Owing to the increasing energy demand, producing more oil from the residual in the old reservoir by water flooding and enhanced oil recovery (EOR) methods should be considered. Water flooding has become the most widely used process by injecting water into the reservoir to displace oil. The chemical EOR is a chemical injection into the reservoir. When water flooding becomes uneconomical, the chemical especially surfactant, has been applied in the flooding process like sodium 4-vinylbenzene sulfonate (SVBS). This study aims to simulate and evaluate the surfactant flooding by using SVBS with various conditions such as surfactant concentration, injection rate, and injection period in Northern oilfield of Thailand. The concentration of SVBS varies from 0 to 4,000 ppm and the injection rate is from 7.95 to 47.7 m3/d. The period of chemical injection is from 0 to 12 y. This technique will be compared with conventional water flooding. From the results, the surfactant EOR can obtain higher recovery factor compared to water flooding. The suitable concentration is 2,000 ppm. For the injection rate, the recovery factor (RF) is higher at higher injection rate, The highest RF is up to 56.92 % from all cases of a parameter change. The period of surfactant injection to enhance oil production is 12 y. RF can be improved up to 4.2 % compared with applying water flooding for the same period. The results from this study can contribute to further EOR application in the actual field at the Northern oilfield in Thailand as a reference in the future.