气井套损修复用纳米SiO_(2)/环氧树脂复合体系的研制与应用

Preparation and Application of Nano-SiO2/Epoxy Composite System for Repairing Gas Well Casing Damage

长庆油田气井套损严重,使用水泥封固时存在气密性差、注入困难等问题。为了提高套损修复用环氧树脂固化后的气密性和强度,通过纳米SiO_(2)掺杂环氧树脂制备了纳米SiO_(2)/环氧树脂复合体系用于修复气井破损,考察了该复合体系固化前的流变性、固化后的力学强度和封堵能力,并采用扫描电镜研究复合体系固化作用机理。研究表明,该纳米SiO_(2)/环氧树脂复合体系具有剪切稀释性和黏弹性,不同温度时复合体系的固化时间均在3 h以上,保证充足的注入时间;与常规环氧树脂相比,引入纳米SiO_(2)后复合体系固化体的抗压强度达106.8 MPa、拉伸强度达72.1 MPa,对孔隙的封堵强度达37.7 MPa,能有效阻止地层流体进入井筒并满足重复压裂时井筒承压要求。纳米SiO_(2)能修复树脂固化后的微裂隙,提升力学强度。长庆油田气井施工表明,该堵剂体系具有较强的密封和承压能力,为套损井修复和重复压裂重建井筒提供支撑。

The casing damage of gas well in Changqing oilfield is serious,and there are some problems such as poor gas tightness and difficult injection during the cement sealing process.In order to improve the air tightness and strength of epoxy resin after curing for casing damage repair,the composite resin was prepared using nano-SiOdoped epoxy resin for repairing gas well damage.The properties of the composite system were evaluated by rheological properties before curing,mechanical strength and plugging ability after curing,and the curing mechanism of the composite system was studied by scanning electron microscope.The results showed that the nano-SiO/epoxy resin composite system had the characteristics of shear dilution and viscoelasticity,and the curing time of the composite system was more than 3 h at different temperatures,providing sufficient injection time.Compared with conventional resin,the compressive strength and tensile strength of the cured nano-SiO/epoxy resin could reach 106.8 MPa and72.1 MPa,and the plugging strength of pore could reach up to 37.7 MPa,which could effectively prevent formation fluid from entering the wellbore.Nano-SiOcould repair the micro-cracks of the cured resin,and thus improve the mechanical strength.Changqing oilfield gas well construction showed that the composite system had strong sealing and bearing capacity,which provided support for casing damaged well repair and re-fracturing wellbore reconstruction.