Evaluation of the effect of acid additives on rheological properties and technological efficiency of zwitterionic and anionic surfactant mixtures

Abstract

Relevance. Various acid additives such corrosion inhibitors, iron stabilizers, demulsifiers, anti-precipitation agents are usually used to provide necessary technological properties to acid compositions. Adding the additives into the acid composition based on viscoelastic surfactants can have a significant impact on the efficiency of their subsequent use, since micelle formation and, consequently, rheology of their solutions are particularly sensitive to the presence of additional components in the system. Accordingly, determination of the acid additives influence on rheological properties and technological efficiency of acid compositions with surfactants is a vital task. Aim. To evaluate the effect of acid additives on rheological behavior of viscoelastic surfactants-based acid compositions (mixture of cocamidopropyl betaine and ethoxylated fatty alcohol sulfosuccinate). Object. Acidic composition based on viscoelastic surfactants (a mixture of anionic and zwitterionic surfactants) and a package of acidic additives – corrosion inhibitor, iron stabilizer, demulsifier and antisludge agent. Methods. Investigation of rheological properties using an MCR52 rheometer (Anton Paar GmBH) in the shear rate range from 1 to 100 s–1 at temperatures from 20 to 90°C, standard tests for selecting acid additives.  Results. The authors have determined the effect of acid additives on rheological properties of the developed self-diverting acid solution based on the viscoelastic surfactant (a mixture of anionic and zwitterionic surfactants). The obtained results confirmed that adding the acid additives into solutions leads to a decrease in partially neutralized solution viscosity. However, it expands the range of manifestation of viscoelastic properties. This will increase the efficiency of the developed composition during acid treatment. Also, the addition of acid additives reduces the initial viscosity, which facilitates acid injection into formation. A viscoelastic gel is not formed with hydrocarbons, which indicates that the treatment is effective in cleaning up the area after acidizing. The temperature test showed that the additives do not affect the temperature range of acid solution application.