This paper mainly studies the droplet breaking behavior in contracted pore throat microchannels. The droplet breaking process consists of four stages: extrusion, stretching, sub-droplet growth and fracture. The effects of interfacial tension and dispersed phase viscosity on droplet rupture were investigated. And changes in the localized pressure drop during droplet breaking. In order to understand the droplet deformation mechanism more deeply, we have successfully used micro-particle image velocimetry (micro-PIV) to describe the velocity distribution in the flow. The results show that the fluid characteristics of the continuous phase dominate the droplet deformation and fragmentation in the microdevice geometry. In addition, we built a model based on Taylor's analogy to predict the size of the child droplet formed when the parent droplet is broken during deformation, and compared it with the experimental data. The predicted model and the experimental data show a satisfactory agreement in terms of approximation.

Temporary plugging agents are critical to oilfield operations such as diversion fracturing, wellbore interventions, and drilling. This study develops a double-crosslinked self-degradable gel (DSDG) using polydopamine and poly(ethylene glycol) diacrylate as crosslinkers for polyacrylamide, targeting low temperature reservoirs. The DSDG system integrates covalent crosslinking via C=C bonds and dynamic crosslinking through amine–catechol interactions. Gelation kinetics, rheological properties, self-degradation mechanisms, and gel breaking performance of DSDG were systematically characterized. By analyzing the influence of components on gelation kinetics and mechanical properties, the composition of DSDG was optimized to include 4–8 wt% acrylamide monomer, 0.5–0.8 wt% initiator, and 0.2–0.6 wt% poly(ethylene glycol) diacrylate crosslinker, with a dopamine to acrylamide mass ratio of (5–8) × 10⁻³. At 60–80 ℃, DSDG transitions from liquid to quasi-solid gel within 30–180 min, with > 80% of the gelation process occurring in a low viscosity phase conducive to pumpable injection. Unoxidized catechol groups, π–π stacking, and hydrogen bonding synergistically enhance tensile strength, fracture toughness, and interfacial adhesion, enabling robust sealing under downhole stresses. Core flooding tests in 5–50 mD cores achieved initiation and breakthrough pressure gradients of 34.6–119 and 86.6–184.6 MPa/m, respectively. In simulated wellbore with an inner diameter of 120 mm, the pressure-bearing capacity reached 1.25 MPa/m. Acidic/alkaline conditions rapidly degrade polydopamine, disrupting network integrity and enabling controllable gel breaking times of 1–20 d. Free dopamine monomers inhibit acrylamide polymerization, reducing post-degradation viscosity to < 10 mPa·s via shortened polyacrylamide chains.