Abstract
Mobilization of crude oil from the subsurface porous media by emulsion injection is one of the Chemical Enhanced Oil Recovery (C-EOR) techniques. However, deterioration of emulsion by phase separation under harsh reservoir conditions like high salinity, acidic or alkaline nature and high temperature pose a challenge for the emulsion to be a successful EOR agent. Present study aims at formulation of Oil-in-Water (O/W) emulsion stabilized by Sodium Dodecyl Sulfate (SDS) using the optimum values of independent variables – salinity, pH and temperature. The influence of above parameters on the physiochemical properties of the emulsion such as average droplet size, zeta (ζ) potential, conductivity and rheological properties were investigated to optimize the properties. The influence of complex interactions of independent variables on emulsion characteristics were premeditated by experimental model obtained by Taguchi Orthogonal Array (TOA) method. Accuracy and significance of the experimental model was verified using Analysis Of Variance (ANOVA). Results indicated that the experimental models were significantly (p < 0.05) fitted with main influence of salinity (making it a critical variable) followed by its interactions with pH and temperature for all the responses studied for the emulsion properties. No significant difference between the predicted and experimental response values of emulsion ensured the adequacy of the experimental model. Formulated optimized emulsion manifested good stability with 2417.73 nm droplet size, −72.52 mV ζ-potential and a stable rheological (viscosity and viscoelastic) behavior at extensive temperature range. Ultralow Interfacial Tension (IFT) value of 2.22E-05 mN/m was obtained at the interface of crude oil and the emulsion. A favorable wettability alteration of rock from intermediate-wet to water-wet was revealed by contact angle measurement and an enhanced emulsification behavior with crude oil by miscibility test. A tertiary recovery of 21.03% of Original Oil In Place (OOIP) was obtained on sandstone core by optimized emulsion injection. Therefore, performance assessment of optimized emulsion under reservoir conditions confirms its capability as an effective oil-displacing agent.
Highlights
The oil and gas industry still being an emerging sector requires an uplift to address the global energy crises
The objective of the present study is to formulate an optimized emulsion using the optimum values of salinity, pH and temperature obtained by analyzing their influence on the properties of surfactant stabilized emulsion with the help of Taguchi Orthogonal Array (TOA) design that can further be applied for industrial applications, such as for enhanced oil recovery
Application of emulsion in Enhanced Oil Recovery (EOR) processes is relatively not new but the studies related to the influence of the subsurface parameters on emulsion behavior are very limited
Summary
The oil and gas industry still being an emerging sector requires an uplift to address the global energy crises. The crude oil present in rock pores usually extracted by conventional methods i.e., primary and secondary recovery leaves about two thirds of Original Oil In Place (OOIP) in the reservoir that cannot be recovered. The uncertain behavior of in-situ emulsions, loss of costly tailor made chemicals or surfactant on rocks surfaces make. N. Kumar et al.: Oil & Gas Science and Technology – Rev. IFP Energies nouvelles 75, 72 (2020)
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