A horizontal drilling campaign in Oman required an engineering solution to address the challenges in the 8.5-in. buildup section. The challenges include high dogleg requirements with dogleg severity (DLS) of 9°/100 ft to 11°/100 ft, long reactive shale intervals, poor wellbore quality, weight transfer issues, trajectory control, hole cleaning, differential sticking, and difficulties running the liner. All of these challenges have resulted in wells being over AFE and in an extreme case, the loss of one well. The typical well plan was designed for a 12.25-in. vertical section, then an 8.5-in. build section from vertical to a 90° inclination at buildup rate of 117100 ft to the reservoir entry, followed by a 6.125-in. lateral.

A joint effort by the operator and directional drilling service provider was carried out to engineer a solution for overcoming the challenges faced by conventional steerable motor assemblies. The 12.25-in. section was drilled vertically with the motor, and the 8.5-in. section was drilled using a new fully rotating hybrid rotary steerable system (RSS). This technology was proposed to overcome all the drilling challenges with faster penetration rates compared to conventional steering assemblies, while still delivering the planned 11°/100 ft DLS while fully rotating. This solution allowed the operator to safely and efficiently drill the 8.5-in. section without issue, both while drilling and running casing, and enabled savings of 3 days from the planned AFE.

This new hybrid RSS has proven to be capable of drilling steerable motor profiles with DLS capabilities up to 17°/100 ft in full rotation. The rate of penetration in these sections is also enhanced as no sliding or tool face orientations are required.

For certain well profiles, this RSS is a step change in the industry and has facilitated steerable motor profiles to be drilled in continuous rotation at higher penetration rates.

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