丁山区块深层页岩气水平井固井技术

Cementing Technology for Deep Shale Gas Horizontal Well in the Dingshan Block

丁山区块页岩层埋藏深,温度、地层压力和破裂压力高,为了满足分段压裂和长期开采的要求,需要对深层页岩气水平井固井技术进行深入研究。在分析深部页岩地层固井难点的基础上,利用数值模拟分析了分段压裂对水泥石力学性能的要求;针对高温高压的地层特点及分段压裂要求,研制开发了高强度弹性水泥浆体系,同时优化前置液,以增强前置液耐温及润湿反转能力,提高固井质量。室内评价试验表明,弹性水泥浆体系耐温140℃以上,最低弹性模量达4.5GPa,水泥石渗透率0.07mD,前置液140℃热滚后7min内的冲洗效率达100%。弹性水泥浆体系及配套工艺技术在丁页2-HF井进行了现场试验,固井质量优质,其中一界面优质井段达到96%以上,满足地面压裂施工压力105 MPa对水泥环完整性的要求。应用效果表明,弹性水泥浆体系、前置液体系及配套工艺能满足丁山区块深层页岩气水平井固井要求,确保了页岩气水平井压裂改造措施的顺利实施。

In the Dingshan Block,shale formation has the characteristics of high temperature,high formation pressure and fracturing pressure due to its deep burial depth.Therefore,cementing issues for deep shale gas horizontal well should be considered carefully to meet the requirement in staged fracturing and long-term production.Towards those difficulties in cementing of deep shale formations,numerical simulations was done to analyses cement mechanical properties to meet the demand in staged fracturing.In addition,high strength flexible cement slurry system was developed,and pad fluid for oil flushing was optimized to improve its heat resistance and wettability.Laboratory experiments showed that the flexible cement slurry system temperature resistivity could go up to 140 ℃,with modulus elasticity 4.5GPa and set cement permeability 0.07 mD.Flushing efficiency reached 100%in 7minutes after pad fluid temperature went up to 140℃.This system and supporting processes were applied in Well Dingye2-HF and resulted in excellent cementing quality with over 96% of satisfactory intervals in the first interface,which ensured the integrity of cement annulus under fracturing pressure of 105 MPa.The application demonstrated that the optimized flexible cement slurry system,pad fluid system and matching processes could meet the demand of cementing in the Dingshan Block,and provided reference for deep shale gas horizontal well cementing.