Research on a Medium-Low Temperature Early-Strength Water-Invasion-Resistant Cement Slurry System for Well Cementing

Severe water invasion occurs during the horizontal well cementing process in a certain area of the Changqing Oilfield, leading to poor cementing quality in the horizontal section. To enhance cementing performance, this study integrates an analysis of the water-invasion-resistant mechanism of cement slurry under dynamic water pressure conditions. Using early-strength inorganic salts as the primary material and highly polar organic amines as reinforcing agents, a medium-low temperature early-strength water-invasion-resistant additive was developed, along with a corresponding cement slurry system. Experiments were conducted to evaluate the system's thickening time, early compressive strength, and static gelation transition time. Results demonstrate that, compared to existing market products, the medium-low temperature early-strength water-invasion-resistant additive reduces the impact on cement slurry thickening time by 20%. The developed cement slurry system achieves a thickening time of 130–140 min (55 °C/25MPa), increases the 6-h compressive strength at 55 °C by 150%, and reduces the static gelation transition time by 10%. This system exhibits remarkable early-strength and water-invasion-resistant properties, effectively improving interfacial bonding quality and resolving water invasion/channeling issues in high-water-content oil and gas wells. It provides strong technical support for enhancing cementing quality in the Changqing Oilfield.