Research and Application of a Thermal-Resistant Fluid Loss Additive

Liquid AMPS-based fluid loss additives, when stored at medium-temperatures (50– 70 ℃), cause the thickening time of a cement slurry to prolong, thereby affecting the thickening stability of the cement slurry. To solve this problem, a series of filter loss reducers were designed and synthesized via free radical copolymerization using AMPS, amide-based monomers and unsaturated acid monomers. Among the final synthesized products, the ternary copolymer fluid loss additive P4, which was synthesized using monomers including AMPS, N,N-dimethyl acrylamide (DMAA) and acrylic acid (AA), was selected as the optimal final product. The effects of residue monomers, types of amide monomers, unsaturated acids and hydrolysis inhibitors on the properties of the final product were investigated and the retarding effect of the fluid loss additive was tested via medium-temperature thermal aging experiments. The experimental results show that at elevated ambient temperatures, a high content of residue monomers tends to cause the fluid loss additive to locally polymerize, the introduction of DMAA significantly inhibit the medium-temperature hydrolysis of the amide groups, and the fluid loss additive synthesized with monobasic small-molecule unsaturated carboxylic acid exhibits stable thickening performance. The hydrolysis inhibitor can inhibit the hydrolysis of the fluid loss additive in the early stage of thermal aging, but fails after long-term of thermal aging. After aging at 60 ℃ for 10 days, 30 days, 90 days and 12 months, the liquid ternary polymer fluid loss additive P4 maintains stable performance, with its comprehensive performance satisfying the requirements of the SY/T 5504.2-2013 standard. This study provides an effective solution to the storage of additives under high ambient temperatures.