As deeper and more complex well designs proliferate throughout oil and gas fields, well completion methods are challenged and new technologies are emerging to ensure safe, cost-efficient, and optimized completions.
The Welltec Flex-Well completion concept is a flexible, single-skin (monobore) system that allows fit-for-purpose completion designs that can be as minimal or intricate as needed for optimal reservoir drainage and do not require the use of cement or swellable packers (Fig. 1).
Reliable and effective annular barriers continue to be crucial to well management for safety and performance. Cementing has been the industry’s conventional means of creating these barriers, having been used for almost 100 years (American Oil & Gas Historical Society 2015). However, the industry is not drilling and completing wells the way that it did a century ago.
The advances in drilling, particularly those related to horizontal well technology, have led to well designs and completion environments that often exceed the capabilities of cement to provide a reliable annular barrier that will last as long as the well. Efforts to overcome the challenges of many of today’s wells with cement can lead to complicated, expensive, and time-consuming operations.
The use of certain swellable packers has arisen as an accepted alternative, primarily because of time savings. However, their degradable polymer content has a significant risk of failure in harsh downhole well environments. Wells with swellables have been shown to leak approximately 50% of the time after 5 years from the time of installation (Plessing and Arnskov 2011).
With more than half of the world’s rigs drilling highly deviated or horizontal wells, and an increasing number of mature fields with depleted well zones, the challenges of such wells call for barriers that not only are cost-efficient but will also remain effective throughout the well’s lifetime.
Expandable Annular Barrier
A key component of the flexible, singleskin completion system is the Welltec Annular Barrier (Fig. 2), an all-metal expandable barrier with a large expansion ratio that was developed for a wide variety of applications in well construction, including well integrity and zonal isolation. Designed for the specific well during its construction phase, before the well is spudded, the barrier delivers reliable annular isolation and maximizes the ability to handle pressure change across the entire borehole, without internal restrictions, over the life of the well.