Maps of hydrocarbon types: Gulf of Mexico example

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Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Critical elements of the petroleum system
Chapter Sedimentary basin analysis
Author John M. Armentrout
Link Web page
Store AAPG Store

Discussion

Hydrocarbon types reflect the composition of the kerogens from which they were generated. Kerogens are the insoluble organic matter in sedimentary rocks. Maps of hydrocarbon types estimate the number and distribution of mature generating source rocks. The map of hydrocarbon types in Figure 1 is based on analyses of more than 2000 oil, 600 gas, and 1200 seep samples correlated to specific source rocks. Nine oil-source-rock families have been identified (labeled 1-9; see Table 1), each having a specific geographic distribution related to mature source-rock location and migration paths. We will focus on the High Island-East Breaks area, where families 1 and 6 overlap (bold arrow).

Source table

Figure 1 Map of hydrocarbon types is based on analyses of more than 2000 oil, 600 gas, and 1200 seep samples correlated to specific source rocks. Modified from Gross et al.[1]

Table 1, modified from Gross et al.[1] lists source-rock ages, oil types, and map numbers for Figure 1.

Table 1.
Source-rock age Oil type Map #
Lower Tertiary (centered on Eocene, ~50-40 Ma)
  • Tertiary marine [t 1]
  • Tertiary intermediate [t 1]
  • Tertiary terrestrial
 ①
①
②
Upper Cretaceous (centered on Turonian, ~85-95 Ma)
  • Marine; low sulfur; no Tertiary influence
  • Calcareous; moderate sulfur; no Tertiary influence [t 2]
 ③
④
Lower Cretaceous (centered on Aptian, ~115-105 Ma)
  • Carbonate; elevated salinity; Lower Cretaceous
  • Calcareous; moderate sulfur; Lower Cretaceous [t 2]
 ⑤
④
Uppermost Jurassic (centered on Tithonian, ~140-130 Ma)
  • Marine; high sulfur; Jurassic [t 3]
  • Marine; moderately high sulfur; Jurassic [t 3]
  • Marine; moderate sulfur; Jurassic [t 3]
  • Calcareous; Upper Jurassic or Lower Cretaceous?
 ⑥
⑥
⑥
⑦
Upper Jurassic (Oxfordian, ~ 152-145 Ma)
  • Carbonate; elevated salinity;
  • Jurassic [t 4]
 ⑧
Triassic (Eagle Mills Formation, > 210 Ma)
  • Triassic; lacustrine
 ⑨
  1. ↑ 1.0 1.1 Tertiary marine and Tertiary intermediate are mapped together.
  2. ↑ 2.0 2.1 Calcareous; moderate sulfur; no Tertiary influence and Calcareous; moderate sulfur; Lower Cretaceous are mapped as an undifferentiated unit.
  3. ↑ 3.0 3.1 3.2 Oil subtypes related to variations in sulfur content and associated geochemical parameters have not been subdivided on Figure 1.
  4. ↑ Oil subtypes reflecting differences in salinity and clastic input to source facies are known but are not delineated on Figure 1.

Summary

By overlaying maps of total overburden thickness above major source-rock intervals, thermally mature source-rock distribution, hydrocarbon occurrences, and major structural features, the regional elements of the petroleum system(s) begin to emerge.

See also

References

  1. ↑ 1.0 1.1 Gross, O. P., K. C. Hood, L. M. Wenger, and S. C. Harrison, 1995, Seismic imaging and analysis of source and migration within an integrated hydrocarbon system study, northern Gulf of Mexico basin: Abstracts, 1st Latin American Geophysical conference, p. 1–4.

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