Influence of Altitudes and Air Humidity to the Minimum Gas Injection Rate in Air Underbalanced Drilling

Three aspects, such as the optimization of calculation model for the minimum gas injection rate, the effect of elevation on the minimum gas injection rate, the effect of air humidity on the minimum gas injection rate, have been reviewed in this paper. Considering the influence of altitude and air humidity, correction factor for gas injection rate is calculated. The value of gas injection for altitude correction factor generally increases with the increase in altitude, especially when conducting air drilling in high altitude areas of western China the correction factor of Qinghai oilfield can be calculated as high as 1.5. When the air humidity increases, the gas injection humidity correction factor also increases; especially before raining in summer, the air humidity correction factor can be close to 1.1, under the condition of relatively high air humidity and temperature. In the light of the calculation result and example analysis, it can be found that combining with this article’s altitude and air humidity correction, the result of the amended minimum kinetic energy standard using Boyun Guo’s correlation is the closest to the actual one, which can be used for the calculation of the minimum gas injection rate in industry practice while other methods have relatively larger errors.