Spontaneous imbibition characteristics of carbon nanofluids in carbonate reservoirs. (November 2021)

• Record Type: Journal Article
• Authors: Sakthivel, Sivabalan; Kanj, Mazen Yousef
• Is Part Of: Energy reports. Volume 7(2021)
• Page Start: 4235
• Page End: 4248
• Publication Date: 2021-11
• Subjects: Wettability -- NMR measurements -- Contact angle -- Amott cell -- Spontaneous imbibition; Power resources -- Periodicals; Energy industries -- Periodicals; Power resources; Periodicals; Electronic journals; 621.04205
• DOI: 10.1016/j.egyr.2021.07.002
• Languages: English
• ISSNs: 2352-4847

Abstract

Abstract: Altering the wettability of the rock–oil–brine system plays a substantial role in the oil recovery process from carbonate reservoirs. Hence, there arises a need for understanding the wetting and wettability alteration of this system. In this study, we ran a suite of spontaneous imbibition tests and investigated the efficiency of Carbon nanodots (CND) and an in-house cationic Gemini surfactant (GS8) on the wettability alteration of and recovery from oil-wet carbonate rock samples. The study considered the effects of additives concentrations, sample aging, initial water saturation, and rock permeability. Both CND and GS8 proved efficient at concentrations below 200 ppm. At 200 ppm, separately CND in seawater and GS8 in seawater demonstrated each about 22%–25% incremental oil recovery over neat seawater. Low field nuclear magnetic resonance (NMR) measurements supported this observation. NMR T 2 distribution and NMR T 2 D fluid typing measurements helped evaluate the recovery in terms of the pore size distribution and the oil and brine water saturation at different imbibition stages. CND exhibited a strong positive effect on the wettability of all tested samples, and accordingly, on the imbibition characteristics and oil recovery. It altered the wettability from strongly oil-wet to water-wet with equal efficiency in all pore systems making it a strong candidate for enhanced oil recovery (EOR). GS8, on the other hand, was most efficient in the macropores. Unlike CND, the efficiency of GS8 decreased in the mesopores and more so in the micropores. Rock–oil–brine surface contact angle and oil–brine interfacial tension measurements supported the imbibition test results and helped interpret the recovery mechanism. Overall, CND proved effective for EOR in the harsh carbonate reservoir environment and demonstrated itself as a viable and economical substitute to the more costly and complex oilfield chemicals for recovery operations. Highlights: Spontaneous imbibition with CND in SW resulted in 20-25% of additional recovery. CND altered the wettability of carbonate rocks favorably. CND enhanced the disjoining pressure and reduced the capillary pressure. NMR measurements confirmed a positive CND effect in all pore systems. CND proved effective for EOR in the harsh carbonate reservoir environment.