The increasing demand for crude oil has necessitated the discovery of new oil fields, significantly impacting the environment due to the extensive drilling operations required. Research now focuses on recovering unconventional oil from existing, older oil fields to mitigate these effects. This process is known as enhanced oil recovery (EOR). One of the challenges faced during EOR is the recovery of waxy crude oil. Wax in the oil can deposit in the reservoir, reducing permeability. This makes it difficult for injected fluids to displace the oil effectively. The IFT between the injected fluid and waxy oil must be reduced to minimise this issue. The waxy oil deposit on the sandstone can be recovered by changing it to water-wet from oil-wet. Anionic (sodium dodecyl sulfate and sodium dodecyl benzene sulfonate) and cationic (cetyltrimethylammonium bromide and dodecyl trimethylammonium bromide) surfactants were used to investigate IFT and contact angle. IFT was also measured after adding sodium chloride and partially hydrolysed polyacrylamide. All four surfactants significantly reduce the IFT values, which are further reduced by adding salt. In contrast, no significant change in IFT was observed due to the addition of partially hydrolysed polyacrylamide. Experimental evidence shows that surfactant systems alter intermediate-wet sandstone rocks' wettability to become water-wet. We discovered that SDBS can reduce IFT to as low as 0.25 mN/m at its critical concentration, which may help recover waxy crude oil. X-ray fluorescence and Fourier transform infrared spectroscopy analysis of sandstone rock was performed, and the thermogravimetric analysis of all surfactants was also performed to check their stability for higher temperatures. This study aims to optimise the use of surfactants to recover waxy crude oil, which has significant implications for environmental control and the economic efficiency of industries.
Keywords: Anionic surfactants; EOR; Hydrolysed polyacrylamide; Waxy oil.
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