In this study, the adsorption of 5-nm silica nanoparticles onto montmorillonite and illite is investigated. The effect of surface functionalization was evaluated for four different surfaces: unmodified, surfacemodified with anionic (sulfonate), cationic (quaternary ammonium (quat)), and nonionic (polyethylene glycol (PEG)) surfactant. We employed ultraviolet-visible spectroscopy to determine the concentration of adsorbed nanoparticles in conditions that are likely to be found in subsurface reservoir environments. PEG-coated and quat/ PEG-coated silica nanoparticles were found to significantly adsorb onto the clay surfaces, and the effects of electrolyte type (NaCl, KCl) and concentration, nanoparticle concentration, pH, temperature, and clay type on PEG-coated nanoparticle adsorption were studied. The type and concentration of electrolytes were found to influence the degree of adsorption, suggesting a relationship between the interlayer spacing of the clay and the adsorption ability of the nanoparticles. Under the experimental conditions reported in this paper, the isotherms for nanoparticle adsorption onto montmorillonite at 25°C indicate that adsorption occurs less readily as the nanoparticle concentration increases.
TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractMultiphase technology is improving everyday in order to provide solutions for even most difficult design problems in most aspects of engineering. In drilling engineering, twophase flow occurs during underbalanced drilling operations, especially in multilateral and extended reach wells. It has been a challenge for years to identify the flow patterns and predict the frictional pressure losses through circular pipes. Even less is known for annular geometries. In this study, a mechanistic model is developed in order to determine the frictional pressure losses occurring during flow through horizontal eccentric annular conduit. The flow pattern maps and estimated frictional pressure losses using the model are compared with experimental data gathered at METU-PETE-CTFL multiphase flow loop. The results show that model can accurately predict the flow pattern and frictional pressure losses for eccentric annulus. It is also observed that, the flow pattern boundaries for annular geometries differ from those for pipes having same hydraulic diameter.
One of the most difficult tasks in petrolum industry is to characterize the behavior of non-Newtonian fluids flowing through eccentric annulus. Many empirical and semi-empirical approaches have been introduced which attempt to solve this problem. Also, there are few analytical methods proposed, however, the performance of them were not promising. This study aims to approach the problem using finite element method (FEM), which became popular lately due to the developments of the computer technology. Defining a typical wellbore size commonly encountered in CT applications, three different non-Newtonian fluids were tested at three different eccentricities. Different FE mesh types were used to increase the accuracy of the results. The FEM results were compared with different conventional methods as well as experimental results which were available in the literature. The results showed that, as the eccentricity is increased, FEM can estimate the frictional pressure losses more accurately than conventinal methods. It is observed that, as the eccentricity is increased, frictional pressure loss is decreased, if all the other parameters are kept constant. Moreover, the velocity profile across the wellbore can easily be determined, which is very important to identify the hole cleaning performance of a fluid. Introduction In petroleum industry, the flow of Power Law fluids is present approximately in every stages of this engineering branch. During production stages, oil, which can be characterized as a Power Law fluid, is flowing through horizontal or inclined pipelines from the well head to the refinery. In drilling process, the problem is more complicated since the flow geometry includes pipes as well as annular geometries In horizontal wells, multi-lateral wells and coiled tubing applications, the flow geometry is the combination of vertical, inclined and horizontal pipe and annuli, mostly with a significant eccentricity. Moreover, a stationary bed formation might occur in the horizontal sections of the wellbore, which the engineers have to deal with flow of non-Newtonian fluids through eccentric as well as non-circular geometries. The accurate determination of pressure losses may prevent possible problems during fluid circulation and actual drilling operations, i.e. tripping, cementing, well control operations. In the literature, there are several methods, including analytical and empirical approaches, for determining the frictional pressure losses of non-Newtonian fluids flowing through eccentric annulus. However, most of these methods are not practical, or do not give accurate results. The main focus of this study is to determine frictional pressure losses of Power Law fluids flowing through both concentric and eccentric horizontal annuli using finite element method (FEM) and discuss the performance and applicability of FEM.
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