Salt diapir velocity assessment from temperature and thermal indicator anomalies: application to Lulu-1, Danish North Sea

A method is exhibited for assessing the time of onset of diapirism and salt flow-speed. Using vitrinite reflectance measurements from wells drilled on top of a salt structure it is possible to determine the excess maturity caused by the focusing of heat due to the higher thermal conductivity of salt. The method is based on calculation of the thermal anomaly surrounding a rising salt diapir. For a given salt speed, predicted vitrinite reflectance values are calculated and compared with the observed values at given depths. The process is repeated with various speeds of the rising salt until consistency of predicted and observed values is obtained, thus constraining an assessment of the velocity of the salt. The method can easily be tailored to thermal indicators other than vitrinite reflectance, thereby enhancing the resolution of the thermal history, and constraining both the onset of salt rise as well as the speed. The well, Lulu-1, from the Danish North Sea, is used to illustrate the procedure.