ABSTRACT:

The lean casing profile principle has been successfully applied in Italy since 1997. This type of profile provides numerous benefits in term of safety, environmental impact, performances and costs. While improvement in the drilling technology allowed the developing and the refining of the technique in vertical holes applications, experience in drilling this type of profile in deviated hole is still limited to one well where an inclination of ~30° was reached. Cerro Falcone 5 OR is the first application of the "lean profile" principle in a deviated hole reaching almost 60° inclination. A near to vertical "lean hole" to 1701m TVD was drilled before starting the deviated section. The deviated lean casing profile consists of two sections. A 17½" section for 16" casing was drilled for the first time and for the second time 13 3/8" casing was run in 14¾" hole. The upper 17½" section was drilled using a modified automated vertical drilling device which kicked off the well from 0 deg to 7.4 deg at 1998 m TVD. To minimize well bore tortuosity in the 14¾" phase, a rotary steerable system (RSS) was used. The profile was built from 7.4 to 58.96 deg and then tangent maintained to TD casing point. To reduce drag during the 13 3/8" casing run, a particular mud additive was used. It is composed of small styrene plastic spherical bead of an average size of 160µ to 250µ that acts as a lubricant without changing the rheological proprieties of the drilling fluid. This paper presents in detail the experience gathered during operations, demonstrates the feasibility of high angle lean casing profile and highlights benefits, both in terms of performance and economic

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