PRESENT-DAY THERMAL REGIME OF THE SANTOS BASIN, BRAZIL

Abstract

The discoveries made in the pre-salt of the Santos Basin are among the world’s most important in the past decade. This reality confers to the basin a strategic position to meet the great global demand for energy, especially due to the prospectivity in unexplored areas. The study of the present day thermal regime of a basin is a key step in the assessment of the petroleum system (maturity of source rocks), risk of biodegradation, reservoir diagenesis, as well as to guide drilling and development. The gathering of the temperature data was done for 275 wells distributed in different geological settings of the Santos basin. These included wells in the Albian gap area, where the salt withdraws or it is very thin, the salt diapir province and in the area with a more continuous thick salt layer. Most data points come from BHT, Horner corrected temperature, MDT, PVT samples, and DST. Although the great majority of the data are for the interval just below the base salt, there are data for the post salt sequence, and some data close to 1km deep into the pre-salt section. These data allowed the estimation of geothermal gradient (GG) trends for the different geological settings and post-salt, salt and pre-salt intervals. The high thermal conductivity of salt bodies creates a thermal disturbance, above and below, that has been recognized and studied by different authors in different basins (e.g. O‘Brien and Lerche, 1987; and Yu et al. 1992). The abundant data compiled for the pre-salt section clearly show the thermal anomaly below the thick salt bodies of the Santos basin. A thermal anomaly above the salt is not always so clear, being more difficult to demonstrate, due to the lower amount of available temperature data in the post salt. The observed regional GG for the Santos basin in the area of salt withdrawal is in the 30-34C/km range, in the salt layer it is 11-13ºC/km, while in most of the pre-salt section it is in the 23-26C/km range. Genesis 1D models have been built using the temperature data, for them to be integrated in a regional petroleum systems model to generate temperature and maturity maps for the Santos basin.

AAPG Datapages/Search and Discovery Article #90325 © 2018 AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin, Lisbon, Portugal, May 2-3, 2018