In this study, the position of the truncation boundary, which is an important issue when modeling the reservoir in the finite element formulation and determining the hydrodynamic pressure on the dam, is investigated. Water in the reservoir is assumed to be compressible, and the Sommerfeld boundary is used to model the far field. The Euler-Lagrange method is used to analyze the reservoir-dam interaction. The serendipity element is used to model the reservoir and dam. The foundation is considered to be rigid. Most researchers assume that the truncation boundary is located three times the total height of the dam away from the dam body, and they use the Sommerfeld boundary at this location. For this purpose, the reservoir was disconnected at different intervals. The Pine Flat Dam is commonly analyzed with a Taft earthquake. The results of the analyses for different positions of the truncation boundary in reservoir models show that the position of the Sommerfeld boundary at five times the height of the dam away fromthe dam body is a proper place for the truncation boundary. Moreover, comparing the results of the present study based on the compressibility of water and those of previous research based on the incompressibility assumption indicates that the maximum hydrodynamic pressure is approximately 153.8% for a Taft earthquake. Therefore, the assumption of water compressibility plays an important role when evaluating the Pine Flat Dam.

Estimation of the breakthrough time of injected fluid in water injection process is useful for process design and injection pattern during reservoir development. Conventional approach to this is to use reservoir simulation. An alternative is to use percolation theory approach. However, some of the assumptions used in developing the scaling function of breakthrough time such as similarity of viscosity of both injection and production fluids limits its applications to field scale. In this study, we use the dimensionless time approach for breakthrough which is based on a characteristic time. By using various reservoir simulation cases the effect of fluids viscosities was studied. The results showed that the suitable characteristic time for scaling of breakthrough time depends on both NTG and viscosity ratio of phases in a power law form with exponent of 1. 3.

Sampling process is one of the important tasks in petroleum engineering which is used to specify the fluid type and estimate its PVT characteristics. In this study a detailed step by step procedure has been proposed. Based on the temperature and pressure conditions in each step, one or more oil or gas properties have been calculated using appropriate formula. Since the sampling from down-hole cannot provide sufficient volume for PVT analysis and other fluid calculations, the surface sampling and recombination processes is of great importance. To validate the proposed procedures, we studied a surface recombination process on a volatile reservoir fluid from an oil field in Middle East. The results indicate reasonable agreements between recombined fluid properties and reservoir fluid properties obtained from routine analysis. The error of 3.2 % has been observed in saturation pressure values compared with the down-hole reservoir fluid.

In light of the importance of reinforced concrete reservoirs, as well as the increasing number of Explosion damages, this study attempts to evaluate the performance of reinforced concrete reservoirs containing a fluid with response to TNT explosion at different distances while considering the Fluid-structure interaction (FSI) in relation to the loading impact from the blast wave. The LBE method in the LS-DYNA software was used for this research. The amounts of TNT used are 20, 40, 60, and 80 Kg at distances of 3, 4. 5, 6 and 7. 5 meters from the top of a concrete reservoir in simulated buried and non-buried situations. One of the most important results of this research is an increase of 14%, 33%, 35% and 41% of pressure in the blast impact on the reservoir with respectively 1. 2, 1. 4, 1. 6 and 1. 8 times of the TNT amount in the buried situation at a distance of 3 meters. Furthermore, the maximum pressure on the reservoir in the buried state at a distance of 3 meters was associated with an increase of 13%, 23%, 30% and 36%, respectively. The simulation results also illustrate the effect of soil as a protective cover in reducing the blast impact on the reservoir.

Drilling troublesome shales is one of the major problems in drilling operations. Borehole instability during drilling of shale layers results in increasing rig time and consequently increased operational cost. Thus, the correct choice of drilling fluid for drilling shale layers reduces drilling time and cost. One of these fluids is formate fluids. Potassium and cesium formate brines are among the best water based shale inhibitor fluids. Formate fluids according to their inherent properties create very good borehole stability. By the use of formate salts, we can design high density fluids with minimum solid content for drilling shale and reservoir sections. The obtained results showed that formate fluids are stable at high temperatures and show very good shale recovery like OBM. The results show that recovery shale of sodium/potassium formate fluid is higher than that of glycol, silicate, and KCl fluids. Formate fluids showed good compatibility with various kinds of polymers. The result of lubricity test showed that lubricity properties of formate fluids are comparable with other WBM. They do not need any lubricants.

Due to majority of relative permeability in reservoir engineering studies and its dependency to some physical properties, relative permeability measurement is the most complicated task in special core analysis studies. Equilibrium in front flow during flooding and recognizing the end effect capillary pressure in relative permeability tests is very important. For this reason the usage of in-situ saturation measurement methods has a paramount importance. Also performing SCAL tests in reservoir conditions and using reservoir oil creates correct and real data for reservoir engineers to apply in reservoir models. In this study, the goal of which is the determination of in-situ saturation during flooding in reservoir conditions, first four plug samples from Asmari formation were selected and thin section studies were done to recognize the lithologies and important features. Then using relative permeability apparatus in ambient condition, the average saturations of fluids in the cores were determined by measuring the volume of fluids expelled from the samples in the flooding test and the relative permeability curves were plotted. In the next step using x-ray relative permeability apparatus, the relative permeability experiments in the reservoir conditions were performed and the value of in-situ fluid saturation and the average saturation were determined via measuring the intensity of x-ray passes through the core. The results obtained from relative permeability tests in ambient and reservoir condition were then compared. Dead crude oil from Asmari formation has been used in all experiments.

Drilling fluids have the potential for reservoir damaging, which can be investigated in laboratories. Laboratory results indicate that the permeability of fractured reservoirs decreases due to using drilling fluid in pay zones. For reducing or returning the permeability of reservoirs many additives such as sized materials can play an important role in removing an increasing permeability of damaged sections. A set of experiments was performed which clearly showed that drilling fluids could cause large irreversible damage to fractures and then could dramatically reduce the productivity of wells producing from a natural fracture network. Using sized additives in drilling fluids can significantly reduce the depth and extent of formation damage. Laboratory results showed that sized calcium carbonate (CaCO3) were less effective comparing with acid soluble fibers; therefore, they were recommended for reducing pay zoon damage in fractured reservoirs. It is worth mentioning that according to the laboratory results aggregated fibers bridge across the face of the fracture and then bentonite in drilling mud forms an effective mud cake, which finally minimizes the invasion of solids and filtration to the formation and dramatically reduces formation damage (with filtration volume of 9 ml/5hr and 50% permeability improvement).

Constructing phase diagram and its subsequent quality lines for lean gas condensate reservoirs is always crucial and challenging topic in reservoir fluid studies. Due to small amounts of liquid drop-outs in lean gas condensates at reservoir conditions, full experimental tracking of phase diagram and its relevant quality lines is almost impossible for lean gas condensates. On the other hand, EOS models of reservoir fluid characterization softwares are always unable to estimate condensed liquid drop-outs at different pressures and temperatures precisely. This study aims to present a commingled experimental-simulation method which was designed to pinpoint and keep track full phase diagram with correspondent quality lines for a lean gas condensate fluid.

Introduction: Use of an adhesive with a suitable composite resin is an important factor in tooth-colored restorations and increasing marginal sealing ability. The aim of this study was to evaluate the microleakage of various adhesives with composite resins using fluid filtration and dye extraction techniques and assessment of the correlation between these two techniques.Materials and Methods: In this in vitro study, class II cavities were prepared on the proximal surfaces of 48 extracted sound human premolar teeth, measuring 1.5±0.5 mm in gingival width, 4 mm in occluso-gingival height and 1.3 of the inter-cuspal distance in width. The samples were divided into four groups (n=12). Group 1; OptiBond Solo Plus adhesive/Herculite XRV composite resin; Group 2: OptiBond Solo Plus adhesive/Master Dent composite resin; Group 3: Prime & Bond NT adhesive/Herculite XRV composite resin; Group 4: Prime & Bond NT adhesive/Master Dent composite resin. Microleakage was assessed primarily by fluid filtration and then by dye extraction techniques. Data were analyzed with Kruskal-Wallis and Mann-Whitney tests, with Bonferroni correction and Spearman's rho correlation test at 95% confidence interval.Results: The minimum and maximum mean microleakage values were recorded in fluid filtration and dye extraction techniques groups 1 and 4, respectively. There were significant differences between the experimental groups in microleakage with the two methods of leakage assessment (p value=0.001). Spearman's rho revealed a strongly direct correlation between the two methods (r=0.797, p value=0.000).Conclusion: In both methods of microleakage assessment, use of ethanol-based in comparison to acetone-based adhesive resulted in microleakage reduction. Application of light-cured composite resin contrary to self-cured composite resin with both types of adhesives increased marginal sealing ability.