Degradable Packing Element for Low-Temperature Fracturing Applications

Abstract

Abstract Plug-and-Perf with composite plugs is a commonly used method for multistage hydraulic fracturing treatment in North America shale plays. Composite plugs must be drilled out after the fracturing operation to allow flow of hydrocarbons or produced fluids to the surface. This paper presents a completely degradable packing element for low temperatures, at 125°F or above, and high-pressure (10,000 psi) applications that require no subsequent drilling-out operation. The degradable packing element is made of a polyurethane material and special fillers using an innovative manufacturing method to achieve the desired degradability at temperatures of 125°F or above. Three-dimensional solid modeling and nonlinear finite element analysis (FEA) were performed to finalize the packing element design. Full functional tests on sealability and degradability to meet specific operational requirements were performed. This new degradable polyurethane sealing material is extremely strong, with a tensile strength > 5,000 psi and high elongation at break > 400%. Degradability and sealability are two key functions of the disintegrating frac plug packing element material. The packing elements degrade completely in light brines in a temperature range from 125 to 200°F. Full plug tests with this degradable material as a sealing element demonstrated the sealing ability to hold 10,000 psi for five hours. All components of the plug including sealing element fully disintegrate after fracturing operation in light brines. A new polyurethane-based degradable packing element material for low wellbore temperatures (from 125 to 200°F) was developed. Introduction of this new sealing material will accelerate the development of interventionless tools for unconventional shale completions at a wide range of application temperatures.