Overview: Horizontal and Complex Trajectory Wells (November 2007)
Authors: Conran Greg 
Published: February 2015

By browsing "historical" industry-related publications, it is clear that horizontal wells were once viewed as low-feasibility options because of associated high costs and risks. Time, progress, and global demand have necessitated change.
With today's industry challenges to meet ever-increasing production targets and to maximize the full potential from maturing fields, horizontal or complex trajectories are now accepted as standard practice or warranted as a viable design for a field development. Annually, we now see horizontal wells being spudded in ever-increasing numbers.
The industry has come a long way since the first "true" horizontal well more than 70 years ago—adding complexity to well-design expectations through advances in directional-drilling, completion, and stimulation techniques and technology. It is still less than 30 years since downhole-steerable-motor technology with measurements while drilling, supplemented by surface top-drive systems, paved the way to progress the design of more-complex trajectories. Further technological advances, with the introduction of rotary-steerable systems to deliver the most-complex-trajectory design routinely, are now often taken for granted by both drillers and geoscientists.
Over the last 15 years, the industry has pushed the limits of drilling extended-reach wells to more than 37,000 ft on several world-class projects, while other projects have repeatedly delivered horizontal sections in excess of 22,000 ft. Parallel advances in completion technology and stimulation techniques have been essential in maximizing the benefits of these horizontal sections.
High-quality 3D-seismic data with associated interpretation have contributed immensely when integrated within the horizontal-well design-engineering team. With increased well complexity and recovery of incremental reserves, acquiring and using real-time formation-evaluation information for improved well placement and navigation through the reservoir are now an evolving expectation on many projects.
Today, an initiative exists toward implementing structured real-time operations support and monitoring centers, providing a continuation of the collaborative platform initiated during the well-design phase. Imagine benefiting from improved well placement and real-time decisions, with a reduction in the overall costs of horizontal-well delivery on every well.
I wait to see, but with the potential of future developments such as drilling automation, in another 10 years a "complex-wells" theme as we know today may also be a topic to pull from the industry archives.
Horizontal and Complex-Trajectory Wells additional reading available at the SPE eLibrary: www.spe.org
SPE 105403 "Drilling With Liner on Horizontal Oil Wells" by M. Terrazas, Pemex E&P, et al.
SPE 103865 "Horizontal-Drilling Application To Recover Incremental Oil in Low-Permeability Carbonate Reservoirs, Partitioned Neutral Zone" by Thanh Tran, CACT China, et al.
SPE 106948 "Effects of Friction in Drain Hole on Productivity of Horizontal and Multilateral Wells" by Boyun Guo, SPE, University of Louisiana at Lafayette, et al.
SPE 105709 "Inflow-Profile Control in Horizontal Wells in a Fractured Carbonate Using Swellable Elastomers" by Rudy W.F. Welling, Petroleum Development Oman, et al.
SPE 102656 "Limited-Entry Perforations in HVO Recovery: Injection and Production in Horizontal Wells" by A. Burtsev, Shell International E&P, et al.