What is the chemical basis for using hot oiling as a method for paraffin wax removal?

Hot oiling is a method for removing paraffin wax deposits based on the principle that the solubility of paraffin waxes in oil increases significantly with temperature. Paraffin waxes are long-chain n-alkanes that precipitate from crude oil when the temperature drops below their wax appearance temperature (WAT). These waxes deposit on pipeline walls, wellbore tubing, and other equipment, reducing flow capacity. Hot oiling involves circulating hot oil, typically crude oil or a refined oil with a high aromatic content, through the affected equipment. The elevated temperature of the hot oil increases the solubility of the wax, causing it to dissolve back into the oil. The hot oil acts as a solvent, breaking down the crystalline structure of the wax deposit and allowing the individual wax molecules to disperse into the oil phase. The effectiveness of hot oiling depends on several factors, including the temperature of the hot oil, the composition of the hot oil (particularly its aromatic content), the contact time between the hot oil and the wax deposit, and the thickness and composition of the wax deposit. Oils with higher aromatic content are more effective at dissolving waxes because they have a greater affinity for the non-polar wax molecules. The dissolved wax is then carried away by the hot oil, restoring the flow capacity of the equipment. After the hot oiling treatment, it is important to properly dispose of the oil-wax mixture to prevent re-deposition or environmental contamination. The key chemical basis is the temperature-dependent solubility of paraffin waxes in oil, which allows the hot oil to effectively dissolve and remove the wax deposits.