Understanding of Visco-Elastic Surfactant and Acid Stimulation Application

Surfactants are divided into four main categories based on their ionic charge. The most common applications can be summarized as corrosion inhibitor, emulsifying and de-emulsifying agents, foaming agent and improver of solids carrying capacity. Visco-Elastic Surfactant (VES) is one of surfactant groups initially used as a friction reducer and to enhance the solids carrying capacity. In this paper many tests were performed on VES samples of newly produced product to study the work frame and the applicability of that product especially through three important factors 1) Viscosity build-up of the VES at different shear rates, 2) Study different concentrations behavior of the VES and its application especially on acid diversion, 3) Salt effect on the formed mixture of VES and its effect on the viscosity behavior, and finally 4) Temperature effect on the Visco-Elastic behavior was examined to define the work frame of that product (VES) application in the oil field in the acid diversion. VES product shows elasticity to stresses through the change in viscosity of the solution. Also, it was found that temperature affects negatively on the VES behavior, which limits the application of the VES in the high temperature reservoir, unless formation cooling action to be carried out before pumping the VES. On the other hand the salts have a positive effect on the VES behavior through increasing the viscosity buildup of the VES, which supports the application of VES in high saline formation water. The tested VES product shows good behavior as Visco-Elastic and could be used in limited temperature ranges, based on that result a case study was demonstrated in which it has been used as an acid diverter in carbonate reservoir. The well after the acid stimulation resulted in improving the well productivity and producing at 4100 BOPD after stimulation.