Speaker
Description
In-situ imbibition imaging experiments were carried out using self-made nanofluid SNF-SL. The effects of nanofluids on oil-water interfacial tension, core wettability and other factors were studied, and the effects of temperature, concentration and fracture morphology on the imbibition effect of low-permeability fractured cores were studied by combining nuclear magnetic resonance imaging technology. The results show that the 0.3wt% nanofluid SNF-SL reduces the oil-water interfacial tension from 10.6 mN·m-1 to 3.5 mN·m-1, and the core surface contact angle decreases from 73.8° to 6.6°. The imbibition recovery rates of vertical fractured cores are 3.59% and 1.6% higher than those of matrix cores and transverse fractured cores, respectively, indicating that imbibition is beneficial to fractured reservoirs. The high temperature is conducive to imbibition and drainage, and the temperature rises from 40°C to 60°C, and the core imbibition recovery rate is further increased by 1-3%. However, this study for the first time discovered that periodic fluctuations lead to a periodic oil displacement effect. When the high temperature remains constant, oil displacement gradually ceases; whereas when the temperature fluctuates periodically, the core resumes oil displacement. The duration of such a cycle ranges from several hours to several weeks. This finding provides a new insight for the development of ultra-low permeability reservoirs.
Key words: low permeability; fractured reservoir; nanofluids; enhanced imbibition; imbibition characteristics
| Country | China |
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