Comparison of Mud Motor and the Rotary Steerable System (RSS) As Two Main Directional Drilling Methods

Abstract

Hossein Askari, Koorosh Tookallo and Mohammad Reza Sayadi

As the global demand for oil and gas continues to rise, the safe, efficient, and cost-effective drilling of directional and horizontal wells demands advanced technology. Achieving these objectives relies on strategic drilling methods, employing techniques such as Rotary Steerable Systems (RSS) and Positive Displacement Mud Motors. Complex well trajectories face drilling operations with lots of challenges, particularly in deep and highly deviated wells. Issues such as high dogleg severity, low Rate of Penetration (ROP), and tool sticking can lead to substantial financial losses for operators. In extreme cases, inadequately drilled directional wells may even lead to abandoning the well. Advancements in both mud motors and rotary steerable systems (RSS) have significantly enhanced directional drilling capabilities over the past decade. While mud motors remain a reliable and cost-effective solution for many projects, the increasing complexity of modern reservoirs and the need for precise well placement has led to widespread use of RSS technologies. This review article compares the mud motor and the rotary steerable system (RSS) as two main directional drilling methods in different aspects. The results show that the application of RSS in comparison with conventional mud motors not only gives technical advantages but also has an economic advantage.

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