海上低渗油藏规模化注气开发关键技术与矿场实践

Key technologies and field practice of large-scale gas injection development in offshore low-permeability reservoirs

海上低渗油藏注气开发注入气组分差异大、注气井井筒温压耦合计算更复杂、注气开发过程气窜程度表征困难。通过室内实验研究了不同气源混合气注入相态变化规律及混相机理,结果表明注气驱较注水驱提高采收率约30个百分点且混合气源注入过程中油藏混相压力逐渐上升;建立了井筒流体温压耦合模型、储层吸气能力方程,通过两者的进一步耦合得到了注气井实时动态监测图版;提出了采用无效循环气体地下体积占比定量表征气窜程度的方法,实现了注气开发过程对气窜程度的定量表征。研究成果指导了海上第一个注气项目涠洲12-1油田生产优化及海上最大混相驱项目文昌9-7油田开发方案制定,在南海西部低渗油藏中应用效果较好。

It is difficult to characterize the degree of gas channeling during gas injection development in offshore low-permeability reservoirs because the composition of injected gas differs greatly,and the coupling calculation of wellbore temperature and pressure is complicated.The phase change law and mixing mechanism of mixed gas injection from different gas sources were studied through laboratory experiments.The results show that the oil recovery of gas injection flooding is about 30 percentage points higher than that of water injection flooding,and the miscible pressure of the reservoir increases gradually during the injection of mixed gas sources.The wellbore fluid temperature and pressure coupling model and reservoir suction capacity equation are established.Through the further coupling of the model and the equation,the real-time dynamic monitoring chart of gas injection wells is obtained.A method to quantitatively characterize the degree of gas channeling by using the underground volume proportion of invalid circulating gas is proposed,which realizes the quantitative characterization of the degree of gas channeling in the process of gas injection development.The research results have guided the production optimization of WZ12-1 Oilfield,the first offshore gas injection project,and the development plan of WC9-7 Oilfield,the largest offshore miscible flooding project,with good application effect in low-permeability reservoirs in the western South China Sea.