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It has been proven that vehicle emissions such as oxides of nitrogen (NOx) are negatively affecting the health of human beings as well as the environment. In addition, it was recently highlighted that air pollution may result in people being more vulnerable to the deadly COVID-19 virus. The use of biofuels such as E5 and E10 as alternatives of gasoline fuel have been recommended by different researchers. In this paper, the impacts of port injection of water to a spark ignition engine fueled by gasoline, E5 and E10 on its performance and NOx production have been investigated. The experimental work was undertaken using a KIA Cerato engine and the results were used to validate an AVL BOOST model. To develop the numerical analysis, design of experiment (DOE) method was employed. The results showed that by increasing the ethanol fraction in gasoline/ethanol blend, the brake specific fuel consumption (BSFC) improved between 2.3% and 4.5%. However, the level of NOx increased between 22% to 48%. With port injection of water up to 8%, there was up to 1% increase in engine power whereas NOx and BSFC were reduced by 8% and 1%, respectively. The impacts of simultaneous changing of the start of combustion (SOC) and water injection rate on engine power and NOx production was also investigated. It was found that the NOx concentration is very sensitive to SOC variation.

Salt precipitation during CO2 storage in deep saline aquifers can have severe consequences on injectivity during carbon storage. Extensive studies have been carried out on CO2 solubility with individual or mixed salt solutions; however, to the best of the authors’ knowledge, there is no substantial study to consider pressure decay rate as a function of CO2 solubility in brine, and the range of brine concentration for effective CO2 storage. This study presents an experimental core flooding of the Bentheimer sandstone sample under simulated reservoir conditions to examine the effect of four different types of brine at a various ranges of salt concentration (5 to 25 wt.%) on CO2 storage. Results indicate that porosity and permeability reduction, as well as salt precipitation, is higher in divalent brines. It is also found that, at 10 to 20 wt.% brine concentrations in both monovalent and divalent brines, a substantial volume of CO2 is sequestered, which indicates the optimum concentration ranges for storage purposes. Hence, the magnitude of CO2 injectivity impairment depends on both the concentration and type of salt species. The findings from this study are directly relevant to CO2 sequestration in deep saline aquifers as well as screening criteria for carbon storage with enhanced gas and oil recovery processes.

Summary Research currently has shown two contradicting conclusions about silica nanoparticle (SNP) application in mud fluid. While different studies have concluded that adding SNPs reduces the rheological properties, others have found that this is not the case. Therefore, this work was carried out to add to the literature and research that has already been done by different scholars on the performance of SNPs in water-based muds (WBMs). The synthesis of SNPs was performed by the sol-gel process based on the Stöber method in a mixture of a catalyst ammonium hydroxide containing tetraethyl orthosilicate (TEOS), ethanol, and water. The distribution of particle dispersion, size, and zeta potential of SNP analysis was obtained using the dynamic light scattering analysis. Rheological analysis indicated good rheology at different temperatures with 0.5 wt% and 1.0 wt% silica concentration. Furthermore, viscosity and yield point (YP) were stabilized with nanoparticles (NPs at elevated temperatures (up to 176°C) as well as the reference mud maintained rheology (up to 121°C) and above that temperature, there was a drastic change indicating failure. Aging at temperatures above 121°C for 16 hours showed that NP WBMs remained stable with minor changes in rheology. Using bigger sized SNPs than previously used resulted to enhancement in the rheology of WBMs. Previous studies had used SNPs in sizes of 20–40 nm which negatively affected mud rheology. In this study, SNP of a bigger size resulted in rheological property enhancement. It is believed that particle size with other dynamics and mechanisms that still need to be investigated, for example, zeta potential, repulsive and attractive forces are some of the factors in play that affect nanoparticle performance in mud fluids. The obtained rheological data for different NP muds were matched to the traditional drilling mud rheological models to ascertain the best fit model that would be applied to an efficient design and the data fitted the Herschel-Bulkley model. Filtration tests at high pressure and high temperature (HPHT) conditions also indicated that synthesized SNPs used in the mud fluid resulted in a slightly low permeable thin mudcake and a low API gravity filtration loss which have great advantages when drilling through highly permeable formations. Filtrate loss was reduced by 7.5, 9.1, 15.4, and 6.7% when temperature increased to 100, 121, 149, and 176 °C at 1 wt% silica concentration, respectively. The mudcake was also improved and thickness reduced by 30 and 25% at 0.5 wt% silica concentration when temperatures increased from 149 and 176°C, respectively, compared to the reference mud (R) under HPHT conditions. The research results provide a comprehensive evaluation of an enhanced WBM using SNPs for HPHT applications. The investigated NP has the potential to improve drilling mud properties which may led to less formation damage and efficient drilling operations.