Extended Reach Drilling (ERD) is directional drilling of very long non-vertical wells. The aims of ERD are: a) to reach a larger area from one surface drilling location, and b) to keep a well in a reservoir for a longer distance in order to maximize its productivity and drainage capability.
Challenges in ERD are hole cleaning, managing the mechanical loads on the drill string and downhole pressure, and cost. [1]
Early ERD-well definitions related wells to those that exceeded some step-out/vertical-depth ratio (often 2:1). However, for most highly deviated wells in deepwater environments, this definition clearly does not fit. Some methods have evolved to categorize wells according to their stepout within different vertical-depth ranges. ERD wells then can be described conveniently as shallow, intermediate, deep, and ultradeep. Other variants are associated with operating in deep water and high-pressure/high-temperature environments. Currently, there is no generally accepted ERD-well definition.
What exactly determines a well to be "extended reach" varies over time and location with the development of technologies and of experiences. [2]
New technologies have emerged that claim to be pushing the existing boundaries of ERD. One of these is the Reelwell Drilling Method.[ clarify ]
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