Rotary Steerable System (RSS)

What is a Rotary steerable system (RSS)?
It permits downhole directional control whilst continuously drilling in rotary mode. At present, three classes of rotary steerable system exist:

• fully steerable systems, allowing down hole control of both inclination and azimuth;
• semi steerable systems, providing down hole control of inclination only (adjustable stabilizers)
• vertical drilling systems, that actively seek vertical

The aim of this document is to provide information on:

• the experience to date of rotary steerable systems
• available rotary steerable;
• technical, cost and usage data; and
• the perceived benefits and drawbacks of these systems

Advantages of RSS over conventional mud motor techniques
Firstly, due to the elimination of the need for slide drilling:

• Improved ROP, reducing drilling time;
• Improved hole cleaning / lower ECD;
• Reduced torque and drag, giving greater reach for ERD wells;
• Reduced axial stick / slip problems.

It is also believed that rotary steerable systems give:

• Smoother well bore, requiring less reaming;
• More controllable build rates;
• Improved bit life.

Types of wells that may benefit from rotary steerable technology include:

• ERD wells that are beyond current comfort zones;
• Designer wells where sliding limits achievable targets;
• Deep, hot, directional wells where motors have problems;
• High build rate, small diameter re-entry work;
• Wells where slide drilling causes high ECD's / well bore stability problems;
• Vertical wells where directional control is difficult;
• Deep wells to reduce torque and drag generated at surface