Development of Novel Hybrid Dissolvable Frac Plugs with Polyglycolic Acid Based Materials

Abstract Recently, dissolvable frac plugs have been widely used in hydraulic fracturing operations due to their operational advantages, including reduced drill-out times. Novel hybrid dissolvable frac plugs with a short-ramp design were developed and studied. These plugs consist of a Polyglycolic Acid (PGA) ramp cone, dissolvable magnesium alloy slips and dissolvable polyurethane sealing element. The designed plugs had successfully passed the pressure-holding test and showed great potential for the downhole fracturing applications. To investigate the PGA materials, mechanical property testing, thermal analysis (DSC), degradability studies (in brine) and microscopy were performed. The integrity and pressure-holding performance of the hybrid plugs at elevated temperature were evaluated using a special designed testing fixture, with the hybrid plugs set at approximately 30,000 lbs of force. Degradation studies of the whole hybrid plugs were also conducted in KCl solution at elevated temperatures. The ramp cones were machined from extrusion molded rods of PGA. The PGA materials demonstrate exceptionally high mechanical strength reaching approximately 100 MPa from injection molded tensile bars (ASTM D638). The degradation of the injection molded PGA plaques reached 50% weight loss after approximately 2.5 days at 90 °C in KCl solution. The hybrid dissolvable plugs with PGA ramp cones successfully passed the pressure-holding tests at 50 MPa/93 °C. Post-test examination showed no cracking in the PGA ramp cones, indicating excellent mechanical integrity after setting and testing. The degradability of whole hybrid plugs was further examined at 80 °C in KCl solution, showing that both PGA cone and the magnesium alloy slips reached 50% weight loss within 5 days. To our knowledge, this is the first hybrid dissolvable frac plug with short-ramp design in which the dissolvable polymer PGA was used as major structure component. In conclusion, the hybrid PGA dissolvable frac plugs (ramp design) were successfully developed and further field tests are currently underway.