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Thermal Regime Deep Water Sergipe and Potiguar Ceara Basins Brazil Related to Fracture Zones, Active Faults and Volcanic Activity. Observations from Wells and Seismic Data Applied to Petroleum Systems Modeling


Thermal Regime Deep Water Sergipe & Potiguar Ceara Basins Brazil Related to Fracture Zones, Active Faults & Volcanic Activity. Observations from Wells & Seismic Data Applied to Petroleum Systems Modeling

Murphy’s New Ventures team has, over the last year, been evaluating the petroleum potential of the Sergipe-Alagoas and Potiguar-Ceará basins located in ultra-deep water offshore Brazil. One of the most important factors from a petroleum systems perspective, is the accurate assessment of the present day thermal regime and its evolution through time. 

Temperature data has been collected through several different methodologies. These temperature data are presented to provide an assessment of the present day thermal regime.

Across these basins the calculated geothermal gradient ranges from 30 to 50 0C/km and appears to be dominantly controlled by fracture zones, active faults, volcanism, and a variety of crustal domains, continental to transitional, hyper-extended and oceanic.

One important observation is that high geothermal gradients are associated not only with fracture zones as expected, but also with the presence of transitional or hyper-extended crust creating thermal anomalies.

The distribution of these thermal anomalies deeply impacts basin modeling results in terms of both expulsion timing and present-day maturity. Ultra deep water areas have previously been avoided due to the expectation of low thermal regimes. Now these neglected areas have been demonstrated to have potential for significant oil and gas generation and expulsion.

To fully understand the distribution and impact of these thermal anomalies over time, a combined analytical effort is required. Long streamer and long record seismic data acquisition is essential in establishing the depth to the Moho and for the identification of the appropriate crustal type to provide the basis for the associated thermal modeling parameters. The mapping of various volcanic events and the determination of their timing, origin and impact on the local thermal regime is also critical in the building of a comprehensive model.

Though the driving forces for these thermal anomalies are still largely unknown, this initial evaluation concludes that following the early rifting phase sustained igneous activity from the Cretaceous to present day resulted in the temperatures not following a typical “cool down” trend. The regional thermal regime thereby remained substantially higher than established models would suggest.