Sharif Digital Repository

In this work, the rheological changes of several crude oil samples exposed to ultrasonic waves for different time intervals in addition to the effect of temperature on viscosity behavior of heavy crude oils were investigated using a series of steady shear flow and oscillatory tests. The colloidal structural evolutions of flocs in oil samples were illustrated by analysis of the size distribution of flocculated asphaltene particles (confocal microscopy tests). The rheological investigations indicate that the ultrasonic irradiation dissolved heavy components in crude oil. After ultrasonic treatment, the Kouh-e-Mond crude oil was found to be pseudoplastic. In addition, confocal microscopy... 

Based on series of crude oil rheological properties and asphaltene flocculation confocal microscopy analysis, Najafi et al., (2011) reported the existence of an optimum radiation time at which asphaltenic crude oils reach the minimum kinematic viscosity. Accordingly, they proposed the idea of asphaltene flocculation inhibition due to wave radiation.The present investigation is a continuous effort to provide more information about the process of flocculation inhibition. Confocal microscopy and rheological analyses are performed on different crude oils to prove the repeatability of the observed phenomena. The asphaltene content analysis was done based on IP143 procedure, which provides more... 

Recently, it was found that ultrasonic wave technology can be used as a method for asphaltene deposits removal from the near wellbore region. However, ultrasounds can affect asphaltene resolution.In this work, asphaltene resolution in several crude oil samples exposed to ultrasonic waves for different time intervals is studied by confocal microscopy. The colloidal structure of flocks is described by analysis of asphaltene particle size distribution to investigate ultrasonic application in solving asphaltene deposition problems.. The results show that for the first 90 minutes of flocculation time, the size of aggregates increases rapidly, and reaction limited aggregation model matches well... 

Asphaltene which cover range of 1% to over 10% of oil by weight, is well-known as most problematic part of oil that can deposit during production in reservoir, well tubing, and surface production lines, and consequently impose a serious restriction on production which in turn increases total cost of entire operation. Through decades an extensive research has been performed in order to identify asphaltene molecular structure, its behavior at different condition, and its separation mechanism from oil. One of most critical parameter associated with asphaltene precipitation modeling is flocculated asphaltene weight percentage in oil at given operation condition. In this study, to eliminate cost... 

Asphaltene deposition during enhanced oil recovery (EOR) processes is one of the most problematic challenges in the petroleum industry, potentially resulting in flow blockage. Our understanding of the deposition mechanism with emphasis on the rate of the asphaltene deposition is still in its infancy and must be developed through a range of experiments and modelling studies. This study aims to investigate the rate of asphaltene deposition through a visual study under different gas injection scenarios. To visualise the asphaltene deposition, a high-pressure setup was designed and constructed, which enables us to record high-quality images of the deposition process over time. Present research... 

This work is concerned with the monitoring of ultrasound effects on inhibition, as well as the reversible kinetics modeling of asphaltene flocculation in toluene-n-alkane systems, which has been rarely reported in the literature. A crude oil sample was exposed to ultrasound waves, and then the colloidal structural evolutions of flocculated asphaltene particles induced by addition of n-alkane were studied, using a confocal microscopy. Observations confirmed that radiation of ultrasound can change the irreversibility of asphaltene flocculation in crude oil. To interpret the kinetics of asphaltene flock aggregation, the Smoluchowski model was used, and the time dependent size distribution of... 

In this study, it is aimed to compare the efficiency of ultrasonic wave technology on asphaltene flocculation inhibition of crude oils with different American Petroleum Institute (API) gravities. A set of confocal microscopy test is performed and a series of statistical analysis is done. According to the results of this study, there is an optimum radiation time for both crudes at which the viscosity and the flocculation rate of asphaltenic crude oils reduces to its minimum. This optimum appears at later times of radiation for extra heavy oil. Also, it is shown that the rate of changes in the properties measured in this study is sharper for extra heavy crude oil. It could be concluded that... 

Recently, ultrasonic wave technology has received much attention as a method for removal of asphaltene deposits from the near wellbore region. However, very little is known about another feature of this technology on the kinetics of asphaltene molecules aggregation. In this work, the kinetics of asphaltene flocculation in several crude oil samples exposed to ultrasonic waves for different time intervals is studied by confocal microscopy. The colloidal structural evolutions of flocks are described by analysis of size distribution of flocculated asphaltene particles. The results show that for the first 90 min of flocculation time, the size of aggregates increases rapidly, and a... 

In this work, the electrokinetic properties of asphaltene particles have been investigated. Micro-electrophoresis method by applying DC electric field, was utilized to different mixtures containing asphaltene to determine its electric charge. It was observed that in the case of using n-heptane and its mixture with toluene (heptol), the asphaltene particles were showed to be positively charged however for toluene itself, they expressed no tendency toward the electrodes. While it is expected that larger asphaltene aggregates carry higher electric charge, the results contradictorily showed that they are mainly governed by gravity rather than electro-static force and that “aggregation” reduces...