Visco-Elastic Surfactant Improves Sweep Efficiency and Interfacial Tension in Chemical Flooding

Document Type : Original Article

Authors

1 Faculty of Petroleum and Mining Engineering, Suez University, Egypt

2 Harold Vance Department of Petroleum Engineering, Texas A&M University, USA

Abstract

Enhanced oil recovery methods hold promise for recovering oil remaining after conventional waterflood.  High demands for oil and high oil prices are driving more research in chemical EOR in particular. The total world oil production from EOR has remained relatively level over the years, contributing about 3 million barrels of oil per day, compared to around 85 million barrels of daily production, or nearly 3.5% of the daily production. Visco-Elastic surfactant (VES), has many applications in oil industry as friction reducer, improves carrying capacity and finally in acid diversion. VES can reduce the interfacial tension (IFT) and can build viscosity with saline water, through the reaction between the di-valent cation within the formation water and the active group of the VES. The VES gel can be broken upon contacting hydrocarbon phase or flushing with mutual solvent; this feature will help to reduce the formation damage. Mixing of 2vol%VES with 2wt% CaCl2 can build a moderate viscosity that can sweep the oil ahead. Formation water will help to sustain the VES viscosity and reduce the gel degradation effect, on contrary to polymers. On the other hand, the VES will help to improve the interfacial tension (IFT).   Berea Sand Stone standard cores of different permeabilities and 20-22% porosity range were used to conduct core flooding experiments using a mixture of 2 vol %VES with 2 wt % of CaCl2 to form a 25 cp VES solution. The core flooding was done at ambient condition. The cores were initially saturated with brine, then de-saturated using 29o API crude oil of 20 cp viscosity.  The cores were undergone water flooding to produce the max oil recovery before the water breakthrough, then the VES solution was pumped at 2cc/hr to maximize sweeping of the remaining oil. The VES flooding resulted in producing additional 33% of the oil remained after water flooding. About 11% of the produced oil from VES flooding was at mobility ratio less than unity. The water breakthrough was delayed until 24% of the remaining oil was recovered by VES flooding. Above results indicate the possible application of VES in tertiary recovery to improve the oil productivity through improving the mobility ratio while reducing the IFT

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