天然气井套间气窜自修复技术

On self-healing technology for gas channeling in the cemented annulus

井口套间气窜即套间带压一直是困扰天然气井安全生产的技术难题,仅靠固井和修井技术难以从根本上解决问题。基于对天然气井套间气窜原因的分析和水泥基自修复理论,建立了气井井口环空气窜的两种自修复模式。采用在模拟套管的钢管中浸泡钻井液和使用冲击式造缝仪两种方法,来模拟固井水泥环损伤后形成的气窜通道(即微裂缝和微间隙),用GSN渗透结晶型自修复剂配制天然气井套间气窜自修复液,在XAN-RC封堵模拟实验流程中进行了水泥环损伤自修复模拟试验。结果表明,GSN自修复剂能够自动渗入气窜通道,形成渗透结晶水化产物,密闭固井水泥环的微间隙和微裂缝,有较好的自修复效果,明显提高了损伤水泥环的抗气窜强度。该研究成果对实现气井井口环空气窜的动态即时自修复,保持水泥环封固的可靠性和耐久性,解决气井环空带压问题有重要的工程运用价值。

Gas breakthrough or gas channeling in a cemented wellbore annuli has long been a technical challenge threatening the safety of gas production activities.It is not to be radically solved merely by well cementing and workover techniques.Herein in this paper,we proposed two self-healing models based on the analysis of causes of gas breakthrough and the cement base self-healing theory for annular gas breakthrough at the well head.We simulated the gas channels(i.e.,microcracks and microgaps) formed in a damaged cement sheath by injecting drilling fluid into the steel pipes as the casings and by using a fracture-generating impact to generate cracks.Then we used GSN penetrative crystallization-type self-healing agent to prepare the gas breakthrough self-healing fluid.Finally we performed cement sheath damage self-healing experiment in the process of an XAN-RC plugging simulation.As shown in the experiment,the GSN self-healing fluid could automatically seep into the gas channels to form a penetrative crystallization-type hydration product that sealed the microgaps and microcracks in the cement sheath.This self-healing capability obviously helped improve the resistance of the cement sheath to gas breakthrough.The research findings are of significant engineering values to realizing the dynamic and prompt self-healing for annular pressure buildup(APB) at gas well heads,maintaining the reliability and durability of cement sheaths,and solving APB problems as a result.