Sharif Digital Repository

Improved methods of constructing wells and producing wells are one of the keys to increasing field profitability. In the areas of well construction and well productivity optimization, many of the problems encountered are related to the geomechanics of the reservoir and the overlying layers; these problems include well-bore stability, sand production and hydraulic fracturing. Hydraulic fracturing is a complicated phenomenon in which deformation of the porous medium and fluid leak-off to the surrounding area take place simultaneously. Their interaction, therefore, must not be overlooked. In the past, some experimental researchers performed laboratory investigations on the phenomenon of... 

The construction of a facies model could be employed as a conditional data for any property simulation that results in a more reliable reservoir characterization in further steps. In this study, an Iranian gas reservoir with six wells was studied to determine the 3D reservoir facies model. Fifteen reservoir facies were first detected along one of the wells with detailed core and thin section descriptions. Due to the significant difference between the core and log data resolution, facies were clustered into four major groups regarding the digenetic processes and petrophysical lithofacies properties (permeability and porosity). The lithofacies specification effect on petrophysical properties... 

In this paper the framework for a constitutive model which is developed for a cemented gravely sand is presented. The model is based on separation technic namely the separation of the behavior to the uncemented soil and the cemented bonds. They are combined in a manner to satisfy the deformation consistency and energy equilibrium equations. The uncemented soil behavior is modeled using a modified model originally proposed by Pastor et al. (1985) for sandy soils. Also, based on the results of the experiments, a new model for the bonds is developed. Combination of these two parts results in the modeling of the behavior of cemented gravely soils in drained and undrained states  

Detailed geological models of a reservoir may contain many more cells that can be handled by reservoir simulators due to computer hardware limitations. Upscaling is introduced as an effective way to overcome this problem. However, recovery predictions performed on a coarser upscaled mesh are inevitably less accurate than those performed on the initial fine mesh. Dual mesh method is an approach that uses both coarse and fine grid information during simulation. In the reconstruction step of this method, the equations should be solved numerically within each coarse block, which is a time consuming process. Recently, a new coarse-grid generation technique based on the vorticity preservation... 

Reservoir flow simulation involves subdivision of the physical domain into a number of gridblocks. This is best accomplished with optimized gridpoint density and a minimized number of gridblocks, especially for coarse-grid generation from a fine-grid geological model. In any coarse-grid generation, proper distribution of gridpoints, which form the basis of numerical gridblocks, is a challenging task. We show that this can be achieved effectively by a novel grid-generation approach based on a background grid that stores gridpoint spacing parameters. Spacing parameter (L) can be described by Poisson's equation (▽2L = G), where the local density of gridpoints is controlled by a variable source... 

Reservoir flow simulation involves subdivision of the physical domain into a number of gridblocks. This is best accomplished with optimized grid point density and minimized number of gridblocks especially for coarse grid generation from a fine grid geological model. In any coarse grid generation, proper distribution of grid points, which form basis of numerical gridblocks, is a challenging task. We show that this can be effectively achieved by generating a background grid that stores grid point spacing parameter. Spacing (X) can be described by Poisson's equation (∇2 L = G) where the local density of grid points is controlled by a variable source term (G). This source term can be based on... 

This paper presents a novel coarse grid generation technique based on using vorticity as a measure of the impact of heterogeneity on flow. Vorticity is a maximum when the total flow is high and perpendicular to a large permeability gradient. Maps of vorticity were generated from single-phase flow simulations and used to generate coarse simulation grids from finely gridded geological models. The resulting grid was more refined in areas of high vorticity and coarser in areas of low vorticity. The method is first demonstrated on a simple five-layered model before being applied to three, 2D models of geologically realistic heterogeneity. The homogenized model generated from vorticity maps shows... 

In this study amount of soil erosion in watershed of JAJROOD is estimated by use of the RULSE model with the help of GIS12. JAJROOD River is located in upstream of LATIAN Dam and is one of the most important water sources of Tehran. Also, this River has a big role in preventing the flood. modeling Results show that the amount of soil erosion is high due to high slope of the land, lack of plant coverage and the quality of soil and changing the land application, lead to increase in erosion potential. modeling Results have estimated the amount of erosion in this basin about 1,524,511 tons in a year. In order to evaluate Results and efficiency of the model, all of obtained results are compared... 

An effective procedure to incorporate kinematic interaction (KI) aspects in seismic analysis of soil-structures systems was presented. In this regard, first, the effect of KI on the structural response was investigated with special focus on the role of rocking component of foundation input motion (FIM). This was performed parametrically for a wide range of selected nondimensional parameters, which well define the introduced simplified soil-structure model. It was observed that ignoring the effect of rocking input motion may introduce errors, which can be on the unsafe side especially for slender structures with large embedment ratios. On the other hand, it was known that introducing the... 

The concept of equivalent linearization, in which the actual nonlinear structure is replaced by an equivalent linear single-degree-of-freedom (SDOF) system, is extended for soil-structure systems in order to consider the simultaneous effects of soil-structure interaction (SSI) and inelastic behavior of the structure on equivalent linear parameters (ELP). This is carried out by searching over a two-dimensional equivalent period-equivalent damping space for the best pair, which can predict the earthquake response of the inelastic soil-structure system with sufficient accuracy. The super-structure is modeled as an elasto-plastic SDOF system whereas the soil beneath the structure is considered... 

In this paper, Lattice Boltzmann method (LBM) has been used to study the effects of permeability and tortuosity on flow through saturated particulate media and identify the relationships between permeability and tortuosity with other parameters such as particles diameter, grain specific surface, and porosity. LBM is a simple kinematic model that can incorporate the essential physics of microscopic and mesoscopic processes involved in flow through granular soils. The obtained results indicate that the 2D LB model, due to its inherent theoretical advantages, is capable of demonstrating that the porosity and specific surface are the most influential parameters in determining the intrinsic... 

The need for simplified physical models representing frequency dependent soil impedances has been the motivation behind many researches throughout history. Generally, such models are generated to capture impedance functions in a wide range of excitation frequencies, which leads to relatively complex models. That is while there is just a limited range of frequencies that really influence the response of the structure. Here, a new methodology based on the response-matching concept is proposed, which can lead to the development of simpler discrete models. The idea is then used to upgrade an existing simple model of surface foundations to the case of embedded foundations. The applicability of... 

The process of coarsening the detailed geological model of a reservoir to simulation models is known as upscaling. There are two fundamental steps in the procedure of upscaling, i.e., defining the coarse grid geometry and calculating the average properties for the generated coarse grid. In this paper, the focus will be on investigating the applicability of optimization in the context of coarse grid geometry definition. To do so, different objective function candidates will be defined, and their behavior in terms of predicting the two-phase flow accuracy of coarse grids will be analyzed to determine the proper objective function. A modified objective function employing the idea of analytical... 

In this paper, a simple finite element model for seismic analysis of retaining walls is introduced. The model incorporates nonlinearity in the behavior of near wall soil, wall flexibility and elastic free field soil response. This model can be employed in nonlinear modeling of retaining walls and bridge abutments. The advantages of this model are simplicity and flexibility in addition to acceptable precision. Using this finite element model, an analytical study is conducted on several soil-wall systems using nonlinear time-history analysis by applying real earthquake records. Based on the results of these analyses, new seismic soil pressure distributions are proposed for different soil and... 

For studying the behavior of structure in an earthquake, it is advisable to model the structure as a multi-degrees of freedom system, consisting of numerous single-degree of freedom substructures and pay attention to soil-structure interaction. System identification is divided into two categories: namely time domain method and frequency domain approach. In this paper, a localized substructure identification of shear building considering the soil-structure interaction is presented using a frequency domain approach. In order to deal with noise-corrupted data, a spectral smoothing technique with Parzen's window reduction method is adapted. It is shown that better convergence and accuracy can be... 

Constructing an accurate geological model of the reservoir is a preliminary to make any reliable prediction of a reservoir's performance. Afterward, one needs to simulate the flow to predict the reservoir's dynamic behaviour. This process usually is associated with high computational costs. Therefore, alternative methods such as the percolation approach for rapid estimation of reservoir efficiency are quite desirable. This study tries to address the Well Testing (WT) interpretation of heterogeneous reservoirs, constructed from two extreme permeabilities, 0 and K. In particular, we simulated a drawdown test on typical site percolation mediums, occupied to fraction "p"at a constant rate Q/h,... 

Surface waves generated during vibration of machine foundations are sometimes troublemaking and cause some damages to the nearby sensitive structures or people. Considering the function of the machines located on the foundations the dynamic loading could be harmonic or impact type. The main part of the generated energy is transferred to the ground by Rayleigh surface waves. One of the most reliable and economic methods for reduction of the effects of these generated waves is using open trenches around the dynamic sources, so called active isolation in literature. In this paper applicability and affecting parameters of the open trenches around the impact dynamic source is studied using... 

SUMMARY: In this paper, a numerical model is developed for the fully coupled hydro-mechanical analysis of deformable, progressively fracturing porous media interacting with the flow of two immiscible, compressible wetting and non-wetting pore fluids, in which the coupling between various processes is taken into account. The governing equations involving the coupled solid skeleton deformation and two-phase fluid flow in partially saturated porous media including cohesive cracks are derived within the framework of the generalized Biot theory. The fluid flow within the crack is simulated using the Darcy law in which the permeability variation with porosity because of the cracking of the solid... 

The soil permeability coefficient plays a key role in the process of numerical simulation of the liquefaction phenomenon. Liquefaction causes a considerable increase in soil permeability, due to the creation of easier paths for water flow. The work presented in this paper tries to investigate the effects of permeability coefficient on the results of numerical modeling of the liquefaction phenomenon. To do this, a fully coupled (u-P) formulation is employed to analyze soil displacements and pore water pressures. Two different versions of a well-calibrated critical state bounding surface plasticity model, which possesses the capability to utilize a single set of material parameters for a wide... 

Nanocomposite films based on low density polyethylene (LDPE), containing of 2, 3, and 4. wt.% organoclay (OC) and ethylene vinyl acetate (EVA) copolymer as a new compatibilizer were prepared and characterized using rheological tests, X-ray diffraction, differential scanning calorimetry, oxygen permeation measurements, and tensile tests. There was no exfoliation or intercalation of the clay layers in the absence of EVA, while an obvious increase in d-spacing was observed when the samples were prepared with EVA present. This issue was reflected in the properties of nanocomposites. The oxygen barrier properties of the LDPE/EVA/OC film were significantly better than those of the LDPE/OC film....