Synthesis And Application Of Amphoteric Fluid Loss Additive

Fluid loss additive has been a research hotspot as the key additive for water-based drilling fluids.Based on amphoteric polymers,a temperature-resistant and anti-salt fluid loss additive AST was synthesized.The anti-polyelectrolyte effect is enhanced by selecting similar anionic and cationic functional monomers at the front end,and the fluid loss is less under the condition of salt intrusion.Four potential mainstream explanations were analyzed: rheological properties,dispersion of platelets,surface of filter cake and cross-section of filter cake,and three filter cake models were presented.A “sandwich” structure was found on the cross-section of the filter cake,and it is considered as the key factor affecting fluid loss.This conjecture was confirmed by energy dispersive spectrum(EDS).In addition,emulsion synthesis was carried out,and two kinds of emulsion products E22 and E27 with different molecular weights and ionicities were developed,and the combination of the two is more suitable for practical application.The AST further temperature resistance improvement was studied.The Laponite was used to moderately crosslink the polymer to further improve the temperature resistance.The final performance can control the fluid loss in 6.2 m L,after 200? hot rolling for 16 h,saturated Na Cl(36%wt),2% bentonite,1% L-AST.