塔河油田含氮天然气回注安全性及经济性研究

塔河油田随着注氮开采的进行,其采出气氮含量不断上升,天然气热值不达标,故有必要开展含氮天然气回注的安全性及经济性研究。从含氮天然气对注气井腐蚀速率、含氮天然气爆炸极限和含氮天然气临界氧比例等3个方面讨论了含氮天然气回注的安全性,并进一步分析了含氮天然气注气工艺和变压吸附制氮注氮工艺的能耗。结果表明:塔河油田含氮天然气中的氧对注气井无腐蚀危险；在注气压力下,含氮天然气爆炸极限范围极窄,含氮天然气中氧含量远低于临界氧比例,回注无爆炸危险,含氮天然气回注安全性较高。工艺能耗对比结果表明,含氮天然气回注工艺所需能耗仅为变压吸附制氮注氮工艺的三分之一,具有更好的经济性。 

Study on safety and economy of nitrogen-containing natural gas reinjection in Tahe oilfield

With the progress of nitrogen injection exploitation in the Tahe Oilfield, the nitrogen content in the produced gas is rising continuously, resulting in the failure to reach the standard of the heat value of natural gas, so it is necessary to conduct the study of the safety and economy of the nitrogen-containing natural gas reinjection. In this paper, the safety of nitrogen-containing gas injection was discussed in three aspects:the corrosion rate of gas injection wells, the explosion limit and the critical O₂ ratio. Furthermore, the energy consumption of nitrogen-containing natural gas reinjection process and that of pressure swing adsorption (PSA) nitrogen injection process were compared. The results showed that O₂ in nitrogen-containing natural gas from Tahe Oilfield has no corrosive risk to gas injection wells. Additionally, the range of nitrogen-containing natural gas explosion limit was narrow under the gas injection pressure, and the O₂ contents in nitrogen-containing natural gas was much lower than its critical O₂ ratio, which means that nitrogen-containing natural gas process has no risk of explosion and can be considered safe. The comparison of the process showed that the energy consumption of nitrogen-containing natural gas reinjection process was only one-third of that of the PSA nitrogen injection process, indicating that nitrogen-containing natural gas reinjection process was more economical.