The employment of predictive techniques combining kinetic and thermodynamic analyses is the succinct solution to effectively control asphaltene precipitation during crude oil production. Although thermodynamic processes and conditions have been well studied in the literature, the effect of long-time kinetics on the key factors affecting the precipitation of asphaltenes was not critically studied. This work employed a model oil for asphaltene precipitation long-time kinetic observations. Filtration and confocal microscopy experimentations for time periods of 0-7200 min were utilized to study asphaltene yields and sizes at room and high temperatures (25, 50, and 70 °C), rotation speeds (60 and 150 rpm), and precipitant concentrations (50 and 60 wt %). The results from both experiments were fitted with DLVO models. The experimental results confirmed that the effects of temperature, rotation speeds, and precipitant compositions on asphaltene precipitation were significantly affected by time. The asphaltene yields increased from 27 to 83% within 7200 min when the heptane concentration increased from 50 to 60 wt %. Conversely, increasing temperatures from 25 to 70 °C reduced the cumulative asphaltene yields by 20-40% when observed for a long time (0-7200 min). Significant reductions in the mean equivalent diameter (MED) of precipitating asphaltenes upon increasing temperature within the studied timeframes were observed via the confocal experimentations. The rotation speeds also showed an inverse relationship with asphaltene yields and particle size. A reduction from 30 to 50% of the yield was observed as the rotation speeds of the system were increased from 60 and 150 rpm. The results of this work confirmed the significant impact of contact time on the precipitation of asphaltenes. In addition, DLVO theory employed to predict the experimental data obtained from the confocal microscopy fitted the data with mean absolute errors ranging from 4.44 to 5.15, which showed significant limitations upon increasing temperature. This development is progress toward enhancing the predictability of a production route devoid of asphaltene-related problems.
A. K. Quainoo and A. Imqam, "Long-Time Kinetic Impact on Key Factors Affecting Asphaltene Precipitation," Energy and Fuels, vol. 36, no. 18, pp. 11108 - 11122, American Chemical Society, Sep 2022.
The definitive version is available at https://doi.org/10.1021/acs.energyfuels.2c01963
Geosciences and Geological and Petroleum Engineering
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15 Sep 2022