Coupling Mechanisms of Wax Precipitation and Wellbore Deposition Prediction in HTHP Condensate Gas Wells

Wax precipitation and wellbore deposition commonly occur during the development of high-temperature and high-pressure condensate gas wells, posing significant challenges to flow assurance and production stability. In this study, a high-temperature and high-pressure dynamic wax precipitation apparatus was employed to determine the wax appearance temperature under flowing conditions based on abrupt changes in pressure difference. The effects of pressure, gas–oil ratio (GOR), flow rate, injection gas medium, and wax content on wax precipitation in condensate oil–gas systems were systematically investigated, and a gas–liquid–solid three-phase wax precipitation phase behavior model was established. The results show that the wax appearance temperature is jointly controlled by liquid-phase wax supersaturation, gas–liquid compositional partitioning, and deposition kinetics. Under high-pressure dynamic conditions at 50 MPa, an increase in wax content by 7.40 percentage points, from 26.56% to 33.96%, increased the wax appearance temperature by 8.7 °C. The pressure effect exhibits a nonmonotonic, dew-point-controlled segmented pattern: as pressure increases from 10 to 57.8 MPa, the wax appearance temperature rises from 26.6 to 34.0 °C, whereas it decreases to 32.9 °C when pressure further increases to 77.8 MPa. When the GOR increases from 850 m3/m3 to 1600 m3/m3, the wax appearance temperature decreases from 30.4 to 23.8 °C. Among the different injection gases, the wax appearance temperature follows the order N2 > produced gas > CO2. Flow rate has only a weak effect on wax appearance temperature and mainly regulates wax deposition intensity. The proposed phase-behavior model reasonably captures the turning behavior of wax appearance temperature near the dew-point pressure and enables wax deposition risk prediction when coupled with wellbore pressure–temperature profiles. These findings provide mechanistic insights into wax precipitation and deposition in high-temperature and high-pressure condensate gas wells and offer a theoretical basis for optimizing wax control strategies.