Preparation and Characteristics of a pH Intelligent Response Blocking Agent for the Microcrack in the Cement Sheath

[Image: see text] Microcracks in the annular cement sheath of oil wells frequently cause annular water channeling. Traditional cement squeeze technology has a low success rate in controlling this issue. Based on the conventional profile control water-blocking agent for underground in situ gelling and polyacrylic acid, a pH intelligent response microcrack-blocking agent was developed to block the microcrack in the cement sheath. The study investigated the influence of pH on the viscosity characteristics of the new blocking agent, the impact of polyacrylic acid on the compression recovery ability of the new blocking agent after gelling, the change in viscosity of the blocking fluid after flowing through the microcrack in the cement sheath, and the blocking effect after gelling. The results indicated that the new blocking agent has excellent viscosity-increasing ability with pH. After flowing through the microcrack in the cement sheath, the viscosity of the blocking agent increased significantly with the extension of the contact distance between the blocking agent and the microcrack in the cement sheath, which is very conducive to the retention of the blocking agent in the microcrack of the cement sheath. Polyacrylic acid had a negligible effect on the compression recovery ability of the blocking agent after gelling. At a fracture length of 5 cm, the pressure-bearing capacity of the blocking agent could reach 6 MPa.