جستجوی مقالات مرتبط با کلیدواژه « Porous media » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

This paper presents a control volume finite element model (CVFEM) to simulate simultaneous flow of two immiscible fluids in non-deformable porous media. The method is fully conservative at the local and global level. It keeps the data structure of the common finite element method (FEM). A pressure-based formulation is presented in this paper. The proper choice of primary unknown variables is a critical step in developing an efficient solution of the multiphase subsurface flow problems. Pressure-based models are one of the common choices to this end. This type of models consists of strong nonlinear terms and encounters convergence difficulties when the Jacobian matrix are poorly approximated. The most severe problem is related to the relative permeability term that appears as a function of volume fraction (or degree of saturation) of the wetting phase. Since water saturation is not a primary unknown variable, the relative permeability terms become a function of two primary unknowns, i.e. wetting and non-wetting pressures, together. A fully implicit first order accurate finite difference scheme is employed for temporal discretization of the equations. A full Newton method with exact Jacobian is considered in this work, and a rapid convergence has been achieved. The model is used to simulating a five-spot problem in a block heterogenous porous medium.

Asphaltene-induced formation damage is one of the complicated processes of permeability damage in porous media, particularly in the near-wellbore area. Asphaltene particles precipitate out of the bulk fluid phase during production as a consequence of pressure drop, which may reduce permeability owing to both deposition of asphaltene nanoparticles on porous media surfaces and plugging of pore throats by larger asphaltene agglomerates. Asphaltene precipitation and deposition in production tubes and surface facilities are well-documented concerns, and many solutions for managing them are available. However, the effects of asphaltene in the reservoir, particularly in the near-wellbore zone, are little known. In this study, using an artificial porous medium, experimental data on pressure drop due to changes in parameters such as flow rate, type of precipitant n-alkane solvent (N-heptane alkane solvent and n-decane are used), and percentage of precipitant were obtained. Next, the amount of permeability reduction due to asphaltene deposition in a porous medium has been calculated. To identify the dominant mechanism in reducing clogging, experimental data was fitted with the proposed quasi-experimental models at different time intervals. One of the study's accomplishments was determining the major mechanism of permeability reduction (in vitro) using a reasonably basic model with the least dependent parameters and a decent approximation. According to the findings, pore throat plugging becomes the dominant mechanism of permeability reduction, although filtration cake formation and surface deposition may exist during the tests.

This study has been investigated, the effects of three different polar polyacrylamides (anionic, cationic, and nonionic) on asphaltene deposition in porous media. All experiments were carried out in various dead oil flow rates (0.2, 0.1 and 0.02 cc/min) and different polymer concentrations (500, 2500, 4000 ppm). The results indicated that asphaltene precipitation was affected by the presence of polar additives such as charged polyacrylamide. In general, anionic polyacrylamide increased the asphaltene deposition. The amount of deposition is proportional directly to the increasing concentration of anionic polyacrylamide. Anionic polyacrylamide with the concentrations of 2500 and 4000ppm behaved as a promoter while the hydrophilic property of nonionic polyacrylamide acts as an inhibitor of the precipitation. Stabilization of asphaltene deposition was disturbed in the presence of cationic polyacrylamide. Moreover, the electrostatic and acid-base mechanisms had showed a retarding effect on it. The flow rate is another parameter, which is taken into account besides other factors.