4046 r2010 American Chemical Society pubs.acs.org/EF Energy Fuels 2010, 24, 4046–4053 : DOI:10.1021/ef100106r Published on Web 06/15/2010 Prediction of Asphaltene Precipitation: Learning from Data at Different Conditions Javad Sayyad Amin,* Abdolmohammad Alamdari, Nasir Mehranbod, Shahab Ayatollahi, and Ehsan Nikooee Enhanced Oil Recovery (EOR) Research Center, School of Chemical and Petroleum Engineering, Shiraz University, Shiraz 7134851154, Iran Received January 28, 2010. Revised Manuscript Received May 31, 2010 Asphaltene precipitation affects enhanced oil recovery processes through the mechanism of wettability alteration and blockage. Asphaltene precipitation is very sensitive to the reservoir conditions and fluid properties, such as pressure, temperature, dilution ratio, and injected fluid molecular weight. A Bayesian belief network (BBN) was used in this study as an artificial intelligence modeling tool to investigate the effect of different variables/parameters on asphaltene precipitation. The predicted results from the BBN model were compared to the experimental precipitation data obtained using high-resolution images captured in a high-pressure cell and processed by image analysis software. The cell accessories facilitate in situ visual monitoring of nuclei growth of asphaltene at high pressures and specified temperatures. The average relative absolute deviation between the model predictions and the experimental data was found to be less than 4.6%. Burst of nucleation or the onset of asphaltene precipitation was also determined at different conditions directly by the developed BBN model. A comparison between the prediction of this model and the alternatives showed that the BBN model predicts asphaltene precipitation more accurately and covers a wider range of affected variables/parameters. 1. Introduction Gas injection is widely used as an enhanced oil recovery (EOR) process in the petroleum industry. Gas injection would maintain the reservoir pressure and increase the sweeping efficiency at high-pressure conditions through the immiscible or miscible displacements. Gas injection may encounter as- phaltene precipitation through which a sticky, asphalt-like substance plugs the reservoir and production equipment. 1 On the basis of solubility, asphaltene is defined as that fraction of petroleum that is insoluble in n-alkanes and completely soluble in aromatics, such as toluene and benzene. 2 The extent of asphaltene precipitation depends upon the composition of the crude oil, the precipitating agent, and the pressure and temperature of the reservoir. 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