Thermal Impacts of Mobile Salt on Mudstones and Sandstones of the Lusitanian Basin, Portugal

Brett Perry
University of Nevada Las Vegas, Las Vegas, NV

Salt can be 2-4x more thermally conductive than other sedimentary rocks, and as a result can produce both areas of increased heat flow and decreased heat flow. It has been recognized for several decades that the high thermal conductivity of rock salt can impact adjacent sediments, specifically source rock maturities and reservoir qualities. Several workers have numerically modeled heat flow around salt. However, many of these models are based on limited/no field data and have proven lacking in predictive power, particularly within the petroleum industry. Therefore, a field based study that analyzes the thermal impact of salt on adjacent sediments may produce a better understanding of how heat flow is distributed around a salt diapir. Quartz cement, albite, illite/smectite, and vitrinite in sandstones and mudstones can be used as temperature proxies to constrain paleo thermal gradients and basin temperatures.

The Lusitanian Basin contains numerous salt diapirs that crop out at or near the surface of the Earth and therefore present a unique opportunity to study their past effects on adjacent sediments. Therefore, we predict that paleotemperatures were hotter proximal to the salt structures and that thermal maturities and diagenetic processes should be suppressed with increasing distance from salt. A clearer understanding of heat flow around salt is integral in better predicting reservoir quality and thermal maturity of source rocks within salt-bearing basins.

AAPG Search and Discovery Article #90181©2013 AAPG/SEG Rocky Mountain Rendezvous, University of Wyoming, Laramie, Wyoming, September 27-30, 2013