Sharif Digital Repository

The aim of the present work is to evaluate the effect of fractures geometrical properties such as orientation, density, location, and networking on the conventional fire flooding (CFF) process performance through simulation analysis. Combustion parameters of a fractured low-permeable carbonate heavy oil reservoir in Iran called Kuh-E-Mond (KEM); applied for simulation study and simulator has been validated with KEM combustion tube experimental data. The validated model was modified to study CFF in 3D semi-scaled combustion cells. Simulation results confirmed that CFF is more feasible in the case of densely fractured reservoirs such as those in the Middle East  

Spontaneous imbibition of water into the matrix blocks because of capillary forces is an important recovery mechanism for oil recovery from naturally fractured reservoirs. In modeling this process, it has been assumed classically that local equilibrium is reached and, therefore, capillary pressure and relative permeability functions are only a function of water saturation, resulting in the appearance of the self-similarity condition. In some works published in the last 2 decades, it has, however, been claimed that local equilibrium is not reached in porous media, and therefore, opposite the classical local-equilibrium/self-similar approach, non-equilibrium effects should be taken into... 

Despite numerous experimental and numerical studies, fundamental understanding of how the matrix block height, the density difference between petroleum and gas, and matrix capillary pressure could affect the oil recovery from a single matrix block in naturally fractured reservoirs remains a topic of debate in the literature. In this work a one-dimensional gravity drainage model developed by Firoozabadi and Ishimoto (1994) is considered and numerically solved. The Fourier series method is applied for a numerical Laplace inversion of the dimensionless mathematical model; this type of inversion method has rarely been used in petroleum applications. The obtained results revealed that by... 

It is widely accepted that, in fluid flow and transport in fractured porous media, there exists some degree of block-to-block interaction that may lead to capillary continuity. The formation of liquid bridges causing interaction between blocks will affect oil recovery from naturally fractured reservoirs. However, the accurate modeling of the growth and detachment of liquid bridges that may cause capillary continuity between matrix blocks remains a controversial topic. In an attempt to improve our understanding of the problem, a mechanistic model is developed in this work for the formation of liquid bridges between porous blocks. The proposed model considers growth and detachment of pendant... 

Gravity drainage is known to be one of the most effective methods for oil recovery in fractured reservoirs. In this study, both free fall and controlled gravity drainage processes were studied using a transparent fractured experimental model, followed by modelling using commercial CFD software. The governing equations were employed based on the Darcy and mass conservation laws and partial pressure formulation. Comprehensive examination was done on variables such as fluid saturation, velocity, and pressure distribution in the matrix and fracture, as well as fluid front level and production rate. Additionally, effects of the model parameters on the gravity drainage performance were... 

Spontaneous imbibition, defined as the displacement of nonwetting phase by wetting phase in porous media by action of capillary forces, is important in many applications within earth sciences and in particular in naturally fractured oil and gas reservoirs. Hence, it is critical to investigate the various aspects of this process to correctly model the fractured reservoir behavior. In this study, twenty four experiments were conducted to study the effect of rock properties, lithology of porous medium, brine viscosity and boundary conditions on displacement rate and final recovery by cocurrent spontaneous imbibition (COCSI) in brine-oil systems. The results can be extended to brine-gas systems,... 

The discrete fracture network (DFN) and Multiple-Continua concept are among the most widely used methods to model naturally fractured reservoirs. Each faces specific limitations. The recently introduced recovery curve method (RCM) is believed to be a compromise between these two current methods. In this method the recovery curves are used to determine the amount of mass exchanges between the matrix and fracture mediums. Two recovery curves are assigned for each simulation cell, one curve for gas displacement in the presence of the gravity drainage mechanism, and another for water displacement in the case of the occurrence of the imbibition mechanism. These curves describe matrix-fracture... 

The Discrete Fracture Network and Dual Continuum concept are two common methods to model naturally fractured reservoirs. Each has specific limitations. The newly introduced recovery curve method is believed to be a compromise between these two current methods. In the recovery curve method, two recovery curves for water and gas displacements are used to more realistically calculate matrix-fracture mass exchanges. This paper presents a new approach to determine appropriate recovery curves by using the recovery curve method and production data. In particular, two recovery curves were determined for a column model by matching phase contact positions throughout the production data. Hybrid genetic... 

Most of the reservoirs in Iran and also around the world are in the middle of their production life and have passed their natural production period. Therefore, they should be a candidate for immiscible injection, e.g., water injection for secondary recovery, and/or miscible injection, like solvent injection for tertiary recovery. Also, it should be pointed out that most of the Iranian reservoirs are carbonate reservoirs. This type of reservoir is fractured and heterogenic. Heterogeneity causes an earlier breakthrough and immiscible injection causes an unstable front, which leads to a lower recovery. This article presents the modified equation of Buckley-Leverett and fractional flow... 

The aim of this contribution is to evaluate the performance of an expanding solvent steam assisted gravity drainage (ES-SAGD) process in naturally fractured systems. Steam-assisted gravity drainage (SAGD) and ES-SAGD processes have been investigated in both conventional and fractured reservoir models and the effect of networked fractures on the recovery mechanism and performance of ES-SAGD has been investigated. Operational parameters such as steam quality, vertical distances between wells, and steam injection temperature have been also evaluated. Finally, to study the effect of a well's horizontal offset, a staggered ES-SAGD well configuration has been compared to a stacked ES-SAGD  

In this work, studies of underground gas storage (UGS) were performed on a partially depleted, naturally fractured gas reservoir through compositional simulation. Reservoir dynamic model was calibrated by history matching of about 20 years of researvoir production. Effects of fracture parameters, i.e. fracture shape factor, fracture permeability and porosity were studied. Results showed that distribution of fracture density affects flow and production of water, but not that of gas, through porous medium. However, due to high mobility of gas, the gas production and reservoir average pressure are insensitive to fracture shape factor. Also, it was found that uniform fracture permeability... 

The amount of residual oil trapped in the matrix of a fractured reservoir after water drive, either natural water drive or water injection, depends on the wettability of the matrix rocks. Gas oil gravity drainage (GOGD) has been proposed as the tertiary oil recovery process for this type of oil reservoir. The current work focuses on experimental investigation of tertiary GOGD in fractured porous media under different types of matrix wettability. Results of a set of experiments performed in artificial porous media composed of sand packs and glass beads of different wettability have been used to check the GOGD rate and the ultimate oil recovery for previously waterflooded models. A novel... 

Vapour extraction (VAPEX), a newly developed heavy oil recoveiy (HOR) method, has been extensively studied, both theoretically and experimentally, in conventional sandstone models. However, the applicability of this process to naturally fractured reservoirs has not yet been addressed. The objective of this work is to evaluate the effects of fractures' geometrical properties, such as orientation, length of extension, discontinuity in both the upper well region (UWR) and the far well region (FWR) and vertical fracture location on VAPEX performance. Additionally, the effects of horizontal and vertical fracture dispersion in various density, dispersion scheme and networking on the performance of... 

Including gravity and wettability effects, a full analytical solution for the frontal flow period for 1D counter-current spontaneous imbibition of a wetting phase into a porous medium saturated initially with non-wetting phase at initial wetting phase saturation is presented. The analytical solution applicable for liquid-liquid and liquid-gas systems is essentially valid for the cases when the gravity forces are relatively large and before the wetting phase front hits the no-flow boundary in the capillary-dominated regime. The new analytical solution free of any arbitrary parameters can also be utilized for predicting non-wetting phase recovery by spontaneous imbibition. In addition, a new... 

Oil reservoirs are very complex with geological heterogeneities that appear on all scales. Proper modeling of the spatial distribution of these heterogeneities is crucial, affecting all aspects of flow and, consequently, the reservoir performance. Reservoir connectivity and conductivity evaluation is of great importance for decision-making on various possible development scenarios including infill drilling projects. This can be addressed by using the percolation theory approach. This statistical approach considers a hypothesis that the reservoir can be split into either permeable (good sands) or impermeable flow units (poor sands) and assumes that the continuity of permeability contrasts... 

A lot of laboratory experiments have been carried out to investigate each aspect of ultrasonic wave s role on fluid flow behavior through porous media. Despite all experimental works, little attention has been paid for modeling the ultrasonic wave influence on capillary imbibition, which is the main mechanism of production in fractured reservoirs. At this work the process of imbibition with and without applying ultrasonic waves is mathematically modeled by modification of piston-like model. In contrast to this model s assumption, in which mobility ratio is assumed to be constant, here permeability variation due to increase in water saturation is considered in numerical solution. To evaluate... 

The knowledge of the conductivity across the reservoir that is based on the swept fraction controls the recoverable rates of the hydrocarbon in the secondary displacement processes. Most of the time, we need a fast estimation of the conductivity for decision making during field development. Percolation theory is a very useful tool to get this goal. According to this fact that the results of this method are universal, they could be used widely. In this study connectivity and conductivity percolation models are developed and the universal exponents for connectivity and conductivity in fractured reservoir as well as their dependency on the correlation length are investigated. For L< ξ the... 

Till now, no mathematical model is presented to model the flow under sonic field be applied in fractured reservoirs. This will be more noticeable when we bear in mind that several reservoirs in Middle East region are fractured. In this work the effects of elastic waves on capillary trapping and mobility of Bingham plastic fluids in fractures have been investigated. Eventually, a model for predicting the influence range of the wave in fractured reservoirs is presented. The results of this study clarified that radiation of wave with low frequency and intensity extremely increases the flow rate and decreases the minimum pressure gradient required for flow of Bingham plastic fluids in fractured... 

In naturally fractured reservoirs, modeling of mass transfer between matrix blocks and fractures is an important subject during gas injection or contaminant transport. This study focuses on developing an exact analytical solution to transient tracer transport problem along a discrete fracture in a porous rock matrix. Using Gauss-Legendre quadrature, an expression was obtained in the form of a double integral which is considered as the general transient solution. This solution has the ability to account the following phenomena: advective transport in fractures and molecular diffusion from the fracture to the matrix block. Certain assumptions are made which allow the problem to be formulated... 

In the optimization of naturally fractured reservoirs, it is required to take into account their complex flow behavior due to high conductivity fractures. In this regard, the possible effects of fractures must be included in the optimization procedure. In a water-flooding project, fast water breakthrough from injection to production wells may be occurred because of high permeability fractures. To consider the effect of the fracture system, a multi-criterion optimization procedure is proposed in this work. For this contribution, Non-dominated Sorting Genetic Algorithm version II (NSGA-II) is implemented for the optimization purposes. Considering the effect of the fracture system on the flow...