超稠油注空气辅助蒸汽吞吐开发氧化结焦机制及其对生产效果的影响

Coke formation during air injection assisted cyclic steam stimulation process of ultra heavy oil and its effect on recovery performance

深入分析注空气辅助蒸汽吞吐过程低温氧化微观生焦机制,结合基于原油四组分及局部平衡反应的低温氧化生焦模型,通过数值模拟方法研究氧化结焦对储层物性及开发效果的影响。结果表明焦炭沉积会对注空气辅助蒸汽吞吐采收率产生不利影响;在数值模拟中需要考虑焦炭沉积对储层孔渗的影响,不考虑渗透率变化时预测所得采收率偏高;同时,结焦过程需要考虑生焦诱导期的影响,不考虑生焦诱导期将使预测采收率相对偏低;注减氧空气辅助蒸汽吞吐有助于降低氧化结焦的消极影响,在提高采收率的同时降低施工过程的安全隐患。

In this study,the microscopic mechanism of coke formation due to low temperature oxidation during air injection assisted cyclic steam stimulation process was investigated,and a coke formation model based on SARA fractions and partial equilibrium reaction was established.A series of numerical simulations were conducted to analyze the effects of coke deposition on formation properties and oil recovery performance.The results show that coke formation and deposition can cause a detrimental effect on oil recovery,and the reduction of formation permeability owing to coke formation should be considered in the numerical simulation of the air injection process,otherwise the recovery factor could be over-estimated.In addition,the influence of coke induction period should be taken into account in the numerical simulation,and the predicted oil recovery factor could be lowered if the coke induction period was not considered.Injection of oxygen-reduced air can be beneficial to mitigate the negative impact of coke deposition,and reducing the safety hazard in field operation while improving oil recovery.