THERMODYNAMIC MODELLING OF WAX PRECIPITATION IN PRODUCTION TUBING

A generalized thermodynamic model was developed based on continuous thermodynamic phase equilibria employing two-parameter (α, β) gamma distribution function with a generalized correlation to split and characterize the lumped fraction. New Molecular Weight (MW)-dependent thermodynamic property correlations were developed and used to calculate the solid-liquid-equilibrium-ratios (KiS-L). The model was validated with data obtained from experiments conducted on 32 different hydrocarbon fluids from the Niger Delta, North Sea, Gulf of Mexico, East Asia, and Middle East fields. The model for wellbore fluid temperature distribution predictions was derived using the steady-state energy equation incorporating dimensionless time solution and heat-transfer mechanism in the wellbore. The models were applied to 17 waxy fluids from the Niger Delta and the pour point, viscosity, and API gravity of the fluids were measured using ASTM standards.