An Investigation on Phase Behaviors of Wax Precipitation in Waxy Gas-Condensate Reservoir

Wax precipitation has causes a great damage to natural gas production and transportation for waxy gas-condensate reservoir. The main focus of this work is to evaluate the phase behavior of wax precipitation in gas-condensate reservoir. Based on the wax module of PVTsim simulator, the pressure-temperature condition and total amount of wax precipitation were analyzed. The results show that there are four phase regions in the pressure-temperature figure: gas-wax region, gas-liquid-wax region, gas-liquid region and gas region. The reservoir fluid develops toward to dry gas as the gas-oil ratio (GOR) increases. It is observed that the smaller the GOR of reservoir fluid, the larger the temperature and pressure of wax precipitation. The amount of wax precipitation for the reservoir fluid increases with the temperature decrease, and lower pressure can cause more wax precipitation. The temperature has a greater effect on the wax precipitation than the pressure. The amount of wax precipitation increases as the GOR of reservoir fluid decreases. The influence of GOR on the wax precipitation of reservoir fluid is larger than that of degassed surface oil. Under different pressures, the relationship between vapor or liquid phase volume and temperature is different.