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Extended reach wells

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An extended-reach well is one in which the ratio of the measured depth (MD) vs. the true vertical depth (TVD) is at least 2:1.

Extended reach well achievements and records


Extended reach wells can be extremely long (measured depth) and relatively shallow vertically, as well as relatively short and very shallow vertically - and everything in between. The extremely long reach wells are typically drilled to distant reservoirs to reduce the infrastructure and operational footprint that would otherwise be required to access the resource. The relatively short reach wells may be drilled to provide needed reservoir contact length in very shallow reservoirs. The current world record (circa 2013) for the longest measured depth ERD well is the Chayvo Z-42 well (Exxon Neftegas Limited, Sakhalin Island, Russia) with a measured depth of 41,667 ft. and horizontal departure of 38,514 ft. Relatively short wells with MD/TVD ratio’s approaching 12 have reportedly been drilled in Western Canada in very shallow bitumen sands that are too deep to develop using surface mining techniques.

Horizontal departure limits

Other notable extended reach achievements in pushing the horizontal departure distance from 30,000 ft. to 40,000 ft. (circa 2013) include:

  • 25 wells drilled by Exxon Neftegas Limited on the Sakhalin-1 project, Sakhalin Island Russia, (MD/TVD = 3.9 to 6.9)
  • 1 well drilled by Maersk Oil Qatar in the Al Shaheen field, Qatar (MD/TVD = 11.1)
  • 2 wells drilled by BP on the Wytch Farms project, England (MD/TVD = 6.9 to 6.6)
  • 1 well drilled by Total in Argentina, Cullen Norte #1 (MD/TVD = 6.7)
  • 1 well drilled by ExxonMobil in the Santa Ynez Unit, offshore California, USA (MD/TVD = 5.36)

Benefits of extended-reach wells

Extended-reach wells are expensive and technically challenging.[1] [2] [3] [4] [5] [6] [7] However, they can add value to drilling operations by making it possible to reduce costly subsea equipment and pipelines, by using satellite field development, by developing near-shore fields from onshore, and by reducing the environmental impact by developing fields from pads.


  1. Scott, P.W. 1991. Increasing Reach From 3,000 m to 5,000 m. Presented at the SPE/IADC Drilling Conference, Amsterdam, Netherlands, 11-14 March. SPE-21983-MS.
  2. Payne, M.L., Abbassian, F., and Hatch, A.J. 1995. Drilling Dynamic Problems and Solutions for Extended-Reach Operations. In Drilling Technology, ed. J.P. Vozniak, PD-Volume 65, 191–203. New York: ASME.
  3. Modi, S., Mason, C.J., Tooms, P.J. et al. 1997. Meeting the 10km Drilling Challenge. Presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 5-8 October. SPE-38583-MS.
  4. Guild, G.J., Hill, T.H., and Summers, M.A. 1995. Designing and drilling extended reach wells: Part 2. Petroleum Engineer International 67 (1): 35-41.
  5. Sonowal, K., Bennetzen, B., Wong, P., Isevcan, E., 2009. How Continuous Improvement Lead to the Longest Horizontal Well in the World. Presented at the SPE/IADC Drilling Conference and Exhibition, Amsterdam. SPE-119506.
  6. Walker, M.W., Andrew J. Veselka, A.J., Harris, S.A., 2009. Increasing Sakhalin Extended Reach Drilling and Completion Capability. Presented at the SPE/IADC Conference, Amsterdam. SPE-119373.
  7. Walker, M.W., 2012. Pushing the Extended Reach Envelope at Sakhalin: An Operator’s Experience Drilling a Record Reach Well. Presented at the SPE/IADC Conference, San Diego. SPE-151046.

See also

Types of directional wells


Noteworthy papers in OnePetro

External links