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The continuous growth of energy requirements, together with diminishing production, necessitates tireless efforts to develop new technology frontiers in oilfield operations. The hydrocarbon reservoirs residing below the shale and near to the depletion stage are not recoverable using conventional methods. Therefore, innovation is necessary to drill non-traditional hydrocarbon reservoirs present in the basin scale with a difficult approach. An understanding of drilling fluid rheology helps to design a fluid system with better features that can overcome issues faced during unconventional drilling processes. The attention of the scientific community has been diverted towards the water base drilling fluid system that has a low environmental footprint. When the water base drilling fluid physically and chemically interact with clay, this may cause swelling, bit balling, or blockage of the wellbore. The aim of this paper is to provide a comprehensive review of inhibitors, aiming to understand the clay swelling mechanisms and the development of water-based mud additives for hydration restriction. The suitable shale inhibitors must not only efficiently diminish the clay hydration swelling but also fulfill the progressively rigorous environmental regulations, even though staying cost-efficient. The green shale inhibitors reported in the literature include amines, acrylamide, alcohols, biomolecules and silica-based additives for water-based mud. Further critical analysis is provided with a comprehensive understanding of the inhibition mechanisms for shale and the development of effective water-based shale inhibitors. The gaps in the current literature are identified to help readers to identify prospects for improvements in the drilling fluids that can help to explore possible future directions.

Octane rating is an essential property for gasoline-type fuels because it is the major factor that determines the maximum compression ratio (CR) allowed in spark-ignition engines. In practice, a base gasoline, which is a mixture of various refinery streams, is dosed with octane-booster additives for meeting the minimum octane requirements set by regulation standards. Coal-based methanol is widely used in China as a gasoline octane-booster. In addition to its high octane rating, methanol’s cooling effect derived from its low latent heat and its high octane sensitivity also contribute to engine knocking suppression in spark-ignition direct-injection (DISI) engines. Thus, fully understand the role of methanol addition in gasoline is highly relevant to estimate the potential thermal efficiency gain for methanol blends. The novelty of this paper is that methanol’s chemical effect, cooling effects and octane sensitivity effects on engine knocking suppression are quantitatively converted to an effective octane index (EOI), a parameter for comprehensively describing the anti-knocking properties of a gasoline-type fuel. Then ΔEOI of methanol blends (EOI_blend − EOI_base) was used for estimating engine thermal efficiency gain in compression ratio (CR) matched DISI engines. Results suggest that methanol’s cooling effect is as significant as its high octane rating. For example, the cooling effect of methanol corresponds to 19 unit of octane in a blend with 70 vol% methanol (M70). The indicated thermal efficiency gain is up to 30% for M70 with RON81.1 base gasoline. The reduction in the lower heating value (LHV) of methanol blends lead to higher fuel consumption, which can be partially or even entirely offset by the improved indicated thermal efficiency. Overall, this paper highlighted the effectiveness of methanol as an octane and thermal efficiency booster.

The present study is geared towards the investigation of the impact of fuel temperature, ambient pressure, and fuel properties on the spray characteristics of a 6-hole gasoline direct injector. High speed imaging is employed to verify the spray structural variation of various fuels including iso-octane, gasoline, methanol, and ethanol over wide range of operating conditions in an optical vessel. These structural parameters were correlated to the ratio of the ambient to saturation pressure ratio (Pa/Ps) that represents the superheated degree. At a constant pressure of 150 bar the fuel was injected, and the fuel temperature ranged between 25 and 120 °C, whilst the ambient pressure ranged from 0.1 to 1 bar. The results indicated that for all the fuels, the spray width was reduced, and the adjacent plumes collapsed into single bulk as the (Pa/Ps) decreased. Furthermore, at very low (Pa/Ps = 0.065), the spray getting longer, and for iso-octane the fuel spray shrinkage toward the injector centreline and shaped like a Fish with sharpen spray tip. The spray cone angle for ethanol, methanol, and gasoline was reduced when the Pa/Ps ratio was decreased from 1 to 0.16 with the exception that at Pa/Ps = 0.54 for ethanol the cone angle was increased and then decreased with the reduction of Pa/Ps. Then a massive increase in the cone angle was noticed by reducing the Pa/Ps ratio reduced from 0.16 to 0.065. For iso-octane, the behaviour is chaotic and not follow any specific trend with the reduction of Pa/Ps. Furthermore, the appearance of interstitial streams in the gaps between the original spray streams was noticed at Pa/Ps ratio ≤ 0.28. Phase Doppler data showed for the Pa/Ps ratios of 0.85, 0.54, and 0.28, that the interstellar streams consistently had a lower mean droplets velocity and a very narrow head stage compared to that of spray main streams. Moreover, reducing the Pa/Ps ratios of 0.85, 0.28, resulted in a significant reduction in Sauter mean diameter with approximately 49.5%.

A new burner was developed in order to achieve very stable lean flames at lower equivalence ratio and higher level of turbulence intensity. The air-fuel mixing process of the current burner was controlled either by using different levels of partially premixed or by changing the turbulence generator disk slit diameter, ds. Initially, the distributions of turbulent intensity and air volume fraction inside the burner were numerically investigated using three-dimensional computational fluid dynamic (CFD) modelling. Then the lean flame stability limits corresponding to the lean natural gas (NG)/air mixture at an equivalence ratio of φ = 0.6, under five degrees of partially premixed and two turbulent generators disk slit diameters were delineated. Based on the stability limits map, laser induced breakdown spectroscopy (LIBS) technique was employed for further quantitative measurements of the mixture fraction or the equivalence ratio distributions of NG/air mixture. The results indicated that the maximum burner stability for smaller ds was achieved at mixing length to diameter ratio (L/D) of 1:1, whilst for larger ds the maximum stability was achieved at L/D ratio of 2:1. Furthermore, the largest disk slit diameter yielded a homogeneous mixture fraction distribution and lower rms fluctuation, compared to that of lower disk slit diameter. Consequently, this improved the conduction effectiveness in preheating the unburned gases layers resulting in higher flame propagation speed.

Black liquor (BL) rich phenolic and complex compounds is generated from pulp and paper mill manufacturing processes which should be treated before reaching the environment. The potential of achieving several sustainable development goals (SDGs) by recovering energy and valuable by-products from BL was extensively investigated. Results revealed that under a dark-fermentation process, the organic content in BL was effectively bio-degraded by anaerobes to achieve a hydrogen yield (HY) of 0.62 ± 0.04 mol/molglucose. Fortunately, the HY was significantly increased up to 1.41 ± 0.13 mol/molglucose by immobilizing the anaerobes onto magnetite nanoparticles (MN). α-amylase, xylanase, CM-cellulase, polygalacturinase, and protease enzymes activities were increased by 2.3, 23.7, 2.7, 26.8, and 31.1 folds with supplementation of MN. Moreover, the conversion efficiencies of protein and carbohydrate were improved by values of 36 and 113.3% and total phenolic compounds (TPC) were enhanced by 23.5% compared with the control test. Electron-equivalent and COD mass balances were estimated to comprehensively describe the effect of Mn supplementation on the HY performance and fermentation pathways. Digestate generated from the fermentation process was utilized to produce biochar, having C (58.2%), O (32.4%), Na (4.7%), and P (1.1%). The study outputs were interlinked to bio-energy generation, pollution minimization, biochar as a soil amendment, nanoparticles and paper manufacturing industrialization, meeting environmental, economic, and social related SDGs.

Experimental optical tests were carried out in two concentric tubes burner, to obtain a comprehensive understanding of the turbulence level effects on flame kernel propagation in partially premixed flames. Two ND-YAG lasers with first and second harmonic wavelengths were employed for laser ignition and flow field velocity measurements, respectively. For the current study two parameters were considered, first the geometrical parameter, namely turbulence generator disk diameter (ds), which changes the turbulence intensity, whilst the second parameter was the jet velocity. These parameters were investigated under constant degree of partial premixing, and Liquid petroleum gas (LPG) was used as a fuel. The effect of the equivalence ratio and the jet velocity on the minimum ignition laser energy (MILE) and flame stability maps of different turbulence generator diameters were measured and employed to determine the suitable overall equivalence ratio and the operating conditions for the current study. Based on the analysis of the MILE and the stability limits, one constant jet equivalence ratio of φ = 2 and different jet velocities were used for the whole tests. The turbulent flow field was captured using two-dimension particle image velocimetry (2D PIV) system, and after times of 150, 300, 500, 1000, 1500, and 2500 μs from the start of ignition. The results demonstrated that the MILE for LPG increased as the equivalence ratio increased, especially for rich conditions. In addition, near the stoichiometric conditions, the MILE trends were closely matched for all the jet velocities, although the MILE trends of lean condition were marginally higher. The flame stability maps of different turbulence generator diameters illustrated three extinction curves, which were separated between two regions, lifted flames and blowout. Smaller (ds) was more stable compared to other (ds). The turbulence chemistry interactions influenced the flame kernel propagation rate; at lower jet velocities chemistry effects were dominant, whilst at higher jet velocities turbulence became dominant. The propagation rate for LPG flames increased either by increasing ds or by increasing jet velocity.

An optical-based experimental study of the injector deposit effect on a multi-hole GDI injector was performed first. After carefully calibrating the spray model with the experiment data, a three-dimensional computational fluid dynamics (CFD) simulation was then carried out to study the deposit effect on the air/fuel mixture preparation process in an optical research GDI engine. Six different injection timings were used for full-cycle simulations. The numerical engine condition was at stoichiometric ratio, 1200 rpm and 150 bar injection pressure. The experimental results showed that injector deposit would lead to lower fuel mass flow rate, with 5.4%, 5.7% and 6.1% loss at 50, 100 and 150 bar respectively. Injector deposit resulted in longer penetration length and the effect displayed hole to hole difference. The maximum increment was observed for the ignition jets with 11.6% at 150 bar. Injector deposit led to higher droplet velocity and larger droplet size and the difference increased with injection pressure. For the air/fuel mixing simulation, the injector deposit led to more fuel impingement on the piston and cylinder walls, as well as a lower mean equivalence ratio during late injection events. The distorted spray pattern led to higher fuel stratification level. In very late injection cases, the injector deposit led to a very lean mixture near the spark plug which could result in unstable engine performance; while the rich regions at the cylinder sides could result in higher emissions. Comparison of computed results with PLIF (planar laser induced fluorescence) images provided a satisfactory validation for the model.

Multiobjective optimization (MOO) techniques are of much interest with their applications to petroleum refinery catalytic processes for finding optimal solutions in the midst of conflicting objectives. The rationale behind using MOO is that if objectives are in conflict, a set of trade-off optimal modeling solutions must be obtained to help management select the most-preferred operational solution for a refinery process. Using MOO does not involve hyperparameters thereby reducing the expensive parameter tuning tasks. A true MOO method allows numerous Pareto-based optimal solutions to be identified so that management and decision-makers' preference information can be used to finally select a single preferred solution. This review discusses MOO algorithms and their applications in petroleum and refinery processes. The survey provides insights into the fundamentals, metrics, and relevant algorithms conceived for MOO in petroleum and refinery fields. Also, it provides a deeper discussion of state-of-the-art research conducted to optimize conflicting objectives simultaneously for three main refinery processes, namely hydrotreating, desulfurization, and cracking. Finally, several research and application directions specific to refinery processes are discussed.

Ethyl esters have been considered as promising second-generation biofuel candidates, due to the available production from low grade biomass waste. Furthermore, with desirable energy densities, emissions performance, low solubility and higher Research Octane Number (RON), ethyl esters have proven attractive as fuel additives or alternatives for gasoline. In this study, high-speed schlieren photography was used to investigate the laminar burning characteristics of three ethyl ester fuels: ethyl acetate, ethyl propionate, and ethyl butyrate, in comparison with gasoline and ethanol at different initial temperatures and a variety of equivalence ratios, with an initial pressure of 0.1 MPa in a constant-volume vessel. For the five fuels, the stretched flame speeds, the un-stretched flame speeds, Markstein lengths, Markstein number, laminar burning velocities and laminar burning flux were calculated and analysed using the outwardly spherical flame method. The results show that for all examined initial temperatures (60 °C, 90 °C and 120 °C) and equivalence ratios; ethanol had the highest un-stretched flame propagation speeds, whilst ethyl acetate (EA) had the lowest. At high initial temperatures (120 °C), it was observed that the un-stretched flame speed trends of ethyl propionate (EP) and ethyl butyrate (EB) proved faster compared to gasoline, especially for rich conditions. The EB and EA flames demonstrated greater stability when compared to ethanol, EP, and gasoline. Analysis showed that ethanol yielded the fastest flame velocities, whilst EA consistently had the lowest among all the five fuels. The laminar burning velocities of the EP fuel were faster compared to EB and EA, whilst slower than ethanol and gasoline at 60 °C. Further increase of the initial temperature, up to 120 °C, showed the laminar flame speed of EP and EB to be faster than gasoline, indicating a fast-burning property, and potential of improving engine thermal efficiency.

A film-shear reactor was used to significantly enhance the oxidative desulfurization (ODS) of model fuels using hydrogen peroxide as the oxidant. Significant increases in the amount of sulfur removed were seen in comparison to conventionally stirred ODS reactions. For example, up to 50% desulfurization occurred in a single pass of the model fuel through the film-shear reactor at 10 °C. The desulfurization reactions were very fast in the reactor, occurring on the time scale of seconds to minutes. Desulfurization was studied under a variety of conditions, and a statistical design of experiment (DOE) showed that the fuel to oxidant ratio was the only statistically significant parameter to impact the extent of desulfurization: a larger amount of oxidant led to higher desulfurization. A variety of benzothiophene contaminants (benzothiophene, 2-methylbenzothiophene, 5-methylbenzothiophene, dibenzothiophene, and 4,6-dimethyldibenzothiophene) were examined, and the film-shear reactor was effective in removing all of these contaminants. The film-shear reactor was effective at both low (0.5–2.0 mL/min) and high (100–300 mL/min) flow rates. Experiments showed that oxygen in air was not an effective oxidant for ODS in the film-shear reactor. Experiments using Mo(CO) 6 as a molecular thermometer showed that “hot spots” are not forming in the film-shear reactor, and thus the increase in the ODS rate cannot be attributed to intense thermal activation occurring within the film-shear reactor. It is suggested that superb mixing of the aqueous and fuel phases is responsible for the increased rate of ODS in the reactor.