The use of ultra-deep resistivity tools and its impact on cost saving, casing design optimization and drilling risks reduction during well planning phase.

The ultra-deep azimuthal EM LWD technology consists of a modular system design tailored initially for landing, geosteering and reservoir mapping applications. It features a depth of investigation that can exceed, in the most favorable cases, 100 ft [30 m] in radius around the borehole. Recently the tool’s capacity of boundary detection has also been applied for detecting resistivity variations ahead of the bit, in vertical or low angle wells. The plan of using the EM Look-Ahead service in an upcoming well in the Norwegian sea, combined with the standard look-around capability, allowed, during the well planning phase, to largely reduce the risk of setting the casing atop a highly depleted reservoir in the 17 ½’’ phase and to avoid the drilling of a pilot hole while landing the 12 ¼’’ section. A thorough pre job model (feasibility phase) permitted to precisely asses the applicability of the approach in the specific geological scenario for the two cases; being the target formations quite heterogeneous, in terms of resistivity response, some alternative scenarios were built and evaluated. This example describes the effectiveness of new LWD technology application, in order to contribute to safest operations and in significant cost saving.