Sharif Digital Repository

Multiphase flows are commonly encountered in oil and gas industries. Flow fields in production operations are often complex and include multiphase flows of gas and liquid. The prediction of pressure gradients, liquid holdup and flow patterns occurring during the simultaneous flow of gas and liquid in pipes and wellbores is necessary in designing production facilities. Previously, due to their complex nature, these flow patterns have been mostly investigated only experimentally and empirical correlations based on the experimental data. From another point of view, it is almost impossible to experimentally realize all the flowing conditions for each of the flowing patterns. Nowadays, computer... 

Low salinity water injection is one of the new and important methods of enhancing oil recovery. Experimental studies show the fact that the change in water salinity affects the interfacial properties of water-oil (Fluid-fluid interactions) And the change in wettability that represents the porous media (Rock-fluid interactions) is effective for Oil-recovery. Recently, progress have been made in simulating the process of injecting low-salinity water into the field or core dimensions. However, the simulation of the low salinity water injection process has been much less studied considering the fluid / fluid and fluid / rock interactions at the pore scale. The purpose of this study is to... 

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... 

So far, many studies have been carried out on the core-scale regarding the effects of hysteresis on the macro-scale properties of systems including fluids and porous rock, however, many issues related to the physics of the problem (especially regarding the way fluids are distributed and the trapping of the non-wetting phase) at the pore-scale need further investigation. In the process of multiphase fluid flow in porous media, hysteresis refers to the dependence of the results of the fluids’ displacements on the history of fluid saturation and the direction of saturation changes (increasing or decreasing). The first step to investigate the hysteresis effect is to determine the amount of fluid... 

Visual investigation of the low salinity water injection into micromodel is the goal of this research. Although many researches have been performed to realize the dominating mechanism behind the increased oil recovery after low salinity water injection, many contradictions exist among the studies. Mechanisms are generally divided into two classes. One class is due to fluid/fluid interactions and the other one is due to fluid/rock interactions. A comprehensive set of experiments are conducted in this study to find out the dominating mechanism behind low salinity water injection under the existing conditions of the experiments. Effect of different wettability condition and presence and absence... 

Given the broad role of oil and gas playing in the world economy, finding the hydrocarbon reservoir that economically is affordable is quite significant. Some of the unconventional oil and gas reservoirs are important from the economic point of view since they produce insufficient hydrocarbon due to either low permeability or damage during drilling and production. Hydraulic fracturing is one of the most significant methods for improving the productivity of wells and reservoirs. Hydraulic fracturing acts by affecting on reservoir rock physic. In the current century, this approach has an essential effect in enhancing the permeability and production of reservoirs by creating, extending and... 

In this work, an improved model for simulating carbonate core acidizing, with the ability of correctly modeling fluid diversion in dual-core experiments is created based on an existing two-scale continuum model. The improvements are applied on the momentum transfer equation, continuity equation, pore-scale structure-property relations and fluid rheology model. Also a more realistic injection scenario and geometry configuration are presented for simulating the diversion experiments. The Darcy-Brinkman-Stokes equation is implemented instead of Darcy’s equation and the continuity equation is modified by adding the mass source term. A global rheology model is developed capable of capturing exact... 

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... 

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... 

According to the reported field experiences, excess water production from high permeable thief zones of oil reservoirs is the main source of severe operational problems and economic issues. Application of Preformed Particle Gels (PPGs) is an effective technique to overcome this problem. Static test analysis is a primary method for evaluating the performance of PPGs material at different conditions of pH, salinity, etc. However, the effect of the presence of oil and rock on the kinetics of swelling/de-swelling of PPGs is not well understood. Also, considering the vast field application of Co_2-based oil recovery methods, it is interesting to study the effect of carbon dioxide gas on swelling... 

In this work, a pore-scale analysis of nonaqueous phase liquid (NAPL) flow, transport, dissolution, and mobilization in heterogeneous and homogeneous porous media was presented. First, dissolution processes and distribution of NAPL phase were investigated using micromodel experiments. The tests were conducted at different injection rates in NAPL-saturated porous media using distilled water, surfactant, and nanoparticles-assisted surfactant. Changes in residual NAPL volume and interfacial area were measured using image analysis method to calculate the mass transfer coefficient, k, and the lumped mass transfer rate coefficient, K. Based on the experimental results, empirical Sherwood... 

Wettability of reservoir rock is one of the effective parameters in determining the mechanisms of production and consequently the amount of residual oil inside the porous media. In addition, the salinity of injected water is important factor in the recovery of reservoir oil in waterflooding.On the other hand, the role of the hysteresis on the residual oil saturation as well as the flow functions such as relative permeability curves is very important. In this project, the effects of reservoir wettability and injected water salinity on the hysteresis and residual oil saturation in two-phase water-oil flow systems are studied. Core-scale experiments were carried out using sandpacks and were... 

Gas injection process is one of the main methods to increase the hydrocarbon reservoirs. Minimum Miscibility pressure is a key parameter that controls the efficiency of the gas injection process. It depends on the temperature, the composition of the injected gas and the composition of the reservoir fluids. In this study, the interfacial tension of the live oil-gas system of one of the reservoirs of southwestern Iran was obtained by analyzing the Pendant drop method at 225 ° F and different pressures, and then by using the Vanishing Interfacial Tension method, the Minimum Miscibility Pressure has been computed .In this study, pure and base gases such as nitrogen, methane and injection gas of... 

Gas injection is one of the most common methods to enhance oil recovery. But due to the low viscosity and density of gas, viscous fingering and gravity over ride usually happens which lead to reduction of gas injection performance to oil production. Foam injection is one of the techniques that has the potential to improve oil production by increasing. Foam apparent viscosity is higher than gas and its liquid which is made from it. So it can increase sweep efficiency and enhance oil recovery. However, presence of oil can destabilize foam. Beside, salinity has different effects on foamability and foam stability. Foam stability in high saline environment is a challenge. Therefore, the stability... 

Recognizing the preformed particle gel (PPG) transport mechanisms in fracture and the effective parameters on them, is a necessary knowledge to design a successful gel treatment operation. In this research the transport behavior of PPGs was investigated in two fractured micro-models. During PPG propagation in fracture, the gel dehydration causes to produce a large filtrate volume and sweep the matrix oil. In the fracture/matrix interface, the gel particles can deform, break or shrink, then penetrate a few millimeters into matrix pores and form an impermeable gel cake, which is the main mechanism of conformance control. The effective parameters on PPG transport behavior such as Nano-silica... 

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,... 

Oil and gas production from oil reservoirs is significantly affected by rock and fluid properties. Relative permeability and capillary pressure are two key flow functions that are used in the numerical modeling of processes related to the porous environment of oil and gas reservoirs at the core scale and above. The use of incorrect relative permeability and capillary pressure curves can lead to inappropriate prediction of the future behavior of the reservoir, which in turn affects future management decisions. Due to the time-consuming nature of obtaining flow functions from the steady state method, history-matching techniques are generally used to estimate these functions as accurately as... 

Well stimulation techniques are used to increase the productivity of oil and gas wells. One of the effective well stimulation methods, is matrix acidizing. During matrix acidizing, acidic solution is injected into the formation at pressure below the formation fracture pressure. Most of the time, acid needs to be reached to low permeability layers for more efficient damage removal. Divertors are used for diverting acid from high permeability to low permeability layers.Successful performance of a viscoelastic acid during an acid job, is highly dependent on the surfactant rheological properties. For a betaine viscoelastic surfactant, we have studied the effect of different parameters on the... 

Today, increasing the productivity of reservoirs is more important than in the past, while the use of nanoparticles to change the wettability of rock and increase the recovery factor from the reservoir has been considered by many researchers. Despite previous studies on the use of nanoparticles to change the wettability of rock to gas-wet, the use of nanocomposites with super gas-wet at high temperature and pressure in the crude oil-gas system has rarely been considered. In this research, several nanocomposites with different structures have been synthesized in the laboratory and nanofluids with different formulations have been used to coat the rock thin sections and measure droplet contact...