Well interventions in long lateral-reach wells, i.e., wells with laterals 10,000-ft or longer, continues to challenge the oil and gas industry around the world. Without specialized friction reduction technologies, typical-size coiled tubing (CT), such as 2- or 2 3/8-, 2 5/8-, or even 2 7/8-in., has enough rigidity to transfer weights-on-bit (WOBs) to the bottom hole assembly (BHA) in only a part of the current horizontal wells. For instance, 2- in. CT could effectively intervene in about the first half of the 5 1/2-in. completed laterals. Increasing the CT diameter or rotating the CT, entirely or partially, remain theoretical options to improve reach. However, larger-diameter CT creates logistical challenges with onshore road transport and offshore crane-lifting/deck-loading limitations. Also, CT rotation, similar to drill pipe rotation, is not economically practical with current CT technologies. Technologies such as lubricants, vibratory and tractor tools are traditionally used to extend the CT reach. Although fluid hammer tools and tractors have extended the CT reasonable operational range significantly, they also increase circulating pressures and operational complexity. To reach a 10,000-ft lateral, metal-on-metal lubricants are required to work with the other friction reduction technologies. However, most of the lubricants currently used for well interventions perform worse in the field than at atmospheric conditions in the laboratory. In addition, field success can depend on factors besides the lubricant's friction reduction capability, such as its synergy with the other commonly circulated brines and fluid friction reducers or its regain permeability performance. Despite a broad use of the CT lubricants and their importance for the predictability and success of the well interventions in extended-reach wells, reliable and consistent field validation studies of their friction reduction capabilities are rare. Field performance data are mostly anecdotal or proprietary. In addition, there was no available literature review of the knowledge gained to date. Thus, a critical review of studies addressing the CT lubricants and scientific demonstrations of their field performance will indicate the challenges and limitations currently encountered in the field. This will hopefully trigger further research and development and best field practices for CT lubricants and well intervention operations in extended-reach wells.
