversals during discharging. The peak energy and exergy rates increase with the increase in the flow-rate for the two storage systems. The single PCM system shows slightly higher average energy and exergy rates compared to the cascaded system possibly due to its higher thermal conductivity. The cascaded PCM system shows higher average stratification numbers at all the flow rates considered. The non-cascaded system exhibited slightly higher exergy recovery efficiencies compared to the cascaded PCM system possibly due to its higher thermal conductivity at all flow-rates considered. The effect of the initial discharging temperature is also investigated with a discharging flow-rate of 6 mL/s after charging with set heater temperatures of 260°C, 280°C and 300°C, respectively. Comparable thermal profiles are seen for both systems for the three set temperatures; however, the single PCM system shows slightly higher storage temperatures. The single PCM shows slightly higher but comparable peak and average discharging energy rates compared to the cascaded system. The exergy rates for the two systems are also comparable. However, the cascaded system shows slightly higher exergy rate values for the lowest set temperature whereas the single PCM system shows slightly higher exergy rate values for the other two set temperatures. Energy and exergy rates are almost independent of the initial storage tank temperatures induced by different set charging temperatures. The average stratification number shows no correlation with set temperature for both storage systems. The cascaded system shows slightly higher average stratification numbers at different set temperatures. Exergy recovery efficiencies for different set heater temperatures are comparable for the two storage systems and vary only marginally with the increase in the set temperature. Overall, the effect of the flow-rate is more pronounced than the effect of the set heater temperature.     

Polypeptide Profile,Amino Acid Composition and Some Functional Properties of Calabash Nutmeg (<Emphasis Type="Italic">Monodora myristica</Emphasis>) Flour and Protein Products

The aim of this work was to compare the physicochemical and functional properties of calabash nutmeg (Monodora myristica) seed protein flour with those of protein-enriched products (albumin, globulin, and protein isolate). Defatted M. myristica seed flour (MMF) was used to prepare various protein products. A NaCl extract of MMF was dialyzed against water to obtain the soluble albumin fraction (MMA) and a precipitated globulin fraction (MMG). MMF was also extracted with NaOH, the extract adjusted to pH 4.0 and the precipitated proteins collected as the isolate (MMI). Non-reducing gel electrophoresis showed that the MMF, MMG and MMI had similar composition that was dominated by 55 and 110 kDa polypeptides while MMA consisted mainly of smaller (<35 kDa) polypeptides. However, under reducing conditions, the 110 kDa polypeptide was not observed. Amino acid composition revealed an Arg/Lys ratio that increased in the extracts (1.92, 2.28 and 2.11 for MMA, MMG and MMI, respectively) relative to that in MMF (1.85). MMA had 67.5–86.5% protein solubility in the pH 4.0–6.0 range while those of MMF, MMG, and MMI were 37.7–63.8, 2.7–69.4 and 3.8–55.1%, respectively. MMA, MMG and MMI were found to be better emulsifiers based on their smaller oil droplet sizes (8–14 μm) compared with the 14–33 μm for MMF emulsion. Maximum foaming capacity was highest for MMI (205%) when compared with MMA or MMG (150%) and MMF (89%). We conclude that protein enrichment led to significantly enhanced emulsion and foam-forming properties but high solubility may have contributed to reduced emulsion stability.