Following the many successful applications of the "Lean Profile" (LP) technique, developed by Eni E&P some ten years ago, a further step towards production maximization with simultaneous increase of operational safety and decrease of the overall drilling cost has been recently achieved with the introduction of the "Extreme Lean Profile" (XLP).Compared to a conventional profile, the LP has allowed running an additional casing between the 18 5 / 8 " and 13 3 / 8 " strings, the XLP introduces a further casing also between the 13 3 / 8 " and 9 5 / 8 " strings.Previous papers have described this new concept. Instead, our main intent herein is to highlight how the use of the XLP can really make the difference for the success of drilling operations when it comes to drill long extended-reach wells.This is the case of the onshore well Cerro Falcone 4 Or in the Val D'Agri field (Italy), the first ever deviated well being drilled by applying the XLP concept, without which the target could not be reached with the borehole size required for constructing the planned multilateral well.The need to apply the XLP technology required overcoming many challenges due to the severe operational conditions experienced in drilling previous wells (hard, unhomogeneous and abrasive formations, hole instability, severe vibrations, mud losses).This paper provides a comprehensive description of the well profile requirements, the associated operational issues, the chosen solutions and the actual challenges encountered during drilling operations. The achieved results are also described.Based on the success of this XLP application, Eni E&P is considering to further develop this concept of narrow annuli, to insert additional casing strings: for instance a 8 1 / 8 " casing between the 9 5 / 8 " and 7" strings and a 5 3 / 4 " casing between the 7" and 4 1 / 2 " strings.