Study on Mechanical Performance of Set Cement Modified with CNT

The development of unconventional petroleum is demanding more and more rigorous requirements on the job quality of cementing ultra-deep wells, complex wells and shale gas wells. Most of the cementing materials cannot satisfy these requirements and study should be done to find out new cementing material for field application or improvement of the performance of set cement. A carbon nanotube (CNT) dispersion has been developed with good stability for use in cement slurry. Laboratory experiments on cement slurries treated with the developed CNT, such as compressive strength test, flexural strength test, uniaxial/triaxial mechanical properties test and micro structure determination, were conducted to determine the treatment concentration of the CNT, to understand the dispersing effect of the CNT, and to analyze how CNT affects the mechanical property of set cement. It was found, through these experiments, that addition of 0.05%-0.1% CNT in cement slurry enhanced the compressive strength and flexural strength of set cement, and the effects of CNT on the two strengths were increasing with time. CNT was found to be able to reduce the elastic modulus of set cement and to improve the toughness of set cement by increasing its plastic deformation. Mechanisms in which the CNT increases the strength and toughness of the micro structure of set cement are pulling, bridging, nano-inductive effect and network filling effect. Dispersed CNT has good compatibility with cement slurry.