Changes

  | part    = Critical elements of the petroleum system

  | part    = Critical elements of the petroleum system

  | chapter = Evaluating source rocks

  | chapter = Evaluating source rocks

  | frompg  = 6-1

  | frompg  = 6-31

  | topg    = 6-41

  | topg    = 6-31

  | author  = Carol A. Law

  | author  = Carol A. Law

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch06/ch06.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch06/ch06.htm

}}

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[[file:evaluating-source-rocks_fig6-14.png|left|thumb|{{figure number|1}}. Copyright: Lingerer et al., 1991; courtesy John Wiley & Sons.]]

[[file:evaluating-source-rocks_fig6-14.png|thumb|{{figure number|1}}Decreasing HI trend for a source rock beginning to generate hydrocarbons at a depth of approximately 2200 m. Copyright: Ungerer et al.;<ref name=Ungerer1991>Ungerer, P., P. Forbes, and J. L. Rudkiewicz, 1991, Computer modeling of the interplay between generation and expulsion of petroleum: a new advance in synthesizing geochemical data: Proceedings of the 13th World Petroleum Congress, Buenos Aires, p. 179–189. ''Discusses the relationships between a number of maturation indicators and petroleum generation and migration.''</ref> courtesy John Wiley & Sons.]]

Gross trends of hydrogen indices (HI) can be used as a maturation indicator. The hydrogen index is calculated from Rock-Eval data using the following formula:

Gross trends of hydrogen indices (HIs) can be used as a maturation indicator. The hydrogen index is calculated from Rock-Eval data using the following formula:

:<math>\mbox{HI} = \mbox{S}_{2} \mbox{ (mg/g)}/\%\mbox{TOC} \times 100</math>

:<math>\mbox{HI} = \mbox{S2} / \mbox{TOC} \times 100</math>

 

==How to apply HI==

==How to apply HI==

Hydrocarbon generation zones can be indicated in the HI data for a uniform source section when HI decreases with depth. Inconsistencies due to changes in organic facies or the chemistry of the source rock can produce shifts in the HI data which are not indicative of maturation trends. Therefore, be sure the source is of uniform character when applying this concept.

[[Petroleum generation|Hydrocarbon generation]] zones can be indicated in the HI data for a uniform source section when HI decreases with depth. Inconsistencies due to changes in [[organic facies]] or the chemistry of the [[source rock]] can produce shifts in the HI data which are not indicative of [[maturation]] trends. Therefore, be sure the source is of uniform character when applying this concept.

[[:file:evaluating-source-rocks_fig6-14.png|Figure 1]] shows a decreasing HI trend for a source rock beginning to generate hydrocarbons at a depth of approximately [[depth::2200 m]].

[[:file:evaluating-source-rocks_fig6-14.png|Figure 1]] shows a decreasing HI trend for a source rock beginning to generate hydrocarbons at a depth of approximately [[depth::2200 m]].

* [[Spore coloration and thermal alteration indices]]

* [[Spore coloration and thermal alteration indices]]

* [[Production Index (PI)]]

* [[Production Index (PI)]]

==External links==

==External links==

[[Category:Critical elements of the petroleum system]]  

[[Category:Critical elements of the petroleum system]]  

[[Category:Evaluating source rocks]]

[[Category:Evaluating source rocks]]