|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|
Tmax is the temperature at which the maximum rate of hydrocarbon generation occurs in a kerogen sample during pyrolysis analysis. The S2 peak represents the rate of hydrocarbon generation (the area under the curve represents the amount). The temperature at the time the S2 peak is recorded during pyrolysis is Tmax, given in °C. Figure 1 shows output from a pyrolysis analysis and when Tmax is recorded.
We can use the general guidelines for maturation levels given below for Rock-Eval pyrolysis Tmax for types II and III kerogens. Different pyrolysis techniques have different cutoffs for pyrolysis oil and gas generation zone boundaries. Pyrolysis Tmax can be significantly different for type I kerogen or kerogen containing high sulfur concentration and is not a reliable indicator of maturity for these kerogen types.
|Hydrocarbon generation zone||Rock-eval pyrolysis Tmax, °c|
|Oil (from type II kerogen)||435–455|
|Oil (from type III kerogen)||435–465|
|Gas (from type II kerogen)||> 455|
|Gas (from type III kerogen)||> 465|
- Evaluating source rock maturity
- Vitrinite reflectance
- Apatite fission track analysis
- Spore coloration and thermal alteration indices
- Hydrogen Index (HI)
- Production Index (PI)
- Tissot, B., P., Pelet, R., Ungerer, P., 1987, Thermal history of sedimentary basins, maturation indices, and kinetics of oil and gas generation: AAPG Bulletin, vol. 71, p. 1445–1466. Excellent review of the relationships between maturation indicators and hydrocarbon generation from kerogens.