Iranian Journal of Oil & Gas Science and Technology
Volume:5 Issue: 3, Summer 2016

Tedious calculations and simulations are needed to obtain an efficient production scenario and/or proper field development strategy. Capacitance-resistance model (CRM) is proved to be a fast reservoir simulation tool using just the field-available data of production and injection rates. This approach sets a time-constant and a weighting factor (or well-pair connectivity parameter) between each pair of injection and production wells according to their histories. In this study, we investigated the behavior of the CRM parameters in synthetic reservoir models with different porosity and permeability maps. Four reservoirs are considered with different porosities and permeabilities to study their effects on CRM response. We defined a new parameter, named error to mean production ratio (EMPR), to analyze the CRM performance. Some fluctuations are exerted on the production data to evaluate the capability of CRM against variable production records. Porosity showed a stronger effect on CRM parameters than the permeability based on the calculated EMPR. Unstable production history would result in large error which can be corrected with some smoothing techniques on variable production data. Also, a linear trend of EMPR was obtained with the change of porosity and permeability or a combination of the two parameters within the reservoir.

In this study, a chemical additive made by a combination of polymer, alkaline, and silica nano particles is used to control the oil recovery and relative permeability curves. Various parameters including the type and concentration of polymer, alkaline, and nanosilica particles have been studied. To evaluate the efficiency of these additives, we performed unsteady state displacement experiments under the JBN method and determined the pressure gradient across the core samples. The experimental observations emphasized that by using the appropriate chemical additives the relative permeability of the phases is changed towards higher oil relative permeability values, which results in the oil recovery. The results of this study can improve the chemical flooding for heavy oil recovery.

A consequence analysis was performed in one of the gas refineries in Iran to investigate the risks and potential losses resulted from accidents. Specifically, the consequences of an explosion in LPG spherical tanks were modeled using PHAST and MATLAB software. In this paper, three methods of calculation of PHAST software TNT, multi-energy, and BST were used. The results showed that multi energy method is the best method to evaluate overpressure. It was 0.150 bar and 0.159 bar in a distance of 1000 m far from the blast using PHAST and MATLAB respectively. This overpressure can damage a wall with 30 cm thickness. It also affects the human threshold (1%) ruptured eardrum. Finally, it was found that 100% lethality in a minute happened at 285.5 m and 37.5 kW/ 2 when the explosion happened.

In this paper, exergy and exergoeconomic analysis is performed on the recently proposed process for the coproduction of liquefied natural gas (LNG) and natural gas liquids (NGL) based on the mixed fluid cascade (MFC) refrigeration systems, as one of the most important and popular natural gas liquefaction processes. To carry out this analysis, at first, the proposed process is simulated, and then the exergy analysis of the process equipment is performed; finally, an economic model is used for the exergoeconomic analysis. The results include cost of exergy destruction, exergoeconomic factor, exergy destruction, and exergy efficiency. The results of the exergy analysis demonstrate that the exergy efficiency of the proposed process is around 53.83%, and its total exergy destruction rate is 42617.5 kW at an LNG and NGL production rates of 68.99 kg/s and 27.41 kg/s respectively. The results of exergoeconomic analysis indicate that the maximum exergoeconomic factor, which is 69.53%, is related to the second compressor in the liquefaction cycle and the minimum exergoeconomic factor, which is 0.66%, is related to the fourth heat exchanger in the liquefaction cycle. In this process, demethanizer tower holds the highest relative cost difference 100.78) and the first air cooler in liquefaction cycle has the lowest relative cost difference (1.09). One of the most important exergoeconomic parameters is the cost of exergy destruction rate. The second heat exchanger has the highest exergy destruction cost (768.91 $/Gj) and the first air cooler in the liquefaction cycle has the lowest exergy destruction cost (19.36 $/Gj). Due to the high value of fuel cost rate (as defined in exergoeconomic analysis) in heat exchangers, their exergy destruction cost is much higher than other devices.

The Taguchi design of experiments (DOE) approach is adopted here to evaluate the impact of effective factors such as nanoparticles type, nanoparticles to model solution mass ratio, asphaltene structure, and temperature on asphaltene adsorption equilibrium. Herein, the toluene asphaltene solution model is applied. Three commercially nanoparticles (SiO2, Al2O3, and TiO2) are used. Asphaltene characterizations are carried out by X-ray diffraction (XRD) analysis. It is found that the nanoparticle type and asphaltene structure with a respective influence of 48.5% and 3.11% have the maximum and minimum contribution on the amount of adsorbed asphaltene at the selected levels respectively. Aluminum oxide nanoparticle has the maximum and silicon oxide nanoparticle shows the minimum adsorption. The temperature has no statistical significance. Asphaltenes with higher aromaticity have more tendencies for adsorption on nanoparticles.

In some engineering fields, wear resistance and a low friction coefficient are required at the same time. In this research, PTFE nanoparticles and carbon nanotubes were co-deposited within Ni-P matrix to obtain an Ni-P-PTFE-CNT hybrid coating for wear resistance and a low friction coefficient. The tribological properties of the deposits were evaluated by pin on disc tribometer. The morphology of the coatings and worn surface was evaluated by scanning electron microscopy. However, the results showed that the addition of PTFE nanoparticles to the Ni-P electroless coating caused the friction coefficient to decrease to values lower than 0.2, which led to an improvement in friction behavior because of its self-lubricity properties; it, however, decreased the strength of coating due to polymeric and soft structure of the molecules. The simultaneous incorporation of PTFE nanoparticles and carbon nanotubes can provide the properties of both molecules and increased the strength of coating with a low friction coefficient and self-lubricity properties. Therefore, the wear rate and the degradation of surface were decreased during the wear process.