Abstract: Thermal Anomalies Related to Modern Fluid Flows in the Central Graben, North Sea

C. G. Fleming, G. D. Couples, R. S. Haszeldine

The subsurface temperature regime is of great importance to the petroleum industry as enhancement or depression of the temperature field affects both the maturity of source rocks and chemical reactions (diagenesis). We are investigating links between modern temperature anomalies and fluid flow within the Central Graben, North Sea.

Temperature and lithologic data were obtained from forty-six released wells within both the Norwegian and UK sectors. These wells are distributed along a SW-NE section line from the Mid-North Sea High, across the Central Graben, onto the Egersund High, and to the Norwegian-Danish basin.

Temperature profiles across the Central Graben show temperature variations of +/-19°C. Thermal modelling demonstrates that variations in thermal conductivity (e.g., basement and sedimentary fill) cannot explain the observed temperatures. Thus another mechanism of heat transfer must be operating within the basin, and we suggest that significant fluid flow may be responsible.

Rapid flows within the basin have great potential to modify the temperature field. Using OILGEN, a finite element package written by Prof. Grant Garven of Johns Hopkins University, a basinwide model for the Central Graben has been constructed extending from the Pennines in England to southern Norway. This model shows that localised conduits (in this case steeply-dipping faults) can provide paths along which heat from depth can be advected upwards. The resulting temperature fields are similar to those observed from down-hole measurements.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994