Effect of carbon chain lengths of cationic surfactant on inhibition rate of acid-rock reaction

Abstract

Reduce the rate of acid-rock reaction is a key problem in the acidizing field. In order to reduce the damage of adsorption of traditional gelled acid in carbonate porous media, and further reduce its damage to permeability of dense carbonate rock after stimulation. Cationic surfactants can change the surface properties of rocks and control the contact area between H+ and rock surface. In order to explore the effect of different carbon chain lengths of cationic surfactants on retarding properties of acid-rock reaction, the critical micelle concentration(Ccmc) and critical surface tension value(γcmc) of seven different carbon chain lengths of cationic surfactants are determined. The results indicate that Ccmc decreases significantly with the increasing of carbon chain length. The adsorption morphology of CnTAC(n = 8,10,12,14,16,18,22) species at the solid-solution interfaces is dominated by monolayer. On negatively charged calcite surface, a large number of cationic species RNH3+ can easily adsorb on abundant CO32− sites, which causes a significant increase of zeta potential for calcite. Meanwhile, the wettability of hydrophilic solid surface is modified from strongly hydrophilic to weakly hydrophilic after adsorption to control the surface rate of acid-rock reaction. The acid solution with a concentration of 1.02 × 10−2 mol/L C14TAC has the best retarded performance which the retardation rate is 71.01%. This research is helpful to understand the retarding performance of surfactant, improving the retarded acid system and the effect of carbonate reservoir stimulation.