Spore coloration and thermal alteration indices (SCI and TAI): usage

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Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Critical elements of the petroleum system
Chapter Evaluating source rocks
Author Carol A. Law
Link Web page
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How to use SCI and TAIthermal alteration index

SCI (spore coloration index) and TAIthermal alteration index (thermal alteration index) are maturation indicators that measure the color of palynomorphs. Color changes as a function of maturity.

There are a number of scales for both SCI and TAIthermal alteration index within the exploration industry. The SCI and TAIthermal alteration index scales have been standardized to the vitrinite reflectance (Ro) maturity scale. Users of SCI and TAIthermal alteration index data need to have access to the maturation relationship used by the lab supplying the data, and users should be aware of how the scales compare from one lab to another in order to apply the data correctly. These relationships should be available from the vendor performing the analysis.

Correlation of SCI & TAIthermal alteration index with other parameters

The table below shows a very generalized correlation of kerogen maturity parameters with SCI and TAIthermal alteration index (after[1]).

Vitrinite reflectance (%Ro) Spore coloration index (SCI) Thermal alteration index (TAIthermal alteration index) Pyrolysis Tmax (°C) Generalized hydrocarbon zone
0.40 4.0 2.0 420 Immature
0.50 5.0 2.3 430 Immature
0.60 6.0 2.6 440 Oil
0.80 7.4 2.8 450 Oil
1.00 8.1 3.0 460 Oil
1.20 8.3 3.2 465 Oil & wet gas
1.35 8.5 3.4 470 Wet gas
1.50 8.7 3.5 480 Wet gas
2.00 9.2 3.8 500 Methane
3.00 10 4.0 500+ Methane
4.00 10+ 4.0 500+ Overmature

See also

References

  1. Waples, D., 1985, Geochemistry in Petroleum Exploration: Boston, IHRDC, 232 p.

External links

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Spore coloration and thermal alteration indices (SCI and TAIthermal alteration index): usage
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