Thermal history modelling is an exercise undertaken during

basin modelling Basin modelling is the term broadly applied to a group of geological disciplines that can be used to analyse the formation and evolution of sedimentary basins, often but not exclusively to aid evaluation of potential hydrocarbon reserves. At its m ...

to evaluate the temperature history of stratigraphic layers in a

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsidence ...

. The thermal history of a basin is usually calibrated using thermal indicator data, including

vitrinite Vitrinite is one of the primary components of coals and most sedimentary kerogens. Vitrinite is a type of maceral, where "macerals" are organic components of coal analogous to the "minerals" of rocks. Vitrinite has a shiny appearance resembling gla ...

reflectance and

fission track Ion tracks are damage-trails created by swift heavy ions penetrating through solids, which may be sufficiently-contiguous for chemical etching in a variety of crystalline, glassy, and/or polymeric solids. They are associated with cylindrical d ...

s in the

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common ...

and

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...

. The temperatures undergone by rocks in a sedimentary basin are crucial when attempting to evaluate the quantity, nature and volume of

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

s ( fossil fuels) produced by

diagenesis Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play ...

kerogen Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It ...

s (a group of chemicals formed from the decay of organic matter).

Fourier's Law Conduction is the process by which heat is transferred from the hotter end to the colder end of an object. The ability of the object to conduct heat is known as its ''thermal conductivity'', and is denoted . Heat spontaneously flows along a te ...

provides a simplified one-dimensional description of the variation in heat flow ''Q'' as a function of

thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...

''k'' and thermal gradient ''dT''/''dz'': :

Q=-k\frac

(The minus sign indicates that heat flows in the opposite direction to increasing depth, that is, towards the Earth's surface.) If the assumptions used to justify this simplified approximation (i.e. steady-state heat conduction, no

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...

advection In the field of physics, engineering, and earth sciences, advection is the transport of a substance or quantity by bulk motion of a fluid. The properties of that substance are carried with it. Generally the majority of the advected substance is a ...

) are accepted, we define the simple 1-dimensional heat diffusion equation where temperature ''T'' at a depth ''z'' and time ''t'' is given by the equation: :

T_ = T_^0 + Q_t \int_0^z\frac

where ''T''_t⁰ is the surface temperature history, ''Q''_''t'' is the

heat flow Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...

history and ''k'' is thermal conductivity. The integral thus represents the integrated thermal conductivity history of a 1-dimensional 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 Back-stripping (also back stripping or backstripping) is a geophysical analysis technique used on sedimentary rock sequences. It is used to quantitatively estimate the depth that the basement would be in the absence of sediment and water loading. ...

References

See also