Abstract
The use of hole opening tools in conjunction with Rotary Steerable Systems (RSS) has increased dramatically in the past few years. Although excellent performance has been delivered with the mainstream commercial tools, alternate options have been developed to enable an RSS to drill the pilot hole in conjunction with a string tool to open the hole in a single run.
The most popular current option involves a weight or hydraulic activated underreamer. However, fixed blade, multi-diameter reaming tools have recently been developed for use within Rotary Steerable (RS) assemblies:
An eccentric string reamer that will pass through a small pilot hole but then drill and produce a larger hole. This provides a significantly lower-cost hole opening option.
A concentric string reamer that utilizes a tapered design incorporating a mid and main reamer section. This innovative design uses a mid-reamer that enlarges the pilot hole to an intermediate size and stabilizes the main reamer above it on its gauge pads. Because of its unique design, the mid reamer is able to stabilize the tool even if the pilot hole is of poor quality or is overgauge. This is particularly beneficial with RS tools in soft formations, leading to improved borehole quality and BHA stabilization. It also enables the use of smaller RS tools, thus providing greater directional potential. Additionally, a single RSS can be used to drill multiple hole size intervals, minimizing BHA changes, which in turn increases rig floor safety and lowers costs.
Several distinct applications are documented where these fixed bladed solutions, in combination with both Push and Point RS tools, have proven extremely successful. This has provided greater flexibility with regard to tool selection and well planning options, delivering lower cost per foot in RS projects. Case studies are presented from the Far East, Norway, and the Gulf of Mexico.
