Modelling of solid precipitation in waxy multicomponent synthetic systems with ideal solid solution model and RKPR

QUINZIO, MARTINA JULIETA; RODRIGUEZ REARTES, SABRINA BELÉN; CISMONDI, MARTÍN

CABA

Congreso; 11th World Congress of Chemical Engineering (WCCE11); 2023

Asociación Argentina de Ingenieros Químicos

Reservoir fluids exhibit great compositional diversity and complexity, and typically contain heavy paraffinic compounds that can precipitate in the form of wax. Since the conditions under which this phenomenon occurs are within the range of conditions encountered in oil production or transportation, it has valuable operational and economic implications for the oil industry.Accurate prediction of the wax appearance temperature (WAT) and solid phase composition is essential to avoid or minimise this problem. To model the paraffin precipitation phenomenon in reservoir fluids, two main modelling approaches exist in the literature. One is the solid solution approach [1], and the other is the multi-solid approach. Within the solid solution models, the simplest that consider the solid phase as an ideal solid solution and use different approaches to describe the liquid phase. They also differed in the inclusion or not of a term to account for the effect of pressure. These models were applied with varying degrees of success and with some limitations for the description of real petroleum fluids. On the other hand, the description of fluid phase behaviour has made significant progress in recent years, where the superiority of the Redlich-Kwong-Peng-Robinson (RKPR) equation of state (EoS) for describing the behaviour of the most asymmetric and challenging hydrocarbon mixtures, especially at high pressures, has been clearly demonstrated [2]. With its third parameter (δ1) it overcomes the known limitations of the typical two-parameter cubic Soave-Redlinch-Kwong (SRK) and Peng-Robinson (PR) EoS, mainly in their incorrect predictions of deviations from the ideality of such mixtures. The parameter δ1 is a compound-specific structural parameter that allows to capture the proper evolution of the behaviour in the n-alkane family, and to give sufficient flexibility to the model.In this work, we take the ideal solid solution approach and couple it for the first time to the RKPR-EoS to model fluid phases. In this way, we study the complete phase behaviour of multicomponent synthetic systems containing multiple paraffinic compounds, over wide temperature and pressure ranges, and analyze the extent to which the limitations reported in previous models employing the ideal solid solution approach are overcome. Thus, mathematical simplicity is maintained without compromising good prediction accuracy. The results found in this work will be of particular interest at the industrial level where practical and effective solutions are sought.