Overview: Multilateral/Extended Reach (July 2005)
Authors: Wolfson Larry 
Published: February 2015

Ret-ro-spec-tion (n): the act or process of surveying the past.
What does retrospection have to do with multilateral (ML) and extended reach (ER) wells? By the time this issue of JPT is published, I will have retired from 31 years of active duty in the oil patch. Reaching this milestone made me think about the past and the advances in drilling technology and practices.
Approximately 25 years ago, directional drilling was used predominantly to develop reserves, mostly offshore, that could not be accessed any other way. Around 1980, horizontal wells changed that mindset and directional drilling became a reservoir-management tool. The idea of horizontal wells or drain holes was not new; successful applications of the technique were reported as early as 1929.1 Instead of discussing why horizontal wells took 50 years to catch on, let us look at some key well-construction technologies that made it a reality.
By the late 1980s, several technologies—measurement while drilling, steerable motors, top drives, and polycrystalline diamond compact bits2—combined to increase drilling efficiency and reduce drilling and reservoir risk. When first introduced, these technologies were sold as time savers—through connections, surveys, trips, or increased rate of penetration. We know these efficiencies are tangible, but the real value is the drilling system that made horizontal wells an effective reservoir-development tool.
The industry first considered ER technology in the early 1980s to access reserves beyond the original development area from offshore platforms—many of these developments were based on pre-1980s directional-drilling limits of 60°. In these cases, ER wells were more cost-effective than a second platform or subsea completions. However, it was not long before ER wells became an option in the development of offshore reserves from an onshore pad or the basis of a new development plan.
The one-trip retrievable whipstock is considered an enabling technology for MLs. Introduced in the early 1990s, it was considered a timesaving tool. But when combined with Technology Advancement of Multilaterals Level 1, 2, or 3 junctions, this technology resulted in the economical development of several heavy-oil projects. Once again, the real value was in effectiveness, not efficiency.
World-class wells of 10 years ago are considered routine today. What will a world-class well look like 10 years from now? I cannot answer that question. But I am confident that value-adding technologies will be those that break current paradigms, not those that enable us to do things faster or cheaper. I will be watching these pages for the answer.

References
1. Hyland, Craig R.: “Drain-Hole Drilling—An Old Idea Whose Time Is Now,” paper SPE 12792 presented at the 1984 SPE California Regional Meeting, Long Beach, California, 11–13 April.
2. Mills, R.C.: “Bright Lights on Petroleum Technology,” paper SPE 16820 presented at the 1987 SPE Annual Technical Conference and Exhibition, Dallas, 27–30 September.
Available from the SPE eLibrary: www.spe.org
SPE 90245 - “The Analytical Solution for Wellbore Stability in Multilateral Junctions in Nonhydrostatic In-Situ Stress Field,” by S. Hoang, U. of Oklahoma, et al.
SPE 90423 - “Level-6 Multilateral Experiences in the Niger Delta—A Review,” by Ochuko Erivwo, SPE, Shell, et al.
SPE 90385 - “A Novel Technique to Acidize Horizontal Wells With Extended Reach,” by H.A. Nasr-El-Din, SPE, Saudi Aramco, et al.
SPE 90566 - “Intelligent Completions: Lessons Learned From 7 Years of Installation and Operational Experience,” by Alan McLauchlan, SPE, WellDynamics Inc., et al.
SPE 92565 - “Tortuosity Factors for Highly Tortuous Wells: A Practical Approach,” by G. Robello Samuel, Landmark Graphics, et al.