Evolution Behavior Prediction of Elastic Modulus of Cement Paste at Early-Age of Oil Well Cementing Using Microscopic Finite Element Method

The early-age elastic modulus of cement paste is critical for cementing quality. However, predicting the early-age elastic modulus of oil well cement paste (OWCP) under the combined influence of underground temperature and pressure is a significant challenge. Therefore, a method of microscopic finite element analysis is developed to predict the early-age elastic modulus of OWCP with temperature-pressure coupling conditions. Initially, the influence of temperature and pressure on hydration is incorporated into the OWCP volume fraction equation under normal pressure and temperature (NPT) conditions using a scaling factor hydration equation, thus deriving the volume fractions under non-normal pressure and temperature (non-NPT) conditions. Subsequently, the volume content of each phase component is derived from the modified OWCP volume fractions, and a microscopic finite element model of the representative volume elements (RVEs) is developed for homogenization. Furthermore, the distinct contributions of capillary and gel pore water to the structural mechanical response are considered by differentiating between these pore types. Additionally, a calculation formula for the percolation threshold is derived, with the elastic modulus assumed to be zero before the degree of hydration reached this threshold. Finally, the early-age elastic modulus of OWCP is determined through numerical tensile tests. The results indicate that the optimal computational performance is achieved when the voxel size and RVE size are 2 and 100 μm, respectively. Two-step validation against experimental data shows that the correlation coefficients reach above 0.98.