A ductile oil well cement paste (OWCP) with lower autogenous shrinkage is of paramount importance to the integrity of cement sheath under downhole condition. Taking advantage of multiple experimental tests and a micromechanical model, the hybrid effects of nano-rubber (NR) and carbon nanotubes (CNTs) on the mechanical properties, autogenous shrinkage, hydration behavior and microstructure of OWCP were investigated in this study. Results show that the hybrid addition of NR and CNTs effectively enhances the mechanical properties and ductility of OWCP, 7-day tensile strengths of OWCP incorporated with 4 wt% NR and 0.04 wt% (N4C4) cured at 30 °C, 60 °C and 90 °C exhibit 1.4%, 13.7%, 13.0% strength gain with respect to those of plain OWCP (P) at the similar curing temperature; T/E ratios (tensile strength/Young’s modulus) of 7-day N4C4 cured at 30 °C, 60 °C and 90 °C exhibit 82.3%, 39.3% and 40.8% increase as compared to that of P at the similar curing temperature; the hybrid addition of NR and CNTs suppresses the autogenous shrinkage of OWCP, leading to about 31.9%, −12.8%, and 20.8% reduction of 72-hour autogenous shrinkage of OWCP at 30 °C, 60 °C and 90 °C, respectively. The developed micromechanical model is capable of well quantifying the hybrid effects of NR and CNTs on the mechanical/poroelastic properties of OWCPs. The present work is anticipated to shed light on the development of a ductile OWCP with lower autogenous shrinkage under harsh downhole conditions.

中文翻译：

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碳纳米管和纳米橡胶杂化对不同温度固化油井水泥浆体力学性能和微观结构的影响：实验研究与微观力学模型


具有较低自体收缩率的延展性油井水泥浆 （OWCP） 对于井下条件下水泥护套的完整性至关重要。利用多次实验测试和微力学模型，本研究研究了纳米橡胶 （NR） 和碳纳米管 （CNT） 的杂化对 OWCP 的力学性能、自体收缩、水化行为和微观结构的影响。结果表明，NR 和 CNTs 的杂化添加有效提高了 OWCP 的力学性能和延展性，在 30 °C、60 °C 和 90 °C 下固化时，掺入 4 wt% NR 和 0.04 wt% （N4C4） 的 OWCP 的 7 天拉伸强度比普通 OWCP （P） 在相似固化温度下的强度提高了 1.4%、13.7%、13.0%;在相似固化温度下，在 30 °C、60 °C 和 90 °C 下固化 7 天 N4C4 的 T/E 比（拉伸强度/杨氏模量）与 P 相比分别提高了 82.3%、39.3% 和 40.8%;NR 和 CNTs 的杂化添加抑制了 OWCP 的自体收缩，导致 OWCP 在 30 °C、60 °C 和 90 °C 下的 72 小时自体收缩分别减少了约 31.9%、-12.8% 和 20.8%。开发的微力学模型能够很好地量化 NR 和 CNTs 对 OWCPs 机械/多孔弹性特性的混合影响。目前的工作有望阐明在恶劣的井下条件下具有较低自体收缩率的延展性 OWCP 的开发。