Formation damage remediation with novel blend of anionic-cationic surfactants in high temperature and low permeability sandstone reservoirs

Formation damage caused by organic contaminates is one of the most important issues that undermine well injectivity and productivity. Anionic surfactants are commonly used to mobilize the organic contaminates trapped by capillary forces. The electrostatic repulsion between anionic surfactant heads reduces the surfactant density at the oil-water interface, consequently reducing the interfacial efficiency. In this paper, a novel surfactant blend of anionic-cationic surfactants (S-a/c) was designed and showed much higher efficiency than traditional ones because of the strong electrostatic attraction between anionic and cationic surfactants. The oil-water interfacial tension (IFT) was reduced to 3 x 10(-4 )mN/m, and the viscosity of crude oil was reduced by 92%. In addition, the freezing point of the residual oil was decreased by 20.9%. Moreover, S-a/c altered the wettability and inhibited the clay swelling. Field applications were conducted in sandstone reservoirs at temperatures of about 120 degrees C and permeabilities below 10 mD. The average injection pressure drops were greater than 30%. The findings of this study can help for better understanding the advantages of S-a/c with high interfacial activity and revealed that formation damage caused by the organic contaminates in high temperature and low permeability sandstone reservoirs can be effectively remediated by this novel surfactant blend.