Thermodynamic modeling of wax precipitation in waxy condensate oil systems and its field application

During the development and production of condensate gas reservoirs, temperature, pressure, and other operating conditions change as oil and gas are continuously lifted to the surface. Under these conditions, solid-phase substances such as wax, resin, and asphaltenes precipitate from the condensate oil–gas system, posing substantial risks to production safety. In this study, the widely accepted multiphase equilibrium theory is employed. Phase transitions between gas and liquid phases are described using an equation-of-state method, while the non-ideality of the solid phase is characterized using ideal solution theory. To investigate the waxy precipitation behavior in waxy condensate oil systems, thermodynamic models for wax precipitation were developed under complex phase conditions, including gas–liquid, solid–liquid, and gas–liquid–solid systems. Furthermore, based on actual condensate production data, the thermodynamic model was refined to more accurately represent waxy condensate oil systems. The proposed model enables accurate prediction of wax precipitation temperatures and phase envelope characteristics for waxy condensate oils. This work is of substantial importance for mitigating wax deposition risks and ensuring flow safety during the production and transportation of waxy condensate oil.