Drilling performance on horizontal wells typically drilled in re-entry / workover operation is key for the project to become economically feasible to produce hydrocarbon. Due to presence of a non-linear pressure gradient, a re-entry well-construction design required a casing before entering reservoir and drilling further in a slim-hole. A slim-hole ie 3 7/8″ hole, was not meeting well objectives from logging and completion perspective. Hence, a 5 ½″ x 7″ expandable liner was required to be set in order to drill a 5 ½″ production hole. To accommodate a 5 ½″x 7″ expandable liner, a 6 1/8″ pilot-hole was required to be drilled and enlarged up to 7″; this was historically achieved by a dedicated hole opening trip after drilling a conventional 6 1/8″ because the section was drilling through extremely challenging hard anhydrite layers which were not only hostile towards directional work but were also generating malign drilling environment through severe shocks & vibrations and poor penetration rates (causing lot of tool failures and damages). Since the well design called for high dogleg severity well profiles, motor assemblies were used to drill the well because conventional rotary steerable systems (RSS) were unable to deliver the required directional performance due to unfavorable directional response of the formations. In this operation, an integrated engineering approach was developed to design a drilling system that can simultaneously drill and enlarge hole that lead to successful delivery of a high dog-leg severity well profile without causing any tool failures or mechanical damages. This operation was a first such example in the industry where this drilling system was utilized. The success of the operation relied on selection criterions used for adopting technologies in the BHA and was based on the design process followed to conduct advanced engineering studies. The engineering approach taken in this successful operation highlighted how an innovative application of a truly hybrid high build rate RSS tool had expanded an existing drilling envelope to new frontiers.

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