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

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.

Status of surfactant EOR technology

“…For example, an alkaline-surfactant solution was injected to improve well injectivity in the Big Sinking field in the Appalachian Basin of East Kentucky (Miller et al, 2004). Rilian et al (2010) reported that surfactant stimulation increased the formation permeability and decreased skin damage in the Segoma field. Because actual surfactant projects had much higher permeabilities (152 mD from the survey presented in Table 1), the criterion for permeability is set 10 mD, following Taber et al's (1997a & b).…”

“…These projects are the Cottonwood Creek in the Bighom Basin of Wyoming (Xie et al 2005;Weiss et al 2006), the Yates field in Texas (Yang and Wadleigh 2000; Chen et al 2001), and the Baturaja formation in the Semoga field in Indonesia (Rilian et al, 2010).…”

Evaluation of modified cashew nutshell liquid as natural surfactants for chemical flooding in sandstone oil reservoirs

“…The use of surfactants during chemical flooding spans over four decades [15,19]. Several successful field applications have been recorded in various fields across the world such as Semonga field in Indonesia where injection of surfactants into the carbonate reservoir resulted in 8% reduction in water cut and increased oil recovery [33] and the Daqing oilfield (Chao 522 block) in China with a reported 30% increase in oil recovery from a single well after the injection of 1.0% nonionic surfactant [41]. Furthermore, Aslam et al [4] reported an increase in oil recovery during surfactant flooding using 2.05% anionic surfactant-A127 on Tanjung Field in Indonesia.…”

Chemical Enhanced Oil Recovery: Where Do We Stand? Recent Advances and Applications

“…It can be seen that the number for sandstone reservoirs surpasses the number of carbonates [82]. Only two projects were performed in carbonates in the USA-Cottonwood Creek [83,84] and Yates field [85,86], and one project in Semoga field Indonesia [87] However, it is interesting to point out that pilot tests of surfactant injection in carbonate reservoirs gave promising results. For instance, the Yates field pilot test showed a two-fold increase in oil recovery factor by using commercial surfactant Shell 91-8 [84,86].…”