致密低渗气藏气井“四线六区”工况识别方法

A method to identify"four-line and six-zone"working condition for gas wells in low-permeability tight gas reservoirs

大牛地气田致密低渗透气藏的气井产能低,且递减快,需优选合适排采工艺辅助气井稳定生产。目前采用的气井工况识别方法缺少实时性,难以及时改善气井生产状况。因此,从气井产能方程出发,利用临界携液/携泡流量工况工诊断方法,结合不同时期产能曲线刻画出6个特征区,建立"四线六区"气井工况识别方法。结果表明:①该方法根据各种工艺特点和6个特征区生产特征,将全生命周期气井划分为自主携液阶段、泡排阶段、泡排+阶段和泡排后阶段4个排采阶段,可以进行实时气井工况识别诊断,有利于优选气井排采工艺;②采用该办法指导大牛地气田259口病态井治理,使其现有产能由234.5×10^4 m^3/d提升至275.7×10^4 m^3/d,恢复产能41.2×10^4m^3/d。结论认为,该方法能够更加准确地进行气井的实时生产工况诊断,使工艺优化更加合理。

For most gas wells in low-permeability tight gas reservoirs,Daniudi gasfield,their productivity is low and declines rapidly.It's necessary to adopt appropriate drainage gas recovery technologies to keep stable production.However,it's very difficulty for those currently used methods for identifying working condition of gas wells to improve their production in time.So,based on productivity equation and deliverability curves in different stages,six characteristic zones were delineated by one approach to diagnose critical liquid-carrying or bubble-carrying flow condition.Furthermore,a method to identify"four-line and six-zone"working condition was established.Results show that(1)by virtue of this method,the whole life cycle of a gas well can be subdivided into four drainage recovery stages according to the characteristics of each process and the production characteristics of 6 characteristic zones,namely,the independent liquid-carrying stage,the foam drainage stage,the foam drainage+stage,and the post foam drainage stage,so that the working condition can be identified in real time favorable for optimization;and(2)after this identification method was applied to 259 sick wells in Daniudi gasfield,the productivity was increased by 41.2×10^4 m^3/d from 234.5×10^4 m^3/d to 275.7×10^4 m^3/d.In conclusion,this method can increase the real-time diagnosis accuracy and make the optimization more reasonable.