Wax appearance temperature under shear in methane-saturated mineral oil + paraffin wax mixtures: Effects of concentration and pressure

Abstract

Increasing oil production from cold environments, such as offshore deep-water, has resulted in flow assurance issues due to wax deposition and hydrate formation. Understanding of the high-pressure flow properties of waxy oils is important to minimize blockages and related issues. However, the effect of pressure on wax appearance temperature (WAT) and viscosity of waxy oils is not widely studied due to the challenges of high-pressure rheology experiments. Here, a model waxy oil system was investigated using a high-pressure rheology from 0 to 1400 psig at 100 s−1. The focus was on paraffin wax in heavy mineral oil, and we examined wax concentrations of 5, 10, 15, and 20 wt%. First, waxy oils were saturated in methane, and then, temperature was decreased until wax appearance occurred. The findings revealed that wax concentration has a larger effect on WAT than pressure. At a constant pressure of 0 psig, WAT increases up to 13 °C when wax concentration increases from 5 to 20 wt%. Increasing pressure from 0 to 1400 psig results in up to 6 °C depression in wax appearance temperature for 20 wt% wax. The findings of the current study contribute to addressing flow assurance challenges in cold environments by enhancing the understanding of waxy oil rheology under methane-saturated, high-pressure conditions.