难以定量确定既能压开油层又不破坏套管的合理装药量,是制约高能气体压裂全面推广的关键因素之一。针对高能气体冲击破岩的瞬态性、复杂性,及难以用理论精确描述的问题,利用岩石动态损伤模拟实验装置直接对小井眼进行冲击破岩动态模拟实验,得出油井岩石破裂压力与加载速率的定量关系;通过分析套管井井周应力分布,得出了确保套管安全的极限峰压;同时建立了火药爆燃的压力-时间变化模型。最后综合运用上述理论,建立了既能压开油层又能确保套管安全的合理装药量计算模型。应用实例表明,该设计方法安全可靠,可为高能气体压裂的施工设计提供指导。
The determination of a reasonable charge that can fracture reservoir without damaging casing string is one of key factors restricting extensive applications of high-energy gas fracturing. It is very difficult to describe accurately high-energy gas impact theoretically due to its transient and complex charac- teristics. The rock dynamic injury simulation device was used to simulate rock-breaking experiments in slim hole on order to obtain the quantitative relationship between rock break pressure and loading rate of the oil wells. The highest safety casing pressure was obtained through analysis of stress distribution near casing wall. And the mathematical model of the deflagration pressure-time relation was created by the explosion analysis of a certain quality of gunpowder deflagrated in a specific environment. The calculation model was build to calculate a reasonable charge which can fracture reservoir without damaging the casing. Practical applications demonstrate that this method is safe and reliable and can provide guidance for construction design of high-energy gas fracturing.