Changes in group composition and biomarker ratios of crude oil during methanogenic degradation.

<p>Pr/<i>n</i>C₁₇: pristane/<i>n</i>-heptadecane; three replicates in each time points with exception of original day 0. a <i>n</i>-heptadecane was only detected in one of the three replicates; b: <i>n</i>-heptadecane was not detected above the detection limit; Sterilized-330: crude oil sampled from the sterilized control group after 330 days of incubation at 35°C, Sterilized-303: crude oil sampled from the sterilized control group after 303 days of incubation at 55°C.</p><p>Changes in group composition and biomarker ratios of crude oil during methanogenic degradation.