Thermal Anomalies in Sediments near Evolving Salt Structures: Importance for Modeling Timing of Oil Generation: ABSTRACT

Abstract

ABSTRACT The temperature distribution through time in the subsurface has an important impact on the generation of hydrocarbons. It is therefore of interest to model the spatial variation of the temperature through time and the causes of the variation. The thermal conductivity of salt is a factor of two to three times higher than that of typical sediments. Salt structures provide paths of low thermal resistance for the conduction of heat from depth to the surface. The focused heat reenters the sediments near the salt apex so neighboring sediments are warmer than regional sediments, whereas sediments close to the salt base, and in the secondary rim synclines, are cooler than regional sediments. A combined self-consistent model of evolution of salt and sediments has recently been developed, so that the temperature distribution through time can be calculated. The relative thermal anomaly effects caused by height and width variations of salt structures are illustrated. The vertical extension of the oil window promotes earlier onset of maturation in sediments near the salt apex and delays conversion of trapped oil to gas in the deeper sediments when compared with the regional picture. The temperature history can then be incorporated with that of the modeled structural evolution of migration pathways and trap development, thus providing an integrated picture of the dynamic evolution of salt and sediments. Examples illustrate the importance of modeling thermal history in order to reduce hydrocarbon exploration risk near salt structures.