Evaluation of nonylphenol surfactant in enhanced oil recovery by SAG and WAG method

•A new EOR strategy by using nonylphenol foams in situ was proposed.•The performance of the SAG method with nonylphenol was compared to the conventional WAG method.•The fractionation of injection cycles was analyzed for better performance of SAG and WAG. The oil production from reservoirs using foams stabilized by surfactants is currently a promising technique to increase sweep efficiency. However, choosing the ideal surfactant and how it will be applied within the production technique is essential for an expressive oil recovery yield, thus requiring careful studies and tests in order to have a good application performance. In this work, the authors aimed to evaluate the use of a nonionic surfactant with a high degree of ethoxylation (nonylphenol 100EO) to generate divergent foams in the SAG method (surfactant alternating gas injection) in order to compare it with the WAG method (water alternating gas injection process) under the same injection conditions. The experiments showed that the SAG method increased the oil production up to 31.37%, while the WAG increased it up to 27.70%. It was possible to verify through the tests that the SAG containing nonylphenol 100EO exhibited greater efficiency ithin a smaller number of injection cycles (from 26.71% up to 31.37%), while the WAG presented the opposite behavior, which efficiency decreased with the smaller number of injection cycles (from 25.64% to 10.96%).