Research on the Calculation Method for the Wellbore Temperature of Hot Nitrogen Gas Circulation Wax Removal and Plug Removal in Offshore Oil Fields

The problem of wax deposition widely exists in offshore oil fields; waxing of the oil tubing will lead to a reduction in the cross-sectional area of the flow and, in serious cases, the flow path will be blocked, causing the well to stop production. In order to cope with this problem, a thermal dynamic wax removal method has emerged in recent years that utilizes hot nitrogen gas circulation between the oil tube and annulus to raise the temperature of the oil tube to achieve the purpose of wax removal and plug removal and is quick and easy to operate. Unlike conventional wellbore temperature calculation methods, the wellbore temperature field under hot nitrogen circulation conditions is influenced both by the reservoir temperature gradient and the hot nitrogen injection temperature, injection pressure, and injection rate. In this paper, a temperature calculation model for a wellbore considering both annulus injection temperature and tubing temperature and their interactions is modeled, which can consider the effects of different hot nitrogen injection temperatures, injection rates, and injection pressures. The model is used to calculate the temperature distribution for different injection parameters in order to ensure that the tubing temperature is higher than the wax precipitation temperature and that the annulus temperature is not higher than the maximum temperature resistance of the rubber in the packer. The study provides a design method for wax removal and plug removal with hot nitrogen gas circulation.

Automated summary

This study presents a thermal dynamic wax removal method using hot nitrogen gas circulation and develops a temperature calculation model for a wellbore considering different injection parameters. It provides a design method for wax removal and plug removal.