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In water- and wastewater-treatment processes, knowledge of sludge settlement behavior is a key requirement for proper design of a continuous clarifier or thickener. One of the most robust and practical tests to acquire information about rate of sedimentation is through execution of batch settling tests. In lieu of conducting a series of settling tests for various initial concentrations, it is promising and advantageous to develop simple predictive models to estimate the sludge settlement behavior for a wide range of operating conditions. These predictive mathematical model(s) also enhance the accuracy of outputs by eliminating measurement errors originated from graphical methods and visual observations. In the present study, two empirical models were proposed based on Vandermonde matrix (VM) characteristics as well as a Levenberg–Marquardt (LM) algorithm to predict temporal height of the supernatant–sludge interface. The novelty of our modeling approach is twofold: the proposed models in this study are more robust and simpler compared to other models in the literature, and the initial sludge concentration was considered as a key independent variable in addition to the more-customarily used settling time. The prediction performance of the VM-based model was better than the LM-based model considering the statistical parameters associated with the fitting of the experimental data including coefficient of determination (R2), root mean square error (RMSE), and mean absolute percentage error (MAPE). The values of R2, RMSE, and MAPE for the VM- and LM-based models were obtained at 0.997, 0.132, and 5.413% as well as 0.969, 0.107, and 6.433%, respectively. The proposed predictive models will be useful for determination of the sedimentation behavior at pilot- or industrial-scale applications of water treatment, when the experimental methods are not feasible, time is limited, or adequate laboratory infrastructure is not available. [ABSTRACT FROM AUTHOR]

In this paper, the effects of major asphaltene deposition model parameters, particle-particle collision, and particle-wall sticking efficiencies as well as asphaltene content in a hydrocarbon fluid on asphaltene deposition in both a Taylor-Couette device and production tubing are numerically studied. The possibility of an increase in asphaltene deposition rate as a result of adding asphaltene inhibitors is investigated. The computations show that this critical effect is achievable in a Taylor-Couette device operating in a batch regime only if the particle collision and the particle-wall sticking efficiencies are more than an order of magnitude higher than those identified for asphaltenes present in hydrocarbon fluids. Calculations of deposition in the Taylor-Couette device show also that an increase in the asphaltene content causes an increase in the rate of fluid depletion of particles able to deposit. The deposition calculations for a vertical pipe demonstrate that, due to continuous precipitation of primary particles along the tubing, a hydrocarbon fluid cannot be depleted of particles able to deposit; therefore the maximum deposit thickness always increases with an increase either in the major model parameters or the asphaltene content. Thus, the model parameter values indicating critical deposition regimes are different from those inherent to real hydrocarbon fluids; therefore, these regimes cannot be achieved in practical applications. [ABSTRACT FROM AUTHOR]

Precipitation and deposition of asphaltenes and other organic substances in formation rock causes formation damage and reduces effective hydrocarbon mobility, which can result in significant production losses. The development of reliable experimental, analytical, and modelling methods improves the understanding of asphaltene-induced formation damage and provides tools for preventing and/or controlling formation damage due to asphaltenes in oil-bearing formations. To make further advancements in understanding asphaltene impairment, it is important to analyze the current state of technology and research in this area. In addition to analyses of known experimental data and models of reservoir impairment by asphaltenes, prospective directions of future research in this area are also suggested. [ABSTRACT FROM AUTHOR]

Although alkaline-surfactant-polymer (ASP) flooding has proven efficient for heavy oil recovery, the displacement mechanisms and efficiency of this process should be discussed further in fractured porous media. In this study, several ASP flooding tests were conducted in fractured glass-etched micromodels with a typical waterflood geometrical configuration, i.e. five-spot injection-production pattern. The ASP flooding tests were conducted at constant injection flow rates but different fracture geometrical characteristics. The ASP solutions consisted of five polymers, two surfactants, and three alkaline types. It was found that using synthetic polymers, especially hydrolyzed polyacrylamide with high molecular mass, as well as cationic surfactant increases the ultimate recovery. The location of the injection well with respect to the fracture system plays a significant role in the ASP flooding performance, i.e. an increase in the angle associated with the longitudinal extension of fractures with respect to the main flow direction resulted in enhanced oil recovery and also postponed the wetting phase breakthrough time. Mechanistic study of this displacement process revealed that dispersive and diffusive behaviour of the ASP front enhanced the fluid transport from fracture to matrix and increased the microscopic displacement efficiency. Emulsification and coalescence mechanisms were responsible for ASP frontal advancement. Residual oil in the invaded region, which was observed in the form of discontinuous oil ganglia dispersed in the invaded pore bodies or in the form of pendular bridges formed around some of the solid particles, was mobilized in the form of oil wads through the droplets of the displacing phase. [ABSTRACT FROM AUTHOR]