Surfactant Stimulation to Increase Reserves in Carbonate Reservoir: "A Case Study in Semoga Field"

Abstract

Abstract Semoga field, which produces from Baturaja (carbonate) formation, has experienced a decline in production and has a high water cut (WC). The current average water cut in Kaji-Semoga field is 86%, while several producing wells have above 95% WC and even 100%. In 2007, Lemigas conducted a laboratory study to determine the wettability of Baturaja formation (BRF), the result of which was that BRF indicated very oil wet characteristics. However, after being immersed in surfactant, core samples became less oil wet. This test shows that trapped oil can be recovered using tertiary recovery methods. One option for confirming the laboratory test result is to use surfactant huff & puff method in a pilot project. Surfactant is a surface active agent compound which has the ability to reduce the surface tension between the rocks, produced water and crude oil so that wettability may change. The surfactant type to be used on BRF formation is non-ionic. The pilot huff and puff project was conducted on wells X-1 & X-2. High WC wells with low WC at initial (early production) and high liquid production were selected to minimize risk and to yield more oil. This project was evaluated using pressure build-up test (transient analysis) and production performance monitoring before and after the surfactant stimulation job. An economic analysis was also conducted As a result of employing surfactant stimulation, Semoga Field yielded NPV @ 3 month 24,013 USD with a pay-out time (POT) of 11 days. Oil gain would be more significant if the technique was implemented on high production wells.