Geothermics of the Malay basin, offshore Malaysm

Abstract

A review of the temperature, thermal conductivity and heat flow data of the Malay Basin has been carried out by analysing data from fifty nine exploration wells. The thermal conductivity of each well have been determined from logs which has been calibrated to measured thermal conductivity of cores. The formation temperature of the well at logging depth has been estimated by Horner plot by using a new model for derivation of effective circulation time. The effective circulation time has been approximated empirically from the well log data. Revised heat flow, geothermal gradient and thermal conductivity maps of the Malay Basin have been constructed from the new data. A vertical thermal profile of the basin has been analysed. The heat flow anomalies have been observed from the a real as well as vertical profiles of heat flow. The Malay Basin is found to have an average heat flow of 86 mWm(^2-) The average geothermal gradient is 47ºC/km. Both the heat flow and geothermal gradient are high. The heat flow varies over the basin, with regional highs in the Northwest, South and Central portions and a lower heat flow in the Southeastern part and Northeast peripherals. The anomalous heat flow is found to be related to the subsurface fluid movement and the overpressures. The temperature is not related to the top of onset of overpressures directly, however the various mechanisms of overpressuring can be speculated from the regional distribution of the temperatures at tops of the overpressures. Thermal maturity modelling has been carried out for selected wells. It was found that the basin thermal history can be matched to a rifted basin thermal model.