A new dissolvable frac plug has been developed for "plug-and-perf" style hydraulic fracturing applications. The dissolvable frac plug operates like a traditional frac plug and can be set anywhere in the wellbore to isolate individual zones. The new dissolvable frac plug is composed of a high-strength metal that degrades completely in wellbore fluids. Traditional frac plugs are constructed from a composite material. After a hydraulic fracturing treatment is complete, traditional frac plugs create a restriction to production flow and must be removed. Thus, a separate intervention is required to mill out traditional plugs after fracturing. A novel dissolvable frac plug has been developed that eliminates the need for a separate mill run intervention into the wellbore. The new frac plug will degrade completely to leave an unrestricted wellbore for production. The high-strength dissolvable metal allows dissolution in water-based wellbore fluid, formation fluid, or production fluid. Comprehensive laboratory testing was conducted on the dissolvable metal alloy for the new dissolvable frac plug. The dissolvable metal alloy is a metallic alloy that is combined with a dopant. The dissolution behavior is controlled by the interaction between the dopant and the rest of the metal alloy. Metallographic analysis illustrated the effect of the dopant on the dissolution of the metallic alloy. Dissolution is further influenced by the wellbore temperature. The high-strength alloy allows for the creation and use of dissolvable slips, which enables the complete dissolution of a frac plug that can be set anywhere within the wellbore. The novel frac plug is designed for plug-and-perf applications and is composed of a new high-strength engineered metal that dissolves in water-based wellbore fluid, formation fluid, or production fluid. Complete dissolution of the frac plug eliminates the need for a separate mill run intervention into the wellbore, which helps reduce costs, operation time, and risks to personnel. This paper discusses the development of the dissolvable metal and the dissolution behavior of the metal upon exposure to wellbore fluids.
Dissolvable fracturing plugs are used for hydraulic fracturing applications. However, most new dissolvable materials have slow or no degradation in low-temperature formations. A new low-temperature dissolvable fracturing plug was developed for low-temperature formations. This new dissolvable fracturing plug is composed of a high-strength metal with elastomeric seals that dissolves completely in lower-temperature wellbore fluids. Traditional fracturing plugs are constructed from composite materials and nondissolving elastomers. These nondissolving fracturing plugs obstruct production and need to be milled out after fracturing is completed. Dissolvable fracturing plugs dissolve in wellbore fluid, eliminating the need for a separate mill run intervention into the wellbore. However, the dissolution process slows in lower-temperature shale formations and the elastomer often ceases degradation at these lower temperatures. Therefore, a new metal and elastomer was developed that allows for the complete dissolution of the fracturing plug in lower-temperature formations. The new low-temperature fracturing plug is optimized for use with the fluids used and temperatures experienced in the Marcellus and Permian basins. Comprehensive laboratory testing was conducted on the dissolvable metal alloy and dissolvable elastomer for the new low-temperature dissolvable fracturing plug. The dissolvable metal alloy is a metallic alloy that is combined with a dopant. Metallographic analysis illustrates the effect of the dopant on the dissolution of the metallic alloy and the accelerated dissolution needed for lower-temperature formations. The dissolvable elastomer uses a hydrolytic degradation reaction that is accelerated for low-temperature fluids. The result is a high-strength fracturing plug that can be set anywhere within the wellbore and will dissolve completely at formation temperatures between 120 and 180°F. The high-strength dissolvable materials allow dissolution in water-based wellbore fluid, formation fluid, or production fluid. The novel fracturing plug is designed for low-temperature plug-and-perf applications and is composed of a new high-strength engineered metal and elastomer. Complete dissolution of the fracturing plug eliminates the need for a separate mill run intervention into the wellbore, which helps reduce costs, operation time, and risks to personnel. This paper discusses the development of the dissolvable metal, the development of the dissolvable elastomer, and the tested behavior of the low-temperature dissolvable fracturing plug.
Multiple dissolvable materials are becoming available in the energy industry. While dissolvable plastics have their applications, a dissolvable metal has distinct advantages over a dissolvable plastic for hydraulic fracturing.Multiple tests were performed to compare the characteristics of dissolvable metals and dissolvable plastics. The two product families that were explored were dissolvable frac balls and dissolvable frac plugs. For direct comparison, frac balls and frac plugs were constructed using a dissolvable metal and dissolvable plastic. For both dissolvable frac balls, the materials were tested for impact resistance. For both dissolvable frac plugs, the materials were pressure tested.The dissolvable metal frac ball provided higher impact resistance than the dissolvable plastic frac ball. The dissolvable metal frac ball survived impact at 19 bbl/min on ball-to-seat interference as small as 0.035 in. When the same test was performed using a dissolvable plastic ball, the ball shattered and passed through the seat. The seat overlap needed to be increased to 0.125 in. before the dissolvable plastic ball was able to consistently survive impact against the seat. For the frac plugs, the dissolvable plastic was unable to be used as a bottom slip because of the anchoring loads generated while the plug sealed against differential pressure. The dissolvable metal was able to anchor these loads when used as the material for the bottom slip. For a dissolvable plastic mandrel to survive the setting loads, it had to be set in compression. The dissolvable metal mandrel had no issue being set in tension, allowing for the operational setting procedures to be unchanged. Dissolvable plastic also required the inner diameter of the frac plug to be much smaller.Using dissolvable metal instead of dissolvable plastic reduces design requirements for converting non-dissolvable downhole tools to dissolvable ones. Dissolvable metal provides an increased impact resistance, has no issues being set under tension, and allows for using smaller ball-to-seat overlaps, all of which provide more flexibility for use in industry applications.
A new degradable elastomeric element has been developed for frac plugs that enable a fully dissolvable frac plug to be used in "plug-and-perf" style hydraulic fracturing applications. The dissolvable frac plug operates similarly to a traditional frac plug and can be set anywhere in the wellbore to isolate individual zones. The performance of the degradable element has been demonstrated in laboratory testing and in field runs. Traditional frac plugs are constructed with a traditional elastomeric rubber as the sealing element. After hydraulic fracturing is complete, traditional frac plugs restrict production flow and must be removed. Consequently, a separate intervention is required to mill out the traditional plugs after fracturing. Dissolvable metal has been developed to enable the dissolution of the rigid structural components of the frac plug. A hydrolytically degradable elastomer enables the complete elimination of all of the components of the frac plug. As a result, the novel dissolvable frac plug eliminates the need for a separate mill run intervention into the wellbore and leaves an unrestricted wellbore for production. The high-strength dissolvable elastomer enables dissolution of the seal in water-based wellbore fluid, formation fluid, or production fluid. Comprehensive laboratory testing and field jobs have been performed with the new degradable elastomer for the dissolvable frac plug. The degradable elastomer is a polymeric material that can be compression set like a traditional element to form a seal between the mandrel and the casing. The elastomer is a hydrolytically degradable polymer, and the dissolution occurs as the wellbore fluid interacts with the crosslink bonds in the polymer. Dissolution is further enhanced by the elevated downhole formation temperature. The high-strength dissolvable elastomer enables the creation of a seal anywhere in a wellbore. The result is a new dissolvable frac plug that operates like a traditional frac plug and can be set at any position within the wellbore. Dissolvable frac plugs with degradable elastomeric seals have been used successfully in multiple shale zones in multiple countries. The novel frac plug is designed for plug-and-perf applications and provides sealing with a new high-strength engineered elastomer that will degrade in wellbore fluid. The complete dissolution of the frac plug eliminates the need for a separate mill run intervention into the wellbore, reducing operational costs, time and risk. This paper discusses the development of the dissolvable elastomer, performance testing of the elastomer as a frac element, dissolution behavior of the elastomer, and the use of the frac plug in field applications.
Although all plug-and-perf systems require frac plugs to isolate zones in the wellbore, there are alternative approaches to hydraulic fracturing using the plug-and-perf method. The availability of dissolvable frac plugs enables operators to weigh the cost and risk of using non-dissolvable frac plugs against the cost and risk of dissolvable frac plugs. This paper analyzes the cost and value of these varying fracturing approaches for applications in North America in traditional and extended reach wellbores. Frac plugs must be removed from the wellbore before production begins. Non-dissolving frac plugs are removed by milling; this step increases the cost of the overall completion and can sometimes lead to production delays. Risks associated with the milling operation include becoming stuck in the wellbore, damage from the milling debris, and the requirement for larger amounts of water. Consequently, the cost of milling is an added cost to non-dissolvable fracture products. Dissolvable solutions, however, have a larger upfront cost because dissolvable materials are more expensive than non-dissolving materials. There is a trade-off between the larger upfront costs of dissolvable fracturing technology and the milling costs and risks of non-dissolvable fracturing technology. This trade-off depends on the number of stages, wellbore fluids, formation parameters, operational costs, cost of delayed production, and the operator's willingness to accept risk. The trade-offs also vary between operators and regional geographies. The costs of non-dissolving frac plugs are acquired from historical data and include tools, milling, materials, and the time delay to production, as well as the weighted risk of potential formation damage and lost time incidents. The costs of dissolvable fracture plugs are estimated from the experience in the use of this dissolvable technology. These dissolvable costs are modeled for a typical wellbore in North America for both full wellbore and extended reach laterals. The result is an estimate of the trade-off between cost and risk for non-dissolving and dissolvable fracture technology. A dissolvable frac plug adds both cost and value to fracturing operations in the unconventional market. A key advantage for dissolvable frac plugs is the ability to fracture longer extended reach wellbores. This paper enables the operator to balance the tool cost with the value of eliminating operational mill-out steps, overall cost of the completion, risk associated with the completion, and the time necessary to begin production.
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