Rathole elimination (RHE) BHA comprised of hydraulics and ball-drop underreamer has been used in different North Sea fields. RHE success has been very important for operators in completion, cementing, casing running optimization, and handling contingencies by running intermediate liners and casings. One of the major benefits of the RHE system is time saving because the rathole is removed in the same drilling run and the dedicated underreaming run is not required. In today's field operations, this time saving has become considerably important on the older platforms as well. An RHE system has been successfully run on the North Sea continental shelf (NCS) with five different operators and in six challenging fields, resulting in significant time and cost saving for each operator. BHA and hydraulics design are the basis of these successful RHE operations. Starting from a vertical well to whipstock exits and 2D wells followed by 3D complex wells have established that the RHE system is fully directional and steering capability is not compromised by BHA complexity. Suites of applications, including the integrated dynamic design and analysis 4D platform was used for BHA optimization and stability, underreamer and bits cutting structure selection, and directional response prediction. Both push-the-bit and point-the-bit rotary steerable systems (RSS) have been used in these operations. RHE showed great success and technology maturity on NCS in various borehole sizes. This paper presents the historical run summaries and the technology maturity life cycle in the North Sea.

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