{{Short description|Technique used to drill long horizontal wells}} '''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 oil–water separation technology|downhole pressure]], and cost.<ref>Kaiser, Mark J (2007-09-13) [http://www.redorbit.com/news/business/1064648/indices_describe_complexity_of_drilling_directional_extendedreach_wells/ Indices Describe Complexity of Drilling Directional, Extended-Reach Wells] ''Red Orbit'', retrieved October 6, 2008</ref>
==Definition== 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.<ref>Negrao, Alvaro (May 2009) [http://www.spe.org/jpt/print/archives/2009/05/JPT2009_05_15MERFocus.pdf Multilateral or Extended Reach] ''SPE Website'', retrieved October 6, 2008, link updated May 1, 2013</ref> * On 24 April 2015 the world's longest borehole was drilled and completed from the Orlan Platform in the Chayvo Field, Sakhalin-1 Project with a total measured depth of 13,500 m (44,294 ft) and a horizontal displacement of 12,030 m (39,469 ft)<ref>[http://www.worldoil.com/news/2015/4/14/sakhalin-1-sets-new-extended-reach-drilling-record-rosneft-says Sakhalin-1 sets new extended reach drilling record, Rosneft says], 2015</ref> * The previous world record was drilled and completed 30 March 2014 by the Yastreb land drilling rig in the Chayvo Field, Sakhalin-1 Project to a total measured depth of 13,000 m (42,653 ft) and a horizontal displacement of 12,130 m (39,797 ft)
==New developments== New technologies have emerged that claim to be pushing the existing boundaries of ERD. One of these is the [https://uis.brage.unit.no/uis-xmlui/bitstream/handle/11250/183644/Uglebakken,%20Lars.pdf?sequence=1]{{clarification needed span|text=Reelwell Drilling Method.|reason=What is it (specifically), and how does it "expand existing (drilling) boundaries"?|date=June 2024}}
==See also== *[[Underbalanced drilling]] *[[Well drilling]] *[[Drilling fluid]] *[[Lost circulation]]
==References== {{Reflist}}
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[[Category:Drilling technology]] [[Category:Petroleum production]]