Thermal histories and overthrusting—Application of numerical simulation technique

Overthrust belts frequently contain potential exploration targets and an assessment of the effects of overthrusting on temperature histories and hydrocarbon (HC) generation can reduce exploration costs. However, many models oversimplify the problem, for example by neglecting the physical and thermal characteristics of lithologies or by using instantaneous thrust sheet emplacement rates. The adaptation of numerical simulation techniques to handle overthrusting in a two-dimensional simulation enables the 'emplacement' of a previously deposited, and therefore physically and thermally well-defined sedimentary sequence, over a sequence or partial sequence of previously deposited units. The combined effects of factors such as complex lateral and vertical lithological variations, thrust sheet thicknesses, movement rates, compaction and forced fluid flow can be taken into account. The method is demonstrated by its application to a schematic model. The following variables are tested: thrust sheet emplacement rates, thermal conductivities, and heat flow. A thickness of 5 km is used in order to limit the total amount of variables. The results show that simple, one-dimensional models can considerably overestimate temperature differences and effects across thrust sheet planes through time. This can lead to incorrect conclusions on the establishment of a temperature equilibrium in the thrusted sequence and on HC generation timing.