Abstract
Eutectic solvents are currently being proposed as useful chemicals for enhanced oil recovery (EOR). In this work, for the first time, the preparation of eutectics based on surfactants and polymers was proposed for this application. These chemicals can be tailored to offer the most desired properties for oil recovery: water/oil interfacial tension reduction and increase of the aqueous phase viscosity, while concomitantly facilitating their handling due to their liquid character at ambient conditions. Sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and polyethylene glycol (PEG) of three different molecular weights (namely 600, 1000, and 2000 g/mol) were paired in a search for eutectic behaviors. Melting temperatures for all the systems were determined by differential scanning calorimetry. The most promising combination was AOT + PEG-600, which exhibited a melting point of 275 K and thermal stability up to 473 K at a 40:60 molar ratio. A promising value of 5.1 × 10−2 mN/m was obtained for the interfacial tension between the optimized formulation and crude oil. The formulation was tested in core-holder experiments to extract oil from a sandstone rock at room temperature, achieving an encouraging 34% of additional oil recovery after the secondary extraction.
Highlights
In recent decades, global energy consumption has increased exponentially due to the rise in population, economic growth, and technological development
Surfactants and polymers are promising enhanced oil recovery (EOR) chemicals that are currently being combined in order to achieve the water/oil interfacial tension (IFT) reduction required to enhance the mobility of the oil retained in the pores of the rocks, while avoiding adverse mobility ratios
The main conclusion of this study is that polymers and surfactants can be adequately selected to form eutectics, facilitating the preparation of EOR formulations due to the liquid character of the mixture
Summary
Global energy consumption has increased exponentially due to the rise in population, economic growth, and technological development. According to the U.S Energy Information Administration, it is estimated that global primary energy consumption will increase approximately 40% between 2019 and 2050 [1]. In this context, petroleum will be needed for many years both as an energy source and as a raw material for many essential products. The rate of discovery of new oil reservoirs is currently declining; long-term efforts should focus on increasing recovery from already exploited fields [2,3]. Around 90% of the world’s oil is extracted by means of water flooding (secondary recovery). Large amounts of water are required to maintain the pressure gradient inside the reservoir [4]. During the water injection process, the displacement front is unstable, with water flowing faster than crude oil and, reaching production wells, while the crude remains in the earth [5,6]
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