The objective

A Middle East operator needed to enhance production from an existing gas well completed with 4½-in cemented liner with a 7-in packer on 4½-in tubing. The operator planned to use underbalanced CT drilling to drill three additional laterals with sidetracks, which would allow continued production without interruption. During this workover, the operator sought to increase well productivity while minimizing the risk of differential sticking and wellbore instability.

Reservoir conditions required the drilling operation to use underbalanced drilling (UBD) techniques. While UBD offers many advantages, it also involves complex operations that make well planning, design, and execution more complicated. In offset wells, drilling with a high nitrogen rate led to lower power output and slower ROP. Conventional drive systems often sacrifice ROP to mitigate reservoir damage and other negative effects of excess torque.

The solution

To maximize drilling performance, SLB recommended the Neyrfor turbodrilling system with the hybrid turbine. The hybrid turbine efficiently converts hydraulic energy from the mud column into mechanical energy at the bit, delivering significantly greater downhole mechanical drilling power than any other drive system. Its high bit rotary speed produces a consistently smooth wellbore in even the most demanding environments. The hybrid turbine, featuring a one-piece design and enhanced blade profile, optimized power output during drilling, delivering greater reliability and performance compared with conventional drive systems. The unified design ensures maximum power delivery between the power section and bearing section, increasing ROP and reducing rig time during demanding drilling operations.

The results

The operator successfully reentered the well, drilling three laterals for a total of 4,135 ft in a single run. The innovative underbalanced coiled tubing drilling operation resulted in an average ROP of 32 ft/h, allowing the operator to drill the laterals 10 days faster than planned—significantly reducing rig costs. The successful deployment of the Neyrfor turbodrilling systems set a new benchmark for UBD performance, which led to the selection of the Neyrfor turbodrilling system as the primary technology for future drilling campaigns.