Optimization Study of the Mixing Ratio of Multi-scale Carbon Fibers Composite for Toughness of Oil Well Cement

Abstract

This article aims to enhance the toughness performance of oil well cement with an optimized mixing ratio of three different lengths of carbon fibers optimized by response surface methodology. A response surface model was constructed with the impact strength as the response target based on the Box–Behnken design. The influence of carbon fiber mixtures on the impact strength of oil well cement was studied, and the ratio of mixed carbon fibers was optimized. The optimized cement slurry performance was tested, and the microstructure of the cement was analyzed. The results show that the impact strength of cement is significantly influenced by 3 mm carbon fiber and the interaction effect of 1 mm carbon fiber and 3 mm carbon fiber. The optimal mixing ratio of carbon fibers of different scales obtained through optimization is 0.322% for 1 mm carbon fiber, 0.329% for 2 mm carbon fiber, and 0.334% for 3 mm carbon fiber. The toughness cement slurry constructed with the optimized proportion of carbon fibers has a 3-day impact strength of 2.171 kJ/m². The research can guide the construction of cement slurry with good toughness performance, ensuring the integrity of the cement sheath.