Sharif Digital Repository

Acidizing of carbonate oil-wet rocks saturated with oil and saline formation water is subjected failure in some cases due to acid-induced damage such as sludge and emulsion formations. This condition may also lead to mineral precipitation, oil film barrier between acid and rock and diversion chemical malfunctions. Therefore, pre-flush process has been proposed as one of the most efficient stage for oil-wells matrix acidizing to reduce these challenges significantly. Besides, the pre-flush stage would result in more clean rock as the reservoir fluids are pushed back from the near wellbore regions, restoring rock wettability to more water wet state, preventing direct acid-oil contact and... 

Water-in-oil emulsion usually forms during waterflooding in some heavy oil reservoirs. The composition and salinity of the injected water critically affect the w/o emulsion droplet size distribution, which control the emulsion stability and emulsion flow in porous media. The aim of the present work is to assess the effect of different sea water salinities on w/o emulsion stability through microscopic imaging. Therefore, w/o emulsions were prepared with different sea water samples, which were synthesized to resemble Persian Gulf, Mediterranean, Red Sea, and North Sea water samples. The results showed that log-normal distribution function predicts very well the experimental data to track the... 

In the recent years, declination of oil reservoir causes the importance of researches on enhancement of oil recovery processes become more important. One of wide applicable approaches in enhancement of oil recovery is carbon dioxide injection which becomes interested because of relative low cost, good displacement and environmentally aspects. The injection of carbon dioxide to oil reservoir causes the lighter hydrocarbons of crude oil are extracted by CO2. This phenomena can be affected by various factors such the solubility of hydrocarbons in carbon dioxide so in the present investigation Fuzzy c-means (FCM) as a novel approach for estimation of solubility of alkanes in carbon dioxide in... 

The performance of CO2 injection into a semi-heavy oil reservoir was investigated at reservoir conditions, using highly permeable sandstone in a complete series of PVT tests and coreflooding experiments. Analysis of involved parameters such as: injection rate, injectant type and reservoir pressure were also considered. Oil viscosity reduction and oil swelling are the most influential mechanisms of enhanced oil recovery in this process. The results demonstrated that CO2 injection would decrease the interfacial tension for the high permeable medium in the absence of capillarity, but this reduction may not improve the recovery drastically. One of the main important aspects of this work is the... 

The Conventional Fire Flooding (CFF) process application feasibility on fractured carbonated reservoirs remained questionable. In this paper first combustion parameters and reaction kinetics of a naturally fractured low permeability carbonated heavy oil reservoir in Iran called Kuh-E-Mond applied to simulation study. After that, simulator has been validated with Kuh-E-Mond combustion tube experiment. Recovery mechanism in single block matrix is different from one in conventional model since oxygen first flows into the fractures and then diffuses from all sides into the matrix. Combustion of the oil in the fractures produces some water ahead of fracture combustion front which prohibits oxygen... 

Purpose - This paper aims to perform a comparative study between capabilities of two numerical schemes from two main branches of numerical methods for solving hyperbolic conservation equations. Design/methodology/ approach - The accuracy and performance of a newly developed high-resolution central scheme vs a higher-order Godunov-based method are evaluated in the context of black-oil reservoir simulations. Both methods are modified enabling study of applications that are not strictly hyperbolic and exhibit local linear degeneracies in their wave structure. Findings - The numerical computations show that while both schemes produce results with virtually the same accuracy, the Godunov method... 

The Steam Assisted Gravity Drainage (SAGD) process, a developed Enhanced Oil Recovery (EOR) process to recover oil and bitumen, has been studied theoretically and experimentally in conventional reservoirs and models and is found a promising EOR method for certain heavy oil reservoirs. In this work simulation studies of the SAGD process were made on different fractured models consisting of fractures in both Near Well Region (NWR) and Above Well Region (AWR) and even in the presence of networked fractures. At early stage of the SAGD process in fractured system, steam moves through the fractures first and then the matrix blocks are heated primarily by conduction and possibly some steam... 

This study aims to investigate the role of fluid-fluid interactions during low salinity water flooding, using crude oil from an Iranian oil reservoir. To minimize the effects of mineral heterogeneity and wettability alteration, a synthetic sintered glass core was utilized and all coreflooding experiments were performed at low temperatures without any aging process. The effect of fluid-fluid interactions were investigated in both secondary and tertiary injection modes. pH measurements as well as UV-Vis spectroscopy and interfacial tension (IFT) analysis were performed on the effluent brine samples. Results: show that fluid-fluid interactions, mainly the dissolution of crude oil polar... 

Preformed particle gels (PPGs) in solutions have been widely used to suppress excess water production in mature oil reservoirs and, in turn, to improve the amount of oil recovery in brown oil fields. In this study, PPG solutions were meticulously formulated and synthesized in order to be utilized in harsh environments in terms of pressure, temperature, pH, and salinity from a free radical polymerization process. In this work, nanosilica gel at different weight percentages was added to improve the mechanical and thermal stability properties of the PPG at harsh condition: high pressure, temperature, and strain. Moreover, the effects of nanosilica gel at various concentrations, ranging from 0.0... 

A great deal of computational power and time is necessary for the simulation of highly heterogeneous fractured reservoirs with complicated geometry. Simulating such largescale complex reservoirs with both minimum time and maximum accuracy has consistently remained a topic of concern to reservoir simulation engineers worldwide. The currently used linear solvers in well-known commercial simulators that utilize classical methods such as Nested Factorization (NF) and Incomplete LU Factorization (ILU) as their preconditioners, all suffer from severe convergence problems in models with high heterogeneity and/or large number of non-neighbor connections. To overcome such problems, a novel Adaptive... 

Improving oil recovery and decreasing greenhouse gas emissions are two important attractive features of CO2-enriched water injection into oil reservoirs. Regarding these unique features, the main objective of this study was concentrated to evaluate the swelling behavior of crude oil as a fundamental mechanism of carbonated water (CW) flooding. To achieve these goals, the swelling and Bond number of light and heavy crude oils (namely LCO and HCO, respectively) are measured and compared to each other. The results obtained from the measured swelling factors of crude oil/CW show some complicated behaviors. That is, as temperature increases the swelling factor decreases at low pressure... 

In order to understand the potential role of divalent ions involved in smart water, fluid-fluid and rock-fluid interactions are studied through contact angle and interfacial tension (IFT) measurements. Then, the suitable brines in changing contact angle and IFT are brought into measurement with spontaneous imbibition experiments to evaluate the co-impact of fluid-fluid and rock-fluid interactions. The results show the importance of SO42− ions during smart water injection as removing them from the injection water leads to a sharp drop in ultimate oil recovery. Accordingly, when the concentration of SO42− within the injection water increases four times, 10% ultimate oil recovery is recovered.... 

The low salinity water injection has become one of the most important studies in the oil industry for improving oil recovery compared to conventional seawater injection. Thus, extensive studies have been conducted in carbonate and sandstone reservoirs to investigate how the physical properties of rocks and the chemical composition of fluids influence low salinity effect, while, the carbonate reservoir rocks requires more investigation of the effect of molecular and/or ionic interactions. In this experimental work, the effectiveness of various water flooding schemes in carbonate reservoir rock samples is investigated. In this regard, the oil recovery potential of seawater (SW), reservoir... 

Interaction between rock-fluid and fluid-fluid can have a significant effect on oil recovery. Changing the wettability of reservoir rock toward more water-wet or less oil-wet state is one of the expected mechanisms during low salinity water injection (LSWI). pH and salinity are of the most eminent factors of injection water controlling the wettability state of a crude oil/brine/rock system during any waterflooding operation. A small change in pH can affect the surface charges at the rock/water and oil/water interfaces leading to wettability alteration in a porous medium. In this study, the synergic effect of salinity and pH on the wettability state of carbonate rocks is evaluated through... 

In this paper, a computational technique is presented for the isothermal and non-isothermal water injection into naturally fractured oil reservoirs. 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 such reservoirs. In this study, the effectiveness of hot water injection over cold (isothermal) water injection in oil production is quantified. The influence of long and short fractures and their alignments on oil recovery are discussed. To this end, a 2D model for two-phase fluid flow and heat transfer is presented. The medium is assumed to be partially... 

During the low salinity waterflooding (LSWF) of a viscous asphaltic oil reservoir, fluid-fluid interactions have a large influence on the fluid flow, pore-scale events, and thus oil recovery efficiency and behavior. In-situ water-in-oil (W/O) emulsion formation is a consequence of crude oil and brine interfacial activities. Despite the published studies, the pore-scale mechanisms of W/O emulsion formation and the role of injected brine salinity, injection rate, and pore-scale heterogeneity on emulsion formation and stability requires a deeper understanding. To address these, a series of static and dynamic micro-scale experiments were performed. The salinity dependent oil-brine interactions... 

Multilateral well is a promising technology in developing oil reservoirs. Because this technology may increase the production rate per well and reduce the costs of field development, it is rapidly replacing the old methods. This study uses a three-dimensional line-source model with direct search methods, including pattern search and genetic algorithms to optimize the well trajectories. This method was applied to several cases, with different forms of wells and reservoirs. In all cases, significant improvement was observed in the production rate. Furthermore, the production enhancement using the optimized well trajectories which have curved-paths is compared to the case with linear well... 

This review aims to bring together the studies on petroleum reservoirs' sand production control in a comprehensive guide for the researcher to compare various methods for the chemical consolidation of sand. Sand production can be considered one of the major challenges in the petroleum production industry, causing severe operational issues. This study introduces various methods to control and prevent sand production in petroleum wells and evaluates their advantages and performance in tabular form. The use of chemical procedures is considered to be more efficient in counteracting the production and migration of sand. Various chemicals and polymers have been proposed for this purpose. These... 

One of the possible fluid-fluid interactions during water-flooding in oil reservoirs, that is still debated, is the effect of injected brine salinity on asphaltene destabilization. If asphaltene precipitation is induced by salinity changes in the oil reservoirs and surface facilities, this could have a massive impact on the economy of a low salinity water-flooding project. Therefore, this study aims to investigate the effect of brine salinity on the amount of asphaltene precipitation and the governing destabilization mechanisms. Direct asphaltene precipitation measurements, along with the analyses of optical microscopy images and ion chromatography (IC), indicate that the asphaltene... 

In this paper, a computational technique is presented for the isothermal and non-isothermal water injection into naturally fractured oil reservoirs. 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 such reservoirs. In this study, the effectiveness of hot water injection over cold (isothermal) water injection in oil production is quantified. The influence of long and short fractures and their alignments on oil recovery are discussed. To this end, a 2D model for two-phase fluid flow and heat transfer is presented. The medium is assumed to be partially...