Impact of High Pressure on Wax Deposition and Paraffin Inhibitor Performance in a Cold Finger System

Wax deposition in crude oil pipelines is a major flow assurance challenge, especially under high-pressure conditions, where dissolved gas significantly affects wax precipitation and deposition behavior. Most existing studies focus on dead oils, leaving a critical gap in understanding live oil systems. This study aims to investigate the pressure-dependent wax deposition characteristics using an in-house designed high-pressure cold finger apparatus and a methane-saturated model oil (MO-A22), under pressures ranging from atmospheric to 200 bar. The experiments systematically evaluate wax deposit mass, wax content, methane solubility, and the efficacy of a paraffin inhibitor (INHI-1) at a concentration of 500 ppm. Results indicate that wax deposition initially increases upon the introduction of methane, which shifts the system from a single-phase regime to a multiphase regime, with a peak observed around 1 bar. However, at pressures beyond 1 bar, wax deposition declines due to the increased solubility of methane in the oil phase, which suppresses wax precipitation by altering the equilibrium of wax-forming components. The paraffin inhibitor (INHI-1), at 500 ppm, was found to significantly reduce the deposit mass across the pressure range up to 150 bar, highlighting its effectiveness in interfering with wax crystallization phenomena and growth. These results underscore the complex interaction among pressure, gas solubility, crystallization kinetics, and chemical inhibition, providing new insights into wax deposition mechanisms in live oil systems and emphasizing the need for wax mitigation strategies that account for the effects of pressure in flow assurance.