|Title||A numerical method for calculating total oil yield using a single routine Rock-Eval program: a case study of the Eocene Shahejie Formation in Dongying Depression, Bohai Bay Basin, China|
|Author||Li, M; Chen, Z; Ma, X; Cao, T; Li, Z; Jiang, Q|
|Source||International Journal of Coal Geology vol. 191, 2018 p. 49-65, https://doi.org/10.1016/j.coal.2018.03.004|
|Alt Series||Natural Resources Canada, Contribution Series 20180052|
|Media||paper; on-line; digital|
|File format||pdf; html|
|Subjects||fossil fuels; mathematical and computational geology; geochemistry; petroleum resources; hydrocarbons; oil; organic geochemistry; pyrolysis; software; source rocks; hydrocarbon generation; bitumen;
kerogen; temperature; thermal analyses; Eocene; Oligocene; Shahejie Formation; Dongying Depression; Bohai Bay Basin; Methodology; Phanerozoic; Cenozoic; Tertiary|
|Illustrations||tables; graphs; profiles; logs; cross-plots; bar graphs; histograms|
|Program||Geoscience for New Energy Supply (GNES) Shale-hosted petroleum resource assessment|
|Released||2018 03 21|
|Abstract||Obtaining reliable total oil yield in a source rock from routine programed pyrolysis data represents a technical challenge for the characterization of source rocks in early mature and oil window due to
strong interactions between bitumen and kerogen/rock matrix. A common laboratory solution for a robust estimate of total oil yield requires two pyrolysis experiments using a whole rock sample and a post-solvent extracted replicate. In this paper, we
present a numerical solution that provides a reliable estimate of total oil yield directly from a single routine Rock-Eval experiment. In temperature domain, the thermally vaporized products from heavy oil and bitumen adsorbed to the organic matter
and the pyrolyzed products from kerogen show a certain degree of overlap in the default temperature range of S2 peak. By transforming the routine Rock-Eval pyrogram (FID curve) into activation energy variable space, it allows for separation of the
reactants into subgroups by their responses to ramping temperature. The thermally vaporized products can be then discriminated from the thermally pyrolyzed products based on the differences in their thermal stability and decomposition behaviour. The
proposed method was applied to the source rock samples in the Eocene-Oligocene Shahejie Formation of Dongying Depression, Bohai Bay Basin, where programed pyrolysis results from whole rock samples and post-solvent extracted replicates were obtained.
The case study suggests that: (a) the two-step pyrolysis experiment approach may still under-estimate the total oil yield in case that solvent extraction treatment fails to remove all hydrocarbons in the sample; (b) the post-solvent extracted
equivalent S2x values derived numerically from routine Rock-Eval analysis and those derived from post-extracted analysis are comparable with a correlation coefficient of 0.9766, suggesting numerical approach is as effective as additional laboratory
experiment; and (c) the proposed approach can remove all petroleum in the sample numerically, thus providing an un-biased and robust estimate of total oil yield, a cost- and time-effective alternative to the traditional two experiment approach.
|Summary||(Plain Language Summary, not published)|
Assessing oil resource in shale reservoir is difficult because of strong interactions between bitumen and kerogen/rock matrix. To obtain a reliable total
oil yield, a laboratory solution requires two pyrolysis experiments, a whole rock and a post-solvent extracted replicate. We present a numerical solution that provides an estimate of total oil yield using a single experiment without the second one.
The proposed method was applied to rock samples from Eocene Shale in Bohai Bay Basin, where pyrolysis results from whole rock and post-solvent extracted replicate were available for method validation. The validation shows that the post-solvent
extracted equivalents derived numerically from routine analysis and those from post-extracted analysis are comparable with a correlation coefficient of 0.9766, suggesting numerical approach is a cost- and time-effective and environmentally friend
alternative to the traditional two experiment laboratory approach.