(56a) Effect of Electrostatic Field on Asphaltene Aggregation and Deposition Under Dynamic Conditions

Vahid Azari, Erfan Abolghasemi, Shahab Ayatollahi and Vahid Taghikhani

Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran.

Abstract

Asphaltene deposition during oil production is a leading cause in decreasing the production rate. Once occurred in an oil well, it could drastically increase the cost of remediation, workover and production. Therefore, preventative actions to control the asphaltene deposition and remediation of such heavy deposits which leads inevitably to reduction or even cessation in oil production is a main challenge. It has been shown that depending upon the nature of asphaltene molecules and the surrounding solvents, the asphaltene molecules can significantly react against electrostatic field. In other words, by applying electrostatic field precipitation, aggregation and deposition of asphaltene molecules can be controlled. To continue the previous research, in this work, the effect of electrostatic field under dynamic conditions was investigated on different crude oil samples. To do so, a homogenized mixture of crude oil and solvent was pumped into an open channel at various crude oil/asphaltene slurry flow rates using a peristaltic pump. Simultaneously, two parallel side walls of the open channel were connected to the positive and negative terminals of a DC power supply to turn them into the anode and the cathode electrodes in the electric circuit. The results showed that the asphaltene molecules, studied in this work, had tendency to be deposited on the negative electrode. Therefore, the residual surface electric charge on the colloidal molecules of asphaltene in crude oil was confirmed to be positive. Also, the effects of electric voltage, solvent/crude oil ratio and the flow rate of asphaltene/crude oil slurry in the open channel were studied on the amount of asphaltene deposition. It was shown that the electrostatic field can highly affect the aggregation rate and the deposition of asphaltene particles under flow conditions. Increasing the amount electric voltage can increase the aggregation rate of asphaltene molecules as well as and the average size of aggregates. This, in turn, can affect the rate of deposition of asphaltene molecules on the negative electrode. Also, it was concluded that an optimal crude oil flow rate was needed to be used in order to control and minimize the amount of asphaltene deposition. The results showed that the technique, proposed in this study, can be used to manage asphaltene aggregation and deposition as a preventative method. Lastly, the potential of practical application of this technique on a field scale was also discussed.