Estimation of regional heat flux based on borehole temperatures acquired during logging while tripping with the sea floor drill rig MARUM-MeBo2

Abstract

Borehole temperature measurements can be easily conducted  at the end of a drilling operation during trip out of the drill string (logging while tripping) without the need for additional operational time. After the final drilling depth was reached, an autonomous borehole logging tool including a temperature sensor is placed at the lower end of the drill string with the sensor part having passed the drill bit and sticking out in the open borehole between bottom of the borehole and drill bit. During trip out the logging tool is hooked up together with the drill string inside the borehole and measures the fluid temperature within the borehole. Stationary phases occur at regular intervals during disconnecting drill rods from the drill string. The analysis of the borehole temperatures during these stationary phases allow the investigation of changes of borehole temperatures with depth and with time. These temperature changes are a function of the geothermal gradient and the perturbation of the temperature field by the drilling action. Here we present results of a pilot study (Freudenthal et al., 2022) based on borehole temperature measurements acquired with the sea floor drill rig MARUM-MeBo200. By modeling the temperature evolution from the start of the drilling operation on, it is possible to analyze the impact of the drilling perturbation on the temperature field and to conclude on the regional heat flux.