Optimization of wellbore cement sheath resilience using nano and microscale reinforcement: A statistical approach using design of experiments

In this study, silica (SiO2) nanoparticles were deposited on the surfaces of micro-synthetic polypropylene (PP) fibers through the sol-gel process and combined with Alumina Nanofibers (ANF's) to enhance the cement composite mechanical properties. Cement samples were cured at 82.2 degrees C with 20.68 MPa for 24 h to emulate wellbore conditions. Mechanical properties were experimentally tested and modeled through the design of experiments (DOE). Treated PP fibers did not contribute to the ultimate strength mainly due to their inability to resist stresses before cracks appear. Ultimate modulus of elasticity (MOE) and Poisson's Ratio were synergistically improved on the nano and microscale levels. This is due to cement samples remaining in the elastic region and the flexibilities of the fibers. 0.15% ANF and 0.09% PP fibers by weight of cement (BWOC) were considered the optimum values after performing the multi-objective optimization analysis. Derived models were statistically significant and useful for predictions.