A Global
Overview of the Temperature Gradients in
Steen, Øyvind1, Paul Nadeau1
(1) Statoil ASA,
A dataset of c. 50 000 reservoir
formation temperatures in c. 200 sedimentary basins on the continents
world-wide have been analysed in order to characterise the thermal structure of sedimentary basins
and their relationship with the tectonic settings. Attention was paid to the
deeper temperature records (c. 39 000 below 800 m), which are less affected by
near-surface thermal processes, particularly those related to recent climatic
changes, ground water flow, as well as variable sedimentation rates.
Compared with heat flow datasets the
current data has a larger degree of spatial similarity. The modelled
temperature gradients show limited short-distance variation and reflect
large-scale trends (high and lows) which generally fit with the present-day
tectonic settings of the basins. Major changes of the temperature gradient is
found between basins which are bounded by mega-scale tectonic features, for
example active subduction zones and rift zones, and
between basins of different kinematic origins
(divergent, convergent, and wrench systems). Distinct trends of the temperature
gradients are observed from the present-day basin types, of which young
divergent basins and wrench basins display a warm trend and fore-arc- and
foreland basins a cool trend. Positive correlations are observed between modelled seismological crustal
thickness in certain basin types and variations in sub-surface thermal
gradients.
The reservoir formation temperatures
present here represent valuable information which can refine the thermal models
of the crust underlying the sedimentary basins, as well as provide a basis for
predicting the distribution of hydrocarbon resources in under-explored/frontier
basins.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California