Low-pressure modeling of wax formation in crude oils

Organic deposition in the reservoir and pipelines is responsible for huge l osses in profit in petroleum exploration. Among them, wax deposition is of particular concern in offshore and cold climate operation since they are te mperature driven. A thermodynamic model able to anticipate the formation of wax in the oil from the knowledge of its properties would be a very valuab le help for the design of transport facilities and the operation of reservo irs of potentially problematic oils. A new thermodynamic approach is propos ed for the description of wax formation in crude oils at low pressures. Thi s approach is based on the description of the solid-liquid equilibrium of t he n-alkanes present in the fluid. It assumes an ideal liquid phase, allowi ng for the use of any characterization of the fluid, and describes the soli d-phase nonideality using a predictive local composition model. The propose d model, unlike previous published models, is purely predictive since it us es only pure compound properties and the fluid composition to describe the wax formation. On the basis of the knowledge of the detailed composition of about 30 crudes from different origins, correlations are proposed to estim ate the n-alkane content and distribution for waxy crudes. Using the propos ed approach it was possible with very limited information on the compositio n to produce an excellent description of the experimental data available in the literature for different crudes.