The first commercially successful Rotary Steerable Systems (RSS) were introduced in the mid-1990's for 8 ½-in. and 12 ¼-in. sections on high-end drilling applications. As the systems have matured and day rates reduced, they have been adapted to drill all borehole sizes from surface to the target depth.

RSS are highly complex tools consisting of mechanical, hydraulic and electrical systems all functioning simultaneously. Because of their complexity, systems designed for slimhole applications (5 ¾-in. to 6 ¾-in. sections with 4 ¾-in. collars) have typically been challenged with poor reliability. As these slimhole systems have matured, reliability and durability have increased through continuous improvements in some of the most challenging drilling conditions.

This paper presents the design, development and testing phases of a new slimhole RSS. The design stage describes the use of existing experience from larger RSS and methodology to make the assembly adaptable to all drilling applications. The development and testing phases of the project will be described in detail from workshop and drilling facility testing to semi-commercial applications to evaluate performance.

The confidential drilling facility testing was used to evaluate and enhance directional performance and reliability with a wide range of formations, drill bits, bottom-hole assemblies (BHA) and parameters. The testing format was designed around current directional well profiles for 5 7/8-in. to 6 1/8-in. hole where RSS are typically deployed. Reliability improvement was established by gradually step changing drilling and directional parameters to maximum or beyond the design specification of the system.

The initial customer trial phase of the system in established RSS environments is used as a proving ground to further develop the product for superior performance in challenging drilling applications.

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