Strong, Tough, and High-Temperature-Resistant Biodegradable Temporary Plugging Agents for Refracturing in Deep Reservoirs by Two-Step Reactive Extrusion

Temporary plugging and diverting technology is an effective method for enhancing fracture complexity during repeated fracturing operations. PLA-based temporary plugging agents have attracted extensive attention due to their high mechanical strength and environmental friendliness. However, their relatively low softening temperature and poor balance between stiffness and toughness significantly restrict their applicability in deep reservoirs. In this study, a composite biodegradable temporary plugging agent (CB-TPA) with stable interfacial adhesion morphology and excellent physical properties was prepared by a two-step reactive blending with polylactic acid (PLA), polyglycolic acid (PGA), polybutylene adipate terephthalate (PBAT), and a reactive elastomer (ADR). Experimental results indicated that at a PLA/PGA (70:30) to PBAT mass ratio of 3:1, the tensile strength, Vicat softening temperature, and impact toughness reached 64.4 MPa, 110 °C, and 7.7 kJ/m2, respectively. The material had a lower stiffness loss due to the improved compatibility, demonstrating well-balanced heat resistance, toughness, and stiffness. The simulated plugging experiments showed that CB-TPA could effectively withstand pressures up to 20 MPa at 160 °C, which is superior to that of commercial PLA temporary plugging agents. Under aqueous conditions at 160 °C, the weight loss of CB-TPA reached 96.7% within 4 h. The successful development of this composite biodegradable temporary plugging agent provides a new sustainable solution for the exploitation of deep unconventional oil and gas resources.