Sharif Digital Repository

We present a non-monotone trust region algorithm for unconstrained optimization. Using the filter technique of Fletcher and Leyffer, we introduce a new filter acceptance criterion and use it to define reference iterations dynamically. In contrast with the early filter criteria, the new criterion ensures that the size of the filter is finite. We also show a correlation between problem dimension and the filter size. We prove the global convergence of the proposed algorithm to first- and second-order critical points under suitable assumptions. It is significant that the global convergence analysis does not require the common assumption of monotonicity of the sequence of objective function... 

We present a new filter trust-region approach for solving unconstrained nonlinear optimization problems making use of the filter technique introduced by Fletcher and Leyffer to generate non-monotone iterations. We also use the concept of a multidimensional filter used by Gould et al. (SIAM J. Optim. 15(1):17-38, 2004) and introduce a new filter criterion showing good properties. Moreover, we introduce a new technique for reducing the size of the filter. For the algorithm, we present two different convergence analyses. First, we show that at least one of the limit points of the sequence of the iterates is first-order critical. Second, we prove the stronger property that all the limit points... 

Many bitumen reservoirs contain shale layers of varying thickness, lateral extent, and frequency. These shale layers, depending on their size, vertical and horizontal locations, and continuity throughout the reservoir, may act as a flow barrier and severely reduce vertical permeability of the pay zone and slow down the steam-assisted gravity drainage steam chamber development. Therefore, to improve productivity in these reservoirs, understanding of the effects of reservoir heterogeneities has become necessary. This work presents numerical investigation of the effects of shale barriers on steam-assisted gravity drainage performance when applied to produce mobile heavy oil. The most concern of... 

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  

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... 

Various fracture geometrical properties such as orientation, extension, discontinuity, dispersion, location, and networking were investigated. Results indicate improved oil recovery and sweep efficiency in the presence of vertical fractures. Longer vertical fractures seemed to have even more beneficial effects. Horizontal fractures revealed detrimental effects on oil recovery and the performance became worse for longer horizontal fractures. Discontinuous horizontal fractures caused a better performance especially when combined with continuous vertical fractures (networking). Vertical fractures helped the growth of the steam chamber in the vertical direction, which resulted in higher oil... 

Top-down in situ combustion (ISC) involves the stable propagation of a combustion front from the top vertical injector to the bottom horizontal producer. With the exception of laboratory studies of conventional sandstones, no application of the process in fractured carbonates has been addressed. The aim of the present work is to study ISC in the presence of a system of networked fractures using a thermal reservoir simulator from the Computer Modeling Group (CMG; Calgary, AB, Canada). The performance of ISC is compared with nonfractured system under similar conditions. To obtain more realistic results, a history-matched and validated combustion model of an Iranian naturally fractured... 

The Vapour Assisted Petroleum Extraction (VAPEX) process, a newly developed Enhanced Heavy Oil Recovery process, is a promising EOR method for certain conventional non-fractured heavy oil sandstone reservoirs such as those in Canada, but its applicability on low permeable Naturally Fractured Reservoirs (NFR) such as those in the Middle East and Persian Gulf still remained as a question. Previous studies show that the foremost concern for VAPEX application in the case of NFR is the low non-economical production rates. The aim of the present work is to study the effect of fractures geometrical properties such as orientation (vertical or horizontal), density, spacing, location and networking on... 

The top-down in situ combustion (ISC) involves the stable propagation of the combustion front from the top vertical injector to the bottom horizontal producer. Apart from laboratory studies in conventional sandstones, no application of the process in fractured carbonates has been addressed yet. The authors modified a successful combustion tube history matched model of an Iranian low-permeable heavy oil reservoir called Kuh-E-Mond to investigate the feasibility of ISC in fractured carbonate reservoirs mimicking block-scale combustion cells. Effects of fractured geometrical properties such as orientation, location, extension, density, spacing, and dispersion were considered. Results confirmed... 

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... 

Accurate determination of relative permeability (kr) curves and their hysteresis is needed for reliable prediction of the performance of oil and gas reservoirs. A few options (e.g., Carlson, Killough and Jargon models) are available in commercial reservoir simulators to account for hysteresis in kr curves under two-phase flow. Two-phase kr curves are also needed for estimating kr hysteresis under three-phase flow during water-alternating-gas (WAG) injection. Although, most oil reservoirs are mixed-wet, the existing hysteresis predictive approaches have been developed based on water-wet conditions. Experimentally measured data are needed to assess the performance of these methodologies under... 

Perceiving the electrical behavior of the rock/brine and the crude oil/brine interfaces gives insight into the performance of engineered waterflooding. Compared to the rock surface, few studies have attempted to comprehend the complex behavior of the crude-oil surface electrical behavior. To reveal the impact of each ion on the surface charge of crude oil, the zeta potential of crude oil/single-salt brines (including NaCl, CaCl2, MgCl2, Na2SO4, and NaHCO3) was measured in a wide range of salinity. Then, the counterpart interfacial tension (IFT) was measured to determine the capability of each brine in bringing carboxylic acid groups from crude-oil bulk (COOH) to crude oil/brine interface... 

The electrical properties of the oil/brine interface play a principal role in wettability alteration during low salinity/water flooding. There are few existing surface complexation models (SCMs) for the oil/brine interface. Similar to the mineral surface, all models assume that the surface site density of oil/brine is always constant. Assessment of the existing models shows that they ignore the dynamic nature of the crude oil/brine interface and fail to capture experimentally measured ζ potentials appropriately. The current study proposes a novel diffuse layer SCM considering the interfacial concentration of surface carboxylic acid as a function of brine pH, salinity, and composition. The... 

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... 

Dynamic behavior of fluid-fluid interactions can potentially affect the performance of any enhanced oil recovery (EOR) process including low salinity water flooding. In this work, dynamic interfacial tension (IFT) of crude-oil/brine system is measured in a wide range of salinity of sea water (SW), from 50-time diluted sea water (SW50D) to 2-time concentrated sea water (SW2C). Contrary to the most of published IFT trends in the literature, for the system under investigation here, as the brine salinity increases the crude-oil/brine IFT reduces, which cannot be explained using the existing theories. The lack of a physical model to explain the observed phenomena was the motivation to develop a... 

Because of the complex nature of carbonate reservoirs, the required conditions for effective Low Salinity Water Flooding (LSWF) in these reservoirs need further and in depth investigation. In the present study, three calcite cores, i.e. Cal-1, Cal-2, and IL, with the same chemical composition are subjected to tertiary low salinity water flooding (LSWF), while the crude oil and composition of flooding brine kept the same. The experimental results show significant difference in the amount of enhanced oil recovery, as IL had the most additional oil recovery (20.8 % of IOIP), followed by Cal-2 (10.5 % of IOIP) and Cal-1 (3.9 % of IOIP). The results of contact angle, zeta potential, and effluent... 

The In-Situ Combustion (ISC) as a thermal EOR process has been studied deeply in heavy oil reservoirs and is a promising method for certain non-fractured sandstones. However, its feasibility in fractured carbonates remained questionable. The aim of the present work was to understand the recovery mechanisms of ISC in fractured models and to evaluate the effect of fractures geometrical properties such as orientation, density, location and networking on the ISC recovery performance. Combustion parameters of a fractured low permeable carbonate heavy oil reservoir in Middle East called KEM; applied to simulation study. Simulator has been validated with KEM combustion tube experimental data and... 

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  

Toe to heel air injection has been studied on non-fractured sandstone models and is found to be a promising enhanced oil recovery method for certain heavy oil reservoirs, such as those in Canada, but its applicability on fractured reservoirs, such as those in the Middle East, is not investigated yet. The objective of this article is to evaluate the effect of fractures geometrical parameters, such as fracture density, orientation, and location, on the performance of the process in laboratory scale. Simulation results showed that toe-to-heel air injection is more applicable on highly networked fractured reservoirs, such as those that occur in Persian Gulf coast compared to lower density... 

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...