页岩气水平井油井水泥的原位增韧技术研究

针对页岩气水平井开发过程中油井水泥作为一种非均质多孔脆性复合材料,难以承受大型水力压裂带来的非均质载荷,导致水泥环的力学完整性失效破坏问题,开展了油井水泥原位增韧技术研究。研究中采用了固相烧结法和球形重淬技术,获得了微晶铁铝酸钙（MB）作为原位增韧材料。研究结果表明,制备的原位增韧材料在提升力学性能的基础上降低了水泥石的弹性模量,养护7 d后的抗压强度可达24 MPa,抗拉强度提升50%,弹性模量降至5.55 GPa。微晶铁铝酸钙的增韧机制为：“裂纹偏转”、“裂纹终止”、“消耗断裂能”。该研究的开展对满足以页岩气开采条件下的油井水泥服役要求,延长页岩气井寿命,增加页岩气产能具有重要意义。

Technology of In-situ Toughening of Oil Well Cement in Shale Gas Horizontal Wells

As a non-homogeneous porous brittle composite material in the development of shale gas horizontal wells, oil well cement is difficult to withstand the heterogeneous load caused by large hydraulic fracturing, resulting in failure of the mechanical integrity of the cement sheath. Researches on oil well cement in-situ toughening technology was carried out. In the study, solid phase sintering and spherical re-quenching techniques were used to obtain microcrystalline brownmillerite (MB) as an in situ toughening material. The research indicates the prepared in-situ toughening material reduced the elastic modulus of the cement based on the improvement of mechanical properties. After 7 days of curing, the compressive strength ccould reach 24 MPa, the tensile strength was increased by 50%, and the elastic modulus was reduced to 5.55 GPa. The toughening mechanism of microcrystalline brownmillerite is: crack deflection, crack termination, consumption fracture energy. The development of this study is great significance to meet the requirements of oil well cement service under shale gas mining conditions, extend the service life of shale gas wells and increase the production capacity of shale gas.