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Nanofluid enhanced imbibition is a frontier technology to improve the recovery of low permeability，and also has a great application prospect for the development of pressure infiltration in ultra-low permeability fractured reservoirs.
A series of in-situ imbibition experiments of self-made Nanofluid SNFSL combined with the NMR technology were conducted for ultra-low permeability fracture core. The effects of Nanofluid SNFSL on oil-water interfacial tension and core wettability, the influence of nanofluids concentration, temperature and its variation on the imbibition effect, and imbibition characteristics were studied, and the mechanism of nanofluid enhanced suction is explained from the perspective of mechanics. The results show that nanofluid can effectively improve the suction yield, and the higher the concentration of nanofluids, the lower the oil-water interfacial tension, the stronger the hydrophilicity, and the higher the efficiency of oil extraction. Imbibition recovery rate(IRR) of fractured core is 24.59%，and 4.33% higher than that of matrix core. The concentration increased from 0.15% to 0.3%, to 0.45%, IRR is increased by 2.89% and 3.01%. The core imbibition recovery at 60℃ is 18.14% higher than that at 25℃. The temperature decreased from 60℃ to 25℃ and then increased to 60℃, and the oil-free core recovery increased by 1.22% again. These indicates that increasing the temperature and concentration is beneficial to imbibe and drain the oil, especially the periodic change of temperature can drain oil again from the core that cannot drain oil. The study also showed that, 0.15wt%, 0.3wt% SNFSL made oil-water interface tension decrease from 10.6 mNm-1 to 4.7 mm Nm-1 and 3.5 m Nm-1, and contact angle of the core from 73.8° to 9.5° and 6.6°, respectively, the adhesion work of crude oil is decreased by more than 99%. thus, capillary force of imbibition increased by 24% -44.6%, crude oil adhesion energy decreased by 99.2% -99.7%, and flow resistance decreased by 39% -48%. The results show that the nanofluid SNFSL has the comprehensive effect of enhancing the hydrophilicity of the core, reducing the interial tension between oil and water and the viscosity of crude oil, which generates the synergetic mechanical mechanism of increasing the driving force, reducing the oil-wall adhesion work and the internal friction of crude oil, thus improving the imbibition oil displacement effect of the ultra-low permeability oil reservoir.
| Country | China |
|---|---|
| Water & Porous Media Focused Abstracts | This abstract is related to Water |
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