ABSTRACT This study investigated the relationship between component evolution and viscosity reduction in the Menggulin paraffinic crude oil reservoir under reservoir conditions using gas chromatography‐mass spectrometry and viscosity measurements at reservoir temperature (37.2°C). Results show stage‐dependent compositional transformation: in 250–400°C medium‐temperature oxidation, C 6 ‐C 9 components are fully combusted, with displaced oil dominated by residual alkanes and oxygenates, yielding limited viscosity reduction. Above 400°C (high‐temperature cracking), long‐chain n ‐alkanes undergo β‐scission to generate abundant C 10 ‐C 25 + long‐chain α‐olefins, which reduce viscosity via physical dilution and polar interaction with wax crystals/resins. Specifically, 10% addition of 500°C‐displaced oil lowers the original 853 mPa·s viscosity to ∼200 mPa·s (88% reduction), outperforming 250°C‐displaced oil (needing >25% addition). This study reveals that Menggulin crude exhibits a unique olefin‐dominated evolution, identifies long‐chain α‐olefins as the signature products of paraffinic crude during in‐situ combustion (ISC), verifies temperatures above 400°C as the optimal temperature window, and thus provides a scientific basis for the optimization of ISC in similar reservoirs.
Guo et al. (Wed,) studied this question.
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