Prediction of asphaltene precipitation by gas injection in crude oils from western Venezuela

Abstract

In Motatán field, asphaltene deposition has been observed in gas-lift wells, causing various problems that significantly impact production. In an effort to gain a fundamental understanding of the asphaltene precipitation phenomenon, this study will focus on predicting where and how asphaltene precipitation will occur in the well by integrating all available laboratory data, field logs, and thermodynamic models, thus shifting from the current corrective approach to a predictive/preventive strategy. It was found that some of the injected gas dissolves into the oil, and the mixture enters a three-phase gas-oil-asphaltene equilibrium. By studying the effect of different gas injection rates, it was found that APE tends to expand gradually as the injection gas ratio increases, and asphaltene risk remains constant in each of the possible volumetric mixtures. The proposal is to minimize wellhead flowing pressures to reduce the amount of dissolved gas and thus greatly control the problem of asphaltene precipitation in the well.