Sharif Digital Repository

It is widely accepted that under reservoir conditions there exists some degree of block-to-block interaction that may lead to capillary continuity. The formation of liquid bridges causing capillary continuity between blocks will significantly affect the ultimate oil recovery. However, accurate modeling of the growth and detachment of traveling liquid bridges which causes capillary continuity between blocks remains a controversial topic. In this work the generalized continuity and momentum equations along with fracture capillary pressure are combined to develop a mechanistic model for formation of traveling liquid bridges between blocks. Firoozabadi and Ishimoto (1994) model is considered for... 

Gas condensate reservoirs show very complex behavior as wellbore pressure falls below the reservoir fluid dew point pressure and consequently liquid phase appears near the wellbore. Since pressure drawdown is the largest near the wellbore, therefore, this region is the first that experience the liquid dropouts. With continuing the production, reservoir pressures at the other parts of the reservoir fall below the dew point pressure and as a result, condensate appears at these regions. The more the condensate accumulates near the wellbore the more decreasing the gas relative permeability occurs. Condensate accumulating does as a liquid barrier and causes not only decreasing the gas production;... 

Naturally fractured reservoirs are essentially very complicated; therefore we need a systematic and reliable characterization process in order to model, analyze displacement phenomena, simulate, develop, and schedule production and other engineering processes. These kinds of reservoirs have multi-scale asymmetry while there is no specific tool to fully characterize them, and on the other hand the field data (including stratigraphy, core study, well testing and seismology) have different resolutions and accuracies, though their significant role to investigate naturally fractured reservoirs. The objective of this project is to investigate the different data sources and present their... 

Due to the importance of enhanced oil recovery of heavy oil fractured reservoirs, in this work micromodel setup has been used to study the miscible solvent injection in five-spot fractured reservoirs with different fracture geometrical characteristics. Due to the visual nature and flexibility of the micromodel patterns it is a subject of interest to be used in different studies. Different patterns has been constructed by chemical etching and controlled laser etching and saturated with displaced fluid and flooded by constant rate injection of hydrocarbon solvent in abient temperature and pressure. At first, effect of fracture’s length, numbering, orientation, discontinuity and scattering on... 

Gravity drainage is the self-propulsion of oil downward in the reservoir rock. Under favorable natural and operational conditions, it has been found to effect recoveries comparable to water displacement. With modern technical knowledge, the operator can often make a choice between dissolved gas drive, water drive and gravity drainage as the principal recovery agent in a reservoir. So far, gravity drainage has received less consideration than the other two. Gravity drainage is one of the most important processes taking place in fractured reservoirs and it plays a major role in oil recovery from low permeability matrix blocks during gas injection process. Gravity drainage is responsible for... 

Gravity Drainage and Capillary Imbibition are among the most important mechanisms in oil production from carbonate fractured reservoirs. In order to investigate the feasibility and effects of these mechanisms in oil recovery from carbonate cores, some different experiments were carried out at Sharif University Laboratories. Carbonate cores were taken away from the well-known Asmari outcrop, Asmari Mountain in south east of M.I.S. city and used in these experiments. Oil and gas samples were collected from field separators and recombined to reservoir composition. The Gas-Oil ratio was adjusted to obtain the reservoir fluid properties. A core flooding apparatus with various capabilities was... 

Fractured reservoirs show a different behavior from common reservoirs because of the existence of a broad network of fractures. This phenomenon makes it necessary to apply special methods for fractured reservoirs in the procedure of reservoir simulation. Since twenty percent of petroleum content in the world is buried in fractured reservoirs, investigating these reservoirs is of great importance.
The first step in simulation of these kinds of reservoirs is to come up with a geometrical model which can be used to take the fracture network influence into account. In the course for reaching such an objective, various models have been developed which are based on specific assumptions and in... 

Gravity drainage is known as the main mechanism for Enhanced Oil Recovery (EOR) in naturally fractured reservoirs. In fact, this mechanism is active in gas invaded zone. In spite of numerous researches in the area, the literature suffers from the lack of a comprehensive model for controlled gravity drainage. Calculating the accurate oil recovery and ultimate recovery factor is inevitable for a successful field development plan as well as enhancing oil recovery. To obtain the accurate values of the aforementioned parameters, an accurate model to solve nonlinear differential equations is necessary. To this end, COMSOL, the well known commercial CFD software, has been used for the modeling of... 

This paper presents finite-element simulation results for hydraulic fracture’s initiation, propagation at reservoirs with damaged zone and naturally fractured reservoirs that likely finds in Iranian oil fields. To address this objective, a two-dimensional poro-elastic model was solved and cohesive zone modeling was used as the methodology for simulation fractures. This enables us to assign individual criteria for fracture initiation and propagation in each model. Our results demonstrate that hydraulic fracturing is not useful in reservoir with strongly damaged zone around the wellbore, because pore pressure increases at that zone and plastic flow of fracture wall happens, so it is better to... 

A fully coupled numerical model is developed for the modeling of the cracks in porous media with flow of two fluids using the extended finite element method.The governing equations of two-phase fluid flow in deformable porous media, which account for the coupling between various physical phenomena, are derived within the framework of the generalized Biot theory. The solid phase displacement, the wetting phase pressure and the capillary pressure are taken as the primary variables of the formulation. The other variables are incorporated into the model via the experimentally determined functions that specify the relationship between the hydraulic properties of the porous medium, i.e.... 

Hydraulic fracturing process as one of the most important ways to inhanse of production requires careful study and investigation and due to its importance has been studied for decades. The effect of this process on the production at oil and gas industry has many complexities and these complexities with the complex structure of natural gaps, would be multiplied. In this thesis effect of hydraulic fracturing operation on the production of natural fractures at naturaly fractured reservoirs from two aspects of hydraulic and geomechanics will be investigated. First we provide models for fractures network by using UDEC software after that investigate the effect of hydraulic farcture on the natural... 

The discrete fracture network and continuous fracture network are among the most widely used methods to model naturally fractured reservoirs. Each method faces particular limitations. The recently introduced recovery curve method (RCM) is believed to meet the limitations of the common methods. In the RCM the recovery curves are used to more realistically describe matrix-fracture interactions. It is necessary to present appropriate solutions to apply the RCM in the real fileds and also to evaluate it based on the historical production data. In this work at first, the basics of the RCM are presented then with a simple column model this method is validated. Then in a column model and a field... 

One of the most important production mechanisms of fractured reservoirs is wettability alteration. Since most fractured reservoirs are carbonate, and thus are often oil-wet; production of these reservoirs is facing their special challenges. Since most of our country reservoirs are fractured carbonate type, determination of the exact mechanisms of their production is necessary. Thermal EOR methods traditionally have been welcomed by big oil companies. Also, these methods of enhanced oil recovery techniques, have a much greater share in the production history of all EOR methods, rather than other EOR methods. Exponentially decreasing of oil viscosity on heating, is the main reason for using... 

Hydrocarbon recovery projects involve large capital investments and have a very high risk associated with them. To minimize this risk, accurate predictions of reservoir performance must be acquired. Reservoir simulation is a powerful tool for fulfilling this requirement. Physics, mathematics, reservoir engineering and computer programming are combined in reservoir simulation in order to predict reservoir performance under different situations both accurately and efficiently. Performance prediction in fractured reservoirs is a much harder task. This difficulty is due to the higher uncertainties associated with their physical and geometrical parameters. More than 60% of world, and almost 70%... 

Due to the fact that, over 60% of oil reserves are located in fractured reservoirs, this type of reservoirs requires a great deal of attention. The presence of the fractures in porous media results in many complexities in the liquid path and production, consequently, simulation and modeling of flow equations is highly important. In order to achieve a more profound understanding of liquid flow in gravity drainage mechanism, the concept of capillary tubes is initially used. By using the capillary tube concept, at first, the gravity drainage mechanism is investigated in the first block in a stack of blocks and an analytical solution is presented for this case. Then, the stack of blocks is... 

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... 

In this work, simulation of 3D three-phase naturally fractured reservoirs is studied. Both Dual Porosity and Dual Porosity-Dual Permeability models which are commonly used in commercial softwares such as ECLIPSE and CMG, are utilized. The governing equations include the mass (in Black-oil model) and linear momentum (in Darcy law form) equations, which are converted into pressure equations and a set of transport equations for the saturations and mole fractions of phases. These equations are solved once for the matrix domain and subsequently for the fracture domain. These two set of equations are coupled through transfer functions. The accuracy of computations significantly depends on how... 

Enhancing oil production from fractured reservoirs is challenging. The flow characteristics observed in naturally fractured reservoirs are complicated due to interaction between the two different flow domains: fracture and matrix. Spontaneous imbibition is one of the most important recovery processes in water-wet fractured reservoirs. Oil cannot be spontaneously produced from oil-wet rocks, unless the capillary pressure barrier between fracture conduits and matrix is overcome. The flow characteristics in fractured systems thus relate to the wettability of the rocks. Low salinity water injection has been widely studied as a method of enhancing oil recovery in recent years. However, its impact... 

The present article studies the isothermal and non-isothermal water injection into naturally fractured oil reservoirs by numerical simulation. The fractures in naturally fractured reservoirs can possess different characteristics. In addition. a remarkable number of naturally fractured reservoirs contain relatively heavy oils that could not be extracted economically; hence. the thermal recovery methods are extensively used for these reservoirs. Hot water injection is one of the thermal recovery methods that has not been explored enough compared to its alternatives. In this study. the effectiveness of the hot water injection over the cold (isothermal) water injection in oil production is... 

Many of oil reservoirs in Iran that are fractured, do not have high Recovery Factor (RF), therefor Enhanced Oil Recovery (EOR) methods are exerted in them. In fractured reservoirs, due to high capillary pressure in matrix and low amount of it in fracture, the wetting phase tends to imbibe to the matrix from the fracture. Altering the wettability of reservoir rock from Oil-Wet (OW) to Water-Wet (WW) enables the injected water to imbibe to matrix and sweep its oil. Also reducing oil/water IFT turns oil to small droplets, helps them to pass narrow pores and be produced. In one of the new EOR methods called chemical EOR, chemical additives are injected to the reservoirs along with water to...