(74f) PVT Modeling of Crude Oils: Development of Advanced Characterization Methods and Accurate Prediction of the Onset of Asphaltene Precipitation

With ever-increasing complexities in production environments – including gas injection for EOR or deep sea Pressure-Temperature conditions – and the high cost of sampling reservoir fluids, accurate modeling of PVT properties with minimal field data is critical. These difficulties necessitate a continual reevaluation of the characterization methods for crude oils as well as the Equation of State (EoS) models used to predict PVT properties. The impact of such accurate PVT characterization and modeling of crude oils in reservoir simulations and EOR applications cannot be over-emphasized. In this work, we review well known methods for characterizing the plus fraction of black oil and gas condensate mixtures and compare various equations of state in predicting the phase behavior of the reservoir fluids in a wide range of pressures and temperatures. The equations of state studied in this work are the conventional cubics (i.e. Soave-Redlich-Kwong and Peng-Robinson) with and without volume correction and PC-SAFT. We will revisit previous characterization methods and discuss the development of new, simplified characterization methods. A thorough discussion is presented on the characterization procedures, advantages and disadvantages of the different methods, and the performance in the prediction of PVT properties.

From the flow assurance stand point, accurate prediction of asphaltene precipitation is absolutely critical for (a) understanding the likelihood of asphaltene deposition problems, (b) implementing proper mitigation strategies and (c) developing suitable EOR strategies, as gas injection can potentially increase the propensity of asphaltene precipitation. In this regard, we build on our previous work in the use of PC-SAFT EoS along with simplified correlations relating the PC-SAFT parameters of Asphaltenes, Aromatics and Resins to their MW (or a MW distribution) and a new parameter called aromaticity. Further, the accuracy of newly developed characterization methods in the prediction of bubble pressure curves and asphaltene onset curves will be discussed.