Masoud Aghajani

Experimental Study of Asphaltene Precipitation Behavior During Miscible Carbon Dioxide Injection

Many reservoir and production engineers face asphaltene precipitation as a major problem during miscible carbon dioxide flooding projects. Experimental studies regarding asphaltene precipitation are therefore employed to assist in selecting appropriate facilities and proper operation schemes. During this study, a series of high pressure, high temperature experiments are designed and performed to analyze asphaltene precipitation behavior of an Iranian light reservoir crude at reservoir conditions due to natural production and miscible CO2 gas injection. For both sets of experiments, two different temperature levels (including reservoir temperature) are selected to investigate the role of temperature on asphaltene precipitation as well. Results of natural production experiments indicate that the maximum amount of precipitation occurs at reservoir bubble point pressure, while for each specified pressure asphaltene precipitation increases as the temperature is raised for the whole range of pressures. Carbon dioxide injection experiments, however, have terminated in some remarkable findings: for small CO2 concentrations, CO2 behaves as a hindering agent and lowers the amount of precipitation; on the contrary, for higher fractions (values larger than critical CO2 concentration), the injection of CO2 results in more asphaltene precipitation. An increase in temperature during CO2 injection results in (1) the increase of asphaltene precipitation, (2) the shift of the critical CO2 concentration to lower values, and (3) the decrease of the rate of asphaltene precipitation with CO2 concentration.

Dibenzothiophene removal from model fuel using an acid treated activated carbon

ABSTRACT Sulfur containing compounds are one of the most concerning pollutants in fossil fuels. The increasing rate of fuel consumption around the globe reveals the necessity of further purification of the fuels. In this study, application of adsorption process in removing dibenzothiophene from a model fuel is investigated. A granular activated carbon is treated with aqueous solution of nitric acid and implemented as the sorbent. Treatment of the activated carbon with nitric acid resulted in increasing the adsorption capacity of the activated carbon. Freundlich and TÓth isotherms are capable of sufficiently describing the equilibrium data. Investigation of the kinetics of the process is carried out using the homogeneous surface diffusion model. Internal and external mass transfer coefficients are 9.3917 × 10-6 m2/min and 1.4153 × 10-2 m/min for the virgin activated carbon (VAC) and 4.8738 × 10-6 m2/min and 5.2529 × 10-2 m/min for acid treated activated carbon (AAC), respectively.

Correction of Terminal Velocity Prediction Model for CO 2 -Kerosene and Air-Kerosene Systems by Artificial Intelligence

In this study the essential factors of rising air and CO 2 bubbles in distillated water and kerosene investigate with the experimental and theoretical attitude. Many formulas developed by pervious investigators for bubble terminal velocity prediction in air-water system. By using PSO (particle swarm optimization) algorithm and plotting experimental data of terminal velocity against the size of gas bubbles, suitable was chosen. Results showed that Jamialahmadi model is more practical for air-water and CO 2 -water system. The main aim of this paper is to validate and correct Jamialahmadi model for predicting of bubble’s terminal velocities in air-kerosene and CO 2 -kerosene systems. Jamialahmadi model requires a modification to be utilized for air-kerosene and CO 2 -kerosene system. The developed PSO algorithm model is accurate for prediction of experimental data with an average R 2 value of 0.976.

Experimental and theoretical investigation of CO2 and air bubble rising velocity through kerosene and distilled water in bubble column

Abstract This paper concerns with developing of parameters which influence terminal velocities of air and CO2 bubbles in distilled water and kerosene pools. The objective of this study is to validate and correct the formulas that were developed by previous investigators for prediction of terminal velocities. The investigation revealed that the terminal velocity of a single rigid spherical bubble in Newtonian fluids can be developed by balancing of mechanical forces acting on the bubble. However, for large bubbles, because of deforming of the bubble which is a result of interfacial tension, the effect of surface tension should be considered in the terminal velocity prediction formula. By using PSO algorithm and plotting experimental data of terminal velocity against the size of gas bubbles, the suitable equation for each of systems was chosen. Results showed that Jamialahmadi model is more practical for terminal velocity prediction. Jamialahmadi model requires a modification to be utilized for air-kerosene, CO2-kerosene, air- distilled water and CO2-distilled water systems. The developed PSO algorithm model is accurate for prediction of experimental data with an average R2 value of 0.9722. GRAPHICAL ABSTRACT

An Experimental Study of Secondary WAG Injection in a Low-Temperature Carbonate Reservoir in Different Miscibility Conditions

Abstract This experimental study is aimed at evaluation of the performance of secondary WAG injection in carbonate cores at different pressures. To do so, a comprehensive series of high-pressure high-temperature (HPHT) core flooding tests are conducted. The fluid system includes reservoir dead and live crude oil, CO2, and synthetic brine while the chosen porous media consists of a number of fractured carbonate core samples. Parameters such as oil recovery factor, water and oil production rates, and pressure drop along the core are recorded for both dead and live oil. According to results, at first increasing pressure improves the oil recovery, but this improvement after MMP is not as significant as it is before MMP. Also recoveries of dead and live oils at same pressure show different values due to differences in miscibility condition of injected gas. Then as the graphs demonstrate, relative permeability reduction due to hysteresis effect has dominant effect on pressure drop curves. Finally, as the production rate curves show, nearly all of the remained oil after breakthrough is produced as the gas is being produced and almost no oil can be recovered during water production portions.