Designing and Testing of New Rotary-Steerable System for Use Onshore

Abstract

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 173093, “Designing and Testing a New Rotary-Steerable System (RSS) for the Onshore Drilling Market,” by Andrew Gorrara, SPE, Shona Grant, Tore Kvalvik, SPE, and Stig Bakke, 2TD Drilling, and Peter Clark, SPE, Chevron, prepared for the 2015 SPE/IADC Drilling Conference and Exhibition, London, 17–19 March. The paper has not been peer reviewed. While rotary-steerable systems (RSSs) dominate the offshore directional-drilling markets, the land-based markets are still dominated by conventional directional-drilling tools. This paper presents a new RSS that is being designed and tested specifically for the onshore markets. The new tool is a short RSS that is designed to deliver a buildup rate of 15°/100 ft. It achieves this by the movement of two eccentric shafts relative to one another within the tool. Introduction For directional drilling to be successful, it is important that the drillers have information on the orientation of the tool while they are drilling so they can best align the wellbore orientation to the reservoir target. Commonly, this is achieved with a measurement-while-drilling (MWD) tool that is typically 50 ft or more behind the drill bit. In some cases, these measurements are supplemented with some form of near-bit inclination reading. A further improvement would be to have both inclination and azimuth measured close to the bit and integrated into the drilling tool’s directional response, thereby enabling precise well placement without the need to project and correct continually from the MWD tool that lags considerably behind the drilling tool. This is the method adopted by the RSS described in this paper. In many cases, a downhole positive-displacement motor will be used with the RSS to increase rate of penetration (ROP) and reduce casing wear by minimizing string rotation. The RSS described in this paper was designed to be driven directly by the topdrive or with a mud motor. Three prototypes of the new RSS have been designed and tested so far. The first prototype (Prototype A) successfully demonstrated dogleg-severity capability of 15°/100 ft. The second prototype (Prototype B) was designed to evaluate the efficiency of the selected motor-gear design in moving the eccentric shafts when applying significant side loads. The third prototype (Prototype C) was a complete rotary-steerable tool that verified all aspects of the design, culminating in the drilling of directional holes in concrete blocks. This paper describes the development of Prototype C, covering design, manufacture, and the drill tests that verified the 15°/100 ft dogleg performance through concrete-block drilling. The paper also covers the subsequent design improvements made before manufacture of the field-test prototypes (Prototype D) and the planned environmental and endurance testing of Prototype D before field testing.