Sharif Digital Repository

As the published statistics of prestigious international institutes show, the share of natural gas from the energy basket of the world is rising. This increase is due to some reasons such as decrease in oil reserves, discovery of new gas fields, lower environmental problems, etc. The Islamic Republic of Iran is not an exception of this rule; but also because of huge gas reservoirs that Iran has, it becomes very important for the Iranian government. Hence, research for predicting the behavior of such reservoirs is a necessary need of oil and gas industry.Both thermodynamic and flow behavior of gas condensate fluids are more complicated than other reservoir fluids. Its complex thermodynamic... 

One of the main purposes of this study is to present a robust and yet efficient semi-discretized algorithm for compositional simulation. All the equations including both the mass balance and the phase equilibrium equations are solved simultaneously which forms a Differential-Algebraic set of Equations and is solved by utilizing an efficient MATLAB solver. Furthermore, another formulation and algorithm is proposed which is consisted of two sets of equations, the primary equations (differential mass balance equations) and the secondary equations (the algebraic phase equilibrium equations). The gradient terms in the primary equations are discretized by using finite element method (Galerkin... 

In most of the commercial and academic multiphase flow simulators, the numerical method in use is based on finite difference methods which can lead the solution toward numerical dispersions or even oscillations. These methods are very sensitive to the size of computational grid blocks. Even if we change the numerical method from finite difference to linear finite element (hFEM), still there will be such problems and size of grid blocks will be crucial in getting proper results which can lead to millions of computational grid blocks. One way to deal with this problem is using nonlinear finite element methods (pFEM) also known as higher-order finite element methods, Also compositional... 

In this project, a viscous instability phenomenon in CO2 injection process has been investigated. The viscosity of CO2 is much less than the reservoir fluid and the resultant mobility ratio results in the instability of sweeping front. The instability may occur in a typical permeable thief zone. This is due to severe change in gas saturation and/or relative permeability of the gas, hence reducing the sweeping efficiency. This process severely affects areal recovery and results in the inefficacy or failure of gas injection process. Here we tried to simulate the phenomena by higher order finite element methods and the results are in agreement with the geometry of thief zone. Indeed, lower... 

Most of the Iranian oil reservoirs are reaching end of their natural production life, hence they are suitable candidates for EOR common processes like gas injection and WAG injection. Studies have shown that gas and WAG injection can be applied for optimal oil production. Past studies have been mainly on gas and WAG injection in immiscible or fully miscible conditions and there is a limited amount of data available on performance of these methods in near miscible conditions. Miscible injection is not feasible in old Iranian oil reservoirs due to their depleted pressure. Moreover injection in lower pressures is attractive from both economical and operational standpoints since this reduces the... 

A simultaneous water and CO2 injection study using sandstone cores with 21°API Sarvak (Azadegan field) oil has performed to evaluate oil recovery under four injection modes: secondary immiscible, secondary near-miscible, tertiary immiscible, and tertiary near-miscible. It is demonstrated that swag injection (secondary and tertiary) is an effective method for the recovery of significant amount of oil or residual oil from water-flooded porous media, but there is always some bypassing (at the pore level) of the oil due to topological effects, water-shielding and dead-end pores. In non-homogeneous porous medium, oil recovery is depending to SWAG ratio in immiscible and near-miscible conditions.... 

Phase behavior calculations and compositional simulation for the hydrocarbon systems containing many components, are time consuming and impractical. Therefore the number of the components those describe the fluid description must be kept to a minimum using grouping techniques. In this research, it is tried to apply a new set of grouping techniques in compositional simulation of oil and gas reservoir. In these methods, the components are automatically placed in the pseudo-components, and their critical and thermo-physical properties are calculated simultaneously or after grouping process according to different mixing rules. These set of techniques areworking based on the distances between... 

One of the main purposes of this project is to propose an efficient and stable algorithm of a semi-discretized formulation for compositional simulation of oil reservoirs. In this algorithm, all the equations including both mass balances and equilibrium equations are solved simultaneously. The gradient terms are discretized by the Finite Volume Method (FVM). The resulting Differential Algebraic Equation, the so-called DAE, are solved by MATLAB functions. Another novel technique developed, handles each block equations set, separately. In this block-by-block scheme, there are two set of equations; the primary (mass balance) and secondary (equilibrium) equations. In the primary ones, the... 

The process of gas injection is well-known for Enhanced Oil Recovery (EOR) among researchers in the past few decades. This process depends on both compositional effects and IFT reduction effects as the conditions approach miscibility. This study seeks to evaluate the interactions of these two fundamental mechanisms in the process of enriched gas injection for EOR. At first, we investigate the relative dominance of the key mechanisms, as well as composition paths, component and phase distribution, and component production via compositional simulation of the process of gas injection into 1D homogeneous porous media such as slim tube and core under immiscible and near-miscible conditions. Then,... 

The gas injection is one of the most common methods of increasing recovery from oil reservoirs, especially when a suitable source for gas is available. For example, available sources of carbon dioxide or associated gas produced from the reservoir or adjacent reservoirs. In general, the gas injection may be miscible or immiscible, which is a function of the type and composition of the gas-oil and the reservoir conditions in terms of temperature and pressure. In miscible gas injection, different mechanisms such as molecular diffusion of gas in oil or evaporation of lighter components of oil in gas and condensation of heavier components of gas in the oil phase can be shown. To occur of such...