Design and Application of a New Acid-Alkali-Surfactant Flooding Formulation for Malaysian reservoirs
- Khaled Abdalla Elraies (Universiti Teknologi PETRONAS) | Isa M. Tan (Universiti Teknologi PETRONAS)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil and Gas Conference and Exhibition, 18-20 October, Brisbane, Queensland, Australia
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 5.3.2 Multiphase Flow, 5.4.10 Microbial Methods, 1.6.9 Coring, Fishing, 4.3.4 Scale, 6.5.4 Naturally Occurring Radioactive Materials, 5.4.1 Waterflooding, 5.2.1 Phase Behavior and PVT Measurements, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.2 Reservoir Fluid Dynamics, 2.5.2 Fracturing Materials (Fluids, Proppant)
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A new Acid-Alkali-Polymeric Surfactant (AAPS) flooding formulation has been developed to overcome the precipitation problems caused by the divalent metal cations prevalent with conventional ASP flooding. The acid was evaluated in an acidalkali- surfactant formulation using sodium carbonate and introducing a new polymeric surfactant derived from Jatropha oil. The effect of the new formula on IFT, viscosity, and oil recovery was studied using natural seawater having a large quantity of divalent metal cations. The tolerance of the AAPS towards natural untreated sea water was monitored for 90 days at 90 oC. No precipitations were formed with the acid additive, while precipitations were always generated without the acid. A combination of the new system was found to significantly reduce the IFT between Angsi crude oil and AAPS solution. The most outstanding feature of the AAPS formulation lies in its viscosity insensivity towards an increasing alkali concentration up to 1.2%. Core flood tests with alkali and acid concentrations of 0.6% and 1% respectively confirmed an optimum surfactant concentration of 0.6%. Using the optimum AAPS concentrations, another series of core flood were conducted by changing the injection volume. Only a small incremental recovery was obtained with AAPS slugs higher than 0.5 PV. Injection of 0.5 PV of the formulated AAPS slug followed by chase water produced an additional 18.8% OOIP over water flooding. The benefit of the new system is the use of seawater rather than softened water while maintaining the desired slug properties.
In Malaysia and many other countries, most mature reservoirs are already waterflooded, or are presently being subjected to secondary and tertiary recovery processes. In Malaysian oil reservoirs, only about 36.8% of original oil in place (OOIP) is produced through the entire life of mature reservoirs that have been developed under conventional methods (Hamdan et al., 2005). A significant amount of the hydrocarbon would not be recovered utilizing the current production strategies, and that has motivated Malaysia to attempt Enhanced Oil recovery (EOR).
Recognizing the potential of EOR in the fields, the national oil company (PETRONAS) endorsed a comprehensive EOR screening in year. The screening study on seventy two reservoirs has identified almost a billion barrels of additional reserves can be achieved through EOR (Samsudin et al., 2005). The Chemical Enhanced Oil Recovery (CEOR) was identified as one of the key EOR processes that have good potential for field implementation to increase ultimate recovery in Malaysian oil fields (Othman et al., 2007).
Chemical EOR processes are being considered for large field applications with recent high price of crude oil (Ibrahim et al, 2006). These include surfactant (S), surfactant-polymer (SP), and alkali-surfactant-polymer (ASP). ASP flooding has been used widely in a field application with great success (Pitts et al., 2006; Pratap and Gauma, 2004; Clara et al., 2001; Wang, et al., 1997; Hong-Fu, et al., 2008). It uses the benefits of the three flooding methods simultaneously and oil recovery is sufficiently improved by decreasing the interfacial tension (IFT), increasing the capillary number, and improving the mobility ratio (Pingping et al., 2009). Despite the potential of ASP flooding, the approach towards ASP in Malaysia has taken a conservative route. This could be attributed mostly to the fact that all of the producing fields are located offshore. Offshore environment poses a number of challenges (Hamdan et al., 2005).
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