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

From AAPG Wiki
Jump to navigation Jump to search
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
Store AAPG Store

How to use SCI and TAI[edit]

SCI (spore coloration index) and TAI (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 TAI within the exploration industry. The SCI and TAI scales have been standardized to the vitrinite reflectance (Ro) maturity scale. Users of SCI and TAI 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 & TAI with other parameters[edit]

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

Vitrinite reflectance (%Ro) Spore coloration index (SCI) Thermal alteration index (TAI) 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[edit]


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

External links[edit]

find literature about
Spore coloration and thermal alteration indices (SCI and TAI): usage
Datapages button.png GeoScienceWorld button.png OnePetro button.png Google button.png