Preparation and performance evaluation of degradable IPN-PAM/STA interpenetrating network microspheres for in-depth profile control

Conventional polyacrylamide (PAM) microspheres suffer from rapid uncontrolled swelling, poor temperature/salt resistance, and severe shear fragmentation, which greatly restrict their application in in-depth profile control and water shutoff of complex oil reservoirs. Herein, novel interpenetrating network microspheres (IPN-PAM/STA) were successfully fabricated via reverse emulsion polymerization, using polyacrylamide (PAM) as the primary network and acid-modified starch (STA) as the secondary crosslinking network. Structural characterizations including FTIR, XRD, TGA and DSC verified the successful construction of stable IPN structures, in which the crystalline structure of starch was completely transformed into an amorphous state through hydrogen-bonding interactions with PAM chains. Benefiting from the synergistic dual-network effect, the optimized IPN-PAM/STA microspheres exhibited controllable swelling behavior, excellent thermal stability above 70°C, and prominent adaptability to variable salinity and pH environments. Core flooding tests demonstrated an ultra-high plugging efficiency of 96.3%, far superior to that of pure PAM microspheres. More importantly, the introduced biodegradable starch component endows the microspheres with an outstanding biodegradation rate of over 90% within 120 days, effectively avoiding secondary environmental pollution. This work provides a high-efficiency, shear-resistant, temperature-salt tolerant and eco-friendly plugging material for in-depth reservoir profile control, offering a promising strategy for enhanced oil recovery in heterogeneous and complex oilfields.