In recent years, the deep directional resistivity logging-while-drilling technology has enabled operators to take strategic geosteering decisions by mapping reservoir features before their intersection. As a result, the workflow to understand and update sub-surface structural information while-drilling is increasingly being practiced.

A new service has recently been developed to meet the challenges of geosteering and reservoir mapping operations in slim hole environments. While conceptually based on existing larger tool size options, the new Reservoir Mapping-While-Drilling (RMWD) service involves innovative engineering adaptations to extend its capability to the 6-inch hole size. This technology and first application in Italy is presented in this paper.

Downsizing this technology presents various challenges that require redesign of the transmitter and receivers in order to maintain high reliability, high measurement quality, and very deep depth of detection. For example, 50% less effective antenna areas negatively influence measurement quality and detection depth. Reducing the tool diameter enables handling higher dogleg severity (wellbore direction variations), however this also induces higher bending moments within the tools and creates more misalignment between transmitter and receivers. The new tool service overcomes the mentioned challenges and is capable to delineate multiple subsurface layers in real time with a robust inversion algorithm.

The new Reservoir Mapping-While-Drilling (RMWD) service has been tested in Italy to increase production of a carbonate oil field. Faulted structural blocks and the presence of a potentially moved oil-water contact required a suitable technology that could help safely steer the wellbore close to the top of the formation without exiting or touching the sealing above. With seismic uncertainty, the plan was to use LWD high-resolution imaging and distance-to-boundary measurements to precisely describe the reservoir and interpret the complex structure setting for optimal well placement. An overview of the performance and results are presented in the paper.


The geosteering world is an exciting environment, undergoing continuous innovations in both technology and interpretation solutions.

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