Temperature History
The temperature history over geologic time is decisive for whether or not hydrocarbons may have been formed in the basin. Among other factors, the temperature regime depends on the sedimentary basin evolution and the geometry of structures that are formed during the deformation of the basin.
The temperature history of the basin is calculated in BMT™ by conduction. One of the most important controls for temperature distribution is the thermal conductivity structure. The parameters that control the thermal conductivity structure are defined for each lithology type in the model, and BMT™ predicts the horizontal and vertical thermal conductivity of the lithology. The resulting present- day temperature, shown in Figure 3, and the temperature history reflects the difference in porosity (partly caused by lateral variations in the burial history) and the thermal conductivity of the sedimentary rocks.
BMT™ uses kinetic maturation models along with the temperature history to predict the timing of hydrocarbon formation from a given source rock (see Figure 3). The parameters governing the formation of petroleum are, in addition to temperature history, time (or heating rate) and organic matter type. Thus, the reliability of the prediction of oil and gas formation depends on:
- the reliability of the temperature history; and
- the reliability of the organic kinetic parameters used in the maturation modelling.
Figure 3: Temperature and Maturity Modelling
The left figure shows the calculated present-day temperature distribution for the basin.
The right figure shows the predicted transformation ratio for source intervals for present-day conditions: red colour indicates 100% and blue colour 0% transformed hydrocarbons
Conclusion
Fairly simple exploration methods led to the early discoveries of the structural traps of oil and gasfields globally. A lot of interesting fields are, however, characterised by complicated geological structures. More sophisticated exploration methods are needed to make hydrocarbon discoveries in structural traps in these areas. There is therefore a growing need for basin modelling systems that can handle more of the complex controlling geological processes that lead to generation and migration of hydrocarbons. Better insight into the mechanisms of basin formation has a direct bearing on the predictive power of basin models.
BMT™ has been used in a number of studies of sedimentary basins at the Norwegian continental shelf, in the Gulf of Mexico, South America, Asia and Africa. BMT™ technology, combining tectonic modelling with the temperature history in a single integrated program, gives better insight into the complex structures that we call sedimentary basins.
Category:
Geosciences
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