Evolution of Frac Plug Technologies – Cast Iron to Composites to Dissolvable

A technological revolution in hydraulic fracturing has occurred between early wellbore stimulation techniques and present day stimulation that has reduced cost and increased stimulation performance. Part of this revolution has been driven by the improved technology of frac plugs. This paper discusses how the evolution from cast iron frac plugs to composite plugs, then later to an interventionless stimulation completions process has enabled stimulation in extended-reach wellbores. Drillable frac plugs were initially created from cast iron. Although cast iron plugs met run-in requirements and pressure ratings, the time required to remove these plugs by milling was long. Composite frac plugs were developed to accelerate the mill-out process. The light weight of the composite frac plugs also enabled the frac plugs to be run into a horizontal section of the wellbore. This operational change, combined with the ease of milling the composite plugs, has paved the way for the horizontal completion market for the past 15 years. However, the use of composite frac plugs in extended-reach horizontal wells was limited by the need to drill out the plugs. The development of dissolvable frac plugs eliminated the need to drill out the plugs allowing operators to produce wells much sooner. This elimination of the drill-out step for dissolvable frac plugs has also enabled the successful completion of extended-reach horizontal wells which may be beyond the practical range of coiled tubing or jointed tubing. The need for efficient production in extended-reach wellbores has spurred the continuing evolution of hydraulic stimulation. This paper describes 20 years of new technology and field results to document the changes to the design and construction of frac plugs, as well as changes to the design and operation of the wellbore.