Application Of At Bit LWD Resistivity And Drilling Dynamics Measurements In Early Pre-Salt Reservoir Detection, Deepwater

Brazilian deep water pre-salt reservoirs are located over 200 km from the coastline and 5000 m below sea level, with 2000 m water depth. To reach these oil rich limestone reservoirs, operators drill more than 1000 m of siliciclastic and limestone rocks before encountering the 2000 m thick salt layers. Before entering the reservoir, there is an intermediary borehole section, usually of 17 ½” size, drilled through the salt. Casing has to be set inside competent formation (anhydrite or limestone) with minimal reservoir entrance to guarantee wellbore stability.

Combining local geoscience expertise and high technology drilling services, the drilling operation is optimized to identify changes in drilling dynamics and to perform proper formation characterizations, where resistivity at the bit technology enhances the geological interpretation for an effective and accurate decision while drilling. Such technologies have been successfully applied, minimizing operational risks and reservoir entrance.