Erdila Indriani received a Doctoral Degree in Petroleum Engineering from the ITB Bandung, Bandung, Indonsia in 2019. From 2006 to 2013, she was a Financial and Procurment officer at PEM Akamigas. She also works in PEM Akamigas Cepu and POLNAM Ambon as a lecturer. She is the Current Director of PEM Akamigas since 2022. She is a researcher with speciality of Energy and Mineral.
The Effect of Surfactant Concentration on Residual Oil Saturation and Capillary Number Alteration
Enhanced oil recovery (EOR) is an effort to increase production by injecting certain materials that can change reservoir conditions such as composition, physical fluid properties, and reservoir rock properties. The EOR method that is widely used is chemical EOR, one of which is surfactant injection. Surfactant injection can change the wettability of the rock and reduce interfacial tension (IFT). The IFT parameter in surfactants can increase the capillary number (Nc) so as to lower the oil saturation that remains in the reservoir (residual oil saturation / ROS). Laboratory-scale tests were conducted to investigate this phenomenon with capillary desaturation curve (CDC) testing. The reservoir characteristic of this test is low-salinity sandstone with light oil characteristics. The surfactant used in this test is an anionic surfactant (ANS) as it is compatible with negatively charged sandstone. The test was conducted at a reservoir temperature of 66°C and using injection water. A series of tests were conducted consisting of a surfactant compatibility test (with various concentrations of 0.1%, 0.3%, 0.5%, 1% and 2%), critical micelle concentration (CMC) test, phase behavior, filtration test, thermal stability, injectivity test and CDC. From the laboratory results, it was found that all surfactant concentrations were compatible with injection water. ANS surfactant concentration of 1% reached low IFT in CMC test and microemulsion (W-III) in the Phase behavior test which was stable during the 7-day observation. The filtration result of 1% ANS surfactant showed a value of 1.17. In the thermal stability test, ANS 1% surfactant was stable at reservoir temperature during 30 days of observation at low IFT conditions (order 10^-2 dyne/cm). The injectivity test gave a residual resistance factor (RRF) value of 3.15. The RRF value was 3.15, indicating a change in rock permeability during surfactant injection. Investigation on capillary number alteration was conducted using a synthetic rock sample, Berea core with permeability of 117 mD, and porosity of 22%. From the CDC test results, it was found that 1% ANS surfactant can increase the Nc value from 1.28E-05 to 2.57E-03. With 1% ANS surfactant concentration and IFT value is 1.36E-02 dyne/cm, it can increase the Nc value so that it can reduce the ROS value by 55%