Sharif Digital Repository

In this work effect of composition changes of injection gas, CH4 + CO2, on the performance of immiscible WAG injection in light oil, 41 oAPI, which has been rarely attended in the available literature is investigated. Presence of CO2 helps to reduce the MMP of CH4 significantly. Core flood experiments are conducted at reservoir conditions and fixed flow rate of 0.5cc/min on a sandstone sample with the brine concentration of 5000 ppm, and the influence of injection gas composition as well as WAG ratio on oil recovery is investigated. Different mole percents of methane in mixture, 0%, to 100% are examined, and the tests continued to ten alternate cycles with a slug size of 0.1 pore volumes and... 

Immiscible gas injection is one of the most common enhanced oil recovery methods used under various reservoir conditions. In this work, the immiscible recycle gas injection, as an EOR scenario for improving recovery efficiency in one of the south-west Iranian oil reservoirs, is simulated by a commercial simulator, ECLIPSE. The reservoir fluid is light oil, with an API of 43. The oil bearing formations are carbonate, and so a dual porosity/dual permeability behavior was chosen for better representation of the fracture system. Different sensitivity analyses with respect to several parameters like the number and location of injection/production wells, production/injection rate, completion... 

Asphaltene precipitation during natural depletion and miscible gas injection is a common problem in oilfields throughout the world. In this work, static precipitation tests are conducted to investigate effect of pressure, temperature and gas type and concentration on asphaltene instability. Three different oil samples are studied under reservoir conditions with/without nitrogen and methane injection. Besides applying common thermodynamic models, a new scaling equation is presented to predict asphaltene precipitation under HPHT gas injection. Published data from literature are also used in model development. The scaling approach is attractive because it is simple and complex asphaltene... 

This work examines the operational parameters that may influence the performance of toe-to-heel steamflooding in a laboratory-scale simulation model built on the basis of the fluid and rock samples from a fractured, low-permeable, carbonate heavy oil reservoir in Southwestern Iran, called KEM (Kuh-e-Mond). Using vertical (V) or horizontal (H) injectors (I) and producers (P), the effects of different well configurations including VIVP, VIHP, 2VIHP, VI2HP, HIHP, and HI2HP, injectors' traversal distance, producers' traversal distance, and horizontal producer length have been investigated. In summary, the results show that 2VIHP scheme performs best in terms of oil recovery and areal/volumetric... 

This work is concerned with the role of geometrical properties of fractures on oil displacement efficiency during solvent injection to heavy oil. Here, a series of solvent injection processes were conducted on one-quarter five-spot fractured micromodels that were initially saturated with the heavy oil, at a fixed flow rate condition. The oil recovery was measured using image analysis of the continuously provided pictures. The results show that for the range of experiments performed here, the maximum oil recovery happens at a fracture orientation angle of 45 degrees. Also, increasing the number of fractures leads to a higher oil recovery factor by solvent in 45 degrees, while it does not... 

Asphaltene deposition causes serious problems in the oil industry. Variation of oil composition and reservoir pressure is reported to be the most important factors that influence asphaltene deposition from reservoir oil. In this study, a mathematical model was developed to simulate asphaltene deposition during primary depletion and CO2 injection. The main purpose of this study is to investigate and to compare asphaltene deposition mechanisms due to primary depletion and CO2 injection. The solid model as thermodynamic model was applied to investigate asphaltene precipitation. A numerical model was established to the governing equations both in space and time and model parameters were... 

Experimental Investigation of the Asphaltene Deposition Process during Different Production Schemes - This paper presents the results of asphaltene precipitation and deposition during lean gas injection, CO2 injection and natural depletion in reservoir conditions. In addition, the effect of variations in operating pressure, injection gas concentration and production rate on asphaltene precipitation and deposition were investigated. The severity of asphaltene deposition was found to be more pronounced in lean gas injection in comparison with CO2 injection and natural depletion. Increasing the flow rate in natural depletion xperiments showed a considerable increase in asphaltene deposition,... 

There are different thermodynamic models that have been applied for modelling of asphaltene precipitation caused by various reasons, such as solvent/CO2 injection and pressure depletion. In this work, two computer codes based on two different asphaltene precipitation thermodynamic models-the first being the thermodynamic micellization model with a different characterization approach and the second being the solid model-have been developed and used for predicting asphaltene precipitation data reported in the literature as well as in the obtained data for Sarvak reservoir crude, which is one of the most potentially problematic Iranian heavy oil reserves under gas injection conditions. For the... 

Water and miscible gas injection scenarios are considered in an Iranian oil reservoir for the purpose of recovery improvement. Firstly reservoir fluid modeling and modeling of a slim tube test were performed. Then, water alternating gas (WAG) injection was evaluated by optimizing the WAG half cycle and WAG ratio. Alternatively, hybrid WAG and separate injection of water and gas in the top and bottom of the reservoir were also investigated. The numerical simulation results showed that the optimum WAG, with half cycle of 1.5 years and WAG ratio of one, gave the highest recovery factor. Moreover, economic evaluation of these scenarios indicated that WAG had the highest net present value and was... 

Nitrogen has been appeared as a competitive gas injection alternative for gas-based enhanced oil recovery (EOR) processes. Minimum miscibility pressure (MMP) is the most important parameter to successfully design N2 flooding, which is traditionally measured through time consuming, expensive and cumbersome experiments. In this communication, genetic programming (GP) and constrained multivariable search methods have been combined to create a simple correlation for accurate determination of the MMP of N2-crude oil, based on the explicit functionality of reservoir temperature as well as thermodynamic properties of crude oil and injection gas. The parameters of the developed... 

In this work, application of CO2 saturated with silica nanoparticles in continuous/water alternating gas (WAG) injection for heavy oil recovery was investigated which has been rarely attended in the available literature. Core displacement tests were conducted to monitor heavy oil recovery in both continuous and WAG injection schemes. It has been observed that for continuous nano-saturated CO2 injection, the oil recovery is higher than pure CO2 injection. This observation might be explained by alteration of rock wettability to a more water-wet condition. In WAG injection scheme, water breakthrough happened later in nano-saturated CO2 than pure CO2 injection. This delayed water breakthrough... 

Availability of hydrocarbon gases at the field makes it attractive for gas-based enhanced oil recovery (EOR) methods such as water alternating gas (WAG) injection. Optimization of EOR methods requires too many simulation runs, which are time consuming and expensive. Therefore, developing a proxy model, which emulates simulator outputs, is considered as an appropriate alternative technique. In this work, effects of composition changes of injection gas, WAG ratio, and slug size on produced oil and water were investigated. In addition, the optimum value of the previous parameters, including some constraints, are presented using response surface methodology. Experimental design is also applied... 

In this work, a thermodynamic approach is used for modeling the phase behavior of asphaltene precipitation. The precipitated asphaltene phase is represented by an improved solid model, and the oil and gas phases are modeled with an equation of state. The Peng-Robinson equation of state (PR-EOS) was used to perform flash calculations. Then, the onset point and the amount of precipitated asphaltene were predicted. A computer code based on the solid model was developed and used for predicting asphaltene precipitation data reported in the literature as well as the experimental data obtained from high-pressure, high-temperature asphaltene precipitation experiments performed on Sarvak reservoir... 

A comprehensive understanding of the role of reservoir heterogeneities induced by flow barriers and connate water on sweep efficiency of different EOR scenarios is rarely attended in the available literature. In this work, different miscible/immiscible EOR processes were conducted on various one-quarter five-spot glass micromodels incorporating small-scale flow barriers. Microscopic and macroscopic observations revealed the reduction of sweep efficiency, premature breakthrough of displacing fluids, the severity of fingering at displacement front which leaves a large amount of oil behind the flow barriers untouched, and significant increasing trend of oil recovery after breakthrough in the... 

In this paper, the effect of highly conductive copper oxide nanoparticles on the effective thermal conductivity (ETC) of rock samples was mathematically investigated. To solve the governing conservation equations for the ETC a commercial finite element package (COMSOL Multiphysics) was used. It should be stressed that the single-phase approach was employed to mathematically model the effect of nanofluid on the heat transfer improvement. The computational geometry of the rock samples was obtained by analyzing the microscopic images of the limestone rock samples. The results obtained from the mathematical modeling of the rock samples showed that the conductive heat transfer through porous... 

In fractured oil reservoirs, the gravity drainage mechanism has great potentials to higher oil recovery in comparison with other mechanisms. Recently, the forced gravity drainage assisted by gas injection has also been considered; however, there are few comprehensive studies in the literature. Dual porosity model, the most common approach for simulation of fractured reservoirs, uses transfer function concept to represent the fluid exchange between matrix and its neighborhood fractures. This study compares the results of different available transfer functions with those of fine grid simulations when forced gravity drainage contributes to oil production from a single matrix block. These... 

As the oil production from conventional oil reservoirs is decreasing, oil production through Enhanced Oil Recovery (EOR) processes is supposed to compensate for both the oil production reduction in matured oil reservoirs and the worldwide dramatic increase in oil demand. Therefore, developing a strategy to choose an optimized EOR technique is crucial to find a resolution for production decline in oil reservoirs. A screening tool recommending the most appropriate EOR method is proposed in this study. An expert fuzzy logic system is employed to screen four well-known EOR methods including miscible CO2 injection, miscible HC gas injection, polymer flooding and steam injection based on the... 

The main issue in heavy oils enhanced recovery methods is to reduce their viscosity in order to get a better mobility. This is commonly obtained by blending the oil with light hydrocarbons. Co-solvents are good candidates to improve the hydrocarbon recovery efficiency especially in miscible processes. However, the effect of co-solvents on miscible flooding of heavy oil reservoirs at different pore geometries is not well understood. In this work different one-quarter five-spot network patterns along with those generated from reservoir rocks' thin sections were etches on glass surfaces. The models that had been initially saturated with the heavy crude oil were used to perform a series of... 

Although several investigations have studied the low-salinity water injection (LSWI) performance during the past decades, the effect of crude oil type on the interfacial tension (IFT) and wettability alteration is still in dark. In this regard, this study is aimed to obtain the thermodynamic energies including adhesion, cohesion and spreading coefficient during LSWI. To achieve this goal, IFT and static contact angle values of three different crude oils (i.e. light, medium and heavy) are measured as a function of sea water salinity. The obtained results revealed that the dilution of sea water can change the wettability of reservoir rock from oil wet state towards water wet state, while crude... 

Condensate and water banking around gas condensate wells result in vital well deliverability issues. Wettability alteration of near wellbore region to gas wetting condition is known to be the most novel and the only permanent method, to improve condensate well productivity. In this work, a water based nanofluid is used to change the wettability of sandstone reservoir rocks from strongly liquid wetting to intermediate gas wetting condition. Static contact angle measurements demonstrated significant increase of liquid phase contact angle as a result of chemical treatment with SurfaPore M nanofluid. The characteristics of SurfaPore M adsorption on sandstone rock are quantified through kinetic...