Synthesis and Evaluation of a New Amphoteric Filter Loss Reducer for Cement Slurry

A salt-resistant, high temperature filter loss reducer TSM-1 has been developed through radical aqueous solution polymerization, with acrylamide (AM), acrylic acid (AA), 2-acrylamide-2-methyl propane sulfonic acid and a new cationic monomer (X) as raw materials. The synthesis process was optimized through orthogonal experiment. TSM-1 was characterized with IR spectrometry, NMR and thermogravimetric analysis, and the overall properties of cement slurries treated with TSM-1 were evaluated. Laboratory experimental results show that the molecules of TSM-1 have the characteristic functional groups of the four monomers, rendering TSM-1 good thermal stability. TSM-1 has weak retarding effects, meaning that it does not affect the strength of set cement. TSM-1 is compatible very well with retarding agents commonly used in oil well cement. The introduction of the functional cationic monomer into the molecules of TSM-1 renders TSM-1 a wide working temperature range; the highest temperature under which TSM-1 works properly is 200℃. With TSM-1, the filtration rate of cement slurry formulated with saturated saltwater can be controlled within 50 mL, satisfying the needs for well cementing. Chemical analysis and SEM analysis of TSM-1 indicate that the mechanisms under which TSM-1 functions are that the amphoteric ions are firmly adsorbed on the surface of cement particles through multipoint adsorption, thereby forming a layer of adsorption film. Under the filtration pressure, the adsorption film is pressed and fills into the spaces between cement particles. As such, the water loss channel is plugged and the permeability of mud cakes reduced, thereby reducing water loss of cement slurry.