Thermal history modelling

Thermal history modelling is an exercise undertaken during basin modelling to evaluate the temperature history of stratigraphic layers in a sedimentary basin.

The thermal history of a basin is usually calibrated using thermal indicator data, including vitrinite reflectance and fission tracks[?] in the minerals apatite and zircon.

The temperatures undergone by rocks in a sedimentary basin are crucial when attempting to evaluate the quantity, nature and volume of hydrocarbons (fossil fuels) produced by diagenesis of kerogens[?] (a group of chemicals formed from the decay of organic matter).

Fourier's Law provides a simplified one-dimensional description of the variation in heat flow Q as a function of thermal conductivity k and thermal gradient dT/dz:

<math>Q=-k\frac{dT}{dz}</math>

(The - sign indicates that heat flows in the opposite direction to increasing depth, i.e. towards the Earth's surface).

If the assumptions used to justify this simplified approximation (i.e. steady-state heat conduction, no convection or advection) are accepted, we define the simple 1D heat diffusion equation where temperature T at a depth z and time t is given by the equation:

<math>T_{z,t} = T_{t}^0 + Q_t \int_0^z\frac{dz'}{k_{z'}}</math>

where T_t⁰ is the surface temperature history, Q_t is the heat flow history and k is thermal conductivity. The integral thus represents the integrated thermal conductivity history of a 1D column of rock.

Thermal history modelling attempts to describe the temperature history T_z,t and therefore requires a knowledge of the burial history of the stratigraphic layers which is obtained through the process of back-stripping[?].

See also: petroleum geology.