Advanced Heat Flow and Thermal Maturity Prediction Using a Basin Modelling Tool

Mathieu Ducros
IFP Énergies Nouvelles, Rueil Malmaison, France

It is now accepted that basin modelling has become a standard tool in petroleum system analysis. In basin modelling, thermal maturity estimation is a key step whose impacts can be significant on petroleum system evaluation. Input data for petroleum system simulation generally take the form of basal heat flow maps or lithospheric architecture and thermal properties, as well as its evolution through time.

One of the basin modellers' major task consists in estimating these regional scale input data from local ones (wells). Several methodologies can be applied:
1. Thermal calibration can be performed on 1D models located at wells, and the calibration results are then reported and interpolated in time and space in the 3D model.
2. Most advanced models incorporate the entire lithosphere. Then, model calibration consists in adjusting directly the crustal thicknesses and property variations through time, at the regional scale.

One of the major drawbacks of the first method lies on the simplistic assumptions on the scenario of heat flow evolution through time. Moreover, the interpolation method used to calculate heat flow maps does not usually take advantage of the geological information. Consequently, thermal maturity estimation is poorly reliable between wells. The second method is surely more robust but requires much more data corresponding to the crust history and properties. It is also much more time consuming and it requires much greater modelling skills and expertise.

Some authors (e.g. Dalla Rosa, 2012) proposed methodologies which would bring more geological information when interpolating 1D thermal calibrations. However these interpolation methods require that some properties, like sediment thickness or depth, do correlate with basal heat flow; this latter constraint can be a strong limitation in complex geological settings (salt tectonic, rift basins…).

Our work aims at providing a methodology which would take maximum advantage of the modeller's knowledge of the basin in order to firstly calibrate 1D models where thermal data (temperatures, vitrinite reflectance…) are available. Second step consists in calculating paleoheat flow maps, based on both sedimentary and crustal information, when available. The proposed methodology takes into account the thermal retro-action of the lithosphere (sedimentary deposits and crust) on the basal heat flow through time, for both 1D calibrations and map interpolations. This information is obtained via a first basin model simulation integrating the whole geological information. The method ensures, at each time and location of the basin, that heat flow is consistent with the geological history of sedimentary filling (high sedimentation rates, erosions…), tectonic (salt for instance) and crustal evolution (rifting events…).

This methodology has been used on a 3D basin model where it appeared to be robust and much more predictive than the one which is traditionally used for 3D petroleum system simulation.

AAPG Search and Discovery Article #90175©2013 AAPG Hedberg Conference, Beijing, China, April 21-24, 2013