New Equipment and Method for Evaluating Anti-Water-Invasion Ability of Cement Slurry

In adjustment well cementing of old areas, underground high-pressure water layers can invade the cement slurry, leading to poor cement-stone bonding and compromised cementing quality. Previous studies had primarily focused on developing cement-slurry systems with anti-water-invasion (AWI) materials; however, the evaluation of the AWI ability of the cement slurry was often neglected. This study proposes a method to rapidly evaluate the AWI performance of cement slurries, along with an experimental approach for assessing the water invasion during coagulation. The mechanisms are investigated using Fourier transform infrared (FTIR) spectroscopy and permeable water conductivity, X-ray diffraction (XRD), and thermogravimetric (TG) analyses. The FTIR results indicate the presence of functional groups such as methylene and hydroxyl in the AWI material, which demonstrate adsorption properties, and can improve the cohesion of cement particles and thereby, the AWI ability. The results of the rapid evaluation of the AWI capability of cement slurry show a sudden increase in the conductivity of the AWI cement slurry, but at a later stage than that of the conventional cement slurry. The results of experiments conducted for assessing the water invasion during cement coagulation demonstrate that the conventional cement slurry in high-permeability cores exhibits higher water-invasion rates, wider second-interface cracks, and greater hydraulic conductivity than the AWI cement slurry in low-permeability cores under identical intrusion pressures. This indicates that combining low-permeability cores with AWI materials can effectively reduce the cement-slurry ion losses. XRD and TG analyses reveal that formation-water invasion significantly affects the conventional cement-slurry components in high-permeability cores, while showing minimal impact on AWI cement slurries in low-permeability cores. The proposed method can evaluate the AWI capability of different cement-slurry systems, laying the foundation for improving the AWI capability of adjustment well cementing slurry systems and cementing quality of adjustment wells.