Probabilistic Tectonic Heat Flow Modelling for Basin Maturation: Method and Applications
J.D. van Wees1,2, F. van Bergen1, P. David1, F. Beekman2, and S. Cloetingh2
1TNO, Postbus 80015, 3508 TA Utrecht, The Netherlands
2Vrije Universiteit, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands
Basement heat flow is one of the most influential parameters on basin maturity. Although rapid progress has been made in the development of tectonic models, capable of modelling of the thermal consequences of basin formation and reactivation, these models are currently hardly used on a routinely basis to access heat flow boundary conditions in basin modelling. We believe three major factors obstruct routinely use. Firstly, because of the focus of most tectonic models on lithosphere scale processes a large range of models, including the McKenzie rift model, fail to take into account effects which are of paramount importance for basement heat flow such as transient effects of sediment infill and erosion, and changes in crustal heat production over time. Secondly, lithosphere tectonics models often fail to allow inversion of basin data, making forward tectonic modelling a cumbersome exercise. Thirdly, lithosphere tectonic models generally fail to aid the user to understand the sensitivity of the model results in terms of basin maturation for permissible ranges of tectonic model parameters and for uncertainties in tectonic scenarios such as absence or presence of underplating.Consequently, tectonic modelling is often neglected in the basin modelling workflow and heat flow is considered a user input, often marked by a constant value without temporal or spatial variation, and which only to some degree can be constrained by basin thermal data or maturation data. These stable values are often extrapolated from nearby shallower settings, hereby neglecting the differences in tectonic setting that may be present compared to deeper settings. Constant heat flows can therefore result in erroneous basin modelling outcomes, resulting in false overoptimistic identification of prospective areas or failure to identify prospects. This is particularly true for areas with limited data control such as frontier basin areas, or deep unexplored plays in mature basins.For this reason, we have developed in the recent years a multi-1D probabilistic tectonic heat flow model, which is capable of calculating tectonic heat flows, incorporating a variety of tectonic scenarios (including rifting, underplating, mantle upwelling). The model is capable of inversion of burial histories, calibrated to temperature and maturity data. Calibration and sensitivity analysis is done through Monte Carlo sampling analysis using an experimental design technique for computational efficiency. The tectonic heat flows can easily be used as input for basin modelling in commercially available 3rd party software.The model has been applied for a range of basin settings. For (frontier) deep water basins in the Caribbean and Mediterranean regions, we show that basin maturation is significantly higher and occuring much earlier when adopting tectonic heat flow instead of a constant heat flow. For mature basins in the Netherlands, we show that tectonic heat flow scenarios considerably aid in identifying and understanding of unexplored play systems, by putting temporal and spatial constraints on paleo heat flow. In particular modelling results indicate that the interplay of rifting, underplating and foreland formation and inversion, has resulted in much stronger temporal and spatial tectonic heat flow variations than hithertoo assumed.
AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands