Flow and heat exchange laws in thermal recovery wellbore by steam injection assisting with nitrogen gas

Key words:  thermal process  steam injection  nitrogen gas  annular  flow and

Abstract:

In order to analyze the effect of the heat insulation methods of charged or injected nitrogen gas in the annular of steam injection wells on steam injection，the flow and heat transfer mathematical models of the steam and nitrogen flowing along the wellbore were established on the basis of heat transfer principle and flow theory. The temperature and the pressure distribution of the fluids were calculated. Annular heat insulation effects of charged nitrogen gas and air, and charged or injected nitrogen gas were contrasted. The results show that the insulation effect of charged nitrogen gas or air in annular is negligible ,the insulation method of charging with low pressure gas is well，the insulation effect of injected nitrogen gas is better than that of charged nitrogen gas. When the injecting nitrogen gas volume increases, the steam pressure will ascend, heat loss of steam will increase which is absorbed by the nitrogen gas and injected into the formation, and the actual heat loss will decrease.