基于Pareto前沿的塔河油田高含氮天然气分离过程研究

Separation process of high nitrogen-containing natural gas in Tahe oilfield based on Pareto frontier

注氮气提高原油采收率在塔河油田取得了较好的效果,但随着注氮气规模的扩大,天然气中氮气含量也不断上升,天然气热值不断下降,对用户生产经营造成了影响。本文针对高含氮天然气分离过程,建立了C1损失量关于产品气N2摩尔分数的Pareto前沿搜索模型,并通过遗传算法进行求解,同时根据塔河油田高含氮天然气的脱氮要求,对比了不同分离压力和分离级数下的C1损失量。结果表明,在分离压力为500kPa时且满足C1损失量小于5%的前提下,一级分离可处理N2摩尔分数小于33%的天然气,二级分离可处理N2摩尔分数小于40%的天然气,三级分离可处理N2摩尔分数小于42%的天然气;塔河油田高含氮天然气多级分离单元分离压力应选择为500kPa,并采用二级分离。

Nitrogen injection has achieved good results in improving oil recovery in Tahe oilfield. However, with the expansion of the scale of nitrogen injection, the content of nitrogen in natural gas keeps rising and the heat value of natural gas keeps decreasing, which has affected the production and management of users. In this paper, a Pareto frontier search model of C1 loss with respect to N2 mole fraction of product gas was established for the separation process of high nitrogen-containing natural gas, and the solution was obtained by genetic algorithm. According to the denitrification requirements of high nitrogen-containing natural gas in Tahe oilfield, C1 losses under different separation pressures and separation stages were compared. The results show that under the premise of separation pressure of 500kPa and satisfying the loss of C1 less than 5%, the one stage separation process can treat the natural gas with N2 mole fraction less than 33%;the two stages separation process can treat the natural gas with N2 mole fraction less than 40%;and the three stages separation can treat the natural gas with N2 mole fraction less than 42%. The separation unit for the high nitrogen-containing natural gas in Tahe oilfield was supposed to use a pressure of 500 kPa and two separation stages.