A Systematic Multiscale Investigation of Nanoparticle-Assisted CO2 Enhanced Oil Recovery (EOR) Process for Shale Oil Reservoirs

Shale oil reservoirs are prolific on the short term due to hydraulic fracturing and horizontal drilling but experience significant production decline, leading to poor ultimate recovery and leaving billions of barrels of oil buried in the ground. In this study, a systematic multi-scale investigation of an enhanced oil recovery (EOR) process using relatively inexpensive silicon dioxide nanoparticles and carbon dioxide for shale oil reservoirs was conducted. Using the Tuscaloosa Marine Shale (TMS) as a case study, aqueous dispersions of nanosilica in conjunction with CO2 were investigated at nano-to-core scales. At the nanoscale, atomic force microscope was used to investigate the wettability modification performance of silica nanoparticles by measuring adhesion force between specific functional groups and pure minerals in nanofluid media. At the micron-scale, the roles of silica-based nanofluids in fluid/fluid interactions and rock/fluid interactions were distinguished by characterizing interfacial tension and advancing contact angle using optical tensiometer and the dual-drop-dual-crystal technique, respectively. Core-scale investigations consisted of: high-pressure CO2 EOR coreflood experiment, reservoir rock/fluid characterization, physics-based modelling of capillary pressure and relative permeability using nano-to-core scale experimental data, and compositional simulation. Results showed that hydrophilic silica nanoparticle (HNP) dispersions can effectively improve nanoscale wettability alteration (towards less oil-wet state) by decreasing adhesion force and work required to spontaneously desorb dominant functional groups in TMS crude oil from pure mineral surfaces. However, the grafting of aminosilanes on the surfaces of nanosilica generally increased adhesion force. At the micron-scale, HNP solutions showed great potential for enhancing oil recovery in TMS through wettability modification but not interfacial tension xviii reduction, whereas APTES-modified nanoparticle dispersions showed promising EOR potential through both mechanisms. At the core scale, coreflood experiment and compositional simulation showed that up to 30% of oil-in-place can be recovered with CO2 EOR in TMS. The nano-to-micron scale mechanisms of silica-based nanofluids translated into a notable decrease in capillary pressure, an increase in oil relative permeability and a decrease in water relative permeability. However, the strongly-water state in TMS masked the synergistic effects of nanoparticle-assisted CO2 EOR and thus helped revealed the initial wetting state as an important EOR screening criterion for shale oil reservoirs

Effects of credit, liquidity, and operational risks on efficiency of Islamic banks in Africa

Islamic banks in Africa are characterized with some technical inefficiencies. The low efficiency of Islamic banks in the region has been linked to high exposure to different risk variables. However, adequate attention has not been given to such risk variables in past studies on Islamic bank efficiency. This study therefore assessed the effects of credit, liquidity and operational risks on efficiency of Islamic banks in Africa. Twenty (20) Islamic banks were selected across Africa for a period of eight (8) years from 2012 to 2019. Data were collected from annual reports of the banks and analysed via Data Envelopment Analysis (DEA) and Ordinary Least Square (OLS) regression. The study found that the banks were not efficient as the average overall technical efficiency (OTE) was 0.748. The inefficiencies could be traced to both managerial inefficiencies (PTE, 0.827) and poor selection of operating scale (SE, 0.902). The study also found that non-performing financing ratio (p = 0.002), deposit-asset ratio (p = 0.019), and operating expenses to earnings ratio (p = 0.000), have a negative and significant relationship with OTE at 5% level of significance. The study concluded that Islamic banks in Africa are not technically efficient and that exposure to credit, liquidity and operational risks had impaired their technical efficiencies. The study recommends employment of staff with requisite skills and knowledge of Islamic banking and finance to enhance their efficiency. Timely identification of potential risks and adequate risk management are also necessary to forestall high risk exposure which jeopardize technical efficiency

Evaluation of Natural Radioactivity and Radiation Hazards of Soils around Petroleum Products Marketing Company using Gamma Ray Spectrometry

This study aimed at evaluating natural radioactivity and radiation hazards of soils around a petroleum product marketing company due to anthropogenic influences using gamma ray spectrometry. Top soils (5 cm deep) were collected from diverse locations inside the premises of the Company using standard analytical technique, while control samples were acquired at approximately 200 m from the study area. Mean activity concentrations of the radionuclides in the test soils were 89.36 Bq/kg for 40K, 92.1 Bq/kg for 238U and 10.95 Bq/kg for 232Th, which are more than that of control samples with statistically significant differences. Assessment of the radiological levels of the oil-contaminated soils were done using internal hazard index, external hazard index, annual gonadal dose equivalent, annual effective dose rate, radium equivalent, total absorbed dose rate and representative level index (IŸ). The results showed that mean annual equivalent dose rate of the oil-contaminated soil (0.46 mSv/yr) fell below the permissive annual dose limit (1.0 mSv/yr). Mean internal hazard index (0.55 Bq/kg) and external hazard index (0.30 Bq/kg) values were less than the minimum permissible limit (1.0). Mean annual gonadal dose equivalent value (358.46 µSvy-1) of the radionuclides was close to the world average of 300 µSvy-1, while the mean representative gamma index value (0.78) was also less than unity. Estimated mean value (114.65 Bq/kg) of the radium equivalent was also below the world average of 370 Bq/kg, the values are also more than that of the control samples. Though the soils exhibited low gamma radiation, however lengthy term exposure may pose an inherent cancerous ill-health. It is vital to repeat this investigation periodically to avert precarious effects of anthropogenic influences; also indiscriminate discarding of oils should be discouraged. Keywords:    Gamma ray spectrometry; radionuclide; refined petroleum products; risk assessment; soil

Organoleptic Analysis of Doughs Fermented with Yeasts From A Nigerian Palm Wine (Elaeis guineensis) and Certain Commercial Yeasts

Yeasts isolated from a freshly tapped palm wine obtained from Akure, Nigeria were identified as Schizosaccharomyces pombe, Saccharomyces cerevisiae, Debaryomyces hansenii, Geotrichum lactis and Zygosaccharomyces rouxii. Each of the isolates was used to ferment wheat flour dough and baked. Sensory analysis of the doughs was carried out on leavening, texture, aroma, taste and appearance. Saccharomyces cerevisiae performed best in leavening the dough while Debaryomyces hansenii produced doughs with the best taste and aroma. Appearances of the doughs made with all the isolated yeasts did not differ significantly (P<0.05) from that of the dough that lacked yeast

Extraction, Chemical Analysis, and Smoke Point Determination of Terminalia catappa Linn Seed Oil

Terminalia catappa Linn fruit, also known as tropical almond, is under-utilized. This study on food product development aimed to produce cooking oil out of the Terminalia catappa Linn seeds and determine its properties. The fruits were gathered and dehydrated for 16 hours using the Multi-Commodity Heat Pump Dryer. Each dehydrated Terminalia catappa Linn fruit was crushed to get the seed inside. The seeds were roasted and pulverized. Seeds were then subjected to oil extraction and chemical analysis. The smoke point of the oil extracted was tested in the chemistry laboratory. Based on the results, Terminalia catappa Linn seed yields 53.4% of fat. The distribution of the fatty acids in Terminalia catappa Linn oil is close to the optimum fatty acid balance ratio of saturated fatty acid (38%), monounsaturated fatty acid (MUFA 29%), polyunsaturated fatty acid (33%) of 1:1:1. The smoke point of the Terminalia catappa Linn oil is 392 °F or 200 °C, which is comparable to the smoke points of other common cooking oils. Therefore, Terminalia catappa Linn seed oil can be a healthy and practical option for cooking. Market studies and microbiological tests of the Terminalia catappa Linn oil are recommended.Keywords: chemical analysis, cooking oil, extraction, smoke point, Terminalia catappa Linn see

Transactional Leadership Style and Employee Job Satisfaction among Universities' Guest Houses in South-West Nigeria

This article seeks to establish the relationship that exists between the dimension of transactional leadership style and job satisfaction among employees in Universities’ guesthouses in the hospitality sector of the economy. Quantitative cross sectional research design was adopted for the study. The correlation result reveals that contingent reward of transactional leadership style have weak positive relationship on the employee job satisfaction with 0.267 at Pvalue less than 0.05 level of significance, thus prompting the acceptance of alternative hypothesis

Effect of &#946-Glucuronidase on Extraction Efficiency of Silymarin from Human Plasma Samples Using Validated HPLC-UV Analysis

Purpose: To investigate the effect of &beta;-glucuronidase on the extraction efficiency of silymarin (mainly as silybin) from spiked human plasma using a sensitive and reproducible high performance liquid chromatography (HPLC) method.Methods: The importance of &beta;-glucuronidase was evaluated by comparing the extraction efficiency of silymarin in &beta;-glucuronidase-treated and untreated plasma samples. Isocratic HPLC with simple UV detection (288 nm) was applied to analyze the major silymarin components using Thermo-Electron C18 column (200 mm, 4.6 mm I.D., 5&mu;m particle size). The mobile phase, consisting of methanol and 20 mM potassium dihydrogen phosphate buffer (50:50 v/v pH 2.8), was pumped at 1 ml/min.Results: The mean extraction efficiency was 98.97 % (CV = 1.69 %) for treated and 40.88 % (CV = 2.77 %) for untreated plasma samples, compared with nominal concentrations.Conclusion: The studied method showed 60 % reduced extraction efficiency of untreated samples compared to treated samples.Keywords: Silymarin, Silybin, Extraction Efficiency, &beta;-glucuronidase, HPL