Sharif Digital Repository

Reservoir simulation models are profound tools in reservoir management. Number of grid blocks in a simulation model is much less than the number of grid blocks in geological model, therefore geological model must become upscaled in order to construct simulation model with convenient dimensions. This causes loosing of some details and introduces errors due to discretization and homogenization. One method of construction of an efficient computational grid is use of adaptive mesh refinement (AMR) methods. These methods refine computational grid in regions needing further resolution. An error indicator is used for determining regions candidate for refinement or coarsening. In present study... 

This thesis introduces a fast and accurate two-phase reservoir flow simulation procedure. The speed up is achieved by an upscaling technique where coarsening is applied to the detailed geological reservoir descriptions. This process results to two major error sources affecting the simulation accuracy significantly. The homogenization error is appeared when coarse scale data, such as equivalent permeability, is calculated from the available fine grid model information. It is shown that the error can be reduced adjusting coarse grid (non-uniform Cartesian) distribution. For the first time in this study, the grid distribution optimization is done based on “vorticity” map. In particular, the... 

The results of numerical simulation of underground flows are greatly affected not only by the discretization method of flow equations, but also by the way that the geological domain is upscaled. Including the detailed knowledge of heterogeneous permeability distribution is mostly neither feasible nor computationally efficient. So it is important to develop efficient grid generation and upscaling methods to simplify the fine-scale flow model while still including the impact of the heterogeneities as far as possible. Thus regions where parameters of interest have larger values or higher changes require finer grid blocks and regions with lower values or minor changes should have coarser grid... 

Fluid flow simulation in heterogeneous, full field porous media, like hydrocarbon reservoirs and underground aquifers usually requires multimillion block models, demanding unpractical computation times. Massive researches have been conducted to upscale these fine grid models to coarse models with manageable block numbers. Many upscaling methods have been proposed. These methods differs regarding their gridding techniques (uniform/ structured or disordered), general applicability (process dependency), maximum coursing level achievable, accuracy of the method and their speed-up factor and extend from simple arithmetic averaging to complicated numerical methods. Applying a very powerful... 

In past three decades, use of crude oil’s derivatives increased dramatically. The critical environmental condition of today’s world, which majorly caused by unclean fuels, forces governments to legislate new rules to increase quality of fuels. These rules force refinery industries to produce clean fuels. One of the main processes in producing clean fuels is Desulfurization process. For fuel desulfurization there are different kinds of processes like HydroDesulfruization, Oxidative Desulfurization, Bio-desulfurization, etc. From these processes Hydro-desulfurization is the conventional process for desulfurization. Because of significant problems of this process, like high operational cost,... 

Underground reservoirs are highly complicated due to the presence of spatial heterogeneities at length scales that span from micrometer in pore structure of the rocks to kilometer in the reservoir models. While large-scale flow units need to be characterized using seismic and well data, detailed displacements of fluids in pore space need to be modeled using thin section analysis and pore network modeling. It is therefore necessary to adopt a multi-scale approach to reservoir description to make best use of all the available data that vary over several orders of magnitude, from micro-scale in pore structure to field scale in reservoir flow models. In this thesis, an integrated framework for... 

This paper describes the use of Quad-Tree Decomposition for upscaling of absolute permeability 2D geological models. Quad-Tree Decomposition is a data structure and generates an unstructured upscaled model that preserves the heterogeneity of the original geological model. In other words, in high-variability regions of the geological model, the gridblocks of the upscaled model remain small but in other regions that the permeability variation is low, the gridblocks of the upscaled model are coarsened. Quad-Tree Decomposition is a very simple, efficient and robust method that reduces the total number of gridblocks and results to high saving in time and memory required to flow simulation in the... 

In imbibition process, as one of the main mechanisms of recovery from naturally fractured reservoirs, a wetting fluid enters matrix blocks and produces nonwetting phase from blocks as result of interaction between capillary, gravity and viscous forces. Depending on various characteristics of system different types of imbibition like counter-current spontaneous imbibition, cocurrent spontaneous imbibition and dynamic counter-current imbibition could occur. In order to predict recovery from matrix blocks scaling equations can be used. In this thesis suitable scaling equations are presented for different types of imbibition by using analytical solutions. The studies cases are counter-current... 

Upscaling is an important step in hydrocarbon reservoir modeling which reduces the number of grid blocks of high detailed geological models to prepare them for flow simulation. This helps to speed up computational process, to keep the simulation (CPU) time within a reasonable range and to make future engineering analysis (history matching, comparison of production scenarios, Monte Carlo simulation and etc.) possible. The accuracy of post processing analysis heavily depends on the robustness and validation of the applied upscaling method. Although numerous methods have been proposed in the literature, overemphasizing the effect of scale on the behavior of complex governing equations has... 

Advanced reservoir characterization methods can yield geological models at a very fine resolution, containing 1011-1018 cells while the common reservoir simulators can handle much fewer numbers of cells due to computer hardware limitations. The process of coarsening the fine-scale model to simulation models is known as upscaling. There are three fundamental steps in the procedure of upscaling, i.e. defining the coarse grid geometry, calculating the average properties for the generated coarse grid and simulation of the two-phase flow equations on the generated coarse-scale model. In this thesis, the focus will be on investigating the applicability of optimization in the context of coarse grid... 

Fracture reservoirs are highly heterogeneous. This heterogeneity makes the process of adjusting model parameters to match both the static geological and dynamic production data challenging. For this reason, the characterization of the fracture network of these reservoirs, which is achieved by finding the appropriate probability distributions of the fracture properties in the discrete fracture network model, requires the use of an integrated workflow for the process of history-matching.This thesis, presents an integrated workflow for the process of history-matching of naturally fractured reservoirs with field-scale performance capability. In this methodology, first, multiple discrete fracture... 

Many of gas condensate reservoirs, including rich gas and lean gas, face with fast well productivity decline. The origin of this problem is condense accumulation around the well bore which known as condensate blockage. There are different condensate blockage mitigation methods, one of which is acid fracturing that is suitable for tight carbonate reservoirs with low KH. Acid fracturing simulation is high difficult and have not been undertaken a study that can adopt with experimental and field test results, so researchers usually use practical method and many developed software in this area use correlation form laboratory data. However, the literature show that experimental results can just... 

In this paper we have tried to mention a proper method of upscaling permeability data in a typical Iranian reservoir. Firstly a literature review is made on some common upscaling methods witch have been used so far. We introduced common upscaling methods like full tensor method, streamline method, stone method , vertical equilibrium method and also Kyte & Berry method. Additionally we have explained their advantages and also disadvantages. After selecting two upscaling methods, Kyte & Berry method and vertical equilibrium method, we applied these algorithms for upscaling of permeability data of Soroosh Oil Field. Soroosh oilfield is a heavy oil, Iranian reservoir located in Persian Gulf.... 

In this work, flow transport, distribution, and dissolution of non-aqueous phase liquids (NAPLs) in heterogeneous porous media were modeled by focusing on the dissolution process in pore-level and field scale. First, by adopting advection-diffusion and mass transfer equations, dissolution process and NAPL distribution were investigated in a heterogeneous porous media using pore network modeling. The 2-D developed model was based on observations of micromodel tests. The pore scale simulator which adopted by this work was improved in some aspects in comparison to previous models in the literatures. First, in the phase displacement, by considering more realistic geometries for pore structure... 

In the oil and gas industry, in different stages of exploration and production of oil from hydrocarbon reservoirs, there are several challenges, most of which are due to unbalanced physical-mechanical conditions of the formations. Today, geomechanics of reservoirs is recognized as a key to analyze and solve such problems.Activities such as drilling, perforation, fracturing, production and fluid injection into the reservoir can alter the reservoir stress field and can cause rock deformation. Excessive compaction of reservoir rock can cause surface or seabed subsidence and damage to surface facilities and subsurface tubular. In general, rock compaction can cause many problems if not predicted...